Spin-Torque Ferromagnetic Resonance Investigation of a single La_0.7Sr_0.3MnO₃ layer

La_0.7Sr_0.3MnO₃ (LSMO) is a perovskite oxide material with a paramagnetic insulator to ferromagnetic metal phase transition at a temperature of Tc=350K. Recently, voltage bias in microstructured thin film samples has driven this transition and the formation of a transverse insulating barrier [1]. Here, we report spin-torque ferromagnetic resonance (ST-FMR) studies of this voltage-driven transition. First, we measured magnetic characteristics (M_eff, H_a, and damping) as a function of temperature from 100 to 300K at zero bias. Then, we used ST-FMR to determine magnetic properties as a function of voltage bias. The resonance field increases with bias voltage, with a linear change in linewidth up to 10V, followed by a dramatic linewidth increase, and, at the metal- insulator transition threshold voltage, the resonant signal disappears. The correspondence between the temperature and bias results indicates that applied voltage heats the LSMO, driving the phase transition and separation. These voltage- induced dramatic changes in electrical and magnetic characteristics are of interest for neuromorphic computing.