The influence of Cu-Mn content on the structural and physical properties of bulk CuMnAs

CuMnAs is a room temperature antiferromagnetic semi-metal, which has recently attracted experimental and theoretical interest in the research fields of antiferromagnetic spintronics [1,2], and physics of Dirac fermions [3]. Our current studies on bulk Cu-Mn-As system [4] show that the crystal structure and magnetic properties are very sensitive to the exact composition. While stoichiometric CuMnAs has orthorhombic structure and it orders antiferromagnetically below 350–400 K, already less than 10% of the Mn deficiency turns the material to tetragonal phase with similar lattice parameters to thin films and higher Néel temperature than in the orthorhombic case. On the other hand, Mn excess leads to orthorhombic structures with the unit cell doubled along the a-direction (compared to the stoichiometric CuMnAs); this structure was previously reported for CuMn₃As₂ and Cu₂Mn₄As₃ compounds [5]. From the most stoichiometric tetragonal single crystalline grain, we prepared a transport device using Focused Ion Beam micromachining. For the first time, we report temperature dependence of both in-plane and out-of-plane resistivity, uncovering large transport anisotropy between both principal crystallographic axes. Anisotropic magnetoresistance is also measured and a Stoner-Wohlfarth–type model is applied to analyse it phenomenologically.

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• [5] K. Uhlířová et al., J. Alloys Compd. 650 224-227 (2015)