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Microstructure Of Fe-Nd-B Alloys Tailored To Approach Theoretical Coercrvtty Limits

Published online by Cambridge University Press:  02 July 2020

Kannan M. Krishnan ,
Er. Girt ,
E. C. Nelson ,
G. Thomas  and
Ferdinand Hofer
Kannan M. Krishnan
Affiliation:
Materials Sciences Division, National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA94720, USA
Er. Girt
Affiliation:
Materials Sciences Division, National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA94720, USA
E. C. Nelson
Affiliation:
Materials Sciences Division, National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA94720, USA
G. Thomas
Affiliation:
Department of Materials Science, University of California, Berkeley, CA94720
Ferdinand Hofer
Affiliation:
Research Institute for Electron Microscopy, Graz University of Technology, Graz, A 8010, Austria
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Performance of permanent magnets for a variety of applications is often determined by the maximum energy product (BH)max. In order to obtain high (BH)max permanent magnetic materials have to have large coercivity. In theory the coercive field of ideally oriented, non-interacting, single domain, magnetic particles, assuming Kl is much bigger than K2, was shown to be He = 2K1/Ms - N Ms, where Kl and K2 are the magnetocrystalline anisotropy constants, Ms is the spontaneous magnetization and N is the demagnetization factor. For randomly oriented non-interacting particles the Stoner-Wohlfarth model predicts that the value of Hc decreases to about half. However, experimentally obtained values of the coercitive fields in permanent magnets are 3 to 10 and 2 times smaller for well oriented and randomly oriented samples, respectively. This discrepancy was attributed to inter-particle interaction and the microstructure of the permanent magnets. In order to understand the difference between the theoretically predicted and experimentally obtained results for He we prepared rapidly quenched, Nd-rich, NdxFe14B (2 < x < 150) ribbons.

Type
Magnetic Imaging And Its Application To Materials
Information
Microscopy and Microanalysis , Volume 5 , Issue S2: Proceedings: Microscopy & Microanalysis '99, Microscopy Society of America 57th Annual Meeting, Microbeam Analysis Society 33rd Annual Meeting, Portland, Oregon August 1-5, 1999 , August 1999 , pp. 26 - 27
Copyright
Copyright © Microscopy Society of America

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References

[1] Girt, Er., Krishnan, Kannan M., Thomas, G., Althunian, Z., (in preparation)Google Scholar

[2] Hofer, F., Warbichler, P. and Grogger, W., Ultramicroscopy 59 (1995) 15–31.CrossRefGoogle Scholar

[3] This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy under contract No. DE-AC03-76SF00098.Google Scholar