Diluted antiferromagnets in exchange bias: Proof of the domain state model

The exchange bias coupling at ferromagnetic/antiferromagnetic interfaces in epitaxially grown Co/CoO layers can intentionally be increased by a factor of up to 3 if the antiferromagnetic CoO layer is diluted by nonmagnetic de fects in its volume part away from the interface. Monte Carlo simulations o f a simple model of a ferromagnetic layer on a diluted antiferromagnet show exchange bias and explain qualitatively its dilution and temperature depen dence. These investigations reveal that diluting the antiferromagnet leads to the formation of volume domains, which cause and control exchange bins.