Competing magnetic interactions and superparamagnetism like behaviour in xNiFe<inf>2</inf>O<inf>4</inf> - (1-x)BaTiO<inf>3</inf> (x = 0.2 and 0.3) nano composites

We report on structural, spin glass behaviour and competing magnetic interactions in xNiFe2O4 - (1-x)BaTiO3 (x = 0.2 and 0.3) nanocomposites prepared by sol-gel method. The structure and surface morphology of the NiFe2O4-BaTiO3 composites were examined by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD measurements of composite materials show the presence of both NiFe2O4 and BaTiO3 phases. FESEM and energy dispersive X-ray (EDX) measurements indicate uniformly distributed nano size particles and presence of Ni, Fe, O, Ba and Ti elements respectively. Temperature variation Raman spectra indicates large structural disordering (Peak broadening and shift) around 395 K due to the structural transformation of BaTiO3. Magnetization, zero field cooled (ZFC) and field cooled (FC) measurements were carried out from 2 K to 320 K for both composites. ZFC and FC measurements reveal the spin glass and Superparamagnetism like behaviour along with competing magnetic interaction in both composites. Saturation magnetization value is seen to increase from 6.7 to 10 emu/g with increasing Ni ferrite composition from x = 0.2 to x = 0.3. Distribution function associated with magnetocrystalline anisotropy energy barrier exhibits broad peaks due to the random distribution of spins associated with different particle size in the x = 0.3 composition.