Neodymium-iron-boron sintered magnet alloy NdFeB

spore: profile
id: neodymium-iron-boron
spore_version: 0.2
family: magnet-and-superconducting-alloys
name: Neodymium-iron-boron sintered magnet alloy
abbreviation: NdFeB
role: permanent magnet
category: metals
type: magnet-alloys
summary: >
  Sintered NdFeB is the strongest commercial permanent magnet family. Its magnetic phase is Nd2Fe14B. Arnold's N42H datasheet gives a
  nominal remanence of 1300 mT and a maximum energy product of 330 kJ/m3, but a Curie temperature of only 310 degC, and Eclipse rates
  standard N42 for use up to 80 degC. It needs a coating against corrosion, is brittle, and loses magnetisation under neutron and charged-particle radiation.
best_for: "Very high magnetic output per volume at moderate cost (N42H nominal remanence 1300 mT, maximum energy product 330 kJ/m3)"
weakest_at: "Heat (rated 80 degC for N42, 120 degC for N42H, Curie point 310 degC), corrosion without a coating, and demagnetisation by neutrons and charged particles"
identity:
  formula: Nd2Fe14B
  source: tomse-2024
  where: Introduction ("the Nd2Fe14B hard magnetic phase"; Curie temperature 312 degC for the pure Nd-Fe-B ternary system); the CAS number was not found in a source we opened
tags:
  environments: []
  stresses: [total-radiation-dose, extreme-heat]
  applications: [mechanisms, electronics-and-chips]
properties:
  - benchmark: remanence_br
    label: Remanence Br, grade N42H
    value: 1300
    unit: mT
    scope: material
    conditions: {grade: "N42H", temperature: "room temperature (not stated; datasheet typical values)", value_type: "nominal (min 1280, max 1320)"}
    method: Value listed in the manufacturer datasheet (13,000 Gauss nominal)
    status: ground
    source: arnold-n42h
    where: Magnetic Properties table, row Br, Residual Induction, nominal column
  - benchmark: remanence_br
    label: Remanence Br, grade N42
    value: 1330
    unit: mT
    scope: material
    conditions: {grade: "N42", temperature: "20 degC", value_type: "typical (minimum 1300)"}
    method: Value listed in the manufacturer grade table
    status: ground
    source: eclipse-grades
    where: Table "Characteristic magnetic properties at room temperature (20 degC)", row N42, column BR typ
  - benchmark: coercivity_hcb
    label: Normal coercivity HcB, grade N42H
    value: 979
    unit: kA/m
    scope: material
    conditions: {grade: "N42H", value_type: "nominal (min 955, max 1003)"}
    method: Value listed in the manufacturer datasheet (12,300 Oersted)
    status: ground
    source: arnold-n42h
    where: Magnetic Properties table, row HcB, Coercivity, nominal column
  - benchmark: coercivity_hcj
    label: Intrinsic coercivity HcJ, grade N42H
    value: 1353
    unit: kA/m
    bound: lower
    scope: material
    conditions: {grade: "N42H", value_type: "minimum (17,000 Oersted)"}
    method: Value listed in the manufacturer datasheet
    status: ground
    source: arnold-n42h
    where: Magnetic Properties table, row HcJ, Intrinsic Coercivity
  - benchmark: coercivity_hcj
    label: Intrinsic coercivity HcJ, grade N42
    value: 955
    unit: kA/m
    bound: lower
    scope: material
    conditions: {grade: "N42", temperature: "20 degC", value_type: "minimum"}
    method: Value listed in the manufacturer grade table
    status: ground
    source: eclipse-grades
    where: Table "Characteristic magnetic properties at room temperature (20 degC)", row N42, column Hcj min
  - benchmark: max_energy_product
    label: Maximum energy product (BH)max, grade N42H
    value: 330
    unit: kJ/m3
    scope: material
    conditions: {grade: "N42H", value_type: "nominal (min 318, max 342; 42 MGOe)"}
    method: Value listed in the manufacturer datasheet
    status: ground
    source: arnold-n42h
    where: Magnetic Properties table, row BHmax, nominal column
  - benchmark: max_energy_product
    label: Maximum energy product (BH)max, grade N42
    value: 334
    unit: kJ/m3
    scope: material
    conditions: {grade: "N42", temperature: "20 degC", value_type: "typical (minimum 318)"}
    method: Value listed in the manufacturer grade table
    status: ground
    source: eclipse-grades
    where: Table "Characteristic magnetic properties at room temperature (20 degC)", row N42, column BH(max) typ
  - benchmark: curie_temperature
    label: Curie temperature, grade N42H
    value: 310
    unit: degC
    scope: material
    conditions: {grade: "N42H"}
    method: Value listed in the manufacturer datasheet
    status: ground
    source: arnold-n42h
    where: Thermal Properties table, row Curie Temperature, Tc
  - benchmark: curie_temperature
    label: Curie temperature, sintered NdFeB grades (supplier range)
    value: 310
    value_high: 340
    bound: range
    unit: degC
    scope: material
    conditions: {material: "sintered NdFeB, all grades in the table"}
    method: Range listed in the manufacturer physical-properties table
    status: ground
    source: eclipse-grades
    where: Physical properties at room temperature (20 degC), row Curie Temperature
  - benchmark: curie_temperature
    label: Curie temperature measured on a commercial Ni/Cu/Ni-coated magnet
    value: 310
    unit: degC
    scope: material
    conditions: {method_detail: "DSC on about 100 mg sample, heated in air at 20 K/min to 1000 degC", composition: "Nd 21.95, Pr 7.46, Dy 1.40 wt.%"}
    method: Differential scanning calorimetry, endothermic peak
    status: ground
    source: tomse-2024
    where: Results, discussion of Figure 1 (DSC curves); the paper gives 312 degC for the pure Nd2Fe14B phase
    note: The same paper reports 290 degC for a Ce-containing Zn-coated magnet and 340 degC for a Co- and Dy-rich epoxy-coated magnet, so Tc depends on composition.
