Strain Mediated Voltage Control of Magnetic Anisotropy and Magnetization Reversal in Bismuth-Substituted Yttrium Iron Garnet Films and Mesostructures

We report on magnetic anisotropy modulation in Bismuth-substituted Yttrium Iron Garnet (Bi-YIG) thin films and mesoscale patterned structures deposited on a PMN-PT substrate with the application of a voltage-induced strain. The Bi content is selected for low coercivity and higher magnetostriction than that of YIG, yielding significant changes in the hysteresis loops through the magnetoelastic effect. The piezoelectric substrate is poled along its thickness, which is the [011] direction, by applying a voltage across the PMN-PT/SiO₂/Bi-YIG/Pt heterostructure. In situ magneto-optical Kerr effect microscopy (MOKE) shows the modulation of magnetic anisotropy with voltage-induced strain. Furthermore, voltage control of the magnetic domain state of the Bi-YIG film at a fixed magnetic field produces 90° switching of the magnetization easy axis above a threshold voltage. The magnetoelectric coefficient of the heterostructure is 1.05 × 10^-7 s m^-1 which is competitive with that of other ferromagnetic oxide films on ferroelectric substrates such as La_0.67Sr_0.33MnO₃/PMN-PT and YIG/PMN-PZT. Voltage control of magnetization reversal fields in 5-30 μm wide dots and racetracks of Bi-YIG show potential for energy-efficient nonvolatile memory and neuromorphic computing devices.