X-ray absorption and x-ray magnetic circular dichroism in bulk and thin films of ferrimagnetic GdTiO3

Abstract

Perovskite rare-earth titanates are prototypical Mott insulators in which ${\mathrm{Ti}}^{3+}$ ions with $3{d}^{1}$ electronic configuration exhibit ferromagnetic or antiferromagnetic spin order, depending on the rare-earth size. This peculiar magnetic behavior has, however, been barely studied with element-specific probes, either in bulk or in thin films. The recent finding of fingerprints of ferromagnetism in two-dimensional electron gases at oxide interfaces involving rare-earth titanates has produced a surge of the interest in these complex materials. Harnessing the interfacial magnetic states in these heterostructures calls for a better understanding of their insufficiently explored magnetic states in bulk and especially in thin film form. In this paper, we combine high-resolution transmission electron microscopy with x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD) to determine the structural, electronic, and magnetic structure of $\mathrm{GdTi}{\mathrm{O}}_{3}$ in bulk and thin film form. In both cases, we find that the sample surface is strongly overoxidized but a few nm below, Ti is mostly 3+ and shows a large XMCD. We provide evidence for the ferrimagnetic nature of $\mathrm{GdTi}{\mathrm{O}}_{3}$ with antialigned Gd and Ti sublattices and show that, just as in antiferromagnetic $\mathrm{LaTi}{\mathrm{O}}_{3}$ or ferromagnetic $\mathrm{YTi}{\mathrm{O}}_{3}$, Ti carries no orbital moment.