Effect of Dy-substitution on structural and magnetic properties of Mn[sbnd]Zn ferrite nanoparticles

Abstract

This paper describes the structural and magnetic properties of Dy-substituted MnZn ferrite nanoparticles. MnZnDy ferrite nanoparticles of the composition Mn0.5Zn0.5DyxFe2-xO4 (x=0.05, 0.1, 0.15 and 0.2) were synthesized by a facile chemical co-precipitation method. The samples were characterized through X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) and Curie temperature. The XRD patterns confirm the synthesis of single crystalline phase of MnZnDy ferrite nanoparticles. Lattice parameter increases with increase in Dy-substitution which confirms the replacement of Fe3+ ions by Dy3+ ions. Crystallite size is of the order of 6–8 nm for all these samples. The particle sizes observed from TEM analysis are in good agreement with the XRD values. The magnetic measurements show superparamagnetic nature of the samples. The saturation magnetization decreases with increase in Dy-concentration and can be correlated to modifications in the A-B exchange interactions as a result of the structural modifications due to Dy-substitution. The Curie temperature for Mn0.5Zn0.5Fe2O4 nanoparticles is 124 °C and decreases up to 84 °C with the increase in the Dy-concentration. The decrease in Curie temperature can be attributed to the weakening of the superexchange interaction between A-site and B-site as a result of Dy-substitution. The low value of Curie temperature and higher value of thermomagnetic coefficient kT shown by these samples makes them suitable for the preparation of temperature sensitive ferrofluid for heat transfer applications.