Papers by Abbasher Gismelseed
In this work we present Fe57 Mossbauer study for the alloy system FeO.7-xSiO.3Mnx, where 0 :::; x... more In this work we present Fe57 Mossbauer study for the alloy system FeO.7-xSiO.3Mnx, where 0 :::; x :::; 0.3. Mossbauer spectroscopic results show that all the samples studied are mag netically ordered at 77 K, and at room temperature, except for x = 0.3 at 300 K where it shows paramagnetic behavior. The average magnetic hyperfine field is found to decrease with increasing the manganese concentration at 77 K and 300 K. The average magnetic hyperfine field is found to increase with decreasing the temperature from 300 K to 77 K for all samples under investigation. The average isomer shift is found to decrease with increasing the manganese concentration.
Materials Research Bulletin, 2020
The Open University's repository of research publications and other research outputs Structural, ... more The Open University's repository of research publications and other research outputs Structural, 57 Fe Mössbauer and XPS studies of mechanosynthesized nanocrystalline Nd0.33Eu0.67Fe1-xCrxO3 particles
Hyperfine Interactions, 2019
X-ray diffraction (XRD), Fields Emission Scanning Electron Microscope (FE-SEM) with EDS and Mössb... more X-ray diffraction (XRD), Fields Emission Scanning Electron Microscope (FE-SEM) with EDS and Mössbauer Spectroscopy (MS), were applied to investigate a newly fallen solid piece of debris named the Aba Panu meteorite, after a city in south western Nigeria (Lat: N 08°14′ 25.7″ and Long: E 003°33′ 47.0″). Matching X-ray diffraction results, together with the FE-SEM analysis confirms the presence of four kinds of iron-bearing minerals, namely olivine, pyroxene, kamacite (Fe-Ni alloys) and troilite (FeS). The Mössbauer spectra recorded at 295 K and 78 K consist of two strong paramagnetic doublets emanating from olivine of quadrupole splitting 2.9 mm/s and pyroxene of quadrupole splitting 2.1 mm/s. These are superimposed on two magnetic sub-spectra attributed to kamacite and troilite phases. From the Mössbauer sub-spectra absorption area, the ratio of the olivine absorption area to the pyroxene absorption area indicates that the meteorite can be classified as an L-ordinary chondrite. The mole fraction of the Fe end-member of olivine (fayalite) and the orthopyroxene (ferrosilite) calculated from the EDS data will be used to identify the petrographic type of the meteorite.
Advances in Materials, 2019
The effects of Zn 2+ ions substitutions on the Debye-Waller Factors, structure factor and other r... more The effects of Zn 2+ ions substitutions on the Debye-Waller Factors, structure factor and other related structural properties of the Mg 1-x Zn x NiFeO 4 (where 0.0≤x≤1.0) spinels have been investigated using the XRD, TEM, SEM and FT-IR tools. The Mg 1-x Zn x NiFeO 4 samples were prepared using the conventional ceramic solid state sintering techniques at temperatures around 1100°C. The Mg 1-x Zn x NiFeO 4 spinels have predominantly inverse type structure with inversion factor, λ in the range 0.69 to 0.36. The X-ray diffraction (XRD) patterns of all compositions showed the formation of cubic spinel structure. The lattice constant "a" increases from 8.3397Å for MgFeNiO 4 to 8.3855Å for ZnFeNiO 4 spinels. The increases in lattice parameters have been attributed to the replacement of small Mg 2+ ions (0.66 Å) with the Zn 2+ (0.74 Å) ions of a larger ionic radius. The IR spectra confirm the existence of two main absorption bands υ 1 and υ 2 in the frequency range of (400-1000 cm-1), arising due to the tetrahedral (A) and octahedral (B) stretching vibrations respectively. Values of both υ 1 and υ 2 decrease as Zn content increases. The scanning electron microscope (SEM) and transmission electron microscope (TEM) images showed aggregates of stacked grains. The normalized XRD intensities of the main (hkl) planes were used in the estimation of the Debye-Waller factor. Values of the Debye-Waller factors were estimated to be in the range (0.77-1.44A 2). The calculated and observed relative intensities and areas of the most related plains to cation distributions (i.e.: the (220), (311), (222), (400), (422), (511) and (440) plains) were obtained by normalizing with respect to the most intensive reflection from the (311) plane. An inverse relation between the ordering, Q and inversion, λ factors exists in these partially inverse spinels. Both Q and λ decrease as Zn content (x) increases in the sample. The cation distributions indicate that the sample, MgFeNiO 4 with x=0, λ=2/3 and maximum configurational entropy Sc(=15.876 J/mol, K) should represents the sample of the complete randomness of cation distributions in these spinels and can be written as (Mg 1/3 Fe 2/3)[Mg 2/3 Fe 1/3 Ni 3/3)O 4. In general the variation of the different structural parameters with Zn content lie on two different regions, the first region for x values (0.0-0.6) the "highly normal" and the second region for x values (0.6-1.0) the "highly inverse" type structure.
