Can Mӧssbauer methods of classifying ordinary chondrites help to identify non-representative samples of these meteorites?

Mössbauer spectra of nonweathered ordinary chondrites consist of four main mineral phases: olivines, pyroxenes, metallic phase and troilite. These minerals represent more than 95% of the whole mass of an ordinary chondrite. Distribution of these mineral phases in micro-scale is not homogeneous. Nevertheless, preparation of representative sample of ordinary chondrite for Mössbauer measurements is possible. To do that a part of 1 g nonweathered material, selected from inside of meteorite without any specific intention is needed. The Warsaw group has been working on investigation of meteorites for 25 years and has analysed about 150 Mössbauer spectra of various meteorites. Among them we found 15 spectra, which could be suspected of being non-representative. These spectra were obtained from Baszkówka, Amber, Bjurböle, Krasnoi-Ugol and Chelyabinsk meteorites. The analysis of how the samples of meteorites were selected for investigation, has shown that the non-representativeness of samples may be due to: intentional choice of sample, preparation of sample from a too small part of material or the use of non-credible source of meteoritic samples. For confirmation of these assumptions, we used a new method of classification of ordinary chondrites – the 4M method. It turned out that this method is a very useful tool for investigation of non-representative samples of equilibrated ordinary chondrites.

Mössbauer measurements of GaFeO3 single crystal multiferroic

Mössbauer measurements on single crystal absorbers at room and at low temperatures were performed. The results are fully consistent with previously published reports by other groups. Spectra of single crystals were simultaneously analyzed including magnetic dipole and electric quadrupole interactions. The analysis shows that there is a small component of magnetic moments perpendicular to the magnetic easy axis. Mössbauer data seem not agree with commonly accepted ferrimagnetic structure of GaFeO3.

Lanthanum and Manganese Co-Doping Effects on Structural, Morphological, and Magnetic Properties of Sol-Gel Derived BiFeO3

In this work, lanthanum and manganese co-substitution effects on different properties of bismuth ferrite solid solutions Bi1-xLaxFe0.85Mn0.15O3 (x from 0 to 1) prepared by a sol-gel synthetic approach have been investigated. It was observed that the structural, morphological, and magnetic properties of obtained specimens are influenced by the amount of introduced La3+ ions. Surprisingly, only the compound with a composition of BiFe0.85Mn0.15O3 was not monophasic, and the presence of neighboring phases was determined from X-ray diffraction analysis and Mössbauer measurements. Structural transitions from orthorhombic to cubic and back to orthorhombic were also observed depending on the La3+ amount. Antiferromagnetic behaviour was observed for all of the samples, with the highest magnetisation values for Bi0.5La0.5Fe0.85Mn0.15O3. Additionally, structural attributes and morphological features were evaluated by Raman spectroscopy and scanning electron microscopy (SEM), respectively.

MÖSSBAUER SPECTROSCOPY OF FERROUS FUMARATE IN PHARMACEUTICAL PRODUCT USED TO TREAT ANEMIA

The World Health Organization (WHO) considers iron deficiency anemia a serious public health problem in developing countries and recommends the use of iron tablets containing iron II for prevention and treatment. The results of Mössbauer measurements of the drug “Ferretab”, which is widely used in medicine for the treatment and prevention of iron deficiency anemia, are presented. This drug contains fumarate iron, C4H2FeO4, and has a small amount of folic acid. In this paper, the temperature dependence of isomer shift and quadrupole splitting values of 57Fe nuclei in iron fumarate were studied. The measurements show that when the temperature increases, the isomer shift and quadrupole splitting of 57Fe nuclei in iron fumarate decreases, the decrease in the isomer shift value is associated with the second-order Doppler effect. Based on Mössbauer measurements, the Debye temperature of this drug was determined. The Debye temperature gives us information about the strong bonding of 57Fe atoms with the environment. A high temperature value means a strong bond and vice versa, a small temperature value means a bond with low rigidity. The coupling constant (Debye temperature) defined for “Ferretab” iron nuclei has been compared with different Debye temperatures found in previous studies on some iron deficiency anemia drugs. Additionally, the values were compared with various clinical studies conducted in in-vivo and in-vitro for comparison of the efficacy of some of the most commonly used drugs to treat and prevent iron deficiency anemia. According to these comparisons, it was established a possible relationship between the Debye temperature of the iron atoms of the drugs under study and their effectiveness. It was noted that the lower the Debye temperature of iron atoms of the drug, the more iron absorbs the human body.

