Isothermal low-field tuning of exchange bias in epitaxial Fe∕Cr2O3∕Fe

Moderate dc magnetic fields of less than 1T allow tuning the exchange bias in an epitaxially grown Fe 10nm∕Cr2O3 2.7nm∕Fe 10nm trilayer between negative and positive bias fields. Remarkably, this tunable exchange bias is observed at least up to 395K which exceeds the Néel temperature of bulk Cr2O3 (307K). The presence of spontaneous exchange bias and the absence of training effects at room temperature suggest the existence of stable interface moments independent of antiferromagnetic long range order in Cr2O3. Furthermore, the coercivity remains constant, independent of the exchange bias field. In contrast, large training associated with nonequilibrium spin configurations of antiferromagnetically ordered Cr2O3 appears below 50K.