We present the synthesis and physical properties of a breathing pyrochlore magnet ${\mathrm{CuAlCr}}_4{\mathrm{S}}_8$ via synchrotron x-ray diffraction, magnetization under ambient and applied hydrostatic pressure, heat capacity, and muon spin relaxation/rotation measurements. ${\mathrm{CuAlCr}}_4{\mathrm{S}}_8$ exhibits positive thermal expansion with a concave upward temperature dependence. We observed a sharp antiferromagnetic ordering transition of a purely magnetic nature at 20 K, which shifts by as much as 3.2 K on application of 600 MPa pressure. The breathing factor ($B_f=J^{\prime }/J$) in breathing pyrochlores can be an important parameter to tune the magnetic ground states of the pyrochlore lattice. The breathing factor can be modulated through the breathing ratio, the ratio of the sizes of the two tetrahedra, by using different elements at the $A$ and $A^{\prime }$ sites in the breathing pyrochlore structure. We find that ${\mathrm{CuAlCr}}_4{\mathrm{S}}_8$ has a breathing ratio of 1.0663(8), which is comparable to other sulfur breathing pyrochlores.

• Received 12 January 2022
• Revised 24 March 2022
• Accepted 27 June 2022

DOI:https://doi.org/10.1103/PhysRevB.106.024407