Growth and properties of GdTiO3 films prepared by hybrid molecular beam epitaxy

The paper reports on the thin film growth of a protoptype Mott insulator, ferrimagnetic GdTiO₃, using shuttered molecular beam epitaxy. Substrates were (001) (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.7 (LSAT), with and without epitaxial SrTiO₃ buffer layers, respectively. It was found that on bare LSAT, the starting monolayer was crucial for stabilizing the GdTiO₃ perovskite phase. The quality of the films was evaluated using structural, electric, optical and magnetic characterization. Structural characterization showed that the GdTiO₃ layers were free of pyrochlore impurity phases and that the lattice parameter was close to what was expected for coherently strained, stoichiometric GdTiO₃. The room temperature film resistivity was 7 Ωcm and increased with decreasing temperature, consistent with Mott insulating characteristics. The Curie temperature was 30 K and a small coercivity was observed at 2 K, in good agreement with bulk GdTiO₃ properties reported in the literature.