title: Exchange bias in iron oxide nanoclusters.
abstract: 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.
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, E-28049 Madrid, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Sánchez-Marcos
authors.forename: M
authors.initials: M
authors.lastname: Angeles Laguna-Marco
authors.forename: Rocío
authors.initials: R
authors.lastname: Martínez-Morillas
authors.forename: Eva
authors.initials: E
authors.lastname: Céspedes
authors.forename: Félix
authors.initials: F
authors.lastname: Jiménez-Villacorta
authors.forename: Nieves
authors.initials: N
authors.lastname: Menéndez
authors.forename: Carlos
authors.initials: C
authors.lastname: Prieto