{
  "spore": "profile",
  "id": "iron-oxide",
  "spore_version": "0.2",
  "family": "oxide-ceramics",
  "name": "Iron oxide",
  "abbreviation": "Fe2O3, Fe3O4",
  "role": "magnetic and pigment oxides (hematite, magnetite, ferrite magnets and cores)",
  "category": "ceramics",
  "type": "oxides",
  "summary": "Iron oxides are the oxides of iron. Hematite (Fe2O3) is a red, antiferromagnetic oxide with a Néel temperature of about 948 K. Magnetite (Fe3O4) is a ferrimagnetic spinel with a Curie temperature of 858 K. Ferrites add a second metal oxide: hard strontium hexaferrite (SrO.6Fe2O3) is the most used permanent magnet family, at about 85 wt.% of the permanent magnet market by one review, and soft MnZn ferrites such as TDK N87 carry flux in power transformers. Bismuth ferrite and samarium ferrite are related perovskite-type oxides that are only mentioned here. Iron oxide pigments are colour stable and are used in paint, coatings and concrete. Hematite is also widely present on the surface of Mars.\n",
  "best_for": "Cheap, corrosion-resistant magnets and power-transformer cores, and colour-stable pigments",
  "weakest_at": "Magnetic strength per volume, which is lower than NdFeB or SmCo magnets, and brittleness of sintered ferrite parts",
  "identity": {
    "formula": "Fe2O3 (hematite); Fe3O4 (magnetite); SrO.6Fe2O3 (strontium ferrite)",
    "cas": "1309-37-1",
    "crystal_system": "corundum type (hematite)",
    "designations": [],
    "source": "arxiv-oxidation-iron-oxide",
    "where": "Introduction, paragraph on the hematite crystal structure (isostructural with corundum, oxygen closely packed around the Fe3+ cations); CAS number in the CAS section of the PubChem record (CID 518696)"
  },
  "tags": {
    "environments": [
      "mars-surface"
    ],
    "stresses": [
      "extreme-heat"
    ],
    "applications": [
      "electronics-and-chips",
      "mechanisms"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density, iron(III) oxide (Fe2O3)",
      "value": 5.24,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "form": "iron(III) oxide, PubChem record CID 518696",
        "phase": "not stated in the record"
      },
      "method": "Experimental value printed in the PubChem record; other entries in the same section print 5.25 g/cu cm",
      "status": "ground",
      "source": "pubchem-fe2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Density",
      "source_detail": {
        "title": "PubChem compound record, Iron oxide (Fe2O3), CID 518696 (JSON view)",
        "id": "CID 518696; CAS 1309-37-1",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/518696/JSON",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "neel_temperature",
      "label": "Néel temperature, hematite (alpha-Fe2O3)",
      "value": 948,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "phase": "alpha-Fe2O3, bulk",
        "basis": "value quoted for bulk hematite in the introduction of the paper"
      },
      "method": "Value stated in the introduction of a 2025 arXiv paper on hematite nanospindles",
      "status": "ground",
      "source": "arxiv-hematite-nanospindles",
      "where": "Introduction, paragraph on weak ferromagnetism (Néel temperature TN of ca. 948 K)",
      "source_detail": {
        "title": "Insight into the Correlation of Shape and Magnetism of Hematite Nanospindles",
        "id": "arXiv 2505.14265",
        "url": "https://arxiv.org/pdf/2505.14265",
        "year": 2025,
        "kind": "paper",
        "license": "arXiv preprint (cited, not reproduced)"
      }
    },
    {
      "benchmark": "morin_transition_temperature",
      "label": "Morin transition temperature, bulk hematite",
      "value": 250,
      "value_high": 260,
      "bound": "range",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "phase": "alpha-Fe2O3, bulk",
        "note": "spin reorientation on cooling; smaller particles shift it lower"
      },
      "method": "Range stated in the introduction of the paper for bulk hematite",
      "status": "ground",
      "source": "arxiv-hematite-nanospindles",
      "where": "Introduction, paragraph on the Morin transition (typically between 250 K and 260 K)",
      "source_detail": {
        "title": "Insight into the Correlation of Shape and Magnetism of Hematite Nanospindles",
        "id": "arXiv 2505.14265",
        "url": "https://arxiv.org/pdf/2505.14265",
        "year": 2025,
        "kind": "paper",
        "license": "arXiv preprint (cited, not reproduced)"
      }
    },
    {
      "benchmark": "curie_temperature",
      "label": "Curie temperature, magnetite (Fe3O4)",
      "value": 858,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "phase": "magnetite, Fe3O4",
        "basis": "value quoted in the introduction of the paper"
      },
      "method": "Value stated in the introduction of a 2018 arXiv paper on magnetic properties near the Verwey transition",
      "status": "ground",
      "note": "A 2022 review gives about 850 K for the same transition, consistent with this value.",
      "source": "arxiv-magnetite-verwey",
      "where": "Introduction, first paragraphs (high Curie temperature (858 K))",
      "source_detail": {
        "title": "Evolution of magnetic properties in the vicinity of the Verwey transition in Fe3O4",
        "id": "arXiv 1810.00538",
        "url": "https://arxiv.org/pdf/1810.00538",
        "year": 2018,
        "kind": "paper",
        "license": "arXiv preprint (cited, not reproduced)"
      }
    },
    {
      "benchmark": "verwey_transition_temperature",
      "label": "Verwey transition temperature, magnetite (Fe3O4)",
      "value": 125,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "phase": "magnetite, Fe3O4, bulk",
        "note": "the review says it drops to about 120 K for 20 nm particles"
      },
      "method": "Value stated in an open-access review of the magnetite trimeron bond",
      "status": "ground",
      "source": "pmc-magnetite-review",
      "where": "Introduction and magnetite section (Verwey transition at TV of about 125 K)",
      "source_detail": {
        "title": "Magnetism and the Trimeron Bond (review of the magnetite Verwey transition)",
        "id": "PMC9261838",
        "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9261838/",
        "year": 2022,
        "kind": "paper",
        "license": "open access (cited, not reproduced)"
      }
    },
    {
      "benchmark": "curie_temperature",
      "label": "Curie temperature, strontium hexaferrite (SrFe12O19)",
      "value": 746,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "phase": "SrFe12O19, M-type strontium hexaferrite",
        "basis": "room-temperature intrinsic parameter table"
      },
      "method": "Value in Table 1 of an open-access review on hard hexaferrite magnets (from its reference 34)",
      "status": "ground",
      "source": "arxiv-hexaferrite-review",
      "where": "Table 1 (intrinsic magnetic parameters at room temperature), row SrFe12O19, TC column",
      "source_detail": {
        "title": "Permanent magnets based on hard ferrite ceramics",
        "id": "arXiv 2310.02106",
        "url": "https://arxiv.org/pdf/2310.02106",
        "year": 2023,
        "kind": "paper",
        "license": "arXiv preprint (cited, not reproduced)"
      }
    },
    {
      "benchmark": "saturation_magnetization",
      "label": "Saturation magnetization, strontium hexaferrite (SrFe12O19)",
      "value": 72,
      "bound": "exact",
      "unit": "Am2/kg",
      "scope": "material",
      "conditions": {
        "phase": "SrFe12O19",
        "temperature": "room temperature"
      },
      "method": "Value in Table 1 of the same review (from its reference 34)",
      "status": "ground",
      "source": "arxiv-hexaferrite-review",
      "where": "Table 1, row SrFe12O19, Ms column",
      "source_detail": {
        "title": "Permanent magnets based on hard ferrite ceramics",
        "id": "arXiv 2310.02106",
        "url": "https://arxiv.org/pdf/2310.02106",
        "year": 2023,
