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Permanent Magnets: History, Current Research, and Outlook

  • R. SkomskiEmail author
Chapter
Part of the Springer Series in Materials Science book series (SSMATERIALS, volume 231)

Abstract

Recent developments in permanent magnetism are summarized, considering both intrinsic and extrinsic properties. After a general introduction to permanent magnetism, several classes of materials are discussed in the light of future improvements. Emphasis is on magnets rich in Fe, Co, and Mn. The search for new magnetic compounds with improved magnetization, Curie temperature, and anisotropy is accompanied by the need to realize a microstructure that ensures high coercivity. This need refers to both bulk magnets, where hcp Co and tetragonal FeNi are briefly discussed as negative and positive examples, respectively, and to aligned hard–soft nanocomposites. A very recent concept is imaginary magnetic hardness, which reflects easy-plane magnetism and may be exploited in some ferromagnetic compounds. In aligned two-phase nanostructures, soft-in-hard geometries are better than hard-in-soft geometries, and different shapes behave different in the first and second quadrants of the hysteresis loops. Both intrinsically and extrinsically, the most important task is to maximize the hard phase anisotropy while maintaining a high magnetization. Anisotropy field and magnetic hardness can be maximized by choosing a small magnetization, but this strategy is detrimental to the energy product. The last section deals with the behavior of permanent magnets above room temperature, with emphasis on nanoscale effects. Throughout the chapter, current research trends are critically evaluated, and several common misconceptions are dispelled.

Keywords

Domain Wall Energy Product Permanent Magnet Hard Phase Soft Region 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgment

This chapter is partially based on original research supported by DOE BES (DE-FG02-04ER46152, Sect. 3), ARO (Nr. WF911NF-10-2-0099, Sect. 4), ARPA-E (PNNL/Maryland and Argonne/Delaware), DREaM (Ames), HCC, and NCMN. It has also benefitted from discussions and collaborations with B. Balamurugan, R. Choudhary, J. M. D. Coey, S. Constantinides, J. Cui, B. Das, A. Enders, G. C. Hadjipanayis, S. Hirosawa, Y. Jin, A. Kashyap, L.-Q. Ke, M. J. Kramer, L. H. Lewis, S.-H. Liou, J. P. Liu, Y. Liu, P. Kumar, P. Manchanda, R. W. McCallum, F. Pinkerton, T. Rana, S. G. Sankar, J. E. Shield, D. J. Sellmyer, S. Valloppilly, V. Sharma, I. Takeuchi, and W.-Y. Zhang.

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© Springer International Publishing Switzerland 2016

Authors and Affiliations

  1. 1.Department of Physics and Astronomy and Nebraska Center for Materials and NanoscienceUniversity of NebraskaLincolnUSA

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