Interparticle interactions in magnetic core/shell nanoarchitectures

Magnetization and Specific Absorption Rate Studies of Ball-Milled Iron Oxide Nanoparticles for Biomedicine

“…Journal of Nanoparticles interparticle distances or diminished total particle magnetic moments, or macrospins, leading to the observation of superparamagnetism [36]. It is observed that the Mössbauer spectra for these commercially available iron oxide nanopowders are very similar.…”

“…Deviations of the (A)/[B] ratios compared to the bulk oxides point to the presence of defects and site coordination distortion in the nanophase and a preponderance of (A) sites. It has previously been observed that surface sites in -Fe 2 O 3 nanoparticles behave more as (A) sites due to lower iron coordination number at the surface [36]. For particles of ∼10 nm diameter the surface to volume ratio is high with a large number of (A)-like surface sites.…”

“…The particle moments appear to be blocked; all spectra exhibit broadened magnetic hyperfine structure. This indicates the presence of sizable inter-particle magnetic interactions producing a magnetically frozen, spin-glass-like, state [36], which prevents thermal energies from inducing particle moment reversals within the characteristic measuring time for Mössbauer spectroscopy of ∼10 ns. Nanoparticles in close proximity…”

Structural and Magnetic Properties of Monophasic Maghemite (<i>γ</i>-Fe<sub>2</sub>O<sub>3</sub>) Nanocrystalline Powder

“…It reveals a monophasic sample with wide peaks due to Rietveld Refinement was performed which give a mean grain diameter of 6.4 ± 1 nm. The value of the uncertainty can be associated to the noisy background of the diffractogram commonly obtained in iron oxide magnetic nanoparticles [17]. Table 1 summarizes the refined parameters obtained for maghemite structure.…”

Comparative study of iron oxide nanoparticles as-prepared and dispersed in Copaiba oil using Mössbauer spectroscopy with low and high velocity resolution

“…The majority of Mössbauer studies were done with a low velocity resolution using 512 channels or less for spectra recording. Möss-bauer spectra of magnetically ordered iron oxides (magnetite and maghemite) nanoparticles measured with a low velocity resolution were fitted on the base of spinel structural model with tetrahedral (A) and octahedral (B) sites using two magnetic components represented by individual sextets or hyperfine-field distributions mainly (see, for instance [8][9][10][11][12][13]). However, in some cases Mössbauer spectra were fitted using more magnetic components which were related to the nanoparticle size distribution, non-stoichiometry, Verwey transition for magnetite, etc.…”