Low-temperature magnetization behaviors of superparamagnetic MnZn ferrites nanoparticles

Here, we report microstructure and magnetic properties of MnxZn1-xFe2O4 (x = 0–1) nanoparticles synthesized by sol-gel method. From microstructure studies, it is confirmed that all compositions of the present study exhibited a pure cubic spinel ferrite phase with narrow particle size distribution with an average particle size between 13 and 20 nm. From the temperature and magnetic field dependence magnetization data, a superparamagnetic (SPM)-like behavior is seen with a large magnetic moment (~104 μB) in particles. From the analysis of the difference in field-cooled and zero-field-cooled magnetization data, which presented a distribution of blocking temperatures which in turn supported the microstructural data. Further, the analysis of the thermoremanence magnetization data reveals the activation resulting from multiple anisotropy energy barriers due to the size distribution of the particles. The results obtained from the memory effect studies on temperature dependent magnetization in field-cooled and zero-field-cooled protocols confirm the SPM behavior of the particles.