Unravelling the effect of interparticle interactions and surface spin canting in gamma-Fe2O3@ SiO2 superparamagnetic nanoparticles

• Type: Article in International Scientific Journal
• Date: 2011

Authors

Andre M Pereira (Author) FCUP; Clara Pereira (Author) FCUP; Ana S Silva (Author) Other; David S Schmool (Author) FCUP; Cristina Freire (Author) FCUP; Jean Marc Greneche (Author) Other; Joao P Araujo (Author) FCUP

Journal

Title: Journal of Applied Physics

Vol. 109

Final page: 114319

ISSN: 0021-8979

Publisher: American Institute of Physics

Indexing

ISI Web of Knowledge - 32 Citations

Scopus - 38 Citations

Scientific classification

FOS: Natural sciences > Physical sciences

Other information

Authenticus ID: P-002-R4Q

DOI: 10.1063/1.3583652

Abstract (EN): The present study investigates the magnetic properties of spherical monodispersed maghemite (gamma-Fe2O3) nanoparticles coated with multiple silica (SiO2) layers of different thicknesses, forming core-shell multifunctional nanomaterials. This study was performed using a combination of local probe techniques (Mossbauer spectrometry) and magnetization measurements. At room temperature, both techniques confirm the superparamagnetic state of the samples, even after being coated with the SiO2 shells. The zero-field-cooling-field-cooling magnetization curves of the silica-coated gamma-Fe2O3 nanomaterials with different shell thicknesses allow the evaluation of the intensity of the interparticle dipole-dipole interactions. We estimate the interparticle energy within the framework of dipolar interaction models and relate it with the hyperfine parameters. We further observe that this dipole-dipole interaction increases the superparamagnetic energy barrier, which largely depends on the interparticle distance. Finally, we consider the effect of spin canting at the surface ("dead layer") of uncoated gamma-Fe2O3 nanoparticles manifested by a layer of similar to 0.5(1) nm. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3583652]

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 5