Magnetic anisotropy of the rhombohedral antiferromagntic crystals with S-ions. A quantitative estimation

Abstract The method to investigate the “single-ion” exchange anisotropy (as predicted by pair model) is treated by means of exploration of several isostructural diamagnetic crystals containing magnetic impurities sufficient to pair spectrum of the electron spin resonance (ESR). The ESR spectra were observed for ferric borate isostructural crystals MBO3+Fe3+(M=Ga, In, Lu, Sc). The experimental dependences of the spin-Hamiltonian axial constants of the second DS and fourth (a−F)S order vs. total pair spin S are presented. The contributions arising due to the distortion of the parent crystal lattice MBO3 under the magnetic dilution are estimated. The microscopically derived expressions for the “single-ion” contribution to the anisotropy are also presented. On the basis of the obtained experimental data it turns out to be possible to estimate the “single-ion” exchange contribution for the FeBO3, MnCO3 and α-Fe2O3 crystals at T=0 K. Taking into account “single-ion” and dipole contributions results in satisfactory agreement of the proposed theoretical model with the measured experimental data.