Tailoring the electronic properties of Ca2RuO4 via epitaxial strain

We establish strain engineering of ruthenium oxides as a method to controllably induce phase transitions between electronic ground states with vastly different electrical and magnetic properties. Specifically, we show that the epitaxial strain acting on Ca2RuO4 thin films on NdCaAlO4 (110), LaAlO3 (100), and LaSrAlO4 (001) substrates induces a transition from the Mott-insulating phase of bulk Ca2RuO4 into a metallic phase. Magnetometry and spin-polarized neutron reflectometry reveal a low-temperature, small-moment ferromagnetic state in Ca2RuO4 films on LaAlO3 (100) and LaSrAlO4(001). Thin-film structures may open up new ways to investigate and utilize the electronic response of ruthenates to lattice modification.