Asymmetric Magnetization Reversal in a Single Exchange-Biased Micro Bar

TL;DR

This study investigates the asymmetric magnetization reversal in a single exchange-biased microbar using anisotropic magnetoresistance and magnetic force microscopy, revealing a repeatable rotation and nucleation process influenced by unidirectional anisotropy.

Contribution

It provides detailed insights into the asymmetric reversal mechanism in a single exchange-biased microstructure, combining magnetoresistance and microscopy techniques.

Findings

Asymmetric hysteresis loop with repeatable rotation and nucleation.

Unidirectional anisotropy enhances rotation in one hysteresis branch.

Ferromagnetic domain patterns are imprinted after nucleation.

Abstract

The asymmetric magnetization reversal is studied in a single exchange-biased microbar of 1.5 x 13 micrometer with anisotropic magnetoresistance and magnetic force microscopy. The particle has a moment of less than 10^-9 emu and is not accessible with standard magnetometry. The asymmetric hysteresis loop of CoFe/CrMnPt shows a repeatable rotation process, followed by an irreversible nucleation process that is marked by jumps in the magnetoresistance. The induced unidirectional anisotropy enhances the rotation process in one branch of the hysteresis loop, followed by a sped up nucleation process. Imprinted ferromagnetic domain patterns left behind by the antiferromagnet are observed after the nucleation process occurred but before complete saturation is reached.