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Investigation of Fe _{3} O _{4} Core/Mesoporous SiO _{2} Shell Microspheres Based on Mössbauer Spectroscopy

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3 Author(s)
Yong Hui Li ; Dept. of Phys., Kookmin Univ., Seoul, South Korea ; In-Bo Shim ; Chul Sung Kim

The Fe3O4 core/mesoporous SiO2 shell (Fe3O4@SiO2) microspheres were prepared by a solvothermal reaction method. The crystal structure was determined to be cubic spinel with lattice constant a0 of 8.395 Å for core Fe3O4. Based on transmission electron microscopy (TEM) measurements, the core of Fe3O 4 particle diameter is 300-500 nm and shell thickness of 50 nm. From the magnetic hysteresis curves measured under 10 kOe, magnetization of Fe3O4 and Fe3O4@SiO2 microspheres is determined to be 77.0 and 17.0 emu/g , respectively, at room temperature. The M-T curve confirmed that the magnetic moment transition temperature was around 110 K in Fe3O4 and 32 K in Fe3O4@SiO2. The Mössbauer spectra of the samples were analyzed with three six-line hyperfine patterns. It is noticeable that from the Mössbauer absorption area ratio between A(8a) and B(16d) sites, the area ratio of sextet increases from 40:60 for Fe3O4 to 56:44 for Fe3O4@SiO2, respectively. The Fe valence state of A site was determined to be ferric, and B (B1, B2) site was ferric (B1 site) and ferrous (B2 site) from the isomer shift values.

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Magnetics, IEEE Transactions on  (Volume:47 ,  Issue: 10 )