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X-ray diffraction pattern of ZnO-core/CoFe2O4-shell nanoparticles system. The Bragg diffraction position for the hexagonal P63mc ZnO phase (#36-1451) and cubic Fd3m CoFe2O4 (#22-1086) phase are also included.
(a) TEM image of the ZnO-core/CoFe2O4-shell nanoparticles system with lognormal diameter distribution (see inset), where a clearer bright for the shell is noticed; the corresponding electron diffraction pattern is presented in (b), the rings are indexed with the P63mc ZnO and Fd3m CoFe2O4 phases. (c) Dark field image recorded using a fraction of the (220) CoFe2O4 diffraction ring, the bright contrast corresponds to the CoFe2O4 spinel phase. (d) Electron diffraction pattern of the CoO-core/CoFe2O4-shell nanoparticles system where the tabulated rings position for the Fm3m CoO and the Fd3m CoFe2O4 are shown and the corresponding dark field image (e) reconstructed from the a fraction of the (111) CoFe2O4 diffraction ring.
Temperature dependence of the ZFC and FC magnetization of the ZnO/CoFe2O4 nanoparticles measured with an applied field of 100 Oe. Inset: Temperature dependence of the anisotropy energy barrier distribution, f(T) ∝ (1/T) d(MZFC − MFC)/dT experimental data, the maximum corresponds to 〈TB〉.
Temperature dependence of the coercive field for the ZnO/CoFe2O4 and the CoO/CoFe2O4 core/shell nanoparticles. The inset shows the M vs H loops at T = 5 K for both systems.
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