Magnetic properties, phase stability, electronic structure, and half-metallicity of L21-type Co2(V1-xMnx)Ga Heusler alloys

Magnetic properties, phase stability, electronic structure, and spin polarization ratio of L2(1)-type phase in Co-2(V1-xMnx)Ga Heusler alloys have been investigated experimentally and theoretically. The experimental magnetic moments M-s at 4.2 K linearly increase with increasing x, in situ with the generalized Slater-Pauling rule. The experimental Curie temperature T-C(expt.) exhibits a maximum value of about 704 K at x=0.75. The latter behavior is comparable to the calculated Curie temperature T-C(calc). from the theoretical effective exchange constant J(0). Although the order-disorder transition temperature T-t(L21/B2) from the L2(1)- to B2-type phase linearly decreases with increasing x, it is relatively high enough in the entire concentration region. The high value of T-t(L21/B2) means that the L2(1)-type phase can exist stably, which is very important for practical uses. The calculated density of states by the linear-muffitin orbital method with the atomic sphere approximation disclosed that the spin polarization ratio P of the alloy with x=0.75 is the highest in the present substituted alloys.