Effect of applied orthorhombic lattice distortion on the antiferromagnetic phase of CeAuSb2

We study the response of the antiferromagnetism of CeAuSb2 to orthorhombic lattice distortion applied through in-plane uniaxial pressure. The response to pressure applied along a < 110 > lattice direction shows a first-order transition at zero pressure, which shows that the magnetic order spontaneously lifts the (110)/(1 (1) over bar0) symmetry of the unstressed lattice. Sufficient < 100 > pressure appears to rotate the principal axes of the order from < 110 > to < 100 >. At low < 100 > pressure, the transition at T-N is weakly first order; however, it becomes continuous above a threshold < 100 > pressure. We discuss the possibility that this behavior is driven by order parameter fluctuations, with the restoration of a continuous transition being a result of reducing the point-group symmetry of the lattice.