Effects of isovalent substitution on structural and magnetic properties of nanocrystalline Y3−xGdxFe5O12 (0 ≤ x ≤ 3) garnets

We fabricated Gd-doped Y3Fe5O12 (YIG) nanoparticles by a modified sol–gel method. We investigated the effects of isovalent Gd3+-ion substitution on the structural and magnetic properties of Y3−xGdxFe5O12 (0 ≤ x ≤ 3) nanoparticles. Isovalent Gd3+-ion substitution for Y3+ leads to lattice expansion and change in the Fe(a)–O–Fe(d) bond angle. The X-ray photoemission spectroscopy and Mossbauer measurements revealed a high-spin state of Fe3+. The Mossbauer analysis showed an increase in the Fe(d)3+/Fe(a)3+ ratio, indicating a relocation of Y3+ ions at the dodecahedral sites and Fe3+ ions at the octahedral sites. The magnetic properties could be explained in terms of magnetic-structural evolution with increasing Gd3+ content. The field dependence of magnetization indicated a clear decrease of the magnetization while the magnetic anisotropy first decreases and then increases with the increase of Gd3+ content. These Gd3+-ion-substituted nanocrystalline garnet ferrites are suitable for use in a variety of magneto-optical applications.