        "kind": "paper",
        "license": "arXiv preprint (cited, not reproduced)"
      }
    },
    {
      "benchmark": "saturation_flux_density",
      "label": "Saturation flux density Bs, strontium hexaferrite (SrFe12O19)",
      "value": 0.48,
      "bound": "exact",
      "unit": "T",
      "scope": "material",
      "conditions": {
        "phase": "SrFe12O19",
        "temperature": "room temperature"
      },
      "method": "Value in Table 1 of the same review (from its reference 34)",
      "status": "ground",
      "source": "arxiv-hexaferrite-review",
      "where": "Table 1, row SrFe12O19, Bs column",
      "source_detail": {
        "title": "Permanent magnets based on hard ferrite ceramics",
        "id": "arXiv 2310.02106",
        "url": "https://arxiv.org/pdf/2310.02106",
        "year": 2023,
        "kind": "paper",
        "license": "arXiv preprint (cited, not reproduced)"
      }
    },
    {
      "benchmark": "intrinsic_coercivity",
      "label": "Theoretical maximum coercivity, strontium hexaferrite",
      "value": 594,
      "bound": "exact",
      "unit": "kA/m",
      "scope": "material",
      "conditions": {
        "phase": "SrFe12O19, hypothetical single crystal with full alignment",
        "basis": "theoretical limit from the large uniaxial anisotropy along the c axis"
      },
      "method": "Theoretical maximum quoted in the review; not a measured value",
      "status": "calculated",
      "source": "arxiv-hexaferrite-review",
      "where": "Paragraph on the uniaxial anisotropy of the hexagonal lattice (theoretical maximum Hc of 594 kA/m)",
      "source_detail": {
        "title": "Permanent magnets based on hard ferrite ceramics",
        "id": "arXiv 2310.02106",
        "url": "https://arxiv.org/pdf/2310.02106",
        "year": 2023,
        "kind": "paper",
        "license": "arXiv preprint (cited, not reproduced)"
      }
    },
    {
      "benchmark": "neel_temperature",
      "label": "Néel temperature, bismuth ferrite (BiFeO3)",
      "value": 650,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "phase": "BiFeO3, bulk",
        "note": "the same paper also gives 370 degC for the Néel temperature in another place"
      },
      "method": "Value stated in the introduction of a 2024 arXiv paper on magneto-electric coupling in bismuth ferrite",
      "status": "ground",
      "source": "arxiv-bfo-2406",
      "where": "Introduction, paragraph on antiferromagnetic order (TN of about 650 K)",
      "source_detail": {
        "title": "Magneto-electric decoupling in bismuth ferrite",
        "id": "arXiv 2406.16114",
        "url": "https://arxiv.org/pdf/2406.16114",
        "year": 2024,
        "kind": "paper",
        "license": "arXiv preprint (cited, not reproduced)"
      }
    },
    {
      "benchmark": "curie_temperature",
      "label": "Ferroelectric Curie temperature, bismuth ferrite (BiFeO3)",
      "value": 1100,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "phase": "BiFeO3, bulk",
        "order": "ferroelectric"
      },
      "method": "Value stated in the introduction of the same 2024 arXiv paper",
      "status": "ground",
      "source": "arxiv-bfo-2406",
      "where": "Introduction, paragraph on ferroelectric order (TC of about 1100 K)",
      "source_detail": {
        "title": "Magneto-electric decoupling in bismuth ferrite",
        "id": "arXiv 2406.16114",
        "url": "https://arxiv.org/pdf/2406.16114",
        "year": 2024,
        "kind": "paper",
        "license": "arXiv preprint (cited, not reproduced)"
      }
    },
    {
      "benchmark": "neel_temperature",
      "label": "Néel temperature, samarium ferrite (SmFeO3)",
      "value": 680,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "phase": "SmFeO3 single crystal",
        "note": "below this temperature it is a canted antiferromagnet with a weak ferromagnetic vector along c"
      },
      "method": "Value stated in the main text of a 2014 open-access paper on spin switching in SmFeO3",
      "status": "ground",
      "source": "sci-rep-smfeo3-2014",
      "where": "Main text, paragraph on magnetization (Néel temperature TN = 680 K)",
      "source_detail": {
        "title": "Temperature induced Spin Switching in SmFeO3 Single Crystal (Scientific Reports)",
        "id": "Sci Rep, 2014, srep05960",
        "url": "https://www.nature.com/articles/srep05960",
        "year": 2014,
        "kind": "paper",
        "license": "open access (cited, not reproduced)"
      }
    },
    {
      "benchmark": "saturation_flux_density",
      "label": "Flux density Bs at 25 degC, MnZn power ferrite N87",
      "value": 490,
      "bound": "exact",
      "unit": "mT",
      "scope": "material",
      "conditions": {
        "grade": "SIFERRIT N87, MnZn power ferrite",
        "field": "H = 1200 A/m",
        "frequency": "10 kHz",
        "temperature": "25 degC"
      },
      "method": "Value in the material-properties table of the TDK ferrite catalogue",
      "status": "ground",
      "source": "tdk-ferrite-catalogue",
      "where": "Material properties table (continued), N87 column, row Flux density BS (25 degC)",
      "source_detail": {
        "title": "TDK ferrites and accessories catalogue (SIFERRIT material characteristics, N87 and other MnZn grades)",
        "id": "TDK catalogue, April 2013 print",
        "url": "https://www.tdk-electronics.tdk.com/download/519704/069c210d0363d7b4682d9ff22c2ba503/ferrites-and-accessories-db-130501.pdf",
        "year": 2013,
        "kind": "datasheet",
        "license": "manufacturer catalogue (cited, not reproduced)"
      }
    },
    {
      "benchmark": "saturation_flux_density",
      "label": "Flux density Bs at 100 degC, MnZn power ferrite N87",
      "value": 390,
      "bound": "exact",
      "unit": "mT",
      "scope": "material",
      "conditions": {
        "grade": "SIFERRIT N87, MnZn power ferrite",
        "field": "H = 1200 A/m",
        "frequency": "10 kHz",
        "temperature": "100 degC"
      },
      "method": "Value in the material-properties table of the TDK ferrite catalogue",
      "status": "ground",
      "source": "tdk-ferrite-catalogue",
      "where": "Material properties table (continued), N87 column, row Flux density BS (100 degC)",
      "source_detail": {
        "title": "TDK ferrites and accessories catalogue (SIFERRIT material characteristics, N87 and other MnZn grades)",
        "id": "TDK catalogue, April 2013 print",
        "url": "https://www.tdk-electronics.tdk.com/download/519704/069c210d0363d7b4682d9ff22c2ba503/ferrites-and-accessories-db-130501.pdf",
        "year": 2013,
        "kind": "datasheet",
        "license": "manufacturer catalogue (cited, not reproduced)"
      }
    },
    {
      "benchmark": "curie_temperature",
      "label": "Curie temperature, MnZn power ferrite N87",
      "value": 210,
      "bound": "lower",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "grade": "SIFERRIT N87, MnZn power ferrite"
      },
      "method": "Table value printed as a lower limit (above 210 degC)",
      "status": "ground",
      "source": "tdk-ferrite-catalogue",
      "where": "Material properties table (continued), N87 column, row Curie temperature TC",
      "source_detail": {
        "title": "TDK ferrites and accessories catalogue (SIFERRIT material characteristics, N87 and other MnZn grades)",
        "id": "TDK catalogue, April 2013 print",
        "url": "https://www.tdk-electronics.tdk.com/download/519704/069c210d0363d7b4682d9ff22c2ba503/ferrites-and-accessories-db-130501.pdf",
        "year": 2013,
        "kind": "datasheet",
        "license": "manufacturer catalogue (cited, not reproduced)"
      }
    },
    {
      "benchmark": "initial_permeability",
      "label": "Initial permeability, MnZn power ferrite N87",
      "value": 2200,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "grade": "SIFERRIT N87, MnZn power ferrite",
        "temperature": "25 degC"
      },
