Gonzalez Fernandez, M. A.Torres, T.Andrés Vergés, M.Costo, R.Presa Muñoz De Toro, Patricia Marcela De LaSerna, C. J.Morales, M. P.Marquina, C.Ibarra, M. R.Goya, G. F.2023-06-202023-06-202009-100022-459610.1016/j.jssc.2009.07.047https://hdl.handle.net/20.500.14352/42780©Elsevier. The authors acknowledge the financial support from Diputación General de Aragón, Comunidad de Madrid (S-0505/MAT/0194), and Ministerio de Ciencia e Innovación (MAT2005-03179 and MAT2008-01489). GFG and PP acknowledge support from the Spanish MEC through the Ramon y Cajal program.We present a Study on the magnetic properties of naked and silica-coated Fe₃O₄nanoparticles with sizes between 5 and 110 nm. Their efficiency as heating agents was assessed through specific power absorption (SPA) measurements as a function of particle size and shape. The results show a strong dependence of the SPA with the particle size, with a maximum around 30 nm, as expected for a Neel relaxation mechanism in single-domain particles. The SiO₂shell thickness was found to play an important role in the SPA mechanism by hindering the heat Outflow, thus decreasing the heating efficiency. It is concluded that a compromise between good heating efficiency and surface functionality for biomedical purposes can be attained by making the SiO₂functional coating as thin as possible.engAtribución-NoComercial-SinDerivadas 3.0 Españahttps://creativecommons.org/licenses/by-nc-nd/3.0/es/journal articlehttp://dx.doi.org/10.1016/j.jssc.2009.07.047http://www.sciencedirect.comopen access538.9Cancer-therapyGamma-Fe₂O₃ particlesStabilityAgentsFieldFísica de materialesFísica del estado sólido2211 Física del Estado Sólido