Exchange bias between ZnCoO and IrMn

High-quality epitaxial Zn[Co.sub.0.07]O films deposited at room temperature were obtained by using reactive ion beam sputtering. Room-temperature ferromagnetic behavior of ZnCoO was observed with a coercivity of 70 Oe. We observed the loop shift at 5 K in the field-cooled samples of ZnCoO/Cu/IrMn and an enhanced coercivity in the zero-field-cooled samples, which indicated the existence of exchange coupling between ZnCoO and IrMn through a thin Cu layer (0.15 nm). Furthermore, the exchange field of ZnCoO was increased from 55 to 113 Oe by increasing the cooling field from 3 to 15 kOe. Index Terms--Dilute magnetic semiconductor (DMS), exchange bias, IrMn, ZnCoO.