Structural, optical, and magnetic properties of NiO/NiFe2O4 nanocomposites

We report the synthesis of NiO/NiFe2O4 nanocomposites following the thermal annealing-assisted simple wet chemical route. XRD and Raman characterizations confirm the existence of both NiO and NiFe2O4 in forming the composite samples. The 2 M Raman mode of NiO in the composite sample is decreased with increasing the annealing temperature from 500 to 600 °C, indicating the suppression of antiferromagnetic (AFM) correlations which could be due to the disorder induced by defects and the presence of distinct NiFe2O4 phase. Morphological features signify the thermal annealing-induced shape transformation along with the reduction in grain agglomeration. Optical characterization indicated that the decrease of Urbach energy upon increasing annealing temperature ascribed to the decrease of structural disorder in the sample. Photoluminescence study revealed the shift of the color emission from near blue to green region with increasing annealing temperature from 500 to 600 °C. The presence of hysteresis with the perseverance of unsaturation nature indicated the occurrence of weak ferromagnetism in the AFM background of NiO matrix. The magnetic analysis employing modified Bloch’s function further supports the nanocomposite system. The persistence of exchange bias field, saturation magnetization, and anisotropy constant at 300 K in both the samples could be an indication for the usefulness of these materials for realizing the thermal stable magnetic device.