Magnetic and superconducting alloys

magnet-and-superconducting-alloys

12 materials across 2 types

About magnetic and superconducting alloys

Magnetic and superconducting alloys (NdFeB, SmCo, Alnico, permalloy, mu-metal, electrical steel, metallic glass, Nb-Ti, Nb3Sn): magnetic, electrical and thermal data with sources.

Permanent magnets, soft magnetic alloys and superconducting wire are chosen for how they respond to a magnetic field. Permanent magnets hold a field, soft magnetic alloys carry and shield it, and superconductors carry current without loss at low temperature.

Magnetic values depend on temperature and processing, so each page names the grade and condition.

At a glance

Highest density: Mu-metal (Ni-Fe-Mo) reaches 8.75 g/cm³. Lowest: Superconducting wire composites starts at 2.57 g/cm³. (11 of 12 grades have a sourced value.)
Highest melting point: Niobium-titanium (NbTi) reaches 2,300 °C. Lowest: Superconducting wire composites starts at 830 °C. (7 of 12 grades have a sourced value.)
Highest electrical resistivity: NdFeB reaches 0.0000015 Ω·m. Lowest: SmCo starts at 5.0e-8 Ω·m. (9 of 12 grades have a sourced value.)

Ranges run across the conditions each source reports (temper, heat treatment, form), measured at room temperature where the source says so.

How they compare

The same measurements for every material in the collection. A range means the grade has values under several conditions; "at least" means the source gives a specified minimum. "no data" means no sourced value yet. For ranked tables, open a benchmark.

Magnetic and superconducting alloys: how the grades compare
Material	Density	Melting point	Electrical resistivity	Thermal conductivity	Young's modulus	Thermal expansion
NdFeBpermanent magnet	7.5 to 7.6 g/cm³	no data	0.0000015 Ω·m	6.16 W/(m·K)	no data	4 to 7 ppm/K
SmCopermanent magnet	8.2 to 8.5 g/cm³	no data	5.0e-8 to 9.0e-7 Ω·m	11.6 to 12.8 W/(m·K)	1.2 to 1.6 10^11 N/m2	8 to 11 ppm/K
Alnico permanent-magnet alloypermanent magnet	6.8 to 7.4 g/cm³	1,200 to 1,450 °C	4.5e-7 to 7.5e-7 Ω·m	no data	no data	11 to 13 ppm/K
Permendur (Hiperco 50) (FeCoV)soft magnetic core and actuator alloy	8.12 g/cm³	no data	4.2e-7 Ω·m	29.8 to 30 W/(m·K)	190 to 215 GPa	9.4 ppm/K
Cobalt-iron and cobalt intermetallic alloyssoft magnetic alloys and high-temperature intermetallic strengtheners	7.9 g/cm³	no data	3.0e-7 Ω·m	no data	397 to 440 GPa	no data
Permalloy 80 (Ni-Fe-Mo)magnetic shield	8.7 g/cm³	1,450 °C	5.5e-7 to 5.9e-7 Ω·m	19 to 34.6 W/(m·K)	190 to 221 GPa	12 to 12.7 ppm/K
Mu-metal (Ni-Fe-Mo)magnetic shield	8.7 to 8.75 g/cm³	1,450 °C	6.0e-7 Ω·m	19 W/(m·K)	190 to 221 GPa	12 ppm/K
Fe-Sisoft magnetic core	7.6 to 7.85 g/cm³	no data	4.8e-7 to 5.9e-7 Ω·m	21 W/(m·K)	185 GPa	12 ppm/K
Metallic glass (MG)amorphous magnetic core and brazing alloy	7.18 to 7.59 g/cm³	969 to 1,024 °C	0.0000013 to 0.0000014 Ω·m	no data	100 to 110 GPa	12.7 ppm/K
Niobium-titanium (NbTi)ductile superconducting alloy drawn into wire for MRI and magnet coils	6.4 to 6.5 g/cm³	2,300 °C	no data	no data	no data	no data
Niobium-tin (Nb3Sn)A15 superconductor wire for high-field magnets	no data	2,100 °C	no data	no data	no data	no data
Superconducting wire compositesComposite superconducting wire and tape for high-field and power magnets (NbTi and Nb3Sn have their own profiles)	2.57 to 6.4 g/cm³	830 to 1,000 °C	no data	no data	149 to 186 GPa	no data

What these materials are made of

Composition by weight, as printed in the sources for each grade (the first constituents listed).

Composition of each grade
Material	Main constituents
NdFeB	Nd 26.7% · Fe 72.3% · B 1.0%
SmCo	Sm 33.8% · Co 66.2%
Permendur (Hiperco 50) (FeCoV)	Co 48.5% · C 0.01%
Cobalt-iron and cobalt intermetallic alloys	Co 17% · W 12% · Al 15%
Permalloy 80 (Ni-Fe-Mo)	Ni 80% · Mo 4.8% · Mn 0.5% · Si 0.35% · Fe balance
Mu-metal (Ni-Fe-Mo)	Ni 80% · Mo 5% · Mn 0.5% · Si 0.15% · Fe balance
Fe-Si	Fe balance
Metallic glass (MG)	Fe 80% · Si 9% · B 11%
Niobium-titanium (NbTi)	Nb balance

