Positive Exchange Bias in Tb/Cr Bilayers with TC < TN
The exchange bias phenomena in Tb/Cr films, where the Curie temperature (TC) of ferromagnetic Tb is much less than the Néel temperature (TN) of antiferromagnetic Cr, are systematically investigated. For the Tb/Cr bilayers, the exchange bias field HE changes from negative to positive as the temperature goes up. The unusual behavior of HE(T) is due to the spin-density waves spin structure in the Cr layer. For the Tb/Cr/Tb/Cr film, however, HE is negative throughout the temperature range in our experiment and its absolute value decreases monotonously with the temperature, which is ascribed to the coexistence of the interlayer coupling between Tb layers and the interfacial exchange coupling between Tb and Cr layers.
Z. W. Jiao et al., "Positive Exchange Bias in Tb/Cr Bilayers with TC < TN", Advanced Materials Research, Vols. 179-180, pp. 836-840, 2011