      "method": "Value in the material-properties table of the TDK ferrite catalogue",
      "status": "ground",
      "source": "tdk-ferrite-catalogue",
      "where": "Material properties table (continued), N87 column, row Initial permeability",
      "source_detail": {
        "title": "TDK ferrites and accessories catalogue (SIFERRIT material characteristics, N87 and other MnZn grades)",
        "id": "TDK catalogue, April 2013 print",
        "url": "https://www.tdk-electronics.tdk.com/download/519704/069c210d0363d7b4682d9ff22c2ba503/ferrites-and-accessories-db-130501.pdf",
        "year": 2013,
        "kind": "datasheet",
        "license": "manufacturer catalogue (cited, not reproduced)"
      }
    },
    {
      "benchmark": "coercive_field",
      "label": "Coercive field strength, MnZn power ferrite N87",
      "value": 21,
      "bound": "exact",
      "unit": "A/m",
      "scope": "material",
      "conditions": {
        "grade": "SIFERRIT N87, MnZn power ferrite",
        "temperature": "25 degC",
        "frequency": "10 kHz"
      },
      "method": "Value in the material-properties table of the TDK ferrite catalogue",
      "status": "ground",
      "source": "tdk-ferrite-catalogue",
      "where": "Material properties table (continued), N87 column, row Coercive field strength Hc (25 degC)",
      "source_detail": {
        "title": "TDK ferrites and accessories catalogue (SIFERRIT material characteristics, N87 and other MnZn grades)",
        "id": "TDK catalogue, April 2013 print",
        "url": "https://www.tdk-electronics.tdk.com/download/519704/069c210d0363d7b4682d9ff22c2ba503/ferrites-and-accessories-db-130501.pdf",
        "year": 2013,
        "kind": "datasheet",
        "license": "manufacturer catalogue (cited, not reproduced)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, MnZn power ferrite N87 (typical)",
      "value": 4850,
      "bound": "exact",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "grade": "SIFERRIT N87, MnZn power ferrite",
        "basis": "typical value"
      },
      "method": "Typical value printed in the material-properties table of the TDK ferrite catalogue",
      "status": "ground",
      "source": "tdk-ferrite-catalogue",
      "where": "Material properties table (continued), N87 column, row Density (typical values)",
      "source_detail": {
        "title": "TDK ferrites and accessories catalogue (SIFERRIT material characteristics, N87 and other MnZn grades)",
        "id": "TDK catalogue, April 2013 print",
        "url": "https://www.tdk-electronics.tdk.com/download/519704/069c210d0363d7b4682d9ff22c2ba503/ferrites-and-accessories-db-130501.pdf",
        "year": 2013,
        "kind": "datasheet",
        "license": "manufacturer catalogue (cited, not reproduced)"
      }
    },
    {
      "benchmark": "remanence",
      "label": "Remanence Br, hard ferrite grade 28/26 (minimum)",
      "value": 380,
      "bound": "exact",
      "unit": "mT",
      "scope": "material",
      "conditions": {
        "grade": "Hard ferrite 28/26, anisotropic sintered",
        "basis": "minimum value (min row) in the product table"
      },
      "method": "Minimum value printed in the magnetic-properties table of the thyssenkrupp product information",
      "status": "ground",
      "source": "thyssen-hard-ferrite",
      "where": "Magnetic properties table, row Hard ferrite 28/26, Br column",
      "source_detail": {
        "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
        "id": "thyssenkrupp Magnettechnik product information",
        "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
        "kind": "datasheet",
        "license": "manufacturer product information (cited, not reproduced)"
      }
    },
    {
      "benchmark": "intrinsic_coercivity",
      "label": "Intrinsic coercivity HcJ, hard ferrite grade 28/26 (minimum)",
      "value": 260,
      "bound": "exact",
      "unit": "kA/m",
      "scope": "material",
      "conditions": {
        "grade": "Hard ferrite 28/26, anisotropic sintered",
        "basis": "minimum value (min row) in the product table"
      },
      "method": "Minimum value printed in the magnetic-properties table of the thyssenkrupp product information",
      "status": "ground",
      "source": "thyssen-hard-ferrite",
      "where": "Magnetic properties table, row Hard ferrite 28/26, HcJ column",
      "source_detail": {
        "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
        "id": "thyssenkrupp Magnettechnik product information",
        "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
        "kind": "datasheet",
        "license": "manufacturer product information (cited, not reproduced)"
      }
    },
    {
      "benchmark": "max_energy_product",
      "label": "Maximum energy product BHmax, hard ferrite grade 28/26 (minimum)",
      "value": 28,
      "bound": "exact",
      "unit": "kJ/m3",
      "scope": "material",
      "conditions": {
        "grade": "Hard ferrite 28/26, anisotropic sintered",
        "basis": "minimum value (min row) in the product table"
      },
      "method": "Minimum value printed in the magnetic-properties table of the thyssenkrupp product information",
      "status": "ground",
      "source": "thyssen-hard-ferrite",
      "where": "Magnetic properties table, row Hard ferrite 28/26, BHmax column",
      "source_detail": {
        "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
        "id": "thyssenkrupp Magnettechnik product information",
        "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
        "kind": "datasheet",
        "license": "manufacturer product information (cited, not reproduced)"
      }
    },
    {
      "benchmark": "remanence_temperature_coefficient",
      "label": "Temperature coefficient of remanence TK(Br), hard ferrite grades",
      "value": -0.2,
      "bound": "exact",
      "unit": "%/K",
      "scope": "material",
      "conditions": {
        "grade": "hard ferrite, all grades in the table (28/26 shown)",
        "note": "remanence falls as the magnet warms; HcJ rises by 0.4 %/K"
      },
      "method": "Coefficient printed in the magnetic-properties table of the thyssenkrupp product information",
      "status": "ground",
      "source": "thyssen-hard-ferrite",
      "where": "Magnetic properties table, TK(Br) column",
      "source_detail": {
        "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
        "id": "thyssenkrupp Magnettechnik product information",
        "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
        "kind": "datasheet",
        "license": "manufacturer product information (cited, not reproduced)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, sintered hard ferrite",
      "value": 4.7,
      "value_high": 4.9,
      "bound": "range",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "form": "sintered hard ferrite, isotropic or anisotropic"
      },
      "method": "Range printed in the physical-properties table of the thyssenkrupp product information",
      "status": "ground",
      "source": "thyssen-hard-ferrite",
      "where": "Physical properties table, Density column",
      "source_detail": {
        "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
        "id": "thyssenkrupp Magnettechnik product information",
        "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
        "kind": "datasheet",
        "license": "manufacturer product information (cited, not reproduced)"
      }
    },
    {
      "benchmark": "curie_temperature",
      "label": "Curie temperature, hard ferrite magnets",
      "value": 450,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "material": "hard ferrite (strontium or barium ferrite magnets)"
      },
      "method": "Value printed in the physical-properties section of the thyssenkrupp product information (Tc = 450 degC)",
      "status": "ground",
      "source": "thyssen-hard-ferrite",
      "where": "Physical properties, Operating temperature and Curie temperature block",
