Anomalous magnetoresistance behavior of CoFe nano-oxide spin valves at low temperatures

TL;DR

This study investigates the unusual low-temperature magnetoresistance behavior of CoFe nano-oxide spin valves, extending the Stoner-Wolfarth model to explain the observed anomalies through layered magnetic coupling.

Contribution

It introduces a modified model for specular spin valves with separated sublayers, explaining low-temperature anomalies in magnetoresistance.

Findings

Identification of anomalous bumps in low-temperature magnetoresistance curves.

Extension of the Stoner-Wolfarth model to include nano-oxide layer effects.

Correlation between magnetic coupling ratios and observed magnetoresistance behavior.

Abstract

We report magnetoresistance curves of CoFe nano-oxide specular spin valves of MnIr/CoFe/nano-oxidized CoFe/CoFe/Cu/CoFe/nano-oxidized CoFe/Ta at different temperatures from 300 to 20 K. We extend the Stoner-Wolfarth model of a common spin valve to a specular spin valve, introducing the separation of the pinned layer into two sublayers and their magnetic coupling across the nano-oxide. We study the effect of different coupling/exchange (between the antiferromagnetic layer and the bottom sublayer) field ratios on the magnetization and magnetoresistance, corresponding with the experimentally observed anomalous bumps in low temperature magnetoresistance curves.