Tunability of output frequency using Spin Hall Angle in Spin Hall Spin Torque Nano Oscillator

Abstract

We theoretically modelled a couple of Spin Hall Spin Torque Nano Oscillator [SHSTNO] with Current In Plane [CIP] Geometry. In general, the device comprised of bilayer (i.e.) a Ferro magnetic free layer [Co and CoFeB] along with the heavy metal [Pt]. The main motto of the present study is to tune the frequency of the above mentioned devices by altering the Spin Hall Angle [SHA] (θ). The sustained oscillation in the oscillating free layer is studied by the governing Landau-Lifshitz-Gilbert-Slonczewski [LLGS] equation. The devices mainly works under the principle of Spin Hall Effect [SHE], which originates from spin orbit scattering paves for the deflection of conduction electrons with opposite signs oriented in opposite direction. When the spin reaches the free layer due to the Spin Transfer Torque phenomena [STT], persistent oscillation occurs which end up in emitting the microwave frequency. Those are highly tunable with the aid of (θ), which generally varies from 0.1 to 0.9. The author sparks that for maximum frequency tunability, one can easily vary the SHA, (θ) to the maximum with the free layer of minimal thickness paves for the maximum frequency emission by the device. For CoFeB device, at free layer thickness of about 3 nm and the corresponding SHA of about 0.8, the maximum frequency of 67.8 GHz is obtained. The author emphasize that, the results shown here can find the application as spin wave emitters for magnonic applications where the spin waves are used for transmission and processing information on nano scale level.