Synthesis, physical and magnetic properties of CuAlCr4S8: a new Cr-based breathing pyrochlore

A breathing pyrochlore is a promising system to study magnetic frustration. It carries magnetic ions on the alternating array of corner-sharing small and large tetrahedra. This unique combination of bond alternation and magnetic frustration allows it to host various exotic phases. The breathing pyrochlore system is also predicted to host various types of quantum spin liquid. We will present the synthesis, and magnetic and physical properties of new breathing pyrochlore CuAlCr₄S₈ with the help of synchrotron x-ray diffraction (XRD), magnetic susceptibility, specific heat, zero-field (ZF)/ longitudinal-field (LF) muon spin relaxation/rotation (muSR). We find that CuAlCr₄S₈ orders antiferromagnetically at 20 K at ambient pressure, with the ordering temperature increasing to 23 K under 600MPa hydrostatic pressure. CuAlCr4S8 possesses one of the highest bond alternations among the chromium-based breathing pyrochlores discovered so far.