Exchange bias behaviors up to room temperature in NiCo2O4/NiO nanoparticle system

Abstract Exchange bias behaviors up to room temperature have been observed in NiCo2O4/NiO nanoparticle system. The field-cooled magnetic hysteresis loops exhibit shifts both in the field and magnetization axes simultaneously. The variation of exchange bias field and magnetization shift depends strongly on the measuring temperature. In addition, the dependence of exchange bias effect on measuring temperature is not monotonous, which is reflected in the different tendency during the decrease process of magnetization shift and exchange bias field. The exchange bias field is decreased firstly at the range of 10–50 K followed by an increase of 50–200 K and decreased again of 200–320 K. By analyzing various magnetic measurements, the special exchange bias effect in NiCo2O4/NiO can be owing to the spin glass state and the ferrimagnetic/antiferromagnetic coupling during different temperature ranges.