title: Effect of composition and coating on the interparticle interactions and magnetic hardness of MFe2O4(M = Fe, Co, Zn) nanoparticles.
abstract: Single domain superparamagnetic ferrite nanoparticles with the composition MFe2O4(M = Fe, Co, Zn) have been prepared by thermal decomposition of metal acetylacetonates in diphenyl ether or dibenzyl ether, using oleic acid in the presence of oleylamine as a stabilizing agent. The Fe, Co and Zn ferrite nanoparticles are monodisperse with diameters of 4.9, 4.4 and 4.7 nm, respectively. The TG and IR results indicate that four or six carboxylate groups per nm2are bonded at the surface of the particles acting as chelating and/or bridging bidentate ligands depending on the composition. The oleate groups minimize the interparticle interactions in Fe and Zn ferrite samples, while in the Co ferrite sample dipolar interactions produce broad maxima in the ZFC and energy barriers distribution curves. The inversion degree has been estimated from the Raman spectra and the obtained x values have been used to calculate the saturation magnetization and compare them with the experimental MSvalues. Compared to bulk materials, the magnetization value is higher for the Zn ferrite sample due to its mixed spinel cation distribution. For the Co ferrite sample, and probably for the Fe one, the low value of saturation magnetization seems to be due to the surface disordered layer of canted spins. Compared to non-coated nanoparticles with the same composition and similar size, the oleate groups, covalently bonded to the superficial cations, increase the anisotropy field and decrease the magnetization.
authors.affiliation: Departamento Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain. torralvo@ucm.es.
authors.forename: M
authors.initials: M
authors.lastname: Virumbrales-Del Olmo
authors.affiliation: Departamento Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain. torralvo@ucm.es.
authors.forename: A
authors.initials: A
authors.lastname: Delgado-Cabello
authors.affiliation: MALTA-Consolider Team, Departamento de Química-Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain.
authors.forename: A
authors.identifier: http://orcid.org/0000-0003-4504-3197
authors.initials: A
authors.lastname: Andrada-Chacón
authors.affiliation: MALTA-Consolider Team, Departamento de Química-Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain.
authors.forename: J
authors.identifier: http://orcid.org/0000-0002-3108-6594
authors.initials: J
authors.lastname: Sánchez-Benítez
authors.affiliation: Departamento Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain. torralvo@ucm.es.
authors.forename: E
authors.initials: E
authors.lastname: Urones-Garrote
authors.affiliation: Departamento Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain. torralvo@ucm.es.
authors.forename: V
authors.initials: V
authors.lastname: Blanco-Gutiérrez
authors.affiliation: Departamento Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain. torralvo@ucm.es.
authors.forename: M J
authors.initials: MJ
authors.lastname: Torralvo
authors.affiliation: Departamento Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain. torralvo@ucm.es.
authors.forename: R
authors.initials: R
authors.lastname: Sáez-Puche