Investigations of anti-site disorder and half-metallic properties in some Mn/Co based full Heusler alloys

Half-metallic ferromagnets are unique class of materials in which one spin sub band shows a metallic character where as the other exhibit a semiconducting character. This peculiar electronic band structure leads to 100 percent spin polarization of charge carriers at the Fermi level. Among many known half-metals Viz., CrO2, LSMO, Pnictides, etc, Heusler alloys have drawn much attention due to their high Curie temperature and good lattice matching with the semiconductors. Hence half-metallic Heusler alloys are found in magneto electronic device applications. However, the hindrance to the development half-metallic Heusler alloys as spin injection electrodes is the presence of anti-site disorder in these systems. In recent years, many theoretical calculations and experimental studies revealed that a few percentage of B2/DO3 type disorder will destroy the half-metallic character in Heusler alloys. In this talk the structural, magnetic and transport properties of the systems Mn2VGa, Co2FeGe and Mn2-xCoxVZ (X = 0.5, 0.75 and 1; Z= Al, Ga) will be discussed. The half-metallic properties in these systems were investigated through indirect measurements/analysis such as integer magnetic moment, nature of magnetism and absence of spin flip excitations. Neutron diffraction studies were carried out to qualitatively analyze the presence site disorder in the system. Band structure calculations for the samples Mn2VGa and Co2FeGe were done using PWSCF package and the results will be compared with the experimental results.