Crystal Structure and Magnetic Properties of Mn-Doped Zn-Ferrite Nanoparticles

The Mn_xZn_1-xFe₂O₄ nanoparticles with (x = 0, 0.25) , and 0.5 were synthesized by a chemical coprecipitation method. The X-ray diffraction (XRD) patterns were well fitted with single-phase spinel ferrite structure using Rietveld analysis as Fd^-3 m space group. The average crystallite size of the nanoparticles estimated from XRD data analysis varies between 4 and 7 nm. The Mössbauer spectra of the nanoparticles at room temperature were fitted with a well-defined single quadrupole splitting for doublet pattern. The magnetization versus magnetic field data at 5 K show hysteresis loops indicating ferromagnetic (FM) cluster behavior. The superparamagnetic nature of the samples is evident. The temperature-dependent magnetization plots in zero field cooled and field cooled mode show increase in blocking temperature from 31 to 115 K with increase in Mn content from 0 to 0.5. The FM resonance (FMR) spectra indicate slight decrease in FM interactions as x increases from 0 to 0.25 followed by a significant increase with further increase in x value to 0.5. The decrease in resonance field ((H_r) and increase in peak-to-peak linewidth ΔH_PP of the FMR line with decreasing temperature indicates weak antiferromagnetic coupling between the octahedral and tetrahedral sublattices of the spinel ferrite. The replacement of Zn by 50% Mn in Zn-ferrite results in an increase in FM interactions with no significant change in the crystallite size.