Impact of strain and stoichiometric variations on the magnetic and electronic properties of RVO₃ (R = La, Pr, Y) thin films

Abstract

This study demonstrates that controlled engineering of strain and stoichiometry can dramatically alter the magnetic properties of RVO3 (R = Pr, La, Y) thin films. X-ray diffraction measurements reveal substrate-induced distortions of the VO6 octahedra, indicative of strain-driven changes in the local crystal environment. V L3,2-edge X-ray absorption spectroscopy (XAS) indicates a spatial variation in vanadium oxidation states, with V4+ predominantly confined to the film surface and a bulk composition dominated by V3+ in PrVO3, while LaVO3 and YVO3 exhibit mixed V3+/V4+ valence states. Complementary O K-edge XAS measurements show stoichiometry-dependent modifications in the crystal field environment and Vsingle bondO bond lengths, highlighting further distortions in the octahedral geometry. Magnetization measurements reveal a reduction of the antiferromagnetic ordering temperature by ∼25 K in PrVO3 relative to the bulk, attributed to altered V–O–V bond angles and Vsingle bondV bond distances, thereby impacting superexchange interactions. Additionally, PrVO3 exhibits a pinched hysteresis loop, which reflects a superposition of a robust hard component, arising from microstructural variants that act as strong pinning centers, and a soft contribution with dual origins: an intrinsic low-temperature signal from weak canting and/or Prsingle bondV interactions below ∼20 K, and an extrinsic enhancement associated with a V4+-rich paramagnetic dead layer at the film surface. In contrast to their antiferromagnetic bulk counterparts, LaVO3 and YVO3 thin films exhibit an emergent weak room-temperature ferromagnetic phase, as evidenced by bifurcations in zero-field-cooled and field-cooled magnetization curves and well-defined hysteresis loops persisting up to room temperature. This behaviour is attributed to stoichiometry-induced mixed valence states, wherein the coexistence of V3+ and V4+ ions may facilitate the formation of localized ferromagnetic regions embedded within an antiferromagnetic matrix. These findings demonstrate that controlled strain and stoichiometry engineering can effectively tune the magnetic properties of RVO3 thin films, offering pathways for designing novel functional materials.