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We report here high-pressure investigations on Piplia Kalan eucrite–a member of HED (Howardite–Eucrite–Diogenite) family from asteroid 4-Vesta based on synchrotron X-ray diffraction (up to 16 GPa) and 57 Fe Mössbauer spectroscopy (up to 8 GPa). Dominant with anorthite-rich plagioclase, pigeonite-rich pyroxene and clino-ferrosilite, the sample displayed various phase transitions attaining amorphous character at 16 GPa. These phase transitions of individual components could be explained simultaneously through variations in high-pressure XRD patterns and the Mössbauer parameters. Most prominent P2 1 /c to C2/c transition of pigeonite and ferrosilite was exhibited both as sudden variation in Mössbauer parameters and population inversion of Fe 2+ in M1 and M2 sites between 2.9 and 3.8 GPa and variation in intensity profile in XRD patterns at 3.56 GPa. Anorthite seemed to respond more to such impact than other components in the sample. Complete amorphization in anorthite which occurred at lower pressure of ∼12 GPa implied residual stress experienced due to shock impact. The presence of high pressure (monoclinic) phase of pigeonite and ferrosilite at ambient condition in this eucrite sample confirmed earlier suggestions of an early shock event. This report is an attempt to emphasize the role of anorthite in the determination of the residual stress due to impact process in the parent body thus to understand the behavioral differences amongst HED members. [ABSTRACT FROM AUTHOR]

The consequences of swift heavy ion (SHI) irradiation (Li3 + , 50 MeV, fluence = 5 × 1013 ions/cm2) on the structural and microscopic magnetic properties of Y3 + -substituted yttrium iron garnet (Y3 + x Fe5 − x O12, x = 0.0, 0.2 and 0.4) have been studied at 300 K. It is found that an additional YFeO3-phase observed along with bcc garnet phase, is completely removed for x = 0.2 composition while its percentage formation considerably reduces for x = 0.4 composition after irradiation. Similar effect has been observed for specimens sintered at 1,500°C. The SHI-induced ion beam mixing has been revealed through X-ray diffraction and Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, barium hexaferrite powders were prepared by ordinarily mixing and by high energy ball-milling stoichiometric amounts of the BaCO3 and Fe2O3 precursors, followed by heat treatments carried out in the 900–1100°C range of temperature. The structural and magnetic properties of the resulting powders were analyzed by differential thermal analysis, X-ray diffraction, scanning electron microscopy, Mössbauer spectroscopy and magnetization measurements. The milled powder showed a lower decomposition temperature and higher surface area than the ordinarily mixed powder. Formation of the BaFe2O4 intermediate phase was observed in conventionally prepared hexaferrites. Diversely, the mechanical process before annealing allowed for the hexaferrite formation at much lower temperatures but without formation of intermediate phases. The hyperfine parameters showed to be independent of the processing method. Higher saturation magnetization, and coercivity were observed in the barium hexaferrites prepared by high energy ball milling. [Copyright &y& Elsevier]

In the present study, iron-containing pyrochlores of the A2FeBO7 type (where A = Y, Gd, Eu and Dy; B = Sb and Nb) were synthesized by solid-state reaction of precursor oxides. The compounds were structurally and magnetically characterized by X-ray diffraction, Mössbauer spectroscopy and magnetic measurements. The results revealed that the crystallographic structures and magnetic properties depend, basically, on the type of B atoms. [ABSTRACT FROM AUTHOR]

We report here high-pressure investigations on Piplia Kalan eucrite–a member of HED (Howardite–Eucrite–Diogenite) family from asteroid 4-Vesta based on synchrotron X-ray diffraction (up to 16 GPa) and 57Fe Mössbauer spectroscopy (up to 8 GPa). Dominant with anorthite-rich plagioclase, pigeonite-rich pyroxene and clino-ferrosilite, the sample displayed various phase transitions attaining amorphous character at 16 GPa. These phase transitions of individual components could be explained simultaneously through variations in high-pressure XRD patterns and the Mössbauer parameters. Most prominent P21/c to C2/c transition of pigeonite and ferrosilite was exhibited both as sudden variation in Mössbauer parameters and population inversion of Fe2+ in M1 and M2 sites between 2.9 and 3.8 GPa and variation in intensity profile in XRD patterns at 3.56 GPa. Anorthite seemed to respond more to such impact than other components in the sample. Complete amorphization in anorthite which occurred at lower pressure of ∼12 GPa implied residual stress experienced due to shock impact. The presence of high pressure (monoclinic) phase of pigeonite and ferrosilite at ambient condition in this eucrite sample confirmed earlier suggestions of an early shock event. This report is an attempt to emphasize the role of anorthite in the determination of the residual stress due to impact process in the parent body thus to understand the behavioral differences amongst HED members.