Spin-flop phase transition in the orthorhombic antiferromagnetic topological semimetal Cu0.95MnAs

The orthorhombic antiferromagnetic compound CuMnAs was recently predicted to be an antiferromagnetic Dirac semimetal if both the Ry gliding and the S2z rotational symmetries are preserved in its magnetic ordered state. In our previous work on Cu0.95MnAs and Cu0.98Mn0.96As, we showed that in their low temperature commensurate antiferromagnetic state the b-axis is the magnetic easy axis, breaking the S2z symmetry and resulting in a polarized surface state that could make this material potentially interesting for antiferromagnetic spintronics. In this paper, we report a detailed study of the anisotropic magnetic properties and magnetoresistance of Cu0.95MnAs and Cu0.98Mn0.96As. Our study shows that in Cu0.95MnAs the magnetic easy axis is along the b direction and the hard axis is along c. Furthermore, it reveals that Cu0.95MnAs features a spin-flop phase transition at high temperatures and low fields when the field is applied along the easy b axis. However, no metamagnetic transition is observed for Cu0.98Mn0.96As, indicating that the magnetic interactions in this system are very sensitive to Cu vacancies and Cu/Mn site mixing.