Investigation of Polyol Process for the Synthesis of Highly Pure BiFeO3 Ovoid-Like Shape Nanostructured Powders

Exclusive and unprecedented interest was accorded in this paper to the synthesis of BiFeO3 nanopowders by the polyol process. The synthesis protocol was explored and adjusted to control the purity and the grain size of the final product. The optimum parameters were carefully established and an average crystallite size of about 40 nm was obtained. XRD and Mössbauer measurements proved the high purity of the synthesized nanostructurated powders and confirmed the persistence of the rhombohedral R3c symmetry. The first studies on the magnetic properties show a noticeable widening of the hysteresis loop despite the remaining cycloidal magnetic structure, promoting the enhancement of the ferromagnetic order and consequently the magnetoelectric coupling compared to micrometric size powders.

Temperature dependence of spherical electron transfer in a nanosized [Fe14] complex

The study of transition metal clusters exhibiting fast electron hopping or delocalization remains challenging, because intermetallic communications mediated through bridging ligands are normally weak. Herein, we report the synthesis of a nanosized complex, [Fe(Tp)(CN)3]8[Fe(H2O)(DMSO)]6 (abbreviated as [Fe14], Tp−, hydrotris(pyrazolyl)borate; DMSO, dimethyl sulfoxide), which has a fluctuating valence due to two mobile d-electrons in its atomic layer shell. The rate of electron transfer of [Fe14] complex demonstrates the Arrhenius-type temperature dependence in the nanosized spheric surface, wherein high-spin centers are ferromagnetically coupled, producing an S = 14 ground state. The electron-hopping rate at room temperature is faster than the time scale of Mössbauer measurements (<~10−8 s). Partial reduction of N-terminal high spin FeIII sites and electron mediation ability of CN ligands lead to the observation of both an extensive electron transfer and magnetic coupling properties in a precisely atomic layered shell structure of a nanosized [Fe14] complex.

The study of crystal and magnetic properties of MnNi0.85Fe0.15Ge

Magnetic and Mössbauer measurements were performed for MnNi0.85Fe0.15Ge. The Mössbauer data indicate that Fe atoms in MnNi0.85Fe0.15Ge are randomly distributed over two types of metal sites in hexagonal structure. At 77 K, the hyperfine magnetic fields at Fe located in different crystal sites have similar values of about 12.7 and 12.3 T. The random site distribution of the iron atoms in the non-magnetic hexagonal phase at high temperatures is confirmed by the theoretical calculations in fully relativistic Korringa –Kohn –Rostoker (KKR) method.

New Mössbauer measurements of Fe3+/ΣFe in chromites from the mantle section of the Oman ophiolite: evidence for the oxidation of the sub-oceanic mantle

Room temperature Mössbauer and electron-probe measurements of Fe3+/ΣFe in chromite from the mantle section of the Oman ophiolite define two groups of samples: a low Fe3+/ΣFe group (with Fe3+/ΣFe = 0.21–0.36) have cr# = Cr/(Cr + Al) in the range 0.49–0.75, whereas a smaller more geographically localized high Fe3+/ΣFe group (with Fe3+/ΣFe = 0.71–0.78) have a more restricted range of cr# ratios of 0.72–0.75. The low Fe3+/ΣFe chromitites have very variable Fe3+/ΣFe ratios. They are thought to have crystallized from melts that have interacted with depleted mantle and thereby acquired their variable Fe3+/ΣFe ratio. The high Fe3+/ΣFe chromitites are restricted to one small area of the mantle and their high oxidation state is thought to be post magmatic. They are either the product of later heating, related to melt flux or interaction with a later oxidising melt. A difference in oxygen fugacity between the MORB-depleted harzburgite host, which is at the quartz–fayalite–magnetite (QFM) buffer and the later chromite-bearing melts (QFM + 2) implies that there is a real difference in the oxidation state of the MORB and arc-magma sources.