Coercivity and exchange bias near the compensation temperature for inhomogeneous Fe/Gd ferrimagnets

We investigate the coercivity and exchange bias effect in Fe/Gd multilayers. Antiferromagnetically coupled (Fe 4 nm/Gd 4 nm)4 multilayer has a compensation temperature (Tcomp) of approximately 90 K. We observe that the coercivity of the inhomogeneous Fe/Gd ferrimagnet makes a local minimum near the Tcomp. When a 16-nm-thick Gd layer is deposited over a (Fe 4 nm/Gd 4 nm)4 multilayer, exchange bias emerges due to the interfacial interaction of the thick Gd overlayer and the Fe surface of the multilayer. Negative and positive exchange bias were observed below and above the Tcomp, respectively. In addition, there is a continuous transition from negative exchange bias to positive exchange bias across the Tcomp where coercivity makes the local minimum.