Controlling the Dominant Magnetic Relaxation Mechanisms through the shell composition of bi-magnetic core-shell Fe3O4/ZnxCo1-xFe2O4 nanoparticles

E. LIMA JR.; E. DE BIASI; M. VASQUEZ MANSILLA; T. TORRES MOLINA; M.R. IBARRA; G.F. GOYA; E.L. WINKLER; F. FABRIS; H.E. TROIANI; FERNÁNDEZ PACHECO, RODRIGO; R.D. ZYSLER

Brasilia

Congreso; 5th International Conference on Nanoscience, Nanotechnology and Nanobiotechnology (3NANO); 2019

Universidad de Brasilia

We design exchange-biased magnetic nanostructures; bimagnetic core/shell nanoparticles have been fabricated by a thermal decomposition method and systematically studied as a function of the shell composition [1]. By using this nanostructure, we report a simple and effective way to control the heat generation of a magnetic colloid under alternate magnetic fields by changing the shell composition of bimagnetic core?shell Fe3O4 / ZnxCo1−xFe2O4 nanoparticles, and the effective anisotropy that can be tuned by the substitution of Co2+ by Zn2+ ions in the shell [2].Magnetic hyperthermia experiments of nanoparticles dispersed in hexane and butter oil showed that the magnetic relaxation is dominated by Brown relaxation mechanism in samples with higher anisotropy (i.e., larger concentration of Co within the shell) yielding high specific power absorption values in low viscosity media as hexane. Increasing the Zn concentration of the shell, diminishes the magnetic anisotropy, which results in a change to a Néel relaxation that dominates the process when the nanoparticles are dispersed in a high viscosity medium. We demonstrate that tuning the Zn contents at the shell of these exchange-coupled core/shell nanoparticles provides a way to control the magnetic anisotropy without loss of saturation magnetization. This ability is an essential prerequisite for most biomedical applications, where high viscosities and capturing mechanisms are present