Synthesis and physical properties of uranium thin-film hydrides UH2 and UH3

Abstract

Formation of thin uranium hydrides films, UH2 and UH3, synthesized by direct current reactive sputtering of a uranium metal in an Ar-H2 atmosphere, was explored using variable deposition conditions. Obtained U-H films were studied by a variety of methods, both in situ (photoelectron spectroscopy) and ex situ (x-ray diffraction, transmission electron microscopy, electrical resistivity, and magnetometry). Preparation of thin films allowed us to stabilize the non-existent in bulk UH2 phase as well as the transient α-UH3 (as a residual phase in UH2) and the common stable β-UH3 phase. All types of hydrides are ferromagnetic, the Curie temperatures of UH2 and UH3 (both α and β) are approx. 120 and 170 K, respectively. Ferromagnetism in the thin films is robust and does not depend on structure details while electrical resistivity data reflect disorder in both types of hydrides.