      "source_detail": {
        "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
        "id": "thyssenkrupp Magnettechnik product information",
        "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
        "kind": "datasheet",
        "license": "manufacturer product information (cited, not reproduced)"
      }
    },
    {
      "benchmark": "max_service_temp",
      "label": "Maximum operating temperature, hard ferrite magnets",
      "value": 250,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "material": "hard ferrite magnets",
        "basis": "manufacturer Tmax"
      },
      "method": "Value printed as Tmax in the physical-properties section of the thyssenkrupp product information; the Eclipse Magnetics sheet allows up to 300 degC in a few situations",
      "status": "ground",
      "source": "thyssen-hard-ferrite",
      "where": "Physical properties, Operating temperature block (Tmax = 250 degC)",
      "source_detail": {
        "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
        "id": "thyssenkrupp Magnettechnik product information",
        "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
        "kind": "datasheet",
        "license": "manufacturer product information (cited, not reproduced)"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Young's modulus, sintered hard ferrite",
      "value": 120,
      "value_high": 180,
      "bound": "range",
      "unit": "kN/mm2",
      "scope": "material",
      "conditions": {
        "form": "sintered hard ferrite"
      },
      "method": "Range printed in the physical-properties table of the thyssenkrupp product information",
      "status": "ground",
      "source": "thyssen-hard-ferrite",
      "where": "Physical properties table, Young's modulus column",
      "source_detail": {
        "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
        "id": "thyssenkrupp Magnettechnik product information",
        "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
        "kind": "datasheet",
        "license": "manufacturer product information (cited, not reproduced)"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "label": "Thermal conductivity, sintered hard ferrite",
      "value": 5,
      "value_high": 10,
      "bound": "range",
      "unit": "W/m K",
      "scope": "material",
      "conditions": {
        "form": "sintered hard ferrite"
      },
      "method": "Range printed in the physical-properties table of the thyssenkrupp product information",
      "status": "ground",
      "source": "thyssen-hard-ferrite",
      "where": "Physical properties table, Thermal conductivity column",
      "source_detail": {
        "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
        "id": "thyssenkrupp Magnettechnik product information",
        "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
        "kind": "datasheet",
        "license": "manufacturer product information (cited, not reproduced)"
      }
    },
    {
      "benchmark": "cte",
      "label": "Coefficient of linear thermal expansion, hard ferrite",
      "value": 9.2,
      "value_high": 13.3,
      "bound": "range",
      "unit": "10-6/K",
      "scope": "material",
      "conditions": {
        "direction": "in the magnetizing direction (9.2 to 10 normal to it)",
        "form": "sintered hard ferrite"
      },
      "method": "Range printed in the physical-properties table of the thyssenkrupp product information",
      "status": "ground",
      "source": "thyssen-hard-ferrite",
      "where": "Physical properties table, coefficient of linear thermal expansion columns",
      "source_detail": {
        "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
        "id": "thyssenkrupp Magnettechnik product information",
        "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
        "kind": "datasheet",
        "license": "manufacturer product information (cited, not reproduced)"
      }
    },
    {
      "benchmark": "specific_heat",
      "label": "Heat capacity, hard ferrite",
      "value": 500,
      "value_high": 800,
      "bound": "range",
      "unit": "J/kg K",
      "scope": "material",
      "conditions": {
        "form": "sintered hard ferrite"
      },
      "method": "Range printed in the physical-properties table of the thyssenkrupp product information",
      "status": "ground",
      "source": "thyssen-hard-ferrite",
      "where": "Physical properties table, Heat capacity column",
      "source_detail": {
        "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
        "id": "thyssenkrupp Magnettechnik product information",
        "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
        "kind": "datasheet",
        "license": "manufacturer product information (cited, not reproduced)"
      }
    },
    {
      "benchmark": "remanence",
      "label": "Remanence Br, ferrite grade Y30 (typical range)",
      "value": 370,
      "value_high": 400,
      "bound": "range",
      "unit": "mT",
      "scope": "material",
      "conditions": {
        "grade": "Y30, Chinese-standard strontium ferrite grade",
        "basis": "typical values from the grade table"
      },
      "method": "Typical range printed in the grade table of the Eclipse Magnetics ferrite datasheet",
      "status": "ground",
      "source": "eclipse-ferrite-datasheet",
      "where": "Typical values table, row Y30, Br column",
      "source_detail": {
        "title": "Ferrite Magnets / Ceramic Magnets Datasheet (Eclipse Magnetics)",
        "id": "Eclipse Magnetics ceramic magnets datasheet",
        "url": "https://www.eclipsemagnetics.com/site/assets/files/19602/ferrite_ceramic_datasheet.pdf",
        "kind": "datasheet",
        "license": "manufacturer datasheet (cited, not reproduced)"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Water and damp, wet or marine air (ferrite magnets)",
      "headline": "Ferrite magnets do not rust in water, because their iron is already oxidized.",
      "effect": "The Eclipse Magnetics datasheet says ferrite magnets are superb in damp, wet or marine environments and are corrosion free, because the iron is already in a stable oxidized form and cannot oxidize (rust) further in water.",
      "rating": "none",
      "conditions": {
        "material": "strontium ferrite magnets (SrO.6Fe2O3)",
        "exposure": "damp, wet or marine environments"
      },
      "source": "eclipse-ferrite-datasheet",
      "where": "Introduction, first page (paragraph on corrosion)"
    },
    {
      "environment": "Concentrated inorganic acids (hydrochloric, sulphuric, phosphorous, hydrofluoric, oxalic)",
      "headline": "Permanent ferrite magnets are not resistant to concentrated inorganic acids.",
      "effect": "The chemical resistance table lists hydrochloric, sulphuric, phosphorous, hydrofluoric and oxalic acids as not recommended for permanent ferrite magnets. Diluted nitric and sulphuric acids and acetic acid have only limited resistance.",
      "rating": "severe",
      "conditions": {
        "material": "permanent (hard) ferrite magnets",
        "basis": "manufacturer chemical resistance table"
      },
      "source": "thyssen-hard-ferrite",
      "where": "Chemical resistance section (not recommended and moderate effect columns)"
    },
    {
      "environment": "Water, petrol, organic solvents, caustic potash and soda lye",
      "headline": "Ferrite magnets resist water, petrol, organic solvents and alkaline solutions.",
      "effect": "The same chemical resistance table rates water, petrol, organic solvents, caustic potash solution and soda lye as good, and states that ferrite magnets are also resistant to oxidation and climatic influences.",
      "rating": "none",
      "conditions": {
        "material": "permanent (hard) ferrite magnets",
        "basis": "manufacturer chemical resistance table"
      },
      "source": "thyssen-hard-ferrite",
      "where": "Chemical resistance section (good column and text)"
    },
    {
