Enhanced magnetism, memory and aging in Gold-Iron oxide nanoparticle composites

TL;DR

This study systematically investigates how gold nanoparticles influence the magnetic properties of iron oxide nanocomposites, revealing enhanced magnetization, aging, and memory effects, and a transition from superparamagnetic to superspin glass behavior.

Contribution

It demonstrates that incorporating gold nanoparticles enhances magnetization and magnetic memory effects in iron oxide nanocomposites, with detailed analysis of aging and exchange bias phenomena.

Findings

Magnetization increases with gold content.

Transition from superparamagnetic to superspin glass state.

Enhanced aging and memory effects with larger gold nanoparticles.

Abstract

In this report we present systematic magnetic studies of pure iron oxide nanoparticles and gold iron oxide nanocomposite with increasing Au particle size/content. For the magnetic studies of these samples we have measured: (1) zero field cooled (ZFC) and field cooled (FC) magnetization, (2) ac susceptibility, (3) magnetization vs field at various temperatures, (4) thermoremanant magnetization relaxation (TRM) and zero field cooled magnetization relaxation (ZFCM) at fixed temperature for various wait times tw for studying the aging effect, (5) magnetization memory effect and (6) exchange bias as a function of cooling field. The detailed magnetic measurement analysis indicates that the pure Fe3O4 nanoparticles sample behaves like a superparamagnet and on incorporation of gold (Au) nanoparticles the nanocomposite system slowly evolves from superparamagnetic to superspin glass state. The memory and aging effect enhances with the increase of the Au nanoparticle size/content. The most important observation in this study is the enhancement of magnetization with the incorporation of Au nanoparticles. The enhancement increases with the increase in the Au content in the nanocomposite. We have explained the cause of this enhancement of magnetization as due to large orbital magnetic moment formation at the Au/magnetic particle interface.