Theory of Heusler and Full-Heusler Compounds
Department of Materials Science, School of Natural Sciences, University of Patras, GR-26504 Patra, Greece
Spintronics/magnetoelectronics brought at the centre of scientific research the Heusler and full-Heusler compounds, since several among them have been shown to be half-metals. In this review we present a study of the basic electronic and magnetic properties of both Heusler families; the so-called semi-Heusler alloys like NiMnSb and the full-Heusler alloys like Co2MnGe (usual full-Heuslers), Mn2CoAl (inverse full-Heuslers) and (CoFe)MnAl (LiMgPdSn-type full-Heuslers). First-principles calculations are employed to discuss the origin of the gap which is fundamental for the understanding of their electronic and magnetic properties. For half-metallic Heusler compounds the total spin magnetic moment Mt scales linearly with the number of the valence electrons Zt in the unit cell. These simple rules connect directly the magnetic to the electronic properties opening the way to engineer new half-metallic alloys with ”à la carte” magnetic properties such as the quaternary half-metals, the so-called half-metallic antiferromagnets, magnetic semiconductors or even the more exotic spin-gapless semiconductors. Finally, special topics like exchange constants, defects, vacancies, surfaces and interfaces are being discussed.