Peculiarities of Electronic Transport and Magnetic State in Half-Metallic Ferromagnetic and Spin Gapless Semiconducting Heusler Alloys

Resumo

A brief survey of experimental and theoretical studies of half-metallic ferromagnets (HMFs) and spin gapless semiconductors is given, the possible candidates being the X₂YZ (X = Mn, Fe, Co; Y = Ti, V, Cr, Mn, Fe, Co, Ni; Z = Al, Si, Ga, Ge, In, Sn, Sb) Heusler alloys. The data on the electrical resistivity, normal and anomalous Hall Effect, and magnetic properties are presented. It is shown that the Co₂FeZ alloys demonstrate properties of conventional ferromagnets, the HMF properties being also manifested upon variation of the Z-component. The Fe₂YAl and Mn₂YAl alloys show upon variation of the Y-component both metallic and semiconducting electronic characteristics, the magnetic properties changing from the ferromagnetic to compensated ferrimagnetic state. The HMF and spin gapless semiconductor states are supposed to exist in these Heusler alloys systems.