Exchange bias in iron oxide nanoclusters

• Published in: Journal of physics. Condensed matter 2011-11, Vol.23 (47), p.476003-9
• Main Authors: Sánchez-Marcos, Jorge, Ángeles Laguna-Marco, M, Martínez-Morillas, Rocío, Céspedes, Eva, Jiménez-Villacorta, Félix, Menéndez, Nieves, Prieto, Carlos
• Format: Article
• Language: English
• Subjects: Bias; Condensed matter; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Exchange; Ferromagnetism; Iron; Iron oxides; Magnetic properties and materials; Magnetic properties of nanostructures; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Mössbauer effect; other γ-ray spectroscopy; Nanoparticles; Nanostructure; Physics
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/23/47/476003

Iron oxide nanoclusters have been prepared by the gas-phase aggregation technique to form thin film structures with very high exchange bias values (up to 3000 Oe at low temperatures). Composition has been analysed by x-ray absorption and Mössbauer spectroscopies in order to elucidate the actual origin of the observed magnetic behaviour. The formation of a metal-oxide core-shell arrangement to explain the observed exchange bias has to be discarded since results show no metallic iron content and the main presence of α-Fe(2)O(3). The observed weak ferromagnetism and exchange bias are in agreement with the obtained size of α-Fe(2)O(3) nanoparticles: weak ferromagnetism because of the well-known spin canting in this antiferromagnetic structure and exchange bias because of the interaction between different spin sublattice configurations promoted by the modification of iron coordination in α-Fe(2)O(3) nanoparticles. Moreover, the preparation method is proposed for tuning both magnetization and exchange bias values by modification of the preparation conditions of α-Fe(2)O(3) nanoparticles, which open new possibilities in the design of new materials with required properties.