From quasi-two-dimensional metal with ferromagnetic bilayers to Mott insulator with G-type antiferromagnetic order in Ca₃(Ru _1-xTi_x)₂O₇

We report the electronic and magnetic phase diagram of Ca ₃(Ru_1-xTi_x)₂O₇. With Ti doping, the system evolves from a quasi-two-dimensional metal with ferromagnetic (FM) bilayers coupled antiferromagnetically along the c axis (AFM-b) for x=0, to a weakly localized state for 0<x<0.05, and finally to a Mott insulator with G-type antiferromagnetic (G-AFM) order for x≥0.05. The magnetic state switching from the AFM-b to the G-AFM occurs in the weakly localized state near x=0.03. We show that such a magnetic transition is controlled by the charge carrier itinerancy and can be understood in light of competing interactions between FM double exchange and AFM superexchange. An incommensurate component is also observed due to competing magnetic interactions.