  - benchmark: max_service_temp
    label: Maximum operating temperature, grade N42
    value: 80
    unit: degC
    scope: material
    conditions: {grade: "N42", condition: "reference only; depends on the circuit", permeance: "irreversible losses avoided at L/D = 0.7"}
    method: Value listed in the manufacturer grade table
    status: ground
    source: eclipse-grades
    where: Table "Characteristic magnetic properties", row N42, column Max. operating temp.; Remarks on facing table, notes 1 and 3
  - benchmark: max_service_temp
    label: Maximum operating temperature, grade N42H
    value: 120
    unit: degC
    scope: material
    conditions: {grade: "N42H", condition: "reference only; depends on the circuit"}
    method: Value listed in the manufacturer grade table
    status: ground
    source: eclipse-grades
    where: Table "Characteristic magnetic properties", row N42H, column Max. operating temp.; Remarks on facing table, note 1
  - benchmark: max_service_temp
    label: Working temperature, grade N42
    value: 80
    unit: degC
    scope: material
    conditions: {grade: "N42", note: "datasheet label is Working Temperature (Tw)"}
    method: Value listed in the supplier's online specification page
    status: ground
    source: indigo-n42
    where: Specifications table, row Working Temperature (Tw)
  - benchmark: temp_coeff_br
    label: Reversible temperature coefficient of remanence, alpha(Br), grade N42H
    value: -0.12
    unit: "%/degC"
    scope: material
    conditions: {grade: "N42H", range: "measured between 20 and 120 degC"}
    method: Value listed in the manufacturer datasheet
    status: ground
    source: arnold-n42h
    where: Thermal Properties table, row of Induction alpha(Br) and note (1)
  - benchmark: temp_coeff_br
    label: Temperature coefficient of Br, sintered NdFeB
    value: -0.11
    unit: "%/degC"
    scope: material
    conditions: {material: "sintered NdFeB, all grades in the table", temperature: "room temperature"}
    method: Value listed in the manufacturer physical-properties table
    status: ground
    source: eclipse-grades
    where: Physical properties at room temperature (20 degC), row Temp. Coeff. Of Br
  - benchmark: temp_coeff_hcj
    label: Reversible temperature coefficient of coercivity, alpha(Hcj), grade N42H
    value: -0.57
    unit: "%/degC"
    scope: material
    conditions: {grade: "N42H", range: "measured between 20 and 120 degC"}
    method: Value listed in the manufacturer datasheet
    status: ground
    source: arnold-n42h
    where: Thermal Properties table, row of Coercivity alpha(Hcj) and note (1)
  - benchmark: temp_coeff_hcj
    label: Temperature coefficient of iHc, sintered NdFeB
    value: -0.60
    unit: "%/degC"
    scope: material
    conditions: {material: "sintered NdFeB, all grades in the table", temperature: "room temperature"}
    method: Value listed in the manufacturer physical-properties table
    status: ground
    source: eclipse-grades
    where: Physical properties at room temperature (20 degC), row Temp. Coeff of iHc
  - benchmark: cte
    label: Thermal expansion, parallel to magnetisation (C //), grade N42H
    value: 7
    unit: "1e-6 per degC (dL/L)"
    scope: material
    conditions: {grade: "N42H", range: "20 to 200 degC", direction: "parallel to the magnetisation direction"}
    method: Typical value listed in the manufacturer datasheet
    status: ground
    source: arnold-n42h
    where: Thermal Properties table, row Coefficient of Thermal Expansion, note (2)
    note: The same row gives -1 perpendicular to the magnetisation direction, so the expansion is strongly anisotropic.
  - benchmark: cte
    label: Coefficient of thermal expansion, sintered NdFeB
    value: 4
    unit: "1e-6 per degC"
    scope: material
    conditions: {material: "sintered NdFeB, all grades in the table", temperature: "room temperature"}
    method: Value listed in the manufacturer physical-properties table
    status: ground
    source: eclipse-grades
    where: Physical properties at room temperature (20 degC), row Coeff. Of Thermal Expansion
  - benchmark: thermal_conductivity
    label: Thermal conductivity, grade N42H (parallel)
    value: 5.3
    unit: kcal/(m h degC)
    scope: material
    conditions: {grade: "N42H", direction: "parallel to the magnetisation direction"}
    method: Typical value listed in the manufacturer datasheet
    status: ground
    source: arnold-n42h
    where: Thermal Properties table, row Thermal Conductivity
    note: Unit as printed in the source. The perpendicular value in the same row is 5.8.
  - benchmark: density
    label: Density, grade N42H
    value: 7.6
    unit: g/cm3
    scope: material
    conditions: {grade: "N42H"}
    method: Value listed in the manufacturer datasheet
    status: ground
    source: arnold-n42h
    where: Other Properties table, row Density
  - benchmark: density
    label: Density, sintered NdFeB
    value: 7.5
    unit: g/cm3
    scope: material
    conditions: {material: "sintered NdFeB, all grades in the table", temperature: "20 degC"}
    method: Value listed in the manufacturer physical-properties table
    status: ground
    source: eclipse-grades
    where: Physical properties at room temperature (20 degC), row Density
    note: The source prints "7.5/cm3"; g is assumed from context.
