Exchange bias effect in a granular system of NiFe2O4 nanoparticles embedded in an antiferromagnetic NiO matrix

Abstract

A granular system composed of ferrimagnetic NiFe2O4 nanoparticles, about 8 nm in size, embedded in an antiferromagnetic NiO matrix has been synthesized by a high-temperature phase precipitation method from Fe-doped NiO matrix. Both the exchange bias field and vertical magnetization shift can be observed in this system below 250 K after field cooling, above which the exchange bias disappears. Furthermore, the exchange bias field shows a linear dependence on the magnetization shift. This observed exchange bias effect is explained in terms of the exchange interaction between the ferrimagnetic phase and the spin-glass-like phase at the interface.