Structural and magnetic properties of zinc ferrite incorporated in amorphous matrix

Glass ceramics in the (Fe2O3)x·(B2O3)(60−x)·(ZnO)40 (x = 17.5 and 20 mol%) system were prepared by the melt-quench method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and magnetization measurements. The samples contain a unique magnetic crystalline phase, the zinc ferrite (ZnFe2O4), embedded in an amorphous matrix. The ZnFe2O4 crystals precipitate during cooling from melting temperature. From the XRD data, the average unit-cell parameter, crystallite size and the quantitative ratio of the crystallographic phases in the samples were evaluated. FTIR data revealed that the BO3 and BO4 are the main structural units of these glass ceramics network. FTIR spectra of these samples show features at characteristic vibration frequencies of ZnFe2O4. From the magnetization curves it was found that the nanoparticles exhibit ferromagnetic interactions combined with superparamagnetism with a blocking temperature, TB, which is composition dependent. In all samples hysteresis is present below TB. The coercive field is dependent on composition and magnetic field being around 0.05μB/f.u. for measurements performed in maximum 0.4 T. Finally, the magnetic behavior of iron in this system is discussed.