Terahertz Spin Transfer Torque Oscillator Based on a Synthetic Antiferromagnet

TL;DR

This paper predicts the possibility of terahertz frequency oscillations in a synthetic antiferromagnet spin-transfer torque oscillator without external magnetic fields, using simulations based on the Bloch-Bloembergen-Slonczewski equation.

Contribution

It introduces a novel theoretical model for high-frequency THz oscillations in synthetic antiferromagnet-based spin-transfer torque oscillators, highlighting key material and structural conditions.

Findings

High frequency up to the terahertz scale predicted

Stable oscillations depend on strong antiferromagnetic coupling

Oscillation frequency influenced by layer thickness and relaxation times

Abstract

Bloch-Bloembergen-Slonczewski equation is adopted to simulate magnetization dynamics in spin-valve based spin-transfer torque oscillator with synthetic antiferromagnet acting as a free magnetic layer. High frequency up to the terahertz scale is predicted in synthetic antiferromagnet spin-transfer torque oscillator with no external magnetic field if the following requirements are fulfilled: antiferromagnetic coupling between synthetic antiferromagnetic layers is sufficiently strong, and the thickness of top (bottom) layer of synthetic antiferromagnet is sufficiently thick (thin) to achieve a wide current density window for the high oscillation frequency. Additionally, the transverse relaxation time of the free magnetic layer should be sufficiently larger compared with the longitudinal relaxation time. Otherwise, stable oscillation cannot be sustained or scenarios similar to regular spin valve-based spin-transfer torque oscillator with relatively low frequency will occur. Our calculations pave a new way for exploring THz spintronics devices.