      "environment": "Heat treatment in air from 250 degC to 900 degC (iron oxide nanoparticles)",
      "headline": "Heated in air, the maghemite formed in iron oxide nanoparticles converts fully to hematite.",
      "effect": "The paper finds that nanoparticles heat-treated at lower temperatures contain both maghemite and hematite, and that with increasing temperature the remaining maghemite converts completely to hematite. Crystallite size grows from 50 nm to 150 nm over the range. The paper gives no corrosion rate.",
      "rating": "unknown",
      "conditions": {
        "atmosphere": "air",
        "temperature_range": "250 degC to 900 degC",
        "form": "iron oxide nanoparticles, heat treated"
      },
      "source": "arxiv-oxidation-iron-oxide",
      "where": "Abstract (X-ray diffraction results); Results on crystallite size"
    },
    {
      "environment": "Sunlight and long-term outdoor exposure (pigments)",
      "headline": "Iron oxide pigments stay colour stable, while many organic colourants fade in sunlight.",
      "effect": "The USGS says iron oxide pigments are colour stable, low cost and nontoxic, and notes that many organic colourants fade over time from exposure to sunlight.",
      "rating": "none",
      "conditions": {
        "use": "iron oxide pigments in paint, coatings, concrete and plastics",
        "exposure": "sunlight"
      },
      "source": "usgs-mcs2026-pigments",
      "where": "Substitutes section"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "PubChem reports that 66.9% of company reports (2296 of 3433) do not meet GHS hazard criteria. Other notifications give H319 for eye irritation (18.5% of reports) and H411 for aquatic toxicity (12% of reports), with the signal word Warning.",
        "ghs": [
          "H319",
          "H411"
        ],
        "source": "pubchem-fe2o3",
        "where": "Safety and Hazards, GHS Classification (CID 518696)"
      },
      {
        "text": "Individual notifications in PubChem also give H315 (skin irritation), H318 (serious eye damage), H335 (respiratory irritation) and H372 (organ damage on repeated exposure, respiratory system), with the signal word Danger.",
        "ghs": [
          "H315",
          "H318",
          "H335",
          "H372"
        ],
        "source": "pubchem-fe2o3",
        "where": "Safety and Hazards, GHS Classification, second and third notification groups"
      },
      {
        "text": "The OSHA permissible exposure limit for iron oxide fume is 10 mg/m3 (8-hour time-weighted average). NIOSH gives 5 mg/m3 for iron oxide dust and fume as Fe.",
        "ghs": [],
        "source": "pubchem-fe2o3",
        "where": "Safety and Hazard Properties, OSHA Standards and NIOSH Recommendations"
      },
      {
        "text": "PubChem notes that iron dust or fume can cause siderosis, a benign lung condition, after prolonged exposure to high levels (10 to 700 mg/m3). There is no evidence that iron oxide alone causes fibrotic changes.",
        "ghs": [],
        "source": "pubchem-fe2o3",
        "where": "Safety and Hazards, Hazards Summary"
      }
    ],
    "failure_risks": [
      {
        "mode": "Cracking of sintered ferrite magnets",
        "trigger": "Sharp edges, corners or cuts across the pressing direction",
        "consequence": "The manufacturer says the material is brittle, so cracks and fractures can form; holes and grooves can only be made along the pressing direction.",
        "severity": "moderate",
        "source": "thyssen-hard-ferrite",
        "where": "Magnet shapes section"
      },
      {
        "mode": "Loss of magnetism when hot",
        "trigger": "Operation above the rated maximum of 250 degC, or close to the Curie temperature of 450 degC",
        "consequence": "Remanence falls by 0.2 % per kelvin as the magnet warms, and the coercive field rises by 0.3 to 0.4 % as a rule of thumb. A few situations allow up to 300 degC, according to Eclipse Magnetics.",
        "severity": "moderate",
        "source": "thyssen-hard-ferrite",
        "where": "Physical properties, temperature behaviour; Eclipse Magnetics introduction"
      }
    ],
    "side_effects": [
      {
        "text": "PubChem notes that the substance reacts with carbon monoxide, which can generate an explosion hazard. It is classed as noncombustible.",
        "affects": "Process gas and enclosed spaces near furnaces",
        "source": "pubchem-fe2o3",
        "where": "Safety and Hazard Properties, Chemical Dangers; Fire Hazards"
      }
    ],
    "handling": [
      {
        "text": "Sweep spilled material into covered containers. If fume is released, ventilate the area. Use a particulate filter respirator adapted to the airborne concentration.",
        "source": "pubchem-fe2o3",
        "where": "Accidental Release Measures"
      },
      {
        "text": "The manufacturer says ferrite magnets are non-toxic when landfilled, are unaffected by incineration, and that contact with potable water is permitted.",
        "source": "thyssen-hard-ferrite",
        "where": "Toxicity section"
      }
    ],
    "mitigations": [
      {
        "text": "Keep airborne iron oxide dust and fume within the limits above, and use a particulate filter respirator where the concentration is high.",
        "source": "pubchem-fe2o3",
        "where": "Safety and Hazard Properties, OSHA and NIOSH limits; Accidental Release Measures"
      },
      {
        "text": "Keep hard ferrite magnets below their maximum operating temperature of 250 degC.",
        "source": "thyssen-hard-ferrite",
        "where": "Physical properties, Operating temperature (Tmax)"
      }
    ]
  },
  "uses": [
    {
      "application": "electronics-and-chips",
      "device": "MnZn power ferrite cores for power transformers",
      "example": "TDK lists N87 as a MnZn ferrite with a preferred application in power transformers, with an optimum frequency range of 25 to 500 kHz.",
      "source": "tdk-ferrite-catalogue",
      "where": "Material properties table (continued), N87 column, rows Preferred application and Optimum frequency range"
    },
    {
      "application": "mechanisms",
      "device": "Permanent magnets in motors, generators and loudspeakers",
      "example": "The Eclipse Magnetics datasheet says ferrite magnets are extremely popular in motor, generator, loudspeaker and marine designs, and the thyssenkrupp sheet calls hard ferrite the most cost-effective and widely used magnetic material.",
      "source": "eclipse-ferrite-datasheet",
      "where": "Introduction, paragraph on applications; thyssenkrupp sheet introduction (source thyssen-hard-ferrite)"
    },
    {
      "application": "structures",
      "device": "Iron oxide pigments in concrete and construction products",
      "example": "The USGS lists concrete and other construction products among the end uses of iron oxide pigments, which also go into paint, coatings, ferrites, plastics and rubber.",
      "source": "usgs-mcs2026-pigments",
      "where": "Domestic Production and Use paragraph"
    }
  ],
  "supply": [
    {
      "subject": "Iron (ore feedstock for iron oxides); usable ore",
      "producers": [
        {
          "country": "Australia",
          "share_percent": 37.7,
          "year": 2025
        },
        {
          "country": "Brazil",
          "share_percent": 16.2,
          "year": 2025
        },
        {
          "country": "India",
          "share_percent": 11.9,
          "year": 2025
        },
        {
          "country": "China",
          "share_percent": 11.2,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "USGS Final 2025 List of Critical Minerals (Federal Register notice 2025-19813, 60 minerals): iron and iron ore are not on the list",
          "listed": false
        }
      ],
      "recycling": "USGS iron ore chapter: 'None'. It refers readers to the Iron and Steel Scrap chapter.",
      "substitutes": [
        "USGS: the only source of primary iron is iron ore."
