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

Spin-Hall nano-oscillators (SHNOs) are nanoscale spintronic devices that generate high-frequency (GHz) microwave signals for various applications such as neuromorphic computing. Recently our group demonstrated increased microwave power output and lower threshold currents of hybrid permalloy ferromagnetic-metal/ferrimagnetic insulator (FI) SHNOs [1], in which the metal is in the shape of a nanowire and the ferrimagnetic insulator is unpatterned. However, it has not yet been fully understood how the physical parameters of the FI, e.g., its thickness, magnetic anisotropy, Gilbert damping constant, and saturation magnetization, affect SHNO characteristics. Here, we use micromagnetic modeling to explore the relationship between the threshold current and quality factor and material parameters of the FI. We observed only a small effect of FI magnetization on the threshold current but a linear dependence of the threshold current on the FI thickness. We aim to improve the efficiency of the hybrid SHNO by optimization, particularly targeting the increasing the oscillator quality factor and output power.