Thermal effect on magnetic properties of Mg-Zn ferrite nanoparticles

•We report the size dependent magnetic properties of Mg0.5Zn0.5Fe2O4 prepared by solution combustion method.•Saturation magnetization depends on particle size of the samples.•Nanoparticles exhibit superparamagnetism.

Magnesium–zinc ferrite (Mg0.5Zn0.5Fe2O4) powder was prepared by a solution combustion method using a mixture of sugar and urea as fuel. To understand the effect of size and crystallinity on its magnetic properties, combustion derived ferrite powder was subjected to calcination at different temperatures in an ambient atmosphere. The powder X-ray diffraction data of calcined samples was used to determine the effect of calcination on phase formation and crystallite size. The average crystallite size of single phase cubic spinel ferrite nanoparticles was found to increase with an increase in calcination temperature. Transmission electron microscopy images showed a uniform particle size distribution with average particle sizes varying in the range of 30–124 nm. Magnetic properties were found to be affected by particle size; we observed a linear relationship between the saturation magnetization and particle size. Low values of squareness ratio and coercivity implied the superparamagnetic nature of the samples.