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First promising results


Fast micromagnetic simulator for computing hysteresis properties of permanent magnets with complex geometries developed; simulation demonstration of hardening by a superhard shell to negate the effects of surface defects and thermal activation; contributions to total magnetization calculated from first principles showing agreement with experiment.


A 30 % increase in coercivity (HCJ) with only 0.6 wt. % of Dy achieved by combining electrophoretic deposition of DyF3 with a modified grain-boundary diffusion process. With one HRE lean system, a remanence Br > 1.3 T, and a coercivity HCJ > 2000 kA/m was achieved.

NdFeB films have been micro-patterned by lithography followed by lift-off, to produce model structures for the study of grain-boundary engineering.

Significant increases in coercivity were achieved with powders produced from strip-cast HRE-free alloys with an average particle size of 1.5-2 :m, produced by jet milling.

HRE free samples with an ultrafine microstructure were prepared and coercivities reached up to 1600 kA/m. A grain size reduced by 50 % (4 :m → 2 :m) has led to an increase of about 30 % in coercivity.

Corrosion resistance of NdFeB powders was greatly enhanced by sol-gel coating.

Substantial improvement of reliability of interpreting EELS spectra of Dy-containing NdFeB magnets.

Promising new magnetic Heusler alloys have been identified by database mining. The magnetic database is accessible at http://aflowlib.herokuapp.com/. New ternary magnetic Heusler compounds (e.g. Co2MnTi) with high magnetization have been fabricated.

Significant increase in coercivity was observed in milled MnAlC powders, anisotropic MnAlC magnets with promising properties have been produced by hot deformation.

 

References [1] K. Uestuener, M. Katter, W. Rodewald, IEEE Trans. Magn. 42 (2006) 2897.

Development of hard magnets:

-       Ball-milled, partly oriented Y(Co,Fe) alloy powders with energy products of up to 140 kJ/m3

-       Hot extrusion of oriented MnAl alloys with useful energy product.

 

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