Cation distribution, Fe2+/Fe3+ valence states and oxygen vacancies detection in the Y2.98Er0.02Fe5−yCryO12 compound

Abstract

The appropriate physical properties of yttrium iron garnet (YIG), make it an excellent soft magnetic material for applications in microwave, magneto-optical devices, and spintronic. In this sense, the scientific community has made and continues to make numerous investigations to improve the YIG properties. Here, we have presented a study on the cation's distribution, valence states and oxygen vacancies (OV) in the Y2.98Er0.02Fe5−yCryO12 (0.00 ≤ y ≤ 0.05) compound. The coral type structures were observed by Transmission Electron Microscopy (TEM), whereas the Selected Area Electron Diffraction (SAED) confirmed the YIG crystalline nature, by means of bright points corresponding to the (004), (123), (024), (224), (022) and (112) YIG family planes. The valence states of the different atoms and oxygen vacancies defects were identified by the deconvolution of the X-ray Photoelectron Spectroscopy (XPS) spectra. For all YIG samples, the coexistence of Fe3+ and Fe2+ ions were observed and the Fe2+ cations and OV decrease as the Cr3+ cations concentration increases. By using the Electronic Paramagnetic Resonance (EPR) measurements, was detected the magnetic contribution of the Fe cations, while an isotropic line obtained near to 3440 Oe was associated with the Cr3+ cations presence. Finally, an increase of the Cr content led to a decrease in the saturation magnetization (Ms), which was explained in terms of the cation’s occupation, obtained from a phenomenological model.