Evidence of enhanced ferromagnetic nature and hyperfine interaction studies of Ce-Sm doped Co-Ni ferrite nanoparticles for microphone applications

We present the results of the structural, Magnetic and low temperature Mossbauer spectroscopy studies of Co0.5Ni0.5Fe2-(x+y)CexSmyO4 (where x,y = 0.0, 0.01, 0.015 and 0.02) which was prepared by the solution combustion route using mixture of glucose and urea as fuel. The prepared samples were subjected to X-Ray Diffractometer (XRD), Transmission Electron Spectroscopy (TEM), Vibrating Sample Magnetometry (VSM) and Mossbauer Spectroscopy at room temperature and low temperature (15 K) to understand the phase, structure and magnetic behavior of the samples. The results of XRD reveals the formation of a single phase spinel cubic structure with space group Fd (3) over barm. The crystallite sizes are found to be increasing with increasing Ce3+ and Sm3+ content. This is due to the fact that bigger ionic radii of Ce3+ and Sm3+ replace Fe3+ ions at B site. The lattice parameter is found to be increasing with the increasing Ce3+ and Sm3+ content due to increased internal strain upon doping. The TEM micrographs reveals that the particles almost appear as spherical and agglomerated. Magnetic measurements show that all the obtained samples exhibit higher saturation magnetization (M-S), remanence (M-T), coercivity (H-C), anisotropy constant (K) and magneton number (eta(B)). This is due to the increase in A-B super exchange interaction in the samples. Further the increase in H-C with the dopant concentration is interpreted as the enhanced magnetic pinning and ferromagnetic behavior in the samples. The room temperature Mossbauer spectra consist of broadened magnetic sextet and paramagnetic quadrupole-split lines. The presence of the magnetic sextet and doublet component on the Mossbauer spectra indicate the presence of super paramagnetic relaxation with a higher T-B than the room temperature. The obtained results suggest that the rare earth doped Co-Ni ferrites are potential candidates for microphone applications.