Magnetic Phase Transition without Heat Treatment of the as-Deposited Iron Oxide Nanoparticulate Films Prepared by Sparking Process under External Magnetic Fields

Abstract

In this paper, the effect of external magnetic fields on morphology, structural and magnetic properties of the as-deposited iron oxide nanoparticulate (NP) films by the sparking process was investigated. The small and uniform size of iron oxide nanoparticles was deposited on a glass slide substrate by sparking off the iron wires with different external magnetic fields under atmospheric pressure and room temperature. The results showed the roughness and the agglomerated particles of the as-deposited films increased with increasing the external magnetic field due to magnetic and Lorentz forces. The magnetic phase was transformed from maghemite (γ-Fe₂O₃) to magnetite (Fe₃O₄) after sparking under the external magnetic field from 0 mT (without field) to 50 and 100 mT. Moreover, the external magnetic field not only affects the magnetic phase transition but also has a direct effect on the energy band gap and magnetization of the films without heat treatment.

Keywords:

• iron oxide
• sparking process
• magnetic fields
• nanoparticles
• films

Acknowledgements

The authors would like to thank the Development and Promotion of Science and Technology Talents Project (Royal Government of Thailand scholarship) for their support of this work.