Lattice ordering and magnetic structure of high moment Fe and Co based Heusler alloys prepared by mechanical alloying

Co-based and Fe-based full Heusler compounds with composition Co2M'Z or Fe2M'Z (where M' is a transition metal and Z is a main group element) are attracting attention due to their predicted half-metallic behavior, a greatly desired property for spin-dependent electron transport devices. In this work four Heusler compounds (Co2FeGe, Co2FeSi, Fe2CoGe, Fe2CoSi), have been prepared by mechanical alloying. The effect of vacuum annealing on properties was studied. According to the structural measurements 15 hours milling was enough for crystallization of these compounds. During annealing the crystallite size increased and lattice ordering enhanced. Two superlattice peaks appeared in X-ray pattern due to enhancement of lattice ordering of two Si content compounds. In Co-based compounds the saturation magnetization value increased to a closer value of Slater Pauling model because of improvement of lattice ordering. The value of Ms in some Fe-based compounds was higher than that predicted by Slater Pauling model.