Magnetic Order in ErFeO3 Single Crystals Studied by Mean-Field Theory

Recent experiments showed magnetic moment reversal and pronounced exchange-bias (EB) effect in the vicinity of the compensation temperature T-comp of orthoferrites RFeO3 (R = Nd, Sm, Er). Although different orthoferrites exhibit diverse R-Fe interactions, T-comp values, and spin-reorientation temperatures, the EB field in the like manner emerges and diverges upon approaching T-comp and changes its sign with crossing T-comp. In order to explain these observations, a mean-field theory approach for the representative ErFeO3 orthoferrite is proposed. The general case of two sublattices, antiferromagnet with exchange anisotropy and rare-earth-iron interactions, is considered. A small applied magnetic field appears to be a source of additional anisotropy, resulting from canting of sublattice moments. This anisotropy leads to an imbalance of free energy for two different types of magnetic domains, causing a spin jump near the T-comp. The suggested approach allows reproduction of magnetization reversal and main features of the coercive and exchange-bias fields observed in ErFeO3.