MICROMAGNETIC STUDY OF SPIN HALL NANO-OSCILLATORS IN SMALL IN-PLANE FIELDS

Abstract

Spin Hall nano-oscillators (SHNOs) are nanoscopic, highly tunable, and ultra-fast microwave signal generators. Recently, nano-constriction-based SHNOs have drawn much attention thanks to their CMOS compatibility, easier nano-fabrication, and promising applications in neuromorphic computing and nanomagnonics. This study delves into the micromagnetic modeling of nano-constriction based SHNOs to control their magnetization dynamics in applied in-plane fields. The spin-wave dynamics of SHNOs are examined under distinct magnetodynamical parameters, such as e↵ective magnetization and applied in-plane fields. By altering the applied in-plane fields, it is observed that the threshold current decreases monotonically, whereas the onset frequency increases. Similarly, when studying the variation of saturation magnetization, the threshold current and onset frequency increase with increasing saturation magnetization. The micromagnetically simulated spatial profiles at the constriction region confirm qualitatively similar auto-oscillation behavior under di↵erent in-plane fields and saturation magnetization values. We observed two distinct auto-oscillation modes: (i) a ”linear-like” mode near the constriction edges at low threshold current values and (ii) a second, lowerfrequency ”bullet” mode with a large threshold current strongly dependent on both the applied-in-plane fields and the saturation magnetization values. At a specific applied inplane field, both ”linear-like” and ”bullet” modes overlap, possibly due to mode hopping. The strongly tunable auto-oscillation properties demonstrated in our study reveal the versatility of nano-constriction-based SHNOs for low-field microwave signal generation and neuromorphic computing applications.