Preferential site occupancy of Ni ions and oxidation state of Fe ions in the YIG crystal structure obtained by sol-gel method

In this work, we present a study about the preferential site occupancy of Ni ions and the oxidation state of Fe ions in the yttrium iron garnet (YIG) crystal structure of nanoparticles obtained by sol-gel method. Transmission electron microscopy (TEM) showed particles and clusters with irregular shapes. Selected area electron diffraction (SAED) showed bright spots and diffuse rings characteristic of well-defined crystals supporting the presence of fine particles. The distribution of Ni and Fe ions in the tetrahedral (d) and octahedral (a) sites of YIG structure has been revealed by the Mössbauer spectroscopy. The Electron paramagnetic resonance (EPR) results confirmed the inclusion of Ni in the Fe sites and an increase in the g factor for the doped YIG sample. X-ray Photoelectron Spectroscopy (XPS) has been employed to check the valence states, confirming that Y, Ni and Fe are predominantly in the Y3+, Ni2+, Fe3+ and Fe2+ oxidation states. This paper contributes to the understanding of preferential site occupancy of Ni in the yttrium iron garnet; a compound with few studies and high importance in spintronics applications.