CONICET | Buscador de Institutos y Recursos Humanos

The magnetic anisotropy is one of the mainproperties that determine the range of application of magnetic nanoparticles(NPs) system, while the development of materials for high-density data storageand new permanent magnets requires compounds with enhanced effective magneticanisotropy and thermal stability of the magnetic moment; biomedicalapplications, such as hyperthermia or contrast agents for MRI, needbiocompatible NPs with low anisotropy and superparamagnetic behavior at roomtemperature. We present here a simple and effective way to control the magneticanisotropy in exchange coupled bimagnetic NPs with core/shell architecture, bychanging the composition of the shell. This strategy was applied to control thedominant, Brown or Néel, relaxation mechanism in magnetic hyperthermia experiment,and to optimize the heat generation in high viscosity magnetic colloids. Thesystem is constituted by ~10 nm Fe3O4/ZnxCo1−xFe2O4core/shell NPs, where the effective anisotropy is tuned by thesubstitution of Co2+ by Zn2+ ions in the shell. Magnetic hyperthermiaexperiments, of these nanoparticles dispersed in hexane and butter oil, showedthat the magnetic relaxation is dominated by the Brown mechanism in sampleswith larger anisotropy. Increasing the Zn concentration of the shell diminishesthe magnetic anisotropy, which results in a change toward Néel relaxation.Within this range, the SLP was optimized by adjusting the shell composition,showing a maximum (up to 150 W/g, for 571 kHz and 200 Oe) for intermediate Znconcentration. This study shows new tools to control the relaxationmechanism, allows maximize the heat generation in viscous media like cytosoland also permits to reduce the particle sizes for biomedical application.

enviar mensaje