  - benchmark: vickers_hardness
    label: Vickers hardness, grade N42H
    value: 620
    unit: Hv
    scope: material
    conditions: {grade: "N42H", load: "not stated"}
    method: Value listed in the manufacturer datasheet
    status: ground
    source: arnold-n42h
    where: Other Properties table, row Hardness, Vickers
  - benchmark: flexural_strength
    label: Flexural strength, grade N42H
    value: 285
    unit: MPa
    scope: material
    conditions: {grade: "N42H", test: "not stated"}
    method: Value listed in the manufacturer datasheet (41,300 psi)
    status: ground
    source: arnold-n42h
    where: Other Properties table, row Flexural Strength
  - benchmark: tensile_strength
    label: Tensile strength, sintered NdFeB
    value: 8.0
    unit: kg/mm2
    scope: material
    conditions: {material: "sintered NdFeB, all grades in the table", temperature: "20 degC"}
    method: Value listed in the manufacturer physical-properties table
    status: ground
    source: eclipse-grades
    where: Physical properties at room temperature (20 degC), row Tensile Strength
    note: Unit as printed in the source (kilogram-force per square millimetre).
  - benchmark: youngs_modulus
    label: Young's modulus, sintered NdFeB
    value: 1.6e11
    unit: N/m2
    scope: material
    conditions: {material: "sintered NdFeB, all grades in the table", temperature: "20 degC"}
    method: Value listed in the manufacturer physical-properties table
    status: ground
    source: eclipse-grades
    where: Physical properties at room temperature (20 degC), row Young's Modulus
  - benchmark: electrical_resistivity
    label: Electrical resistivity, grade N42H (parallel)
    value: 150
    unit: uohm cm
    scope: material
    conditions: {grade: "N42H", direction: "parallel to the magnetisation direction"}
    method: Value listed in the manufacturer datasheet
    status: ground
    source: arnold-n42h
    where: Other Properties table, row Electrical Resistivity
    note: The perpendicular value in the same row is 130.
  - benchmark: nd_content_hdd_magnets
    label: Neodymium content of hard-drive magnets
    value: 22.9
    unit: wt.%
    scope: material
    conditions: {sample: "magnets from desktop and notebook PC hard disk drives", variation: "standard deviation +/- 2.8"}
    method: Chemical analysis of dismantled hard-drive magnets (the item page reports the mean and deviation)
    status: ground
    source: ueberschaar-2015
    where: Repository item page, Nd/Pr/Dy concentrations in the magnets
  - benchmark: pr_content_hdd_magnets
    label: Praseodymium content of hard-drive magnets
    value: 2.7
    unit: wt.%
    scope: material
    conditions: {sample: "magnets from desktop and notebook PC hard disk drives", variation: "standard deviation +/- 2.2"}
    method: Chemical analysis of dismantled hard-drive magnets
    status: ground
    source: ueberschaar-2015
    where: Repository item page, Nd/Pr/Dy concentrations in the magnets
  - benchmark: dy_content_hdd_magnets
    label: Dysprosium content of hard-drive magnets
    value: 1.4
    unit: wt.%
    scope: material
    conditions: {sample: "magnets from desktop and notebook PC hard disk drives", variation: "standard deviation +/- 1.5"}
    method: Chemical analysis of dismantled hard-drive magnets
    status: ground
    source: ueberschaar-2015
    where: Repository item page, Nd/Pr/Dy concentrations in the magnets
  - benchmark: tid
    label: Gamma dose with no demagnetisation seen (1.17 MeV gammas)
    value: 280
    unit: Mrad
    bound: lower
    scope: material
    conditions: {radiation: "1.17 MeV gamma rays", result: "no demagnetisation observed"}
    method: Reported in the paper's introduction from earlier experiments (not new measurements)
    status: ground
    source: simos-2008
    where: Introduction, sentence on electron and gamma irradiation
  - benchmark: flux_loss_17mev_electrons
    label: Flux loss after 17 MeV electron irradiation
    value: 9
    unit: "%"
    scope: material
    conditions: {radiation: "17 MeV electrons", dose: "260 Mrad"}
    method: Reported in the paper's introduction from earlier experiments (not new measurements)
    status: ground
    source: simos-2008
    where: Introduction, sentence on electron and gamma irradiation
  - benchmark: field_loss_esrf_undulators
    label: Field loss in operating insertion devices (ESRF)
    value: 8
    unit: "%"
    bound: upper
    scope: material
    conditions: {setting: "insertion-device magnets in a synchrotron light source", dose: "several Mrad"}
    method: Operating experience quoted in the paper's introduction ("as much as 8%")
    status: ground
    source: simos-2008
    where: Introduction, paragraph on serious demagnetisation observed in operating light sources
  - benchmark: flux_loss_14mev_neutrons
    label: Flux loss of grade N44H after 14 MeV neutrons
    value: 6.4
    unit: "%"
    scope: material
    conditions: {radiation: "monoenergetic 14 MeV neutrons", fluence: "3.64e13 n/cm2", grade: "N44H", permeance: "Pc = 1.2"}
    method: Earlier experiment (Kawakubo et al.) as reported in the 65 MeV paper's discussion
    status: ground
    source: marechal-2006
    where: Discussion, paragraph on the 14 MeV experiment
    note: Same experiment reported losses from 37% to 1% across grades with coercivity from 880 to 2400 kA/m, so higher coercivity resisted neutrons much better.
