Study of Spin Hall Nano-Oscillators using COMSOL and OOMMF Simulations.

Abstract

Spin Hall nano-oscillators (SHNOs) are emerging energy efficient spintronic de vices that can be employed for microwave signal generation, spin-wave computing, and oscillator-based neuromorphic computing. thanks to their nanoscale footprint, flexible device geometry, CMOS- compatibility, and highly nonlinear properties en abling mutual synchronization in linear chains and large networks. In SHNOs, the spin Hall e↵ect (SHE) phenomenon, which converts lateral in-plane charge current into a transverse spin current in the nonmagnetic heavy metal, drives the magnetiza tion oscillations in the adjacent ferromagnetic layer via the transfer of spin angular momentum. In this thesis, we make use of simulation methods to study the mag netodynamics of SHNOs. Using COMSOL Multiphysics software, we first design and construct the nano-constriction NiFe (Py)/Pt-based SHNO geometry and simulate the critical parameters such as electrical current density and Oersted (Oe) field profiles in the active nano-constriction region. We further study the e↵ect of dc currents and con striction widths on the current density and Oe field profiles in SHNOs. The simulated data from COMSOL serves as an input to Object Oriented Micromagnetic Framework (OOMMF) software to excite auto oscillations in SHNOs. The excited auto-oscillating mode is strongly localized in the constriction region and tunable with both current and applied magnetic field. The obtained simulation results reproduce the experimen tal results and shed light on how di↵erent magneto-dynamical parameters influence the auto-oscillation behavior in SHNOs. The findings of the present simulation study o↵er a promising path to design and optimize SHNO-based devices and potentially be expanded to investigate other complicated magnetic systems.