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

• We have reported the effect of Fe substitution in the Cr-site of NiCr2O4 on its structural and magnetic properties.
• For the first time, we are reporting the exchange bias behavior and the temperature dependence of exchange bias field in Ni(Cr1−xFex)2O4 with x=0.04.
• The mechanism of exchange bias is explained by considering the anisotropic exchange interaction between the ferrimagnetic and the antiferromagnetic components of magnetic moment.
• The exchange bias field is found to decay exponentially with decrease in temperature.
• For the first time, we have shown that the temperature dependence of coercive field follows a function of the form Hceff (0) [1−(T/Tc′′)2].

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 Fd3¯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.