Size dependent magnetic and magneto-optical properties of Ni0.2Zn0.8Fe2O4 nanoparticles

• Ni0.2Zn0.8Fe2O4 nanoparticles were synthesized by combustion method.
• Structure and magnetic properties are studied.
• Magnetic circular dichroism (MCD) of nickel zinc spinel was measured for the first time.
• The MCD spectrum rearrangement was revealed with the change of the nanoparticles size.

Ni0.2Zn0.8Fe2O4 spinel nanoparticles have been synthesized by combustion method. Average particles size varies from 15.5 to 50.0 nm depending on annealing temperature. Correlations between particles size and magnetic and magneto-optical properties are investigated. Magnetization dependences on temperature and external magnetic field correspond to the sum of paramagnetic and superparamagnetic response. Critical size of single-domain transition is found to be 15.9 nm. Magnetic circular dichroism (MCD) studies of nickel zinc spinel are presented here for the first time. The features in magnetic circular dichroism spectrum are assigned to the one-ion d–d transitions in Fe3+ and Ni2+ ions, as well to the intersublattice and intervalence charge transfer transitions. The MCD spectrum rearrangement was revealed with the change of the nanoparticles size.