Where they are used

Uses
Use	Grades
Earbud headphones	NdFeB
Hard disk drive magnets	NdFeB
Electric motors, wind turbines, consumer electronics and home appliances	NdFeB
Linear alternator in a Stirling space power convertor (nuclear fission power system)	SmCo
Motors, sensors, loudspeakers and military systems	SmCo
Traveling wave tubes and electron tubes	Alnico permanent-magnet alloy
Generators and magnetic pump couplings	Alnico permanent-magnet alloy
Automotive, aerospace and military sensors	Alnico permanent-magnet alloy
Actuators, solenoids, magnetic bearings and magnetic shafts in high-speed motors	Permendur (Hiperco 50) (FeCoV)
Magnetic shielding of adiabatic demagnetization refrigerator stages in NASA's Resolve instrument	Permendur (Hiperco 50) (FeCoV)
Electric motor laminations and stamped stacks for high-power-density motors	Cobalt-iron and cobalt intermetallic alloys
Gamma-prime strengthened cobalt-based high-temperature alloys (research stage)	Cobalt-iron and cobalt intermetallic alloys
Magnetic shields and shielding cans for sensitive electronics	Permalloy 80 (Ni-Fe-Mo)
Relays, stepper motors and magnetic sensors	Permalloy 80 (Ni-Fe-Mo), Mu-metal (Ni-Fe-Mo)
Photomultiplier magnetic shield in the DAMPE electromagnetic calorimeter	Permalloy 80 (Ni-Fe-Mo)
Magnetic shielding for sensitive electronics, current sensors and current transformer cores	Mu-metal (Ni-Fe-Mo)

When each grade fits

Best use and weak spots of each grade
Material	Best for	Weakest at
NdFeB	Very high magnetic output per volume at moderate cost (N42H nominal remanence 1300 mT, maximum energy product 330 kJ/m3)	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
SmCo	Strong magnets that must stay stable above 150 degC, with a rated limit of 300 to 350 degC for Sm2Co17 grades (Eclipse)	Room-temperature strength against NdFeB, brittleness (flexural strength 110 to 120 N/mm2), and surface corrosion of Sm2Co17 in water without a coating
Alnico permanent-magnet alloy	Magnetic output that stays steady across a wide temperature range, up to 525 to 550 degC (Eclipse and Electron Energy rated maximums)	Low coercivity (Alnico 5 about 50.9 kA/m, Electron Energy typical) so it demagnetises easily, and irreversible loss above about 538 degC
Permendur (Hiperco 50) (FeCoV)	Soft magnetic cores and actuator parts that need high magnetic saturation (24 kG, per Carpenter)	Hiperco 50 strength, density and magnetic-loss values by temper are not sourced (the VACOFLUX 50 rows are another maker's grade; the VACOFLUX 50 solid material is low in strength, 250 MPa yield); magnetic and electrical properties change with ageing and heat treatment (Goodfellow)
Cobalt-iron and cobalt intermetallic alloys	Cobalt-iron soft magnetic parts where a cheaper grade than 49 % cobalt-iron still needs high saturation (VACOFLUX X1, 17 % Co, per VACUUMSCHMELZE)	No sourced corrosion, failure or cold-service data for any grade in this file; the cobalt-tungsten and cobalt-titanium values are calculated or phase data, not tested alloy parts
Permalloy 80 (Ni-Fe-Mo)	Shielding sensitive electronics from static and slowly varying magnetic fields, and relay, stepper-motor and sensor parts; DC permeability of 470,000 for 1.00 mm strip (Matthey) and a saturation induction of 0.8 T (VDM)	Strength and mass: 170 N/mm2 yield after the final anneal (VDM), 8.7 g/cm3 density, and the permeability falls after plastic deformation, so a formed or shocked part must be handled with care
Mu-metal (Ni-Fe-Mo)	Shielding sensitive electronics from static and low-frequency fields: DC permeability of at least 400,000 and AC permeability of at least 75,000 at 60 Hz in the MuMETAL sheet datasheet	Strength and weight: 160 MPa yield in the final annealed state and 8.7 g/cm3 density, and the permeability falls after shock or plastic strain, which needs a re-anneal to recover
Fe-Si	Laminated cores for transformers, inductors and rotating machines at 50 to 60 Hz, where low iron loss and a high flux density matter (Tata NO35-1750H, DOE)	Corrosion and strength: no corrosion rate was found, and the non-oriented grade has a typical yield strength of 435 MPa (Tata)
Metallic glass (MG)	Tape-wound transformer and switch-mode power cores, where Metglas 2605SA1 has core loss of at most 0.17 W/kg at 60 Hz and 1.3 T, and brazing foils that join stainless steel and superalloys	Heat and thermal stability. The 2714A bulletin gives a continuous service temperature of 90 °C, and the ribbons crystallise at 510 °C (2605SA1) and 550 °C (2714A)
Niobium-titanium (NbTi)	Superconducting magnet wire at 4.2 K up to about 10 T: a manufacturer gives up to 3000 A/mm2 at 4.2 K (Bruker), and Wikipedia gives practical magnet fields up to about 10 teslas	Critical temperature of about 9 to 10 K, so it must be cooled with liquid helium, and no corrosion or space-environment test was found for the alloy
Niobium-tin (Nb3Sn)	Superconducting magnets at about 11 to 13 T and 4 K, where NbTi cannot carry the needed current density (ITER central solenoid designed for 13 T)	Brittleness and strain: large strain causes irreversible cracking of the A15 layer, and the critical current of present conductors falls off swiftly above 12 to 15 T (PRM 2024). The fine powder is also a flammable solid (supplier SDS).
Superconducting wire composites	Magnets and cables at 20 K to 77 K where liquid helium is not wanted: Bi-2223 and REBCO tapes carry about 170 to 200 A at 77 K in self-field, and a Sumitomo review and an academic comparison both report the 77 K case	Brittleness and strain: REBCO and Bi-2223 lose critical current under bending and tension, and no corrosion or space-environment test was found for the REBCO or Bi-2223 wire itself