      ],
      "source": "usgs-mcs2026-iron",
      "where": "World Mine Production and Reserves table, usable ore, 2025e (world total 2,600,000 thousand t; shares calculated by Space Mushroom); Recycling; Substitutes. Critical list: Federal Register notice 2025-19813, the list of 60 minerals and the byproduct table (iron ore appears only as a byproduct host for rare earths)."
    },
    {
      "subject": "Iron oxide pigments (US imports, 2021 to 2024: synthetic from China 44%, Germany 30%, Brazil 8%, Canada 6%; natural from Cyprus 51%, France 23%, Austria 18%)",
      "producers": [],
      "critical_lists": [],
      "recycling": "USGS: Recycling: None.",
      "substitutes": [
        "USGS: milled natural iron oxide pigments are the most commonly used natural minerals for pigments, and synthetic iron oxide pigments compete with them in many colours."
      ],
      "source": "usgs-mcs2026-pigments",
      "where": "Import Sources (2021 to 2024) and Substitutes. The world mine production table for pigments is partly garbled in the PDF text, so no producer shares are entered."
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "PubChem: Iron oxide (Fe2O3), CID 518696, properties, GHS classification and CAS number",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/518696",
      "year": 2026
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Iron Oxide Pigments",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-iron-oxide-pigments.pdf",
      "year": 2026
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Iron Ore",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-iron-ore.pdf",
      "year": 2026
    },
    {
      "title": "Federal Register notice 2025-19813: Final 2025 List of Critical Minerals (USGS)",
      "type": "report",
      "url": "https://public-inspection.federalregister.gov/2025-19813.pdf",
      "year": 2025
    },
    {
      "title": "Hematite nanospindles: shape, magnetism and the Morin transition (arXiv 2505.14265)",
      "type": "paper",
      "url": "https://arxiv.org/pdf/2505.14265",
      "year": 2025
    },
    {
      "title": "Magnetism and the Trimeron Bond (magnetite review, open access, PMC9261838)",
      "type": "paper",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9261838/",
      "year": 2022
    },
    {
      "title": "Evolution of magnetic properties in the vicinity of the Verwey transition in Fe3O4 (arXiv 1810.00538)",
      "type": "paper",
      "url": "https://arxiv.org/pdf/1810.00538",
      "year": 2018
    },
    {
      "title": "Permanent magnets based on hard ferrite ceramics (arXiv 2310.02106)",
      "type": "paper",
      "url": "https://arxiv.org/pdf/2310.02106",
      "year": 2023
    },
    {
      "title": "Magneto-electric decoupling in bismuth ferrite (arXiv 2406.16114)",
      "type": "paper",
      "url": "https://arxiv.org/pdf/2406.16114",
      "year": 2024
    },
    {
      "title": "Temperature induced Spin Switching in SmFeO3 Single Crystal (Scientific Reports, open access)",
      "type": "paper",
      "url": "https://www.nature.com/articles/srep05960",
      "year": 2014
    },
    {
      "title": "Mars: new insights and unresolved questions (arXiv 2112.00596)",
      "type": "paper",
      "url": "https://arxiv.org/pdf/2112.00596",
      "year": 2021
    },
    {
      "title": "Evolution of structural properties of iron oxide nanoparticles during temperature treatment from 250 to 900 degC (arXiv 1111.6204)",
      "type": "paper",
      "url": "https://arxiv.org/pdf/1111.6204",
      "year": 2011
    },
    {
      "title": "TDK SIFERRIT ferrite and accessories catalogue, material characteristics (N87)",
      "type": "datasheet",
      "url": "https://www.tdk-electronics.tdk.com/download/519704/069c210d0363d7b4682d9ff22c2ba503/ferrites-and-accessories-db-130501.pdf",
      "year": 2013
    },
    {
      "title": "thyssenkrupp Materials: Hard ferrite magnets, product information",
      "type": "datasheet",
      "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf"
    },
    {
      "title": "Eclipse Magnetics: Ferrite magnets (ceramic magnets) datasheet",
      "type": "datasheet",
      "url": "https://www.eclipsemagnetics.com/site/assets/files/19602/ferrite_ceramic_datasheet.pdf"
    },
    {
      "title": "NIST Atomic Weights and Isotopic Compositions for All Elements",
      "type": "database",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Fe&all=all&ascii=html"
    }
  ],
  "gaps": [
    "No flight, vacuum or radiation result for an iron oxide pigment or ferrite was found in a source read in this run. The space link is the Mars surface only.",
    "Hematite melting point and magnetite saturation magnetization were not read in a source opened for this profile.",
    "Samarium ferrite: only the Néel temperature (680 K) was read, in one open paper. Bismuth ferrite values come from one arXiv paper, and the review it cites was not read.",
    "Strontium and barium supply (producers of strontium and barium minerals) was not read, so the supply section covers iron ore and pigments only.",
    "The EU critical raw materials list was not checked for iron oxide in this run; only the USGS 2025 list (Federal Register notice) was read.",
    "Crustal abundance of iron was not read in a source opened for this profile.",
    "Magnetite oxidation: the source gives phase changes and a temperature range, but no corrosion rate, so the rating is unknown.",
    "Electrical resistivity of N87 is printed in the TDK table, but its unit did not survive text extraction, so the value is not entered.",
    "Hard ferrite property values are minimum guaranteed values (min rows) from one manufacturer, not typical values. The Eclipse Magnetics Y30 typical remanence is entered separately.",
    "Hazard data rest on the PubChem record (company notifications) and the OSHA and NIOSH limits it prints. No supplier safety data sheet for an iron oxide pigment was read.",
    "The Néel temperature and Morin transition of hematite come from one 2025 arXiv paper; a Wikipedia summary and search snippets gave similar values but were not used.",
    "Non-canonical benchmark names used: neel_temperature, morin_transition_temperature, verwey_transition_temperature, saturation_magnetization, saturation_flux_density, remanence, intrinsic_coercivity, coercive_field, initial_permeability, max_energy_product, remanence_temperature_coefficient.",
    "Oxygen atomic weight is the NIST interval 15.99903 to 15.99977, rounded to 15.999; iron atomic weight is 55.845(2) as printed by NIST.",
    "No images added. The LFP profile has three media entries, none sourced here."
