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We report on hyperthermia measurements on a colloidal solution of 14.2±1.5 nm monodisperse FeCo nanoparticles (NPs). Losses as a function of the magnetic field display a sharp increase followed by a plateau, which is what is expected for losses of ferromagnetic single-domain NPs. The frequency dependence of the coercive field is deduced from hyperthermia measurement and is in quantitative agreement with a simple model of noninteracting NPs. The measured losses (1.5 mJ/g) compare to the highest of the literature, although the saturation magnetization of the NPs is well below the bulk one. [ABSTRACT FROM AUTHOR]

Abstract: We report on the magnetic hyperthermia properties of chemically synthesized ferromagnetic 11 and 16nm Fe(0) nanoparticles of cubic shape displaying the saturation magnetization of bulk iron. The specific absorption rate measured on 16nm nanocubes is 1690±160W/g at 300kHz and 66mT. This corresponds to specific losses-per-cycle of 5.6mJ/g, largely exceeding the ones reported in other systems. A way to quantify the degree of optimization of any system with respect to hyperthermia applications is proposed. Applied here, this method shows that our nanoparticles are not fully optimized, probably due to the strong influence of magnetic interactions on their magnetic response. Once protected from oxidation and further optimized, such nano-objects could constitute efficient magnetic cores for biomedical applications requiring very large heating power. [Copyright &y& Elsevier]