Detecting domain wall trapping and motion at a constriction in narrow ferromagnetic wires using perpendicular-current giant magnetoresistance

TL;DR

This paper introduces a method using perpendicular-current giant magnetoresistance to detect and analyze the trapping and movement of domain walls in narrow ferromagnetic wires, enhancing sensitivity to small domain wall motions.

Contribution

The study demonstrates a versatile CPP-MR technique for detecting domain wall trapping and motion, with detailed analysis of different notch shapes at various temperatures.

Findings

CPP-MR response is enhanced for small domain wall motions.

Notch shape influences domain wall trapping behavior.

Method effective at both cryogenic and room temperatures.

Abstract

We present a versatile method for detecting the presence and motion of a trapped domain wall in a narrow ferromagnetic layer using current-perpendicular-to-plane (CPP) giant magnetoresistance (MR). The CPP-MR response to small motions of the trapped domain wall is enhanced because the CPP current is restricted to the region of wall trapping. We use a Permalloy/Cu/Permalloy spin valve in the shape of a long, ~500-nm-wide wire with a constriction (notch) near its middle that acts as a trapping site for a head-to-head domain wall. Two different notch shapes were studied, mostly at 4.2 K but also at 295K.