Dynamics of a trapped domain wall in a current perpendicular to the plane spin valve nano-structure

TL;DR

This paper investigates the behavior of transverse domain walls in current-perpendicular spin valves, showing how their motion influences noise and can be controlled by external fields or spin torque, with implications for low-power magnetic devices.

Contribution

It demonstrates control of domain wall motion in CPP spin valves using spin torque and external fields, and analyzes associated noise characteristics, advancing low-power magnetic device design.

Findings

Domain wall motion causes low frequency noise in larger devices.

External fields and spin torque can control domain walls in devices comparable to their width.

Spin torque induces 1/f noise in single domain biased spin valves.

Abstract

A study of transverse tail-to-tail magnetic domain walls (DW) in novel current perpendicular to the plane (CPP) spin valves (SV) of various dimensions is presented. For films with dimensions larger than the DW width, we find that DW motion can give rise to a substantial low frequency noise. For dimensions comparable to the DW width, we show that the DW can be controlled by an external field or by a spin momentum torque as opposed to the case of CPP-SV with uniform magnetization. It is shown that in a single domain biased CPP-SV, the spin torque can give rise to 1/f-type noise. The dipolar field, the spin torque and the Oersted field are all accounted for in this work. Our proposed SV requires low current densities to move DW and can simulate devices for logical operation or magnetic sensing without having to switch the magnetization in the free layer.