  - benchmark: neutron_fluence_no_loss_65mev
    label: Fluence of 65 MeV neutrons with no demagnetisation observed
    value: 2.4e9
    unit: n/cm2
    bound: lower
    scope: material
    conditions: {radiation: "65 MeV neutrons, fluence 2.4e9 n/cm2, magnet at 25 degC", grades: "four Neomax grades, TiN coated, 8 x 8 x 8 mm", magnetisation: "parallel to the beam"}
    method: Neutron irradiation at the TIARA cyclotron, change in field measured with a Hall probe
    status: ground
    source: marechal-2006
    where: Results, text and Figure 3
corrosion:
  - environment: Humid or wet conditions, uncoated magnet
    headline: The Nd-rich grain-boundary phases corrode
    effect: The Nd-rich secondary phases are prone to corrosion because neodymium has a very negative reduction potential, and this degrades magnetic performance. Coatings are the usual remedy.
    rating: unknown
    conditions: {reduction_potential_of_Nd: "-2.32 V", note: "no corrosion rate in a source we opened"}
    source: tomse-2024
    where: Introduction, paragraph on multiphase structure
  - environment: Ni/Cu/Ni plated magnet heated to 380 degC (thermal demagnetisation)
    headline: Nickel-copper-nickel coating survived heating
    effect: The Ni/Cu/Ni coating stayed stable after 30 min at 380 degC in air and in vacuum, and the magnetic performance was completely recovered on remagnetisation. A Zn coating was not compatible, and epoxy decomposed in air.
    rating: low
    conditions: {heating: "380 degC for 30 min", atmosphere: "air or vacuum"}
    source: tomse-2024
    where: Abstract, Results (coating stability and Figure 2)
risks:
  hazards:
    - {text: "Neodymium metal (PubChem CID 23934): signal word Danger. Notified hazards are H228 flammable solid (34.3%), H251 self-heating, may catch fire (33.3%), H315 causes skin irritation (41.9%), H319 causes serious eye irritation (41.9%) and H413 may cause long lasting harmful effects to aquatic life (10.6%). PubChem says 56.4% of 463 reports do not meet GHS criteria. This describes the pure metal, not the solid magnet.", ghs: [H228, H251, H315, H319, H413], source: pubchem-neodymium, where: "GHS Classification section"}
    - {text: "Boron (PubChem CID 5462311): signal word Warning. Notified hazard H302 harmful if swallowed (46.4%). PubChem says 52.2% of 485 reports do not meet GHS criteria.", ghs: [H302], source: pubchem-boron, where: "GHS Classification section"}
    - {text: "Iron (PubChem CID 23925): 74.1% of 6013 reports do not meet GHS criteria. The notified hazards are H228 flammable solid (15.5%) and H251 self-heating, may catch fire (21.2%), signal word Danger.", ghs: [H228, H251], source: pubchem-iron, where: "GHS Classification section"}
    - {text: "Solid NdFeB magnet (Digikey supplier SDS): signal word Danger. Hazard codes H260 and H261 are listed for chemical hazards, and prolonged immersion in water or acid can form hydrogen, which could ignite spontaneously in some environments. Health codes H317, H332 and H302 are listed. Broken magnets can have sharp chips and shards.", ghs: [H260, H261, H317, H332, H302], source: digikey-ndfeb-sds, where: "Section 2 Hazards Identification"}
    - {text: "Solid NdFeB magnet (Allstar supplier SDS, Rev 1.0): not classified under GHS-US for the solid, and no label elements apply. The SDS says the hazards arise when the metal is processed, for example as powder or in welding.", ghs: [], source: allstar-ndfeb-sds, where: "Sections 2.1, 2.2 and 2.3"}
    - {text: "Fire risk of NdFeB dust and powder: fine powders oxidise, smoulder and burn rapidly in air or oxygen. Very fine powder (200 mesh) is rated a weak explosive hazard when suspended in air. Cutting, grinding or smashing a magnet can spark and start a fire in a flammable atmosphere. The SDS says the solid is incombustible but can burn as powder or dust.", ghs: [], source: digikey-ndfeb-sds, where: "Section 2 (unusual fire and explosion hazards) and Section 5"}
    - {text: "Fire risk of NdFeB powder (Allstar SDS): dry powders or magnets oxidise, smolder and burn rapidly in air. Dust clouds suspended in air can be explosive, and dust deposits can form an explosive mixture. Powders should be kept in water slurry or under nitrogen or argon. Use earth, sand or Class D dry powder; do not use water or halon agents.", ghs: [], source: allstar-ndfeb-sds, where: "Section 5 Fire-Fighting Measures and Section 7"}
  failure_risks:
    - {mode: "Demagnetisation by heat", trigger: "Operating above the grade's maximum temperature or heating above the Curie point", consequence: "Loss of magnetisation. Heating above Tc is used on purpose to demagnetise magnets for recycling; the Ni/Cu/Ni magnet regained full performance on remagnetisation after 30 min at 380 degC.", severity: high, source: tomse-2024, where: Introduction and Results}
    - {mode: "Demagnetisation by neutrons and charged particles", trigger: "High-energy neutrons, protons, or electrons in accelerators", consequence: "Flux loss of up to 9% at 260 Mrad of 17 MeV electrons, while gammas alone caused none at 280 Mrad. The same paper says charged particles and high-energy neutrons are very effective at demagnetising magnets.", severity: high, source: simos-2008, where: Introduction}
    - {mode: "Demagnetisation by thermal-neutron capture on boron", trigger: "Thermal neutron irradiation", consequence: "Remanent magnetisation changes substantially because of the 10B(n,alpha)7Li reaction; the paper reports no change in coercivity.", severity: moderate, source: klaffky-2006, where: Abstract and Magnetic Measurements}
    - {mode: "Chipping and brittleness", trigger: "Mechanical handling and impact", consequence: "The BNL magnets were plated with a thin nickel coating to eliminate chipping. Hydrogen processing embrittles and pulverises end-of-life magnets, which is used for recycling.", severity: moderate, source: simos-2008, where: Experimental Effort paragraph}
  side_effects:
    - {text: "Irradiated magnets become radioactive: after about 12 months of cool-down they were measured remotely in a hot cell, and the isotopes formed were computed with the ORIGEN code.", affects: "Handling and replacement of magnets in radiation areas", source: simos-2008, where: Post-irradiation results}
  handling:
    - {text: "The manufacturer says the maximum working temperature is for reference only and depends on the circuit the magnet operates in.", source: eclipse-grades, where: Remarks on facing table, note 1}
    - {text: "Customers are advised to consult the supplier for applications near 150 degC.", source: eclipse-grades, where: Remarks on facing table, note 2}
    - {text: "Broken magnets have sharp chips and shards that can cut skin. Impacts can throw chips or bits of magnet material at speed, so wear eye protection, and wear gloves for long handling.", source: digikey-ndfeb-sds, where: "Section 2 and handling section"}
    - {text: "Strong attraction can clamp fingers or skin between magnets or onto ferrous parts. Strong magnetic fields may affect pacemakers and other implanted medical devices.", source: allstar-ndfeb-sds, where: "Sections 2.3 and 7.1"}
    - {text: "Do not breathe dust or powder, and avoid creating or spreading it. Clean up released powder by sweeping or shovelling into sealed containers, not with a vacuum cleaner, because deposits can form an explosive mixture.", source: digikey-ndfeb-sds, where: "Cleanup of released powders (accidental release section)"}
    - {text: "Dust should not accumulate on surfaces. Eliminate ignition sources where dust forms, and take up spills mechanically (sweeping, shovelling) to avoid generating dust.", source: allstar-ndfeb-sds, where: "Sections 6 and 7"}
  mitigations:
    - {text: "Higher-coercivity grades resist neutrons far better: in the 14 MeV test the loss ranged from 37% to 1% as coercivity rose from 880 to 2400 kA/m.", source: marechal-2006, where: Discussion}
    - {text: "Ni/Cu/Ni plating is the coating that stayed stable through heating; 5 micrometre TiN was used on the 65 MeV test magnets.", source: tomse-2024, where: Abstract and Results}
uses:
  - application: electronics-and-chips
    device: Earbud headphones
    example: "Apple's launch press release for the first iPod (2001) says its earbud-style headphones use neodymium magnets, for frequency response and sound quality."
