Role of Er3+ ion in the formation of the ErFeO3 magnetic properties in the region of spin-reorientation phase transition

The 90° reorientation of Er3+ spins in ErFeO3 have been directly observed using optical spectroscopy. The peculiarities of the absorption spectrum of ErFeO3 in the region of the 4I15/2 → 4F9/2 transition of the Er3+ ion in the temperature range of ac-spin reorientation have been studied. It is shown that the spin reorientation phase transition (SRPT) is accompanied by splitting of the ground and excited states into Kramers doublets in the iron exchange field. This fact is a direct evidence of purely magnetic origin of SRPT. The experimental results were used to analyze the magnetic properties of ErFeO3. This analysis showed that the order of magnitude of the magnetic moment, its variation in the SRPT region, and the existence of Tcomp can be interpreted in terms of the single-ion model, taking into account the influence of the crystal field and the molecular field produced by the iron subsystem ions.