Hyperfine Interactions
Preface These are the proceedings of the 27th International Conference on the Applications of the... more Preface These are the proceedings of the 27th International Conference on the Applications of the Mössbauer Effect (ICAME 2003), which was held in Muscat (Oman) during the period 21-25 September 2003. The Iraq war, which took place a few months earlier, shadowed the conference organization during the preparation stages and raised many doubts over its realization. However, the forceful determination and commitment of the faithful participants encouraged the Organizing Committee to carry on. We were pleased of the number of participants that exceeded our expectations. In particular the conference was honored by the participation of Rudolf Mössbauer himself. The proceedings are divided into nine sections according to the conference topics. All papers were reviewed by at least two referees. Out of the thirteen invited talks presented at the conference, nine were submitted for publication. Each topic section starts with the theme's invited talks wherever available. This is followed by the accepted contributions in alphabetical order of the corresponding author. Contributions, for which the abstracts were received late, are placed towards the end of the relevant section. A number of people contributed to the realization of these proceedings.
Hyperfine Interactions
In this work we present Fe57 Mössbauer study for the alloy system Fe0.7−xSi0.3Mnx, where 0x0.3.... more In this work we present Fe57 Mössbauer study for the alloy system Fe0.7−xSi0.3Mnx, where 0x0.3. Mössbauer spectroscopic results show that all the samples studied are magnetically ordered at 77 K, and at room temperature, except for x=0.3 at 300 K where it shows paramagnetic behavior. The average magnetic hyperfine field is found to decrease with increasing the manganese concentration at 77 K and 300 K. The average magnetic hyperfine field is found to increase with decreasing the temperature from 300 K to 77 K for all samples under investigation. The average isomer shift is found to decrease with increasing the manganese concentration.
Materials Research Bulletin, 2015
The influence of ball milling and subsequent sintering of a 3:1 molar mixture of SrCO 3 and a-Fe ... more The influence of ball milling and subsequent sintering of a 3:1 molar mixture of SrCO 3 and a-Fe 2 O 3 on the formation of Sr 3 Fe 2 O 7Àd double perovskite is investigated with different analytical techniques. Milling the mixture for 110 h leads to the formation of SrCO 3-a-Fe 2 O 3 nanocomposites and the structural deformation of a-Fe 2 O 3 via the incorporation of Sr 2+ ions. Subsequent sintering of the pre-milled reactants' mixture has led to the partial formation of an SrFeO 3 perovskite-related phase in the temperature range 400-600 C. This was followed by the progressive development of an Sr 3 Fe 2 O 7Àd phase that continued to increase with increasing sintering temperature until a single-phased nanocrystalline Sr 3 Fe 2 O 7Àd phase was attained at 950 C (12 h). This temperature is $350 C lower than the temperature at which the material is prepared conventionally using the ceramic method. The evolution of different structural phases during the reaction process is discussed. Rietveld refinement of the X-ray diffraction data shows a value of 0.60 for the oxygen deficiency d, in consistency with the Fe 3 + /Fe 4+ ratio derived from the 57 Fe Mössbauer data recorded at both 300 K and 78 K. The Mössbauer data suggests that the Sr 3 Fe 2 O 6.4 nanoparticles are superparamagnetic with blocking temperatures below 78 K. The surfaces of the Sr 3 Fe 2 O 6.4 nanoparticles were shown to have a complex structure and composition relative to those of their cores with traces of SrCO 3 , SrO and SrFeO 3Àd being detected.