    source: apple-ipod-press-release
    where: Paragraph on the earbud headphones
  - application: electronics-and-chips
    device: Hard disk drive magnets
    example: "German PC hard-drive magnets analysed at TU Berlin for rare earth recycling."
    source: ueberschaar-2015
    where: Abstract
  - application: mechanisms
    device: Electric motors, wind turbines, consumer electronics and home appliances
    example: "Listed by the 2024 coating study as the main uses of Nd-Fe-B magnets."
    source: tomse-2024
    where: Introduction, first sentence
  - application: mechanisms
    device: Undulator and insertion-device magnet arrays in synchrotron light sources
    example: "SPring-8 uses in-vacuum undulators whose magnets sit a few millimetres from the electron beam."
    source: marechal-2006
    where: Introduction
supply:
  - subject: Rare earths (Nd, Pr, Dy)
    abundance: "World mine production was 390,000 tons of rare-earth oxide equivalent in 2024, of which China mined 270,000 tons (about 69%, computed from the table). Reserves: China 44,000,000 tons, world more than 90,000,000 tons."
    producers:
      - {country: China, share_percent: 69.2, year: 2024}
      - {country: United States, share_percent: 11.5, year: 2024}
      - {country: Burma, share_percent: 7.9, year: 2024}
    critical_lists:
      - {list: "EU critical raw materials 2023 (heavy and light rare earth elements)", listed: true}
    recycling: "USGS reports that limited quantities of rare earths were recovered from batteries, permanent magnets and fluorescent lamps. The EU Critical Raw Materials Act sets a goal of recycling 25% of magnets by 2030 (as cited by the 2024 coating study)."
    substitutes: ["Substitutes are available for many applications but generally are less effective (USGS)."]
    source: usgs-mcs-2025-re
    where: Salient statistics, World Mine Production and Reserves table, Recycling, Substitutes
  - subject: Heavy rare earths and boron (EU supply)
    abundance: "The EU page states China provides 100% of EU supply of heavy rare earth elements and Turkey provides 99% of EU boron supply."
    critical_lists:
      - {list: "EU critical raw materials 2023: heavy rare earth elements", listed: true}
      - {list: "EU critical raw materials 2023: light rare earth elements", listed: true}
      - {list: "EU critical raw materials 2023: boron/borate", listed: true}
    source: eu-crm-page
    where: Fifth list of critical raw materials (2023) and supply concentration figures
documents:
  - {title: "Arnold Magnetic Technologies N42H sintered NdFeB datasheet", type: datasheet, url: "https://www.arnoldmagnetics.com/wp-content/uploads/2017/11/N42H-151021.pdf", year: 2021}
  - {title: "Eclipse Magnetics sintered NdFeB grades data", type: datasheet, url: "https://www.eclipsemagnetics.com/site/assets/files/2399/neodymium_grades_data.pdf", year: 2011}
  - {title: "USGS Mineral Commodity Summaries 2025: Rare earths", type: report, url: "https://pubs.usgs.gov/periodicals/mcs2025/mcs2025-rare-earths.pdf", year: 2025}
  - {title: "NETL Life Cycle Inventory: NdFeB Permanent Magnet Manufacturing (DF_Stage1_O)", type: report, url: "https://netl.doe.gov/projects/files/DF_Stage1_O_NdFeB_Magnet_Manufacturing-2014-01.pdf", year: 2014}
  - {title: "Allstar Magnetics SDS, Neodymium Iron Boron (NdFeB) Magnet, Rev 1.0", type: sds, url: "https://allstarmagnetics.com/wp-content/uploads/2024/10/Neodymium-SDS.pdf", year: 2024}
  - {title: "SDS/MSDS, NdFeB Magnets (Digikey supplier data sheet)", type: sds, url: "https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/5849/SDS_MSDS%20-%20NdFeB%20Magnets.pdf"}
  - {title: "PubChem compound records: neodymium (CID 23934), boron (CID 5462311), iron (CID 23925)", type: database, url: "https://pubchem.ncbi.nlm.nih.gov/compound/23934"}
gaps:
  - "Use in spacecraft or in orbit: no flight or space-qualification source was found for sintered NdFeB (no NASA/ESA report, vacuum outgassing value, or thermal-cycling result)."
