Macroscopic anisotropy in transition-metal spin-glass alloys

Abstract

The nature of the macroscopic anisotropy in a classical Ruderman-Kittel-Kasuya-Yosida (RKKY) spin-glass with weak Dzyaloshinskii-Moriya interactions is studied in a zero-temperature numerical simulation. For rigid rotations of the spin system from a metastable state, we find the expected unidirectional form for the anisotropy energy. Simulations of rotation and inversion of the magnetization by a magnetic field show nearly rigid rotations of the spin system if the anisotropy energy is much smaller than the RKKY energy. For stronger anisotropy, we find substantial deviations from rigidity, especially for large-angle rotations and inversions, resulting in a behavior characteristic of an anisotropy energy with both unidirectional and uniaxial terms. The simulations qualitatively reproduce several features observed in hysteresis and torque experiments.