Characterization of superparamagnetic MgxZn1-xFe2O4 powders

Structural and magnetic properties of Mg (x) Zn1-x Fe2O4 powders have been studied with respect to the application for thermal cancer therapy (magnetic hyperthermia). Mg (x) Zn1-x Fe2O4 (x=0.1-0.5) powders with particle sizes between 5 and 8 nm were produced by citrate method. The X-ray diffraction patterns of the samples correspond to a spinel phase. The lattice constant and the volume of the elementary cell increase when x changes from 0.1 to 0.5. The FTIR-spectra ascertain the spinel phase formation. The Mossbauer studies reveal the presence of extremely small particles, which undergo superparamagnetic relaxation at room temperature. The core-shell model has been applied to explain quadruple doublets. The quadruple splitting at "shells" is bigger than those at "cores" whereas the isomer shifts remain close. Magnetic studies confirm the presence of extremely small particles that behave as superparamagnetic ones. (C) Versita Warsaw and Springer-Verlag Berlin Heidelberg. All rights reserved.