via epitaxial strain

Magnetism in strongly correlated ruthenates has been a central topic in condensed matter physics, where the spin degree of freedom is has a strong interplay with lattice, charge and orbital degrees of freedom. For instance, the Mott insulator Ca₂RuO₄ (CRO) can be turned into a ferromagnetic metal under epitaxial strain or hydrostatic pressure. Here, we have grown coherently strained CRO thin films on various substrates including SrLaAlO₄ and YAlO₃ via molecular beam epitaxy and investigated the strain effect on their magnetic properties. We have used angle-resolved magnetoresistance measurements to characterize the ferromagnetic easy axes of these films, and found that they are also drastically different from CRO bulk, and show how the magnetic easy axes can be tuned as a function of epitaxial strain. Our results manifest the complex interplay between the spin, lattice and orbital degree of freedom in CRO, as well as demonstrate a practical approach to tailor the magnetic properties in strongly correlated oxide materials via epitaxial strain, in general.