Role of structural defects on exchange bias in the epitaxial CoO/Co system

TL;DR

This study investigates how different types of structural defects in the antiferromagnetic layer Co_{1-y}O influence the exchange bias in epitaxial Co_{1-y}O/Co bilayers, highlighting the dominant role of twin boundaries.

Contribution

It demonstrates that twin boundaries significantly enhance exchange bias, while surface roughness and crystal orientation have minimal effects, advancing understanding of defect roles in exchange bias.

Findings

Twin boundaries increase exchange bias more than surface roughness.

Surface morphology has a lesser impact on exchange bias.

Crystal orientation does not significantly affect exchange bias.

Abstract

We have studied the influence of non-magnetic defects throughout the antiferromagnet Co_{1-y}O on the exchange bias (EB) in epitaxially grown Co_{1-y}O/Co bilayers. These defects are either substitutional or structural (twin boundaries and surface morphology) which both lead to an increase of the EB-field. We find a dominance of twin boundaries over surface morphology (roughness) in enhancing EB which is consistent with the domain state model for exchange bias. In contrast, the crystal orientation of the Co_{1-y}O layer does not show a significant effect on the EB in this system.