Role of interparticle interactions on the magnetic behavior ofMg0.95Mn0.05Fe2O4 ferrite nanoparticles

Abstract

We present here a detailed investigation of the static and dynamic magnetic behavior of aMg0.95Mn0.05Fe2O4 spinel ferrite nanoparticle system synthesized by high-energy ball milling of almostidentical particle size distributions (, 5.1 and 6.0 ± 0.6 nm). The samples were characterized by using x-ray diffraction,Mössbauer spectroscopy, dc magnetization and frequency dependent realχ′(T) andimaginary χ′′(T) parts of ac susceptibility measurements. The zero-field-cooled (ZFC) andfield-cooled (FC) magnetization have been recorded in a low field and showa behavior typical of superparamagnetic particles above a temperature of185 ± 5 K, which is further supported from the temperature dependent Mössbauer measurements.The fact that the blocking temperature calculated from the ZFC magnetization andMössbauer data are almost similar gives a clear indication of the interparticleinteractions among these nanoparticle systems. This is further supported from the FCmagnetization curves, which are almost flat below a certain temperature (lessthan the blocking temperature), as compared with the monotonically increasingbehavior characteristics of non-interacting superparamagnetic particles. A shiftof the blocking temperature with increasing frequency was observed in the realχ′(T) andimaginary χ′′(T) parts of the ac susceptibility measurements. The analysis of the results shows that the datafit well with the Vogel–Fulcher law, whereas trials using the Neel–Brown and power law areunproductive. The role of magnetic interparticle interactions on the magnetic behavior,namely superparamagnetic relaxation time and magnetic anisotropy, are discussed.