Optical properties and photoinduced superparamagnetism of γ-Fe<inf>2</inf>O<inf>3</inf> nanoparticles formed in dendrimer

Abstract

© 2014 Elsevier Ltd. All rights reserved. We are presenting the joint investigation of the optical and photoinduced superparamagnetic properties of a single-domain γ-Fe<inf>2</inf>O<inf>3</inf> nanoparticles (NPs) formed in poly(propylene imine) (PPI)-dendrimer. The optical absorption studies indicated direct allowed transition with the band gap (4.5 eV), which is blue-shift with respect to the value of the bulk material. The influence of pulsed laser irradiation on the superparamagnetic properties of γ-Fe<inf>2</inf>O<inf>3</inf> NPs was studied by Electron paramagnetic resonance (EPR) spectroscopy. It has been shown that irradiation of the sample in vacuo and cooled in zero magnetic field to 6.9 K leads to the appearance of a new EPR signal, which decays immediately after the irradiation is stopped. We suppose that the generation of conduction band electrons by irradiation into the band gap of the γ-Fe<inf>2</inf>O<inf>3</inf> changes the superparamagnetic properties of NPs.