Even and odd crystal fields on Fe²⁺ions, local lattice distortion parameters, electron-deformation interaction, and magnetoelectric coupling in FeCr<inf>2</inf>O<inf>4</inf>

Abstract

Within the framework of the quantum mechanical approach, the available experimental data are analyzed to identify the electronic structure of the multiferroic FeCr2O4. The relative values of the key contributions to the parameters of even and odd crystal fields acting on the 3d electrons of the Fe2+ ion are determined. Data on local lattice distortions are systematized. The parameter of the electron-deformation interaction of the ground term Fe2+ (5 E) is determined considering lattice distortions, and the parameters of binding of the spins of Fe2+ and Cr3+ to the electric field are estimated. The calculation results are compared with the available experimental data on the magnetic and structural characteristics of FeCr2O4, the critical temperature of the transition to an orbitally ordered state, optical conductivity data, the Mössbauer effect study, and measurements of spontaneous electric polarization.