Effect of Mg doping on magnetic, and dielectric properties of NiCr2O4 nanoparticles

The structural, magnetic, and dielectric properties of spinel Magnesium (Mg) doped Nickel chromite (NiCr2O4) nanoparticles (NPs) have been studied in detail. The X-ray powder diffraction exhibited normal spinel phase formation of MgxNi(1-x)Cr(2)O(4) (x = 0, 0.2, 0.4, 0.6, and 1) NPs with a maximum average crystallite size of about 44 nm for x = 0.2 composition. The FTIR spectra of these NPs revealed the characteristic Ni-O and Mg-O and Cr-O bands around 639 cm-1 and 497 cm(-1), respectively which confirmed the spinel structure. Temperature dependent zero field cooled and field cooled graphs of NiCr2O4 NPs showed phase changes from ferrimagnetic to paramagnetic state at 86 K, while MgCr2O4 NPs showed antiferromagnetic (AFM) transition at Neel temperature (TN) at 15 K due to corner-sharing of Cr3+ ions at a tetrahedral lattice site resulting in a highly magnetic frustrated structure. The field dependent magnetization (M H) loops of MgxNi(1-x)Cr(2)O(4) NPs confirmed the competing AFM interactions and ferrimagnetic interactions resulting in a sharp decreased saturation magnetization with Mg doping. Dielectric constant, dielectric loss, and ac conductivity of these NPs showed size dependent variation and depicted maximum value at x = 0.2 Mg concentration. In summary, the magnetic and dielectric properties of Mg doped NiCr2O4 NPs were modified by variations in the average crystallite size and magnetic exchange interactions, which may be suitable for different technological applications.