This work uses epitaxial strain to tune the oxygen stoichiometry and magnetism in UO2+x thin films. The UO2+x films are hypostoichiometric (x<0) when in-plane lattice is tensile strained, while films are hyperstoichiometric (x>0) when in-plane lattice is compressively strained. Induced ferromagnetism is attributed to the epitaxial strain and strain relaxation-induced point defects such as oxygen vacancy and oxygen interstitials. 

We report the growth of single-phase epitaxial UO2, α-U3O8, and α-UO3 thin films using pulsed laser deposition for the first time.