Suppression of phase transitions at low temperature by chromium substitution in vanadium spinel Fe(V1-x Cr x )2O4

Even and odd crystal fields on Fe2+ions, local lattice distortion parameters, electron-deformation interaction, and magnetoelectric coupling in FeCr2O4

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 3delectrons 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⁺(⁵E) 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.