Magnetically coupled clusters in aggregated maghemite ferrofluid: Mossbauer and magnetization study

Mossbauer spectroscopy in a weak static magnetic field and measurements of isothermal magnetization loops were used to study the effect of polymer coating of the gamma-Fe2O3 nanoparticles on the magnetic properties of concentrated ensembles of such nanoparticles. It was found that the individual coating of the nanoparticles by a similar to 1 nm layer of the polymer leads to the observable changes in the shapes of the M " ossbauer spectra and the magnetization curves of the ensembles. Modeling of the experimental magnetization curves in the classical Langevin model and analysis of the M " ossbauer spectra in the generalized multi-level relaxation model revealed that the establishment of interparticle magnetic dipole interactions leads to both a similar to 30 % increase in the magnetic anisotropy constant and a similar to 35 % increase in the width of the hysteresis loop.