Magnetic and Mössbauer study of lanthanum-doped nanosized cobalt ferrite assembly

Nanoparticles of cobalt ferrite are doped with multiple lanthanum (La) amounts up to an unusually high level of doping. They are synthesised using a soft chemical approach. The structural characterisation is conducted using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The crystallite size, micro strain, crystal density, deformation and twin fault probability are found out by Rietveld analysis. Room temperature Mössbauer spectroscopy is performed for determination of spin aberration due to La doping. The values of isomeric shift are obtained in the range of 0.33-0.41 mm/s for different samples as compared to the standard range of 0.32-0.34 mm/s. Large and narrow hysteresis are observed in 5 K and 300 K magnetic measurements, respectively with coercivities in the range 0.2-2 kOe at room temperature. The coercivity is in the range of 0.8-15 kOe at 5 K. The results from magnetic measurement show deviation from standard which is also seen from the inferences from Photoluminescence (PL) which hint at the increased versatility of the ferrite material by doping with rare earth (RE) metals. However, there is an upper limit to this inclusion in the ferrite matrix. As such there is also the existence of wasp-waist hysteresis which is indicative of antiferromagnetic (AFM) to ferromagnetic (FM) interaction but from the Rietveld analysis it is seen that this coupling does not have an undesirable effect on the stability of the nanoferrite.