Room Temperature Ferromagnetic GdO Epitaxial Thin Film without the Gd ₂ O ₃ Impurity Phase: Metallic Electronic States and Thickness Dependence of Magnetic and Electrical Properties

High Resolution Image Download MS PowerPoint Slide Rocksalt-type gadolinium monoxide GdO is a recently found room-temperature ferromagnetic rare-earth oxide. However, its intrinsic electronic and magnetic properties have been obscured by unavoidable Gd 2 O 3 impurities. In this study, we report the synthesis of single-phase GdO epitaxial thin films by introducing a lattice-matching (Ca,Sr)O buffer layer to unveil the intrinsic physical properties. X-ray photoemission and absorption spectroscopies confirmed the [Xe]4f 7 5d 1 electron configuration of the formally divalent Gd ions, indicating the presence of itinerant 5d electrons. Furthermore, the electrical conduction was improved by an order of magnitude. Intriguingly, Curie temperature and magnetization were not reduced with decreasing the film thickness to as thin as 5 nm. The robust room-temperature ferromagnetism concomitant with the metallic conduction is beneficial for spintronic applications.