Tailoring non-collinear magnetism and 3d $-$ 4f exchange interactions in RVO${}_3$ epitaxial thin films

Abstract

In orthorhombic perovskite oxides (RMO${}_3$), substituting R${}^{3+}$ rare-earth cations tailors the spin, orbital, and charge degrees of freedom of the central M${}^{3+}$ transition metal cations through lattice distortions. In turn, these modify also the surrounding environment of R${}^{3+}$. When both R${}^{3+}$ and M${}^{3+}$ exhibit magnetic properties, phenomena such as spin reorientation and magnetization reversal can occur. In fact, the underlying exchange interactions between M-$3d$ spins and R-$4f$ magnetic moments enrich the multifunctional character of RMO${}_3$, particularly when combined with structural distortions. They play a crucial role in achieving appealing properties such as robust magnetoelectricity with non-collinear magnetic orders. Here, we explore the exchange coupling in epitaxial PrVO${}_3$ thin films, selectively probing the magnetism of cation sublattices, and uncovering simultaneous V${}^{3+}$ $3d$ spin reorientation and Pr${}^{3+}$ $4f$ magnetization reversal using spectroscopy techniques. By strain engineering, we manipulate the lattice distortions to rationalize their role in coupling $3d$ spins and $4f$ magnetic moments. Theorectical calculations show that octahedral rotations and Jahn-Teller distortions act as tuning mechanisms, promoting competition between orbital and spin orders. The observed coupling between magnetic cations and lattice distortions can be extended to other orthorhombic RMO${}_3$ systems, advancing the understanding of controlling spins in engineered perovskite heterostructures and superlattices.