Frequency tunability via spin hall angle through spin hall spin torque nano oscillator

Abstract

The present work deals with the theoretical modeling of Spin Hall Spin Torque Nano Oscillator (SHSTNO) using four different Ferromagnetic Materials (FM) (Py, Co, CoFeB and Ni) with Current In Plane (CIP) geometry. The device comprised of bilayer (Pt/X) (i.e.)a top Ferromagnetic Free Layer (FFL) which is notated as (X) along with the heavy metal (Pt). In this work, we tried to tune the frequency of the device by using different materials in FFLand by altering the Spin Hall Angle (SHA), which is notated as (θ). The sustained oscillation in the FFL is studied by the governing Landau- Lifshitz-Gilbert-Slonczewski (LLGS) equation. The device works under the principle called Spin Hall Effect (SHE) that originates from spin-orbit scattering paves for the deflection of conduction electrons with opposite signs oriented in the opposite direction. When the spin reaches FFL due to the phenomena called Spin Transfer Torque (STT), persistent oscillation occurs, resulting in the emission of frequency in the microwave regime. The SHA (θ) is highly tunable up to 0.8 from 0.1. The author mentions that one can vary (θ) to the maximum and use the low Saturation Magnetization (SM) based material in FFL for maximum frequency tunability. The results presented in the article can find the application as spin- wave emitters for magnonic applications where the spin waves may use for transmission and processing information.