Study of exchange bias behavior in Ni(Cr1−xFex)2O4

Single phase samples of Ni(Cr1−xFex)2O4 were prepared by sol–gel method for x=0.0 to 0.1. Structural study at room temperature using X-ray diffraction shows that upon Fe substitution the crystal structure transforms from tetragonal cell with space group I41/amd to cubic cell with Fd 3 ¯ m space group. The ferrimagnetic transition temperature (TC) is found to increase from 73 K for x=0 to 187 K for x=0.1. Presence of large coercivity along with exchange bias phenomenon is observed as per M–H loop measurements. The origin of exchange bias is explained by considering the exchange anisotropy between the ferrimagnetic and the antiferromagnetic components. The temperature dependent behaviors of exchange bias field and the effective coercive field are found to be quite different, while the former one decreases exponentially but the latter one decreases in quadratic form with increase in temperature and both of them approach zero at TC.