Size dependent strain and nanomagnetism in CoFe2O4 nanoparticles

The objective of this work is to investigate strain and magnetism at the nano scale in CoFe2O4 nanoparticles. CoFe2O4 nanoparticles of controlled size were synthesized using a chemical co-precipitation method at different reaction temperatures and molar concentrations of reagents without using any surfactant. Size dependent strain, structural, optical, morphological and magnetic properties of CoFe2O4 nanoparticles were investigated. Particle size was calculated by size distribution curve using FESEM images. It was observed that structural orientation and characteristic features of the strain are dependent on CoFe2O4 particle size. The formation of CoFe2O4 nanoparticles was confirmed by XRD, FESEM, Raman and FTIR spectroscopy. The good correlation between XRD analysis and Raman study was observed with the help of Raman shift (cm(-1)) as a function of uniform and non-uniform strain curves for all sizes of CoFe2O4 nanoparticles. The size-dependent superparamagnetic properties of CoFe2O4 nanoparticles were studied systematically. The blocking temperature, coercivity and saturation magnetization increase on increasing the size of the CoFe2O4 nanoparticles was observed. Blocking temperature is a maximum temperature, above which the exchange bias does not occur. The size of the CoFe2O4 nanoparticles estimated from blocking temperature measurements correlated well with FESEM and XRD measurements. These CoFe2O4 nanoparticles have potential applications in gas sensors operating in hazardous environments.