Long-range oscillatory exchange interaction between antiferromagnetic FeMn layers across a Cu spacer

The exchange interaction between antiferromagnetic FeMn layers across a Cu spacer is studied by employing the exchange bias as a probe in multilayers of "NiFe/thin FeMn/Cu/thick FeMn." With variation of the Cu spacer's thickness, the indirect exchange interaction, monitored through the response of the exchange bias, oscillates with a period of approximately 18-20 Angstrom, about twice that for ferromagnetic films separated by a Cu spacer. This result shows that long-range oscillatory exchange interaction is a basic and universal feature in both metallic ferromagnetic layers separated by nonmagnetic metals and metallic antiferromagnetic layers separated by a nonmagnetic metal, due to the quantum interferences induced by the spin-dependent interface reflection of Bloch waves with different oscillating periods originating from the difference in interface reflection conditions between ferromagnetic and antiferromagnetic spin ordering.