Interparticle interaction and size effect in polymer coated magnetite nanoparticles

TL;DR

This study investigates how particle size and interparticle interactions influence the magnetic properties of polymer-coated magnetite nanoparticles, revealing size-dependent anisotropy and superparamagnetic behavior.

Contribution

It provides new insights into the size and surface effects on magnetization and anisotropy in coated magnetite nanoparticles, combining magnetization and Mossbauer spectroscopy analyses.

Findings

Effective magnetic anisotropy increases as particle size decreases.

Superparamagnetic behavior observed above the blocking temperature.

Hyperfine field temperature dependence mirrors bulk magnetite magnetization.

Abstract

Magnetization and Mossbauer studies have been performed on the polymer coated magnetite nanoparticles with particle size from 5.1 to 14.7 nm. The maximum in the temperature dependence of magnetization (TM) is found to be inconsistent with the particle size (DTEM). The effective magnetic anisotropy (Kan) is found to increase with the decrease of DTEM, which is attributed to the increase of surface anisotropy. The absence of coercivity and remanence of magnetization noticed well above TM indicates the superparamagnetic behaviour, which has also been observed in the temperature dependent Mossbauer results. The temperature dependence of hyperfine field is found to follow similar dependence of saturation magnetization for bulk magnetite.