Magnetic properties of (Mn_1-xRu_x)₃Ga alloys

We found that the pseudo binary alloys (Mn_1-xRu_x)₃Ga, with 0.33 ≤ x ≤ 0.67, have an ordered b.c.c. structure. The lattice constant a is almost constant with respect to x: a = 6.000 Å for x = 0.33 and a = 5.992 Å for x = 0.67. For the alloy with x = 0.33, i.e. Mn₂RuGa, the magnetization is almost saturated in a field of 20 kOe. The saturation magnetization at 4.2 K is 23 emu/g, and the Curie temperature, T_C, is 460 K. The T_C of (Mn_1-xRu_x)₃Ga decreases almost linearly with increasing x, and it vanishes around x = 0.67 (MnRu₂Ga). We also determined atomic and magnetic structures from neutron diffraction experiments. The alloy Mn₂RuGa (x = 0.33) has an ordered structure of CuHg₂Ti type; the magnetic Mn atoms mainly occupy the 4a (0,0,0) and 4d (3/4, 3/4, 3/4) sites. We also observed that the magnetic moments of Mn atoms on the 4a and 4d sites are antiparallel to each other; values of the magnetic moment are μa = 4.6 and μ_d = 3.3 μ_B per Mn atom.