Magnetic Properties of Cluster Glassy Ni/NiO Core-Shell Nanoparticles: an Investigation of Their Static and Dynamic Magnetization.

We review the phenomenology of the exchange bias and its related effects in core-shell nanocrystals. The static and dynamic properties of the magnetization for ferromagnetic Ni-core and antiferromagnetic NiO-shell cluster glassy nanoparticles are examined, along with the pinning-depinning process, through the measurement of the conventional exchange bias, and associated with different cooling fields and particle sizes. Two significant indexes for the dipolar interaction n and multi-anisotropic barrier β derived from the dynamic magnetization are proposed, which provide a unified picture of the exchange bias mechanism and insight into the influence of the cooling field.