Exchange bias effect in hierarchical NiO/NiFe2O4 sub-microcubes fabricated via a self-sacrifice template process

Abstract

In this study, we report a facile in situ synthesis of hierarchical NiO/NiFe2O4 sub-microcubes by annealing Ni3[Fe(CN)6]2 sub-microcubes fabricated via a one-step solution-precipitation method. The temperature-dependent magnetization curves show that there exists a collective freezing of the moments of interface spin clusters at TB≈296K, which further indicates the appearance a coupling interaction between the ferrimagnetic NiFe2O4 and antiferromagnetic NiO nanoparticles. Furthermore, hysteresis loops measurements reveal the existence of an exchange bias effect in the NiO/NiFe2O4 composite system. Interestingly, no training effect of exchange bias is observed, which indicates that the magnetic pinning interaction between NiFe2O4 and NiO is stable and robust. Exchange bias field shows an exponential dependence on temperature and vanishes at about 150 K, which reveals the strong coupling interaction does not improve effectively the thermal stability of exchange bias effect in the current system.