CONTROLLING THE DOMINANT MAGNETIC RELAXATION MECHANISMS THROUGH THE SHELL COMPOSITION OF BI-MAGNETIC CORE-SHELL Fe3O4/ZnxCo1-xFe2O4 NANOPARTICLES

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

Conferencia; 5th International Conference on Nanoscience, Nanotechnology and Nanobiotechnology; 2019

We design exchange-biased magneticnanostructures; bimagnetic core/shell nanoparticles have beenfabricated by a thermal decomposition method andsystematically studied as a function of the shellcomposition [1]. By using this nanostructure, we reporta simple and effective way to control the heatgeneration of a magnetic colloid under alternatemagnetic fields by changing the shell composition ofbimagnetic core?shell Fe3O4 / ZnxCo1-xFe2O4nanoparticles, and the effective anisotropy that canbe tuned by the substitution of Co2+ by Zn2+ ions inthe shell [2].Magnetic hyperthermia experiments of nanoparticlesdispersed in hexane and butter oil showed thatthe magnetic relaxation is dominated by Brownrelaxation mechanism in samples with higher anisotropy(i.e., larger concentration of Co within the shell)yielding high specific power absorption values in lowviscosity media as hexane. Increasing the Znconcentration of the shell, diminishes the magneticanisotropy, which results in a change to a Néelrelaxation that dominates the process when thenanoparticles are dispersed in a high viscosity medium.We demonstrate that tuning the Zn contents atthe shell of these exchange-coupled core/shellnanoparticles provides a way to control the magneticanisotropy without loss of saturation magnetization.This ability is an essential prerequisite for mostbiomedical applications, where high viscosities andcapturing mechanisms are present.[1] G.C. Lavorato, E. Lima, H.E. Troiani, R.D. Zysler,E.L. Winkler, Nanoscale 9, 10240 (2017)[2] F.Fabris et al., Nanoscale 11, 3164 (2019)