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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.

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The irreversible thermoremanent magnetization (m irr TRM ) of a sole, magnetically diluted epitaxial antiferromagnetic Co 1−y O(100) layer is determined by the mean of its thermoremanent magnetizations (m TRM ) at positive and negative remanence. During hysteresis-loop field cycling, m irr TRM exhibits successive reductions, consistent with the training effect (TE) of the exchange bias measured for the corresponding Co 1−y O(100)/Co(1120) bilayer. The TE of exchange bias is shown to have its microscopic origin in the TE of m irr TRM of the magnetically diluted AFM.

No abstract