Distribuição de cátions de Ce3+ e Er3+ na estrutura cristalina do composto Y3Fe5O12 e seu efeito sobre as propriedades estruturais, óticas e magnéticas

Abstract

Herein, we have studied the structural, optical, and magnetic properties of Y3-xCexFe5-yEryO12 (0.00 ≤ x ≤ 0.02), (0.00 ≤ y ≤ 0.06) compound synthesized via sol gel process. Structural characterization by X-ray diffraction (XRD) confirmed the YIG single phase formation, belong to the Ia3d-𝑂ℎ10cubic centrosymmetric crystal structure. The lattice constant, lattice strain, dislocation density and average crystallite size variations were calculated and discussed in terms of the rare earth’s dopant concentrations. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed redshift for the Fe–O stretching modes as the dopant content increase, testifying the crystal lattice expansion. Raman spectra inspection corroborated the YIG single phase formation and shifts in the vibrational modes confirmed the Ce3+ and Er3+ rare earths inclusion in the sites occupied by Y3+ and Fe3+ cations, respectively. The coral-like of YIG nanoparticles were confirmed by scanning (SEM) and transmission (TEM) microscopies, whereas the existence of the elements Y, Fe, O, Ce and Er, were verified by Energy Dispersive Spectroscopy analysis (EDS). The optical band gap (Eg) decreases, while Urbach energy (Eu) increases varying the Er content. The result confirms the effect of Ce3+ and Er3+ addition on the optical properties of YIG, contributing to localized oxygen vacancy defects formation. Using a phenomenological model, it was shown that, the highest probability of Er3+ cations occupation corresponds to octahedral sites. For the Y2.98Ce0.02Fe5-yEryO12 (0.00 ≤ y ≤ 0.06) compound, the theoretical saturation magnetization (Ms) was calculated from the cation distribution obtained by the phenomenological model, resulting a slight increase with the Er content. The result agrees with the experimental Ms measurements, although for y = 0.06 a discrepancy was detected, which can be attributed to the breaking of collinear array of magnetic moments due to high lattice distortions.