Structural analyses of Gd3(Al,Ga)5O12 garnet solid solutions via X-ray and UV absorption spectroscopy experiments for Gd atoms

Abstract

Local structures of Gd atoms in Gd3(Al, Ga)5O12 garnet solid solutions, grown using the Czochralski method, have been studied at low temperatures through X-ray and UV absorption spectroscopy experiments. From the Fourier transforms (FTs) of Gd K-edge extended X-ray absorption fine structure (EXAFS) oscillations, the preferential sites for the occupation of Ga and Al atoms were assigned to the 24d and 16a sites, respectively. The interatomic distances between Gd and neighboring atoms, and the Debye–Waller factors were determined through the fit to the inverse FTs. Positional fluctuations of neighboring O atoms buffered local distortions induced by the occupation of Ga and Al atoms at the same crystallographic sites. The change in the high-resolution UV absorption spectra due to Gd intra-4f transitions on the Ga content is explained by considering the crystal field and Coulomb repulsion on the Gd atom.