Crystal field deformation by Ce3+ doping in spinel Mn-Cr ferrite

We investigated the doping of the spinel structure Mn-Cr ferrite with cations of the rare-earth Ce. The material was characterized by X-ray diffraction, Raman spectroscopy, high-resolution transmission electron microscopy and saturation magnetization. The magneto-impedance showed a step-like drop in impedance that ranges from 10% to 45% at the highest and lowest biased electric field, respectively. There was no crystal structure deformation detected in the diffraction patterns, but rather the deformation of the crystal field was seen in the Raman spectra. We can conclude that doping a large rare-earth cation in a closed packed spinel structure results more in a distortion in the crystal field of the material rather than in its crystal structure. This crystal field distortion results in non-symmetric splitting of the energy states of the doping cations in octahedral and tetrahedral sites, for which Raman scattering shift is very sensitive, and can be seen also in magneto-impedance measurements.