DocumentCode
3560205
Title
Magnetic Properties of
-Fe
O
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, Mossbauer spectroscopy, and SQUID magnetometry. Regardless of the initial Fe valence state of the starting chloride salt, Mossbauer spectroscopy confirmed that gamma-Fe<sub>2</sub>O <sub>3</sub> was the only phase present. As expected, the nanoparticles exhibited superparamagnetic behavior with the magnetic moments becoming frozen with decreasing temperature as evidenced by a bifurcation in the zero-field-cooled (ZFC) and field-cooled (FC) magnetizations and a hysteresis in the <i>Mv</i>-<i>vs.</i>-<i>H</i> curves. The values of effective magnetic anisotropy ( ~ 10<sup>6</sup> ergs/cm<sup>3</sup> ) determined from the differences between the ZFC and FC magnetizations were found to be an order of magnitude larger than the magneto-crystalline anisotropy for bulk gamma -Fe<sub>2</sub> O<sub>3</sub> , and are probably the result of surface and particle size dependent effects. Likewise, the nanoparticle size distributions as deduced from the blocking temperature distribution function <i>f</i>(<i>TB</i>) based on fits to the difference in the ZFC and FC magnetization curves as well as from fits of the <i>MV</i>-<i>vs.</i>-<i>H</i> curves with a Langevin function in the superparamagnetic regime indicate fairly broad distributions of particle sizes with the particle sizes being comparable to those deduced from XRD measurements. The smaller saturated magnetization values found for these nanoparticles than the bulk value combined with the non-zero slope of the high-field magnetization data suggests that these nanoparticles have a non-negligible surface layer of non-collinear spins surrounding a ferrimagnetically ordered gamma-Fe<sub>2</sub>O<sub>3</sub> core.</div></div>
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<div class='row g-0 align-items-center mb-2'><div class='col-12 col-md-3 fullRecLabelEnglish fw-bold mb-2 mb-md-0'><span class='text-muted small'>Keywords</span></div><div class='col-12 col-md-9 leftDirection leftAlign'>Mossbauer effect; SQUID magnetometers; X-ray diffraction; bifurcation; hydrogels; iron compounds; magnetic anisotropy; magnetic hysteresis; magnetic moments; magnetic particles; nanoparticles; particle size; precipitation; superparamagnetism; Fe<sub>2</sub>O<sub>3</sub>; Mossbauer spectroscopy; SQUID magnetometry; X-ray diffraction; XRD; alginate hydrogels; bifurcation; blocking temperature distribution function; chloride salt; ferrimagnetically ordered materials; magnetic hysteresis; magnetic moments; magnetic properties; magnetization curves; magnetocrystalline anisotropy; nanoparticle size distributions; nanoparticles; noncollinear spins; precipitation; superparamagnetic behavior; valence state; zero-field-cooled magnetizations; Maghemite nanoparticles; superparamagnetic properties;</div></div>
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<div class='row g-0 align-items-center mb-2'><div class='col-12 col-md-3 fullRecLabelEnglish fw-bold mb-2 mb-md-0'><span class='text-muted small'>fLanguage</span></div><div class='col-12 col-md-9 leftDirection leftAlign'>English</div></div>
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<div class='row g-0 align-items-center mb-2'><div class='col-12 col-md-3 fullRecLabelEnglish fw-bold mb-2 mb-md-0'><span class='text-muted small'>Journal_Title</span></div><div class='col-12 col-md-9 leftDirection leftAlign'>Magnetics, IEEE Transactions on</div></div>
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<div class='row g-0 align-items-center mb-2'><div class='col-12 col-md-3 fullRecLabelEnglish fw-bold mb-2 mb-md-0'><span class='text-muted small'>Publisher</span></div><div class='col-12 col-md-9 leftDirection leftAlign'>ieee</div></div>
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<div class='row g-0 align-items-center mb-2'><div class='col-12 col-md-3 fullRecLabelEnglish fw-bold mb-2 mb-md-0'><span class='text-muted small'>ISSN</span></div><div class='col-12 col-md-9 leftDirection leftAlign'>0018-9464</div></div>
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<div class='row g-0 align-items-center mb-2'><div class='col-12 col-md-3 fullRecLabelEnglish fw-bold mb-2 mb-md-0'><span class='text-muted small'>Type</span></div><div class='col-12 col-md-9 leftDirection leftAlign'><h2 class='mb-0 fw-semibold'>jour</h2></div></div>
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<div class='row g-0 align-items-center mb-2'><div class='col-12 col-md-3 fullRecLabelEnglish fw-bold mb-2 mb-md-0'><span class='text-muted small'>DOI</span></div><div class='col-12 col-md-9 leftDirection leftAlign'>10.1109/TMAG.2008.2001311</div></div>
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<div class='row g-0 align-items-center mb-2'><div class='col-12 col-md-3 fullRecLabelEnglish fw-bold mb-2 mb-md-0'><span class='text-muted small'>Filename</span></div><div class='col-12 col-md-9 leftDirection leftAlign'>4717554</div></div>
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