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

Abstract

Structural and magnetic studies of monophasic maghemite (γ-Fe2O3) magnetic nanocrystallites (MNCs) synthesized by the co-precipitation chemical route are reported in this paper. For the synthesis, a starting precursor of magnetite (Fe3O4) in basic medium was oxidized at room temperature by adjusting the pH = 3.5 at 80˚C in an acidic medium without surfactants. X-ray diffraction (XRD) pattern shows widened peaks indicating nanometric size and Rietveld Refinement confirms only one single-phase assigned to γ-Fe2O3 MNCs. High Resolution Transmission Electron Microscopy (HR-TEM) demonstrates the formation of nanoparticles with diameter around D ≈ 6.8 ± 0.1 nm which is in good agreement with Rietveld Refinement (6.4 ± 1 nm). A selected area electron diffraction pattern was carried out to complement the study of the crystalline structure of the γ-Fe2O3 MNCs. M(H) measurements taken at different temperatures show almost zero coercivity and remanence indicating superparamagnetic domain and high magnetic saturation.

Chronic exposure of tilapia (Oreochromis niloticus) to iron oxide nanoparticles: Effects of particle morphology on accumulation, elimination, hematology and immune responses

“…Crystallite size for 2θ=33.2° calculated with Scherrer formula was 28.25 nm. The XRD diffractogram for γ-Fe 2 O 3 (maghemite) NPs showed 6 sharp peaks at 2θ: 30.2, 35.5, 43.2, 53.3, 57.2 and 62.7° that were also consistent with previously published values (Guivar et al, 2014). It was highly crystalline (e.g., pure) with crystallite size of 20.5 nm (2θ=35.6°).…”

Hydrothermal Synthesis of Nanooctahedra MnFe2O4 onto the Wood Surface with Soft Magnetism, Fire Resistance and Electromagnetic Wave Absorption

“…Figure 3b,c shows the Fe2p and the Mn2p spectra, respectively. For Fe, the two main peaks Fe2p 1/2 and Fe2p 3/2 at 724.73 eV and 711.13 eV, respectively, indicate the presence of Fe 3+ cations by comparison with the Fe2p 3/2 peaks of Fe 2 O 3 and Fe metal [30,31,32,33]. Two sharp peaks for the Mn2p 1/2 and Mn2p 3/2 at 653.23 eV and 641.43 eV, respectively, indicate the presence of Mn 2+ cations by comparison with the MnO [34].…”

Determining iron oxide nanoparticle heating efficiency and elucidating local nanoparticle temperature for application in agarose gel-based tumor model

“…Since, we investigated MNPs that were predominantly maghemite (γ-Fe 2 O 3 ) for purposes of predicting SAR [32–34], we utilized anisotropy values for maghemite in nanoparticle form. For superparamagnetic maghemite MNPs, the domain magnetization of single domain superparamagnetic MNPs is equal to the saturation magnetization of MNPs at room temperature (using data from magnetization curves) [35], and the effective anisotropy value ranges from 4.7 kJ/m 3 (for bulk maghemite) to 47 kJ/m 3 (for nanoscale maghemite) as reported in the literature [14, 36, 37]. …”