Magnetism of Dilute Oxides

Authored by: J.M.D. Coey

Handbook of Spin Transport and Magnetism

Print publication date:  August  2011
Online publication date:  April  2016

Print ISBN: 9781439803776
eBook ISBN: 9781439803783
Adobe ISBN:

10.1201/b11086-25

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Abstract

Reports of Curie temperatures well above room temperature for wide-bandgap oxides doped with a few percent of transition-metal cations have triggered intense interest in these materials as potential magnetic semiconductors. The origin of the magnetism is debated; in some systems, the ferromagnetism can be attributed to nanoparticles of a ferromagnetic secondary phase, but in others, properties are found that are incompatible with any secondary phase, and an intrinsic origin related to structural defects is implicated. The magnetic interactions in these materials are qualitatively different from those in magnetically concentrated compounds, and the standard “m-J paradigm” of localized magnetism seems unable to explain their behavior. In this chapter, we first summarize the established view of magnetism in the oxides before reviewing data on a selection of the most widely studied materials; then we consider the physical models that have been advanced to explain the magnetism, and raise issues that still have to be addressed. As noted in Chapter 19, some of the concepts also apply to wide-gap III–V compounds.

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