Phase transition in nanomagnetite

Abstract

Recently, the application of nanosized magnetite particles became an area of growing interest for their potential practical applications. Nanosized magnetite samples of 36 and 9 nm sizes were synthesized. Special care was taken on the right stoichiometry of the magnetite particles. Mössbauer spectroscopy measurements were made in 4.2-300 K temperature range. The temperature dependence of the intensities of the spectral components indicated size dependent transition taking place in a broad temperature range. For nanosized samples, the hyperfine interaction values and their relative intensities changed above the Verwey transition temperature value of bulk megnetite. The continuous transition indicated the formation of dendritelike granular assemblies formed during the preparation of the samples.

Highly stable monodisperse PEGylated iron oxide nanoparticle aqueous suspensions: a nontoxic tracer for homogeneous magnetic bioassays

“…This fitting strategy is similar to the one presented by Dézsi et al 20 for magnetite nanoparticles above the Verwey transition. It is worth noting that the ad hoc introduced hyperfine field distribution provides no physically adequate description of eventual dynamic line broadening in this temperature range.…”

“…2. The low temperature spectrum was fitted using five subspectra with the hyperfine parameters corresponding to magnetite 20 and two hyperfine field distributions. The analyzed hyperfine parameters are summarized in Table 1.…”

Iron-containing phases in metallurgical and coke dusts as well as in bog iron ore

“…In the investigated coke dusts samples, the contribution of the components corresponding to magnetite-like phase (G03 + G02) is also relatively low (14-18%); however, the general question occurs, if really the identifi ed phase is a magnetite at all. The values of hyperfi ne fi eld of G03 component (corresponding to the iron in octahedral B site) are reduced by about 0.7 T (Table 2) in comparison with the stoichiometric, bulk magnetite [14,15]. However, more pronounced difference is visible in the  = P(B)/P(A) ratio.…”

“…2a). The hyperfi ne fi eld values of corresponding two components differ by no more than 0.1-0.2 T and isomer shift (IS) values by no more than 0.01-0.02 mm·s −1 in comparison with the reference data for stoichiometric, bulk magnetite (Table 2) [14,15]. However, a signifi cant discrepancy is observed in the ratio of intensities of components G03 and G02, which corresponds to the contributions of Fe 2+/3+ ions in octahedral B sites and iron Fe 3+ ions in tetrahedral A sites in magnetite inverse spinel struc- 4 , respectively.…”

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

“…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. (see, for instance [14][15][16][17][18]). It was shown recently that improvement in velocity resolution in Mössbauer spectroscopy leads to new possibilities in the investigation of various samples from biomolecules up to meteorites and nanocomposites [19][20][21][22][23].…”