DocumentCode :
1329951
Title :
Investigation of Fe 
O 
Core/Mesoporous SiO  microspheres were prepared by a solvothermal reaction method. The crystal structure was determined to be cubic spinel with lattice constant a<sub>0</sub> of 8.395 Å for core Fe<sub>3</sub>O<sub>4</sub>. Based on transmission electron microscopy (TEM) measurements, the core of Fe<sub>3</sub>O <sub>4</sub> particle diameter is 300-500 nm and shell thickness of 50 nm. From the magnetic hysteresis curves measured under 10 kOe, magnetization of Fe<sub>3</sub>O<sub>4</sub> and Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub> 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 Fe<sub>3</sub>O<sub>4</sub> and 32 K in Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>. 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 Fe<sub>3</sub>O<sub>4</sub> to 56:44 for Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>, respectively. The Fe valence state of A site was determined to be ferric, and B (B<sub>1</sub>, B<sub>2</sub>) site was ferric (B<sub>1</sub> site) and ferrous (B<sub>2</sub> site) from the isomer shift values.</div>
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<div class='leftDiv labelDiv col-xs-4 col-sm-2 fullRecLabelEnglish'>Keywords : </div><div class='valueDiv leftDirection leftAlign col-xs-8 col-sm-10 fullRecValueEnglish'>Mossbauer effect; crystal structure; hyperfine interactions; iron compounds; isomer shift; lattice constants; magnetic hysteresis; magnetic moments; magnetic transition temperature; mesoporous materials; silicon compounds; transmission electron microscopy; Fe valence state; Fe<sub>3</sub>O<sub>4</sub> core-mesoporous silica shell microspheres; Fe<sub>3</sub>O<sub>4</sub>-SiO<sub>2</sub>; M-T curve; Mossbauer absorption area ratio; Mossbauer spectra; Mossbauer spectroscopy; TEM measurements; core particle diameter; crystal structure; cubic spinel; isomer shift; lattice constant; magnetic hysteresis curves; magnetic moment transition temperature; magnetization; sextet area ratio; shell thickness; six-line hyperfine patterns; size 300 nm to 500 nm; size 50 nm; solvothermal reaction method; temperature 293 K to 298 K; transmission electron microscopy; Iron; Magnetic cores; Magnetic resonance imaging; Magnetization; Saturation magnetization; Spectroscopy; Temperature measurement; Fe<formula formulatype=)
$_{3}$ O $_{4}$ @SiO $_{2}$ ; Mössbauer spectroscopy; transition temperature; transmission electron microscopy (TEM);
fLanguage :
English
Journal_Title :
Magnetics, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-9464
Type :
jour
DOI :
10.1109/TMAG.2011.2157104
Filename :
6027714
Link To Document :
