Magnetic properties and phase stability of L 2₁ phase in Co ₂ Mn (Ga_1-x Z_x) (Z=Si, Ge, and Sn) Heusler alloys

For the Co₂ Mn (Ga_1-x Z_x) (Z=Si, Ge, and Sn) Heusler alloys, the L 2₁ /B2 order-disorder transition temperature T_t L 2₁/B2 the Curie temperature T _C, and the saturation magnetization M_s were determined. The T_t L 2₁/B2 for all the systems linearly increases with increasing x. Although the T_t L 2₁/B2 was not determined in the high x region because of melting of alloys, those of Co₂ MnGe and Co₂ MnSn could be estimated by extrapolation from the quaternary data. The M_s at 4.2 K and the T_C increase with x, and the M_s for all the systems is in good agreement with the Slater Pauling rule.