  - "Melt-spinning route: only a Wikipedia page was read for the process (secondary). No primary melt-spinning paper or datasheet was opened."
  - "Atomic weights are PubChem values printed to two decimals (Nd 144.24, Fe 55.84, B 10.81). No IUPAC table value was read."
  - "PubChem GHS data are aggregated company notifications to the ECHA inventory, not one SDS for the magnet. The magnet hazards rest on two supplier SDSs (Digikey and Allstar)."
  - "CAS number and crystal structure of Nd2Fe14B: not taken from a source we opened."
  - "Quantified corrosion rate or salt-spray hours for coated or uncoated magnets: not found in an opened source."
  - "Nickel coating thickness and coating-specific performance (the datasheets say to contact the supplier for coating recommendations)."
  - "Grade-by-grade coefficients and curves for temperatures above 120 degC (the Arnold coefficients are valid only between 20 and 120 degC)."
  - "Quantified irreversible flux loss versus temperature (the sources give only maximum working temperatures)."
  - "Recycling rate for NdFeB magnets: no quantified rate from a primary source (only the 25% 2030 goal quoted in a paper and the USGS wording 'limited quantities')."
  - "Radiation tolerance in orbit (protons, electrons, galactic cosmic rays at spacecraft magnet locations): only accelerator experiments were found."
  - "Brittleness measured as fracture toughness: only flexural strength (285 MPa) and tensile strength (8.0 kg/mm2) were found."
composition:
  - {grade: "Zn-coated magnet", Nd: "20.53", Pr: "7.24", Dy: "0.11", Ce: "3.13", Gd: "0.49", Fe: "65.74", Co: "0.21", B: "1.00", unit: "wt.%", method: "ICP-OES after coating removal", source: tomse-2024, where: "Table 1, elemental composition"}
  - {grade: "Ni/Cu/Ni-coated magnet", Nd: "21.95", Pr: "7.46", Dy: "1.40", Gd: "0.55", Fe: "64.48", Co: "0.95", B: "1.02", unit: "wt.%", method: "ICP-OES after coating removal", source: tomse-2024, where: "Table 1, elemental composition"}
  - {grade: "Epoxy-coated magnet", Nd: "20.53", Pr: "0.06", Dy: "11.39", Tb: "0.08", Fe: "63.80", Co: "2.23", B: "1.05", unit: "wt.%", method: "ICP-OES after coating removal", source: tomse-2024, where: "Table 1, elemental composition"}
  - {basis: "Typical commercial NdFeB alloy used as the life-cycle basis", Fe: "72", Nd: "27", B: "1", unit: "% by weight", source: netl-ndfeb-lci, where: "Alloying and strip casting paragraph"}
  - {note: "Curie temperature 310 degC for the Ni/Cu/Ni-coated magnet and 340 degC for the epoxy-coated magnet; the higher value is attributed to 2.23 wt.% Co and 11.39 wt.% Dy", source: tomse-2024, where: "Results, Curie temperature discussion"}
process:
  - {text: "Alloy is strip cast, hydrogen decrepitated, jet milled, aligned and pressed, then vacuum-sintered at pressures of 2-10 mbar and a temperature of 1000 degrees C. Remaining hydrogen is removed, and the block is sliced, ground and polished.", source: netl-ndfeb-lci, where: "NdFeB alloy and sintering paragraphs"}
  - {text: "Melt spinning: molten alloy is splat-quenched onto a water-cooled drum to form ribbon, which is crushed to powder and heat-treated; the powder is bonded with a thermoplastic polymer and moulded.", source: wiki-neodymium-magnet, where: "Bonded magnets section (secondary source)"}
review:
  status: draft
  method: assistant
  checked_values: 35
  unreachable: 0
  caveats: 4
  note: "Written by an AI assistant on 2026-10-17. The Arnold N42H and Eclipse grade values, the USGS table, the Simos and Marechal and Klaffky paper statements, and the Tomse 2024 paper values were read in text extracted from the source PDFs or page. The Indigo page and the TU Berlin item page and the EU page were read once through a web-page summary and not independently re-read. Radiation values from Simos 2008 and the 14 MeV neutron value from Marechal 2006 are secondary: the papers quote earlier experiments. The Eclipse sheet is a 2011 PDF. No values were taken from memory. Producer shares (11.5% US, 7.9% Burma) are computed from USGS table rows by this assistant."
story:
  recipe:
    line: >-
      Nd2Fe14B is the hard magnetic phase: two neodymium atoms, fourteen iron atoms and one boron atom per formula unit. Commercial magnets are not pure Nd2Fe14B. They carry praseodymium, dysprosium and cobalt, and a typical alloy is about 72% iron, 27% neodymium and 1% boron by weight. Sintered magnets are made by strip casting the melt, hydrogen decrepitation, jet milling, aligning and pressing the powder, and vacuum sintering at 1000 degC. Dysprosium and cobalt raise the Curie temperature: the epoxy-coated grade with 11.39 wt.% Dy and 2.23 wt.% Co reached 340 degC, against 310 degC for the Ni/Cu/Ni grade with 1.40 wt.% Dy. Melt spinning is the other route: the melt is quenched on a drum into ribbon, milled to powder and bonded into polymer for moulded magnets.
    parts:
      - {name: Neodymium, symbol: Nd, atoms: 2, atomic_weight: 144.24, role: "The rare-earth atoms of the hard phase. The alloy also carries praseodymium and dysprosium in varying amounts.", source: pubchem-neodymium}
      - {name: Iron, symbol: Fe, atoms: 14, atomic_weight: 55.84, role: "Most of the alloy by weight, about 72% in a typical alloy.", source: pubchem-iron}
      - {name: Boron, symbol: B, atoms: 1, atomic_weight: 10.81, role: "The single boron atom per formula unit. Its 10B isotope captures thermal neutrons, which changes remanence in irradiated magnets.", source: pubchem-boron}
  why: >-
    Neodymium-iron-boron (NdFeB) is a sintered alloy whose magnetic phase is Nd2Fe14B. Sintered means the powder is pressed and fused
    by heat. It is the strongest family of commercial permanent magnets, meaning magnets that keep their magnetisation without power.
