title: Fe-Doping-Induced Magnetism in Nano-Hydroxyapatites.
abstract: Doping of biocompatible nanomaterials with magnetic phases is currently one of the most promising strategies for the development of advanced magnetic biomaterials. However, especially in the case of iron-doped magnetic hydroxyapatites, it is not clear if the magnetic features come merely from the magnetic phases/ions used as dopants or from complex mechanisms involving interactions at the nanoscale. Here, we report an extensive chemical-physical and magnetic investigation of three hydroxyapatite nanocrystals doped with different iron species and containing small or no amounts of maghemite as a secondary phase. The association of several investigation techniques such as X-ray absorption spectroscopy, Mössbauer, magnetometry, and TEM allowed us to determine that the unusual magnetic properties of Fe2+/3+-doped hydroxyapatites (FeHA) occur by a synergy of two different phenomena: i.e., (i) interacting superparamagnetism due to the interplay between iron-doped apatite and iron oxide nanoparticles as well as to the occurrence of dipolar interactions and (ii) interacting paramagnetism due to Fe3+ions present in the superficial hydrated layer of the apatite nanophase and, to a lesser extent, paramagnetism due to isolated Fe3+ions in the apatite lattice. We also show that a major player in the activation of the above phenomena is the oxidation of Fe2+into Fe3+, as induced by the synthesis process, and their consequent specific positioning in the FeHA structure.
authors.affiliation: CNR-SPIN and Department of Physics "E. Pancini", University of Naples "Federico II" , Piazzale V. Tecchio 80, I-80125 Napoli, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Iannotti
authors.affiliation: Institute of Science and Technology for Ceramics (ISTEC), National Research Council (CNR) , Via Granarolo 64, 48018 Faenza, Italy.
authors.forename: Alessio
authors.identifier: http://orcid.org/0000-0002-2077-0411
authors.initials: A
authors.lastname: Adamiano
authors.affiliation: CNR-SPIN and Department of Physics "E. Pancini", University of Naples "Federico II" , Piazzale V. Tecchio 80, I-80125 Napoli, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Ausanio
authors.affiliation: CNR-SPIN and Department of Physics "E. Pancini", University of Naples "Federico II" , Piazzale V. Tecchio 80, I-80125 Napoli, Italy.
authors.forename: Luciano
authors.initials: L
authors.lastname: Lanotte
authors.affiliation: Elettra-SincrotoneTrieste S.C.p.A. , s.s. 14, km 163.5, I-34149 Basovizza, Trieste, Italy.
authors.forename: Giuliana
authors.initials: G
authors.lastname: Aquilanti
authors.affiliation: School of Physics, Trinity College , Dublin 2, Ireland.
authors.forename: John Michael David
authors.initials: JMD
authors.lastname: Coey
authors.affiliation: ISC-CNR , via Madonna del Piano 10, 50019 Sesto Fiorentino (FI), Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Lantieri
authors.affiliation: Department of Physics, University of Florence , via Sansone 1, 50019 Sesto Fiorentino (FI), Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Spina
authors.affiliation: Department of Physics, University of Florence , via Sansone 1, 50019 Sesto Fiorentino (FI), Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Fittipaldi
authors.affiliation: Institute of Nanoscience & Nanotechnology, NCSR "Demokritos" , Aghia Paraskevi, 15310 Athens, Greece.
authors.forename: George
authors.initials: G
authors.lastname: Margaris
authors.affiliation: Institute of Nanoscience & Nanotechnology, NCSR "Demokritos" , Aghia Paraskevi, 15310 Athens, Greece.
authors.forename: Kalliopi
authors.initials: K
authors.lastname: Trohidou
authors.affiliation: Institute of Science and Technology for Ceramics (ISTEC), National Research Council (CNR) , Via Granarolo 64, 48018 Faenza, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Sprio
authors.affiliation: Institute of Science and Technology for Ceramics (ISTEC), National Research Council (CNR) , Via Granarolo 64, 48018 Faenza, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Montesi
authors.affiliation: Institute of Science and Technology for Ceramics (ISTEC), National Research Council (CNR) , Via Granarolo 64, 48018 Faenza, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Panseri
authors.affiliation: Institute of Science and Technology for Ceramics (ISTEC), National Research Council (CNR) , Via Granarolo 64, 48018 Faenza, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Sandri
authors.affiliation: Institute of Science and Technology for Ceramics (ISTEC), National Research Council (CNR) , Via Granarolo 64, 48018 Faenza, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Iafisco
authors.affiliation: Institute of Science and Technology for Ceramics (ISTEC), National Research Council (CNR) , Via Granarolo 64, 48018 Faenza, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Tampieri
mesh_terms: D006882:Hydroxyapatites / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D060328:Magnetic Phenomena; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties
chemical_list: D006882:Hydroxyapatites; D007501:Iron