Enhancing Exchange Bias with Diluted Antiferromagnets

The exchange bias H_E of coupled polycrystalline films of antiferromagnetic CoO and ferromagnetic Co was significantly enhanced by the systematic substitution of nonmagnetic Mg for Co in CoO. Samples in which either Co or Co_1-xMg_xO were deposited first were investigated at temperatures from 10 to 300 K. With Co_1-xMg_xO on the bottom, the increased interfacial uncompensated spin density of the single antiferromagnetic domain Co_1-xMg_xO crystallites produced the enhanced H_E. With Co on the bottom, a thin interfacial oxide layer was primarily responsible for the strongly increased H_E.