AIP Conference Proceedings
Hyperfine Interactions (C), 2002
We have studied the metallic phases in two equilibrated ordinary chondrites Al Kidirate (H6) and ... more We have studied the metallic phases in two equilibrated ordinary chondrites Al Kidirate (H6) and New Haifa (L4) using Mossbauer spectroscopy and synchrotron X-ray diffraction. Mossbauer spectra on taenite-enriched samples from the two meteorites identify the following Fe-Ni phases: the ferromagnetic ordered taenite (tetrataenite) with ∼ 50 % Ni, the ferromagnetic disordered taenite with ∼ 50 % Ni, the low-Ni (∼ 25 %) paramagnetic taenite, and small amounts of the α phase kamacite/martensite. The tetragonal unit cell parameters, in the space group P4/mmmm, of tetrataenite from Alkidirate meteorite are: a = 3.5680 ± 0.0018 A; c = 3.5901 ± 0.0015 A; c/a = 1.0062.
Hyperfine Interactions (C), 2002
Hydro-thermally prepared Sn 4 + and Ti 4 + doped-magnetite samples are characterized through scan... more Hydro-thermally prepared Sn 4 + and Ti 4 + doped-magnetite samples are characterized through scanning electron microscopy and X-ray diffraction (XRD). The samples are studied using 57Fe Mossbauer spectroscopy in the temperature range from liquid nitrogen to room temperature. The XRD pattern shows that the samples are in pure spinel structure. The room temperature Mossbauer spectrum of Sn 4 +-Fe304 exhibits a broadened magnetic sextet superimposed on a paramagnetic doublet while the spectrum of Ti 4 +-Fe304 is very broad with a larger paramagnetic component. However, at liquid nitrogen temperature the two spectra are similar. The influence of the doping of each cation on the iron sites is discussed.
Hyperfine Interactions (C), 2002
Abstract Microcrystals of doped gamma iron oxide samples with copper, magnesium, aluminium, chrom... more Abstract Microcrystals of doped gamma iron oxide samples with copper, magnesium, aluminium, chromium, titanium and tin have been prepared and studied by electron microscopy, x-ray powder diffraction and Mössbauer spectra recorded between 80 and 300K. The Mössbauer spectra at room temperature reveal different degrees of superparamagnetism. The hyperfme interaction parameters have been calculated using a distribution of hyperfme fields and the magnetic anisotropy constant for each sample has ...
Hyperfine Interactions (C), 2002
Abstract The discrete-variational method in the local density approximation is used to calculate ... more Abstract The discrete-variational method in the local density approximation is used to calculate the local properties at the iron central site in iron-copper alloys. The local magnetic moment, hyperfine field and the isomer shift at iron sites are calculated versus the number of copper atoms at the neighboring shells. It is found that the magnetic moment increases with increasing number of copper atoms in the first coordination shell, whereas the magnetic hyperfine field decreases. Assuming a binomial distribution of copper atoms the average ...
Abstract The orthoferrimanganites Nd 0.65 Sr 0.35 FexMn1-xO 3 (x= 0.1, 0.3, 0.6) have been invest... more Abstract The orthoferrimanganites Nd 0.65 Sr 0.35 FexMn1-xO 3 (x= 0.1, 0.3, 0.6) have been investigated using XRD, MÖssbauer spectroscopy, magnetization and conductivity techniques. The XRD reflections exhibit single phase structure. The paramagnetic-superparamagnetic-magnetic transitions were observed from MÖssbauer spectra and magnetization measurements in the temperature range from the liquid nitrogen to the room temperature. The conductivity study of the x= 0.1 and 0.3 show semiconducting behavior ...
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Papers by Abbasher Gismelseed