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 L_3,2-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 VO 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 VV 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 PrV 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.