    Arnold's N42H datasheet gives a nominal remanence of 1300 mT, the field the magnet keeps after magnetising, and a maximum energy
    product of 330 kJ/m3, a measure of how much magnetic work it can do per volume. The price of that strength is sensitivity. The
    Curie temperature, above which a magnet loses its magnetism, is only 310 degC, and Eclipse rates standard N42 for use up to
    80 degC and N42H up to 120 degC. It also needs a coating against corrosion and is brittle.
  uses:
    - where: Hard disk drives
      line: >-
        A TU Berlin study of PC hard drives measured 22.9% neodymium, 2.7% praseodymium and 1.4% dysprosium in the magnets, which shows how
        much rare earth sits in everyday electronics.
    - where: Motors, wind turbines and appliances
      line: >-
        A 2024 coating study lists electric motors, wind turbines, consumer electronics and home appliances as the main uses of Nd-Fe-B magnets.
    - where: Synchrotron light sources
      line: >-
        SPring-8 uses in-vacuum undulators with the magnets a few millimetres from the electron beam, where radiation demagnetisation becomes a design issue.
  can_do:
    - label: Magnetic strength
      value: 1300 mT
      line: >-
        Grade N42H has a nominal remanence of 1300 mT and a maximum energy product of 330 kJ/m3 (Arnold datasheet). The Eclipse table
        gives 1330 mT and 334 kJ/m3 typical for grade N42.
    - label: Resisting demagnetising fields
      value: 1353 kA/m
      line: >-
        Grade N42H has a minimum intrinsic coercivity of 1353 kA/m, against a minimum of 955 kA/m for plain N42. Coercivity is the opposing
        field the magnet can take before it loses magnetisation.
    - label: Heat
      value: Rated 80 degC (N42)
      line: >-
        Eclipse lists a maximum operating temperature of 80 degC for N42 and 120 degC for N42H. It calls this a reference only and says it
        depends on the circuit. The remanence also falls as it warms, by 0.12% per degC (Arnold, 20 to 120 degC), and coercivity by 0.57% per degC.
    - label: Radiation
      value: No loss at 280 Mrad of gamma
      line: >-
        An accelerator paper reports no demagnetisation after 280 Mrad of 1.17 MeV gamma rays but a 9% flux loss after 260 Mrad of 17 MeV electrons.
        These values come from earlier experiments quoted in the paper.
    - label: Stiffness and hardness
      value: 620 Hv
      line: >-
        Arnold gives a Vickers hardness of 620 Hv and a flexural strength of 285 MPa for N42H, with a density of 7.6 g/cm3.
  compare: >-
    Within sintered NdFeB, the grade suffix trades strength for heat tolerance. Plain N42 has an intrinsic coercivity of at least 955 kA/m and
    is rated to 80 degC. N42H keeps the same nominal remanence class but raises the coercivity to at least 1353 kA/m and the rating to 120 degC.
    Coercivity also decides radiation tolerance: in a 14 MeV neutron test the loss ranged from 37% to 1% as coercivity rose from 880 to 2400 kA/m.
  compare_rows:
    - {label: "Remanence (N42H)", benchmark: remanence_br}
    - {label: "Maximum energy product", benchmark: max_energy_product}
    - {label: "Curie temperature", benchmark: curie_temperature}
    - {label: "Maximum working temperature", benchmark: max_service_temp}
    - {label: "Density", benchmark: density}
  handling:
    - "Check the grade's maximum temperature and the magnet's shape before use: the supplier says the rating depends on the circuit."
    - "Keep it coated. Nd-rich phases corrode, and Ni/Cu/Ni plating is the coating that survived heating in the 2024 study."
    - "Treat irradiated magnets as radioactive; the BNL magnets were left for about 12 months and measured in a hot cell."
  good_for:
    - "Strong fields from small volumes where temperatures stay below the grade's rating."
    - "Applications where cost matters more than the heat tolerance of samarium-cobalt (not compared with a source here)."
  watch_out:
    - "Low Curie point (310 degC) and a working limit of only 80 to 120 degC for these grades."
    - "Loss of magnetisation in neutron and charged-particle fields, and secondary radioactivity afterwards."
    - "Corrosion of the Nd-rich phases without coating, and brittle chipping."
    - "Supply: China mined 270,000 of 390,000 tons of rare-earth oxide in 2024, and the EU states China supplies 100% of its heavy rare earths."
  verdict: >-
    A very strong magnet material for ordinary temperatures, backed by good sourced datasheet numbers, but its heat limit, corrosion sensitivity,
    brittleness and radiation sensitivity mean it must be chosen by grade and protected. No space-flight data were found, so its fitness for
    spacecraft is unproven here.
  risk_groups:
    - title: For people
      level: 1
      verdict: "No hazard data found"
      lead: "No safety data sheet was opened, so no classification is stated."
      points:
        - label: Irradiated magnets
          line: "Magnets irradiated at BNL were left to cool down for about 12 months and then measured remotely in a hot cell, because the exposure creates radioactive isotopes."
      gap: "Safety data sheet hazards were not found in an opened source."
    - title: If it fails
      level: 3
      verdict: "Heat and radiation demagnetise it"
      lead: "The loss of magnetisation depends on grade, shape and the radiation type."
      points:
        - label: Heat
          line: "Heating above the Curie temperature (310 degC for the measured magnet) demagnetises it. A Ni/Cu/Ni magnet heated 30 min at 380 degC regained full performance when remagnetised."
