Electrical Side-Gate Control of Anisotropic Magnetoresistance and Magnetic Anisotropy in a Composite Multiferroic

Composite multiferroics consisting of a ferroelectric material interfaced with a ferromagnetic material can function above room temperature and exhibit improved magnetoelectric (ME) coupling compared to single-phase multiferroic materials, making them desirable for applications in energy efficient electronic devices. In this study, we demonstrate electrical side-gate control of magnetoresistance and magnetic anisotropy in single-crystalline ferromagnetic Fe$_{0.75}$Co$_{0.25}$ thin films grown on ferroelectric PMN-PT (001) substrates by molecular beam epitaxy. Fe$_{0.75}$Co$_{0.25}$ is selected due to its large magnetoelastic coupling and low magnetic damping. We find that the magnetoresistance curves of patterned Fe$_{0.75}$Co$_{0.25}$ films are controlled by voltages applied to electrostatic side gates. Angle-dependent magnetoresistance scans reveal that the origin of this effect is strain-mediated variation of the magnetic anisotropy due to piezoelectric effects in the PMN-PT. This electrical control of magnetic properties could serve as a building block for future magnetoelectronic and magnonic devices.