Review of Current High Performance Magnets

R. William McCallumMaterials Sciences

Ames Laboratory USDOEIowa State university

Ames IA 50014

Regular Performance Magnets

• CowMag-A is made of Alnico 5 magnetized with one magnetic pole on each end. It has been polished. CowMag-A has a big ratio of length to diameter so that it keeps strong magnetic power and works for the life of cow. It is non-toxic and non- corrosive staying in cow stomach.

High Performance Magnets

• CowMag-A is made of Alnico 5 magnetized with one magnetic pole on each end. It has been polished. CowMag-A has a big ratio of length to diameter so that it keeps strong magnetic power and works for the life of cow. It is non-toxic and non-corrosive staying in cow stomach.

• CowMag-C is an assembly of Ceramic Grade 5 and Chrome coated metal parts. It has more powerful magnetic field and its life is almost forever. It is non-toxic and non-corrosive staying in cow stomach.

Competition?

• Nd2 Fe14 B magnet floats above a superconducting disk capable of trapping 2.5T

Historical Developments

Historical Developments

Materials Systems• Alnico 3 (Al,Ni,Fe)

– 1932

• Alnico 2 (Al,Ni,Co,Fe,Cu)`– 1934

• Alnico 12 (Al,Ni,Co,Fe,Ti) – 1934

• Alnico 5 (Al, Ni,Cu,Co,Fe)– 1938

• Alnico 5 oriented– 1948

• Alnico 8 (Al, Ni, Co,Fe,Cu,Ti) – 1956

• Alnico 9 (Al, Ni, Co,Fe,Cu,Ti) – 1956

• RECo5– 1966 K. J. Strnat et al

• RE(Co,Fe,Cu)– 1968 Buschow et al

• RE2 TM17– 1970 Mishra et al

• RE2 TM14 B– 1984 Sagawa et al, Croat et al

Commercial Magnets

Temperature Considerations BHmax vs Temperature

Between 150 K and 150ºC, NdFeB outperforms SmCo for flux output. Above ~150ºC NdFeB suffers sufficient loss in induction that SmCo is superior.

SmCo is also superior where induction must be stable over a wide temperature range.

Graph is: Summary of magnetic properties for most commercial permanent magnetic materials at –160ºC to 300ºC.

Graph is by Chen, et alElectron Energy Corporation, 1999

(Numbers in parens are the room temperature BHmax)

Temperature Considerations HcJ vs Temperature

Resistance to demagnetization in SmCo is also superior to NdFeB, especially at elevated temperatures.

Graph is: Summary of magnetic properties for most commercial permanent magnetic materials at –160ºC to 300ºC.

Graph is by Chen, et alElectron Energy Corporation, 1999

(Numbers in parens are the room temperature BHmax)

Exchange Enhanced Magnets• McCallum, R. W.; Kadin, A. M.; Clemente, G. B.; Keem, J. E. High

performance isotropic permanent magnet based on neodymium-iron- boron. Journal of Applied Physics (1987), 61(8, Pt. 2A), 3577-9. Single phase with energy product over 20 MGOe

• Coehoorn, R.; De Mooij, D. B.; Duchateau, J. P. W. B.; Buschow, K. H. J. Novel permanent magnetic materials made by rapid quenching. Journal de Physique, Colloque (1988), Two phase spring magnet 2-14-1 Fe3 B

• Kneller, Eckart F.; Hawig, Reinhard. The exchange-spring magnet: a new material principle for permanent magnets. IEEE Transactions on Magnetics (1991), 27(4), 3588-600. Model for two phase spring magnet

Bonded Magnets

Bonded Magnets

What now?• Anisotropic Exchange Enhanced Magnets

Based on Known Materials• New Materials Class