1 research outputs found
High-temperature ferromagnetism of electrons in narrow impurity bands: Application to CaB
Ferromagnetism with high Curie temperature , 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 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
below its value given by Stoner theory. These ideas are applied to
CaB and a thorough review of the experimental situation in this material is
given. It is suggested that the intrinsic magnetism of the B and O
dimers might be exploited in suitable structures containing these elements.Comment: 26 pages, 2 figure