High Pressure Investigations on the Semi-Heusler Compound CuMnSb

Half metallic Heusler alloys in which charge carriers are in spin polarized states form an intensively studied class of magnetic materials. CuMnSb is a rare example of an AFM Mn-based member among the semi-Heusler compounds with a relatively low Néel temperature near 50K. We investigated polycrystalline CuMnSb under high pressure by four-point electrical resistivity measurements in the temperature range 5-295K to 50GPa as well as synchrotron x-ray diffraction at ambient temperature to 30GPa. Up to 7GPa, pressure is found to enhance the Néel temperature. Above this pressure the temperature dependence of the resistivity shows a dramatic change associated with a first-order structural transition from cubic to a lower symmetry structure. The diffraction peaks of the high pressure phase are significantly broadened, suggesting its metastable nature. In a second x-ray experiment the diamond-anvil-cell was heated resistively to 350^oC to complete the phase transition. Our study highlights the importance of pressure as a tool to explore novel electronic and structural phases in this interesting magnetic material.