High-temperature ferromagnetism of $sp$ electrons in narrow impurity bands: Application to CaB$_6$

D. M. Edwards; M. I. Katsnelson

doi:10.1088/0953-8984/18/31/016

paper

High-temperature ferromagnetism of $s p$ electrons in narrow impurity bands: Application to CaB $_{6}$

arXiv:cond-mat/0605495 · doi:10.1088/0953-8984/18/31/016

Abstract

Ferromagnetism with high Curie temperature $T_{c}$ , well above room temperature, and very small saturation moment has been reported in various carbon and boron systems. It is argued that the magnetization must be very inhomogeneous with only a small fraction of the sample ferromagnetically ordered. It is shown that a possible source of high $T_{c}$ within the ferromagnetic regions is itinerant electrons occupying a narrow impurity band. Correlation effects do not reduce the effective interaction which enters the Stoner criterion in the same way as in a bulk band. It is also shown how, in the impurity band case, spin wave excitations may not be effective in lowering $T_{c}$ below its value given by Stoner theory. These ideas are applied to CaB $_{6}$ and a thorough review of the experimental situation in this material is given. It is suggested that the intrinsic magnetism of the B $_{2}$ and O $_{2}$ dimers might be exploited in suitable structures containing these elements.

26 pages, 2 figures

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High-temperature ferromagnetism of sp electrons in narrow impurity bands: Application to CaB6​

Abstract

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High-temperature ferromagnetism of $s p$ electrons in narrow impurity bands: Application to CaB $_{6}$