        - label: Charged particles
          line: "260 Mrad of 17 MeV electrons caused 9% flux loss, while 280 Mrad of gamma caused none."
        - label: Neutrons
          line: "In a 14 MeV test grade N44H lost 6.4% at 3.64e13 n/cm2, and in a 65 MeV test no change was seen up to 2.4e9 n/cm2."
    - title: Handling and storage
      points:
        - label: Temperature
          line: "Stay within the rated working temperature and ask the supplier for applications near 150 degC."
        - label: Coating
          line: "Protect the surface: the BNL magnets were nickel plated, partly to eliminate chipping."
sources:
  apple-ipod-press-release:
    title: "Apple Presents iPod (press release)"
    id: "Apple Inc., 23 October 2001"
    url: https://www.apple.com/newsroom/2001/10/23Apple-Presents-iPod/
    year: 2001
    kind: web
  arnold-n42h:
    title: "N42H Sintered Neodymium-Iron-Boron Magnets (datasheet, Rev. 210607)"
    id: N42H-151021
    url: https://www.arnoldmagnetics.com/wp-content/uploads/2017/11/N42H-151021.pdf
    year: 2021
    kind: datasheet
    license: manufacturer datasheet
  eclipse-grades:
    title: Sintered Neodymium Iron Boron (NdFeB) Magnets, grades data
    id: neodymium_grades_data.pdf
    url: https://www.eclipsemagnetics.com/site/assets/files/2399/neodymium_grades_data.pdf
    year: 2011
    kind: datasheet
    license: manufacturer datasheet
  indigo-n42:
    title: Specifications for Fully Sintered/Pressed Neodymium Magnets, N42 Grade
    url: https://www.indigoinstruments.com/N42-Magnet-Specs.php
    kind: web
    license: supplier web page
  tomse-2024:
    title: Magnetic Performance and Anticorrosion Coating Stability of Thermally Demagnetized Nd-Fe-B Permanent Magnets for Reuse Applications
    id: doi:10.3390/ma17235927
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC11643009/
    year: 2024
    kind: paper
    license: open access (MDPI Materials)
  ueberschaar-2015:
    title: Enabling the recycling of rare earth elements through product design and trend analyses of hard disk drives
    id: doi:10.14279/depositonce-6368
    url: https://depositonce.tu-berlin.de/items/99e52b20-ebd0-479d-b0ac-341c8996112c
    year: 2015
    kind: paper
    license: In Copyright (item page)
  simos-2008:
    title: An Experimental Study of Radiation-Induced Demagnetization of Insertion Device Permanent Magnets
    id: EPAC08 WEPC053
    url: https://proceedings.jacow.org/e08/papers/WEPC053.pdf
    year: 2008
    kind: paper
    license: JACoW proceedings
  marechal-2006:
    title: 65 MeV Neutron Irradiation of Nd-Fe-B Permanent Magnets
    id: EPAC06 THPCH135
    url: https://accelconf.web.cern.ch/e06/PAPERS/THPCH135.PDF
    year: 2006
    kind: paper
    license: JACoW proceedings
  klaffky-2006:
    title: Thermal Neutron Demagnetization of NdFeB Magnets
    id: EPAC06 THPLS130
    url: https://accelconf.web.cern.ch/e06/PAPERS/THPLS130.PDF
    year: 2006
    kind: paper
    license: JACoW proceedings
  usgs-mcs-2025-re:
    title: Mineral Commodity Summaries 2025, Rare Earths
    url: https://pubs.usgs.gov/periodicals/mcs2025/mcs2025-rare-earths.pdf
    year: 2025
    kind: report
    license: public domain
  eu-crm-page:
    title: Critical raw materials (European Commission)
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    kind: web
    license: EC web page
  pubchem-neodymium:
    title: "PubChem compound CID 23934, neodymium: molecular weight and GHS classification"
    id: "CID 23934"
    url: https://pubchem.ncbi.nlm.nih.gov/compound/23934
    kind: database
  pubchem-boron:
    title: "PubChem compound CID 5462311, boron: molecular weight and GHS classification"
    id: "CID 5462311"
    url: https://pubchem.ncbi.nlm.nih.gov/compound/5462311
    kind: database
  pubchem-iron:
    title: "PubChem compound CID 23925, iron: molecular weight and GHS classification"
    id: "CID 23925"
    url: https://pubchem.ncbi.nlm.nih.gov/compound/23925
    kind: database
  netl-ndfeb-lci:
    title: "NETL Life Cycle Inventory Data Process Documentation: NdFeB Permanent Magnet Manufacturing"
    id: DF_Stage1_O_NdFeB_Magnet_Manufacturing.2014.01
    url: https://netl.doe.gov/projects/files/DF_Stage1_O_NdFeB_Magnet_Manufacturing-2014-01.pdf
    year: 2014
    kind: report
  allstar-ndfeb-sds:
    title: "Allstar Magnetics Safety Data Sheet, Neodymium Iron Boron (NdFeB) Magnet"
    id: "SDS NEO, Rev 1.0, 08Feb2024"
    url: https://allstarmagnetics.com/wp-content/uploads/2024/10/Neodymium-SDS.pdf
    year: 2024
    kind: datasheet
  digikey-ndfeb-sds:
    title: "Safety Data Sheet (SDS/MSDS), NdFeB Magnets (Digikey supplier)"
    url: https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/5849/SDS_MSDS%20-%20NdFeB%20Magnets.pdf
    kind: datasheet
  wiki-neodymium-magnet:
    title: "Neodymium magnet (Wikipedia), bonded magnet process section only"
    url: https://en.wikipedia.org/wiki/Neodymium_magnet
    kind: web
    license: "CC BY-SA"
license: CC-BY-4.0