Single-doublet model of spin reorientation

A simple theoretical model is developed to describe spin reorientation (SR) transitions in rare-earth orthoferrites and orthochromites RFeO3 and RCrO3. Within a ``single-doublet’’ approach, the free energy includes anisotropy contributions from the 3d-sublattice and the splitting of the lower doublet of 4f-ions. The model predicts various types of SR transitions - first-order, second-order, and mixed - depending on anisotropy parameters. Effects of non-magnetic dilution, heat capacity anomalies, and behavior of the rare-earth magnetic moment in the SR region are analyzed.

💡 Research Summary

The paper presents a concise “single‑doublet” theoretical framework for spin‑reorientation (SR) transitions in rare‑earth orthoferrites and orthochromites (RFeO₃, RCrO₃). The free energy per ion is written as Φ(θ)=K₁cos²θ+K₂cos⁴θ−kT ln 2 cosh