Exchange bias and supermagnetism in CoO/Co/Pd multilayer

What is it about?

In this paper we show the relation between exchange bias effect and superparamagnetism in case of CoO/Co/Pd multilayer system. We have found that the decrease of the ferromagnet thickness below the limit for continuous layer formation results in creation of superparamagnetic clusters. These clusters are being progressively blocked and exchange coupled to antiferromagnetic CoO grains as temperature drops down. This results in a unusual dependence of the exchange anisotropy field on temperature and provides very large exchange bias field up to 6 kOe. This progressive blocking of the ferromagnetic clusters also affect the orientation of the easy axis of magnetization.

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Why is it important?

Materials exhibiting exchange bias effect could be applied in a variety of devices i.e. in hard drives and sensors, or in biomedicine as drug carriers. The electronic industry requires a constant miniaturization of devices. Thus, the research on magnetic effects like superparamagnetism can play a crucial role in development of new materials and solutions for industrial applications.