Tailoring the electronic properties of Ca${}_2$RuO${}_4$ via epitaxial strain

We report the synthesis of Ca${}_2$RuO${}_4$ thin films on NdCaAlO${}_4$ (110), LaAlO${}_3$ (100) and LaSrAlO${}_4$ (001) substrates and show that epitaxial strain induces a transition from the Mott-insulating phase of bulk Ca${}_2$RuO${}_4$ into a metallic phase. Magnetometry and spin-polarized neutron reflectometry reveal a low-temperature, small-moment ferromagnetic state in metallic Ca${}_2$RuO${}_4$ films.