Nanoconstriction Microscopy of the Giant Magnetoresistance in Cobalt/Copper Spin Valves

TL;DR

This study employs nanoconstriction microscopy on Co/Cu spin valves to analyze the giant magnetoresistance at the nanoscale, revealing device-specific behaviors and current-induced magnetization changes.

Contribution

It introduces a nanometer-scale point contact approach to investigate GMR in individual Co/Cu domains, highlighting the effects of bias current and magnetic field on magnetization.

Findings

GMR varies significantly between devices due to domain effects.

GMR ratio decreases with increasing bias current.

Distinct GMR plateaus depend on bias polarity and magnetic field sweep direction.

Abstract

We use nanometer-sized point contacts to a Co/Cu spin valve to study the giant magnetoresistance (GMR) of only a few Co domains. The measured data show strong device-to-device differences of the GMR curve, which we attribute to the absence of averaging over many domains. The GMR ratio decreases with increasing bias current. For one particular device, this is accompanied by the development of two distinct GMR plateaus, the plateau level depending on bias polarity and sweep direction of the magnetic field. We attribute the observed behavior to current-induced changes of the magnetization, involving spin transfer due to incoherent emission of magnons and self-field effects.