Self-Consistent Four-Particle Cluster Model of Fe3+ Heisenberg Chains: Spectral and Magnetic Properties of YFe3(BO3)4 Crystals
Magnetic properties of antiferromagnetic quasi‐one‐dimensional YFe3(BO3)4 crystals are studied based on the analysis of the measured optical spectra of the Fe3+ ions in different rare‐earth iron borates and self‐consistent four‐particle cluster approach to helical iron chains. Parameters of crystal fields affecting the Fe3+ ions are calculated in the framework of exchange charge model. Parameters of the isotropic intra‐chain and inter‐chain exchange interactions between the Fe3+ ions are determined from modeling the temperature dependences of magnetic susceptibilities, the phase transition temperature, and spontaneous magnetic moments. The magnetic easy‐plane anisotropy is explained as the result of dipolar interactions between the Fe3+ ions in the trigonal crystal lattice. The developed model can be used to analyze and predict properties of multiferroic multifunctional rare‐earth iron borates and to highlight contributions of the iron subsystem into the magnetoelectric and magnetoelastic effects in these compounds.