Anisotropy of Spin-Glasses from Torque Measurements

The anisotropy of $\mathrm{Cu}\mathrm{Mn}$ spin-glasses was probed by torque measurements. In $\mathrm{Cu}\mathrm{Mn}$ (20 at.%) the anisotropy is $2\pi$ periodic, increasing to its maximum when the spin system is rotated by $\pi$ away from equilibrium. After a rotation by $\pi$ around $\hat{x}$, the anisotropy energy remains at its maximum value during a subsequent rotation around $\hat{y}$ (perpendicular to $\hat{x}$), at least in a limited angle range. These properties are due to the existence of antisymmetric interactions.