HALF-METALLIC FERROMAGNETS

Experimental data, band structure calculations, and theoretical investigations within the many-electron model for half-metallic ferromagnets (HMF) are reviewed. These substances are characterised by the presence of an energy gap for one of the spin projections and make up a separate class of strong itinerant magnets, which includes some Heusler alloys (e.g., PtMnSb), CrO2, etc. Some HMFs and similar systems are promising magnetic materials, in particular they posses unique magnetooptical properties. From the theoretical point of view, HMFs are interesting of distinct nonquasiparticle (spin-polaron) effects, e.g., in the spin polarization of current carriers and in the nuclear magnetic relaxation rate. Ideas of the HMF theory turn out to be useful also for ''conventional'' itinerant magnets including iron group metals.