  ],
  "story": {
    "why": "Iron oxides are cheap, widely available and stable in air and water. Hematite is the red pigment oxide and is antiferromagnetic up to its Néel temperature. Magnetite is a ferrimagnet with a Curie temperature of 858 K. Ferrites carry this magnetism into engineering use: hard strontium hexaferrite is the main permanent magnet in motors and loudspeakers, and soft MnZn ferrite cores carry flux in power transformers. The trade is weaker magnetism per volume than NdFeB or SmCo magnets, in exchange for low cost and good chemical stability. Bismuth ferrite and samarium ferrite are related oxides with magnetic order at higher temperatures; only one source was read for each.",
    "uses": [
      {
        "where": "Magnet motors and loudspeakers",
        "line": "Strontium hexaferrite is the most used permanent magnet family. One review puts it at 85 wt.% of the permanent magnet market, and ferrite magnets are used in motors, generators and loudspeakers."
      },
      {
        "where": "Transformer cores",
        "line": "MnZn ferrite grades such as N87 are sold for power transformers and work across an optimum frequency range of 25 to 500 kHz."
      },
      {
        "where": "Pigments",
        "line": "Iron oxide pigments colour paint, coatings, concrete and plastics. The USGS calls them colour stable, unlike many organic colourants that fade in sunlight."
      },
      {
        "where": "On Mars",
        "line": "Hematite is widely distributed across the surface of Mars. Hematite spherules, called blueberries, were found in Meridiani Planum by the Opportunity rover."
      }
    ],
    "can_do": [
      {
        "label": "Magnetic order",
        "line": "Hematite stays weakly ferromagnetic up to about 948 K. Below its Morin transition, at 250 to 260 K, the spins reorient into a purely antiferromagnetic state.",
        "scope": "material",
        "value": "Néel 948 K"
      },
      {
        "label": "Magnetite",
        "line": "Magnetite is ferrimagnetic below its Curie temperature of 858 K and undergoes the Verwey transition near 125 K.",
        "scope": "material",
        "value": "Curie 858 K"
      },
      {
        "label": "Hard magnets",
        "line": "Hard ferrite grade 28/26 has a minimum remanence of 380 mT, a minimum coercivity of 260 kA/m and a maximum energy product of 28 kJ/m3.",
        "scope": "material",
        "value": "380 mT remanence"
      },
      {
        "label": "Soft cores",
        "line": "MnZn power ferrite N87 has a flux density of 490 mT at 25 °C and 390 mT at 100 °C, with a Curie temperature above 210 °C.",
        "scope": "material",
        "value": "490 mT at 25 °C"
      }
    ],
    "compare": "Iron oxides trade field strength for cost and stability. Ferrite magnets are the cheapest permanent magnets and do not rust in water, but they are weaker per size than NdFeB or SmCo magnets, according to the magnet maker Eclipse Magnetics. A hard ferrite grade at 380 mT remanence is therefore suited to motors and loudspeakers, not to high-field actuators. The table compares density, Curie temperature and remanence with the other oxides in this collection.",
    "compare_rows": [
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Curie temperature",
        "benchmark": "curie_temperature",
        "scope": "material"
      },
      {
        "label": "Remanence",
        "benchmark": "remanence",
        "scope": "material"
      }
    ],
    "handling": [
      "Use a particulate filter respirator where iron oxide dust or fume is airborne.",
      "Sweep spilled material into covered containers, and ventilate the area if fume is released.",
      "Keep hard ferrite magnets below their rated maximum of 250 °C.",
      "Avoid sharp edges and machining across the pressing direction, which cause cracks."
    ],
    "good_for": [
      "Cheap permanent magnets that do not rust in water, used in motors, generators and loudspeakers (Eclipse Magnetics).",
      "Low-loss power transformer cores across an optimum range of 25 to 500 kHz (TDK N87).",
      "Colour-stable pigments for paint, coatings and concrete (USGS)."
    ],
    "watch_out": [
      "Weaker magnetism per size than NdFeB or SmCo magnets, and brittleness of sintered parts.",
      "Magnetism falls as the magnet warms: remanence drops by 0.2 % per kelvin.",
      "Hazard data are mixed. Most PubChem company reports say not classified, but some give H315, H318, H335 and H372."
    ],
    "verdict": "Iron oxides are the low-cost, stable end of the magnetic materials. Their weak point is magnetic strength per volume, so they suit motors, loudspeakers and transformers better than high-field actuators.",
    "recipe": {
      "line": "Iron oxides combine iron with oxygen. Hematite is Fe2O3, with iron in the three-plus state, in a corundum-type structure. Magnetite is Fe3O4, a cubic spinel with iron in two valence states. Strontium ferrite is SrO.6Fe2O3, an oxide in which strontium oxide is combined with six parts of iron oxide, and it forms a hexagonal structure.",
      "parts": [
        {
          "name": "Iron",
          "symbol": "Fe",
          "role": "The metal ion that carries the magnetism. In hematite and magnetite the iron ions order magnetically below their transition temperatures.",
          "atoms": 2,
          "atomic_weight": 55.845
        },
        {
          "name": "Oxygen",
          "symbol": "O",
          "role": "Forms the oxide framework that holds the iron ions. In hematite there are three oxygen atoms for every two iron atoms.",
          "atoms": 3,
          "atomic_weight": 15.999
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "Most company reports in PubChem say iron oxide does not meet GHS hazard criteria, but some notifications give eye, skin and respiratory hazards. The exposure limits for dust and fume are the practical concern.",
        "points": [
          {
            "label": "The powder",
            "line": "PubChem reports that 66.9% of company reports (2296 of 3433) do not meet GHS hazard criteria. Some notifications give H319 eye irritation (18.5% of reports) and H411 aquatic toxicity (12%)."
          },
          {
            "label": "Dust and fume",
            "line": "The OSHA limit is 10 mg/m3 for iron oxide fume, and NIOSH gives 5 mg/m3 as Fe for dust and fume."
          },
          {
            "label": "Long exposure",
            "line": "Prolonged exposure to high levels of iron dust or fume (10 to 700 mg/m3) can cause siderosis, a benign lung condition."
          }
        ],
        "level": 0,
        "verdict": "Most reports say not hazardous; dust limits apply"
      },
      {
        "title": "If a magnet overheats",
        "lead": "Ferrite magnets are rated to about 250 degC. Above that they lose remanence, and they can crack if handled roughly.",
        "points": [
          {
            "label": "Rated limit",
            "line": "The maximum operating temperature of hard ferrite magnets is 250 °C. The Eclipse Magnetics sheet allows up to 300 °C in a few situations."
