Influence of Superparamagnetism on Exchange Anisotropy at CoO/[Co/Pd] Interfaces.

Magnetic systems exhibiting an exchange bias effect are being considered as materials for applications in data storage devices, sensors, and biomedicine. Because the size of new magnetic devices is being continuously reduced, the influence of thermally induced instabilities in magnetic order has to be taken into account during their fabrication process. In this study, we show the influence of superparamagnetism on the magnetic properties of an exchange-biased [CoO/Co/Pd] multilayer. We find that the process of progressive thermal blocking of the superparamagnetic clusters causes an unusually fast rise of the exchange anisotropy field and coercivity and promotes easy-axis switching to the out-of-plane direction.