Ionic Liquid Gating Control of Spin Wave Resonance in La_0.7Sr_0.3MnO₃ Thin Film

Magnonics or spin waves have the potential to serve as the carrier for future information communication. A controllable spin wave resonance (SWR) device is demonstrated in a Au/[DEME]⁺[TFSI]⁻/LSMO/STO capacitor heterostructure, which could be regulated by ionic liquid gating (ILG) method. The SWR critical angle φ_C, excitation position to perform uniform precession, is shifted in a reversible manner (thus recording “off” and “on”) with +1.5 V gating voltage (V_g), measured by quantitative angular dependent electron spin resonance (ESR) spectroscopy. Based on the modified Puszkarski's surface inhomogeneity model, the ILG control SWR at low V_g (V_g < 1.5 V) can be explained by a charge-doping-induced effective surface magnetic anisotropy change. Applying a higher V_g (V_g > 1.5 V) enhances the surface mode SWR and gradually diminishes the body mode SWR. Oxygen vacancies generate at higher V_g (V_g > 1.5 V) resulting in the modulation of superexchange between the Mn ions, evidenced by X-ray photoelectron spectroscopy and secondary ion mass spectroscopy characterization. This ILG control SWR presents a solution for energy efficient and low-voltage control of magnonics and spin wave devices.