Magnetic structure of γ-Mn(Ga) alloys with distorted cubic lattices

γ-Mn alloys containing Ga undergo a distortion from the face-centered-cubic structure to the face-centered-tetragonal structure with c/a < 1 or c/a > 1, depending on composition. The face-centered-orthorhombic structure also exists in a composition range between the two tetragonal phases. The antiferromagnetic structures of these phases have been determined by neutron-diffraction experiments. The tetragonal and orthorhombic phases exhibit collinear and noncollinear moments, respectively. The results are consistent with the theoretical prediction by Jo et al.