Optimizing Hybrid Ferromagnetic Metal-Ferrimagnetic Insulator Spin-Hall Nano-Oscillators: A Micromagnetic Study

Abstract

Spin-Hall nano-oscillators (SHNO) are nanoscale spintronic devices that generate high-frequency (GHz) microwave signals useful for various applications such as neuromorphic computing and creating Ising systems. Recent research demonstrated that hybrid SHNOs consisting of a ferromagnetic metal (permalloy) and lithium aluminum ferrite (LAFO), a ferrimagnetic insulator, thin films have advantages in having lower auto-oscillation threshold currents ($I_{\text{th}}$) and generating larger microwave output power, making this hybrid structure an attractive candidate for spintronic applications. It is essential to understand how the tunable material properties of LAFO, e.g., its thickness, perpendicular magnetic anisotropy ($K_u$), and saturation magnetization ($M_s$), affect magnetic dynamics in hybrid SHNOs. We investigate the change in $I_{\text{th}}$ and the output power of the device as the LAFO parameters vary. We find the $I_{\text{th}}$ does not depend strongly on these parameters, but the output power has a highly nonlinear dependence on $M_s$ and $K_u$. We further investigate the nature of the excited spin-wave modes as a function of $K_u$ and determine a critical value of $K_u$ above which propagating spin-waves are excited. Our simulation results provide a roadmap for designing hybrid SHNOs to achieve targeted spin excitation characteristics.

References in corpus (5)

• Spin-orbit-torque magnonics
• Easy-plane spin Hall nano-oscillators as spiking neurons for neuromorphic computing
• Theory of the Magnon Parametron
• Hybrid spin Hall nano-oscillators based on ferromagnetic metal/ferrimagnetic insulator heterostructures
• Spin wave excitations in a nanowire spin-torque oscillator with perpendicular magnetic anisotropy