          },
          {
            "label": "Temperature effect",
            "line": "Remanence falls by 0.2 % per kelvin as the magnet warms, and the coercive field rises by 0.3 to 0.4 %."
          },
          {
            "label": "Brittleness",
            "line": "Sintered ferrite is brittle, so sharp edges, corners and cuts across the pressing direction can crack the magnet."
          }
        ],
        "level": 1,
        "verdict": "Loses magnetism above its rated temperature"
      },
      {
        "title": "Handling and storage",
        "points": [
          {
            "label": "Dust",
            "line": "Use a particulate filter respirator where dust is airborne, and sweep spills into covered containers."
          },
          {
            "label": "Water and acids",
            "line": "Ferrite magnets resist water and alkaline solutions, but concentrated mineral acids attack them."
          },
          {
            "label": "Disposal",
            "line": "The magnet maker says ferrite magnets are non-toxic in landfill and unaffected by incineration."
          }
        ],
        "verdict": "Dust control and simple disposal"
      }
    ]
  },
  "updated": "2026-10-26",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 30,
    "unreachable": 0,
    "caveats": 4,
    "note": "Read by an AI assistant on 2026-10-26 from the pages and PDFs fetched in that run. The hard ferrite values are minimum values from one manufacturer. The hematite Néel temperature and Morin transition come from one arXiv paper. Samarium ferrite and bismuth ferrite were mentioned from one open paper each. The TDK catalogue is a 2013 print."
  },
  "sources": {
    "pubchem-fe2o3": {
      "title": "PubChem compound record, Iron oxide (Fe2O3), CID 518696 (JSON view)",
      "id": "CID 518696; CAS 1309-37-1",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/518696/JSON",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "usgs-mcs2026-pigments": {
      "title": "Mineral Commodity Summaries 2026, Iron Oxide Pigments",
      "id": "USGS MCS 2026, February 2026",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-iron-oxide-pigments.pdf",
      "year": 2026,
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "usgs-mcs2026-iron": {
      "title": "Mineral Commodity Summaries 2026, Iron Ore",
      "id": "USGS MCS 2026, February 2026",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-iron-ore.pdf",
      "year": 2026,
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "usgs-fr-critical-2025": {
      "title": "Final 2025 List of Critical Minerals (Federal Register notice 2025-19813, 7 November 2025)",
      "id": "Federal Register 2025-19813, 90 FR 50494",
      "url": "https://public-inspection.federalregister.gov/2025-19813.pdf",
      "year": 2025,
      "kind": "report",
      "license": "public domain (US government)"
    },
    "arxiv-hematite-nanospindles": {
      "title": "Insight into the Correlation of Shape and Magnetism of Hematite Nanospindles",
      "id": "arXiv 2505.14265",
      "url": "https://arxiv.org/pdf/2505.14265",
      "year": 2025,
      "kind": "paper",
      "license": "arXiv preprint (cited, not reproduced)"
    },
    "pmc-magnetite-review": {
      "title": "Magnetism and the Trimeron Bond (review of the magnetite Verwey transition)",
      "id": "PMC9261838",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9261838/",
      "year": 2022,
      "kind": "paper",
      "license": "open access (cited, not reproduced)"
    },
    "arxiv-magnetite-verwey": {
      "title": "Evolution of magnetic properties in the vicinity of the Verwey transition in Fe3O4",
      "id": "arXiv 1810.00538",
      "url": "https://arxiv.org/pdf/1810.00538",
      "year": 2018,
      "kind": "paper",
      "license": "arXiv preprint (cited, not reproduced)"
    },
    "arxiv-hexaferrite-review": {
      "title": "Permanent magnets based on hard ferrite ceramics",
      "id": "arXiv 2310.02106",
      "url": "https://arxiv.org/pdf/2310.02106",
      "year": 2023,
      "kind": "paper",
      "license": "arXiv preprint (cited, not reproduced)"
    },
    "arxiv-bfo-2406": {
      "title": "Magneto-electric decoupling in bismuth ferrite",
      "id": "arXiv 2406.16114",
      "url": "https://arxiv.org/pdf/2406.16114",
      "year": 2024,
      "kind": "paper",
      "license": "arXiv preprint (cited, not reproduced)"
    },
    "sci-rep-smfeo3-2014": {
      "title": "Temperature induced Spin Switching in SmFeO3 Single Crystal (Scientific Reports)",
      "id": "Sci Rep, 2014, srep05960",
      "url": "https://www.nature.com/articles/srep05960",
      "year": 2014,
      "kind": "paper",
      "license": "open access (cited, not reproduced)"
    },
    "arxiv-mars-review": {
      "title": "Mars: new insights and unresolved questions",
      "id": "arXiv 2112.00596",
      "url": "https://arxiv.org/pdf/2112.00596",
      "year": 2021,
      "kind": "paper",
      "license": "arXiv preprint (cited, not reproduced)"
    },
    "arxiv-oxidation-iron-oxide": {
      "title": "Evolution of structural properties of iron oxide nanoparticles during temperature treatment from 250 to 900 degC: X-ray diffraction and Fe K-shell pre-edge X-ray absorption study",
      "id": "arXiv 1111.6204",
      "url": "https://arxiv.org/pdf/1111.6204",
      "year": 2011,
      "kind": "paper",
      "license": "arXiv preprint (cited, not reproduced)"
    },
    "tdk-ferrite-catalogue": {
      "title": "TDK ferrites and accessories catalogue (SIFERRIT material characteristics, N87 and other MnZn grades)",
      "id": "TDK catalogue, April 2013 print",
      "url": "https://www.tdk-electronics.tdk.com/download/519704/069c210d0363d7b4682d9ff22c2ba503/ferrites-and-accessories-db-130501.pdf",
      "year": 2013,
      "kind": "datasheet",
      "license": "manufacturer catalogue (cited, not reproduced)"
    },
    "thyssen-hard-ferrite": {
      "title": "Hard ferrite magnets, product information (thyssenkrupp Materials Germany)",
      "id": "thyssenkrupp Magnettechnik product information",
      "url": "https://ucpcdn.thyssenkrupp.com/_binary/UCPthyssenkruppBAMXSchulteMicrositeMagnettechnik/en/downloads/link-thyssenkruppMagnettechnik-Factsheet-ferrite-magnets.pdf",
      "kind": "datasheet",
      "license": "manufacturer product information (cited, not reproduced)"
    },
    "eclipse-ferrite-datasheet": {
      "title": "Ferrite Magnets / Ceramic Magnets Datasheet (Eclipse Magnetics)",
      "id": "Eclipse Magnetics ceramic magnets datasheet",
      "url": "https://www.eclipsemagnetics.com/site/assets/files/19602/ferrite_ceramic_datasheet.pdf",
      "kind": "datasheet",
      "license": "manufacturer datasheet (cited, not reproduced)"
    },
    "nist-atomic-weights": {
      "title": "NIST Atomic Weights and Isotopic Compositions for All Elements (iron and oxygen rows)",
      "id": "NIST Physical Measurement Laboratory, Compositions table",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Fe&all=all&ascii=html",
      "year": 2024,
      "kind": "database",
      "license": "public domain (NIST)"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/iron-oxide/"
}