Microscopic Description of Magnetic Nonequilibrium Phenomena in Erbium Orthoferrite

A model of nonequilibrium thermodynamics of erbium orthoferrite is presented. The quantum-mechanical effects in arbitrary magnetic fields, related both to the direction of a general quantization axis and an influence of anisotropic exchange interactions on the magnetic structure, spin-reorientation phase transition, spin reversals, and hysteresis, are considered. Based on recent experimental data on temperature-induced spin switching [Phys. Rev. B 105, 094424 (2022)], a possible mechanism for the exchange bias of magnetic hysteresis loops is proposed. The main parameters of the model Hamiltonian are determined, which point out a strongly competitive character of exchange interactions in erbium orthoferrite.