Field induced magnetic properties of Ni doped CoCr2O4

Ni doped CoCr2O4, (Co1–xNix)Cr2O4 with x=0.5 and 0.25, nanoparticles were synthesized through sol-gel technique. The as synthesized samples were calcined at 600 °C for 1h. The phase identification of the samples was carried out using X-ray diffraction (XRD) techniques. The Davg for (Co0.5Ni0.5)Cr2O4 and (Co0.75Ni0.25)Cr2O4 were found to be 33 (1) nm and 22 (1) nm, respectively, from the transmission electron microscopy (TEM). Magnetic properties of the nanoparticles were measured down to 2 K using a vibrating sample magnetometer (VSM). Magnetization as a function of temperature measured under 0.1, 0.5 and 1 T applied magnetic field show a hump like feature at the peak temperature, Tp, similar to the superparamagnetic blocking feature observed in many nanoparticle systems. With increasing applied magnetic field the Tp shifts towards lower temperature. Magnetization as a function of applied magnetic field (μ0H= 0.1 T) showed an exchange bias like feature for x= 0.5, whereas no shifting of the loop was observed for x=0.25 sample. The transition related to spiral ordering at temperature TS was observed for both the samples, whereas no lock-in transition at temperature TL was noticed.