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Fe1-xO, although chemically simple, possesses a complex structural and magnetic phase diagram. The crystal structures of Fe1-xO and its magnetic properties at extreme conditions are still a matter of debate. Here, we performed a systematic investigation on Fe0.94O up to 94 GPa and 1700 K using synchrotron X-ray diffraction and synchrotron Mössbauer source spectroscopy. We observe a transition of Fe0.94O to the monoclinic phases above 40 GPa and at high temperatures and use the group theory analysis of the observed phases to discuss their properties and their relation to the ambient pressure phases. The Mössbauer spectra of the rhombohedral and the room temperature monoclinic phase contain a component attributed to Fe2.5+, caused by the electron exchange between the Fe3+ defect and neighboring Fe2+ atoms. Our results present a structural and magnetic transitional pressure-temperature diagram of Fe1-xO and show the complex physicochemical properties of simple Fe1-xO binary oxide under extreme conditions. This work concerns a systematic study of Fe1-xO employing complementary methods of powder and single-crystal X-ray diffraction and synchrotron Mössbauer source spectroscopy up to 94 GPa and 1700 K. It presents a structural and magnetic transitional pressure-temperature diagram of Fe1-xO and demonstrates the complex physicochemical properties of simple Fe1-xO binary oxide under extreme conditions. [ABSTRACT FROM AUTHOR]

We applied the small angle nuclear scattering of synchrotron radiation (SANRS) to investigate anisotropic Galfenol-polyurethane composite comprising Galfenol grains with Fe57 nuclei arranged in the parallel chains surrounded by the non-resonant polymer substance. We aimed to insight into the individual magnetic structure of the particles and particles/polymer interface using the ability to align the synchrotron radiation beam directly on the particle by reducing the analyzed volume and resonant thickness of the composite sample. The size of the studied particles was about 3–7 μm. The results of precise analysis of the rocking curves for electron and nuclear response let to support explanation of the functional composite properties. [ABSTRACT FROM AUTHOR]

In few decades, Nuclear Resonance Scattering of synchrotron radiation developed from a dream to an advanced suite of powerful methods, gathering a wide range of applications from general relativity to nanoscience, combining unprecedented properties of nuclear resonance and synchrotron light, and expanding studies to multiply extreme conditions. This article reviews fundamentals of nuclear resonance physics and properties of synchrotron radiation, provides a short historical overview of the fascinating development, major techniques and instrumentation of the method, and gives a brief snapshot of modern applications and yet coming opportunities. [ABSTRACT FROM AUTHOR]

A Verwey-type charge-ordering transition in magnetite at 120 K leads to the formation of linear units of three iron ions with one shared electron, called trimerons. The recently-discovered iron pentoxide (Fe4O5) comprising mixed-valent iron cations at octahedral chains, demonstrates another unusual charge-ordering transition at 150 K involving competing formation of iron trimerons and dimerons. Here, we experimentally show that applied pressure can tune the charge-ordering pattern in Fe4O5 and strongly affect the ordering temperature. We report two charge-ordered phases, the first of which may comprise both dimeron and trimeron units, whereas, the second exhibits an overall dimerization involving both the octahedral and trigonal-prismatic chains of iron in the crystal structure. We link the dramatic change in the charge-ordering pattern in the second phase to redistribution of electrons between the octahedral and prismatic iron chains, and propose that the average oxidation state of the iron cations can pre-determine a charge-ordering pattern. [ABSTRACT FROM AUTHOR]

The use of single molecule magnets (SMMs) as cornerstone elements in spintronics and quantum computing applications demands that magnetic bistability is retained when molecules are interfaced with solid conducting surfaces. Here, we employ synchrotron Mössbauer spectroscopy to investigate a monolayer of a tetrairon(III) (Fe4) SMM chemically grafted on a gold substrate. At low temperature and zero magnetic field, we observe the magnetic pattern of the Fe4 molecule, indicating slow spin fluctuations compared to the Mössbauer timescale. Significant structural deformations of the magnetic core, induced by the interaction with the substrate, as predicted by ab initio molecular dynamics, are also observed. However, the effects of the modifications occurring at the individual iron sites partially compensate each other, so that slow magnetic relaxation is retained on the surface. Interestingly, these deformations escaped detection by conventional synchrotron-based techniques, like X-ray magnetic circular dichroism, thus highlighting the power of synchrotron Mössbauer spectroscopy for the investigation of hybrid interfaces. [ABSTRACT FROM AUTHOR]

Sound velocities of bridgmanite measured in the laboratory are a key to deciphering the composition of the lower mantle. Here, we report Debye sound velocities determined using nuclear inelastic scattering (NIS) for one majorite composition (MgFeSiO) and five bridgmanite compositions (MgFeSiO, MgFeSiAlO, MgFeSiO, MgFeSiAlO, MgFeSiAlO) measured in a diamond anvil cell at pressures up to 89 GPa at room temperature. Debye sound velocities for majorite determined from NIS are consistent with literature data from Brillouin scattering and ultrasonics, while Debye sound velocities for bridgmanite are significantly lower than literature values from the same methods. We calculated partial and total density of states (DOS) for MgSiO and FeSiO bridgmanite using density functional theory and demonstrate that Debye sound velocities calculated from the reduced DOS using the same approach as for the experimental data (i.e., the limit of D(E)/E as energy goes to zero) give the same sound velocities for each phase irrespective of which partial DOS is used. In addition, we show that Debye sound velocities calculated using this approach are consistent with values obtained from the calculation of the full elastic tensor. Comparison of the calculated DOS with the one obtained from NIS indicates that the experimental DOS has enhanced intensity at low energies that leads to a different slope of the DOS and hence a lower sound velocity. This effect is present in all of the bridgmanite samples examined in this study. [ABSTRACT FROM AUTHOR]

Biogeochemistry investigates chemical cycles which influence or are influenced by biological activity. Astrobiology studies the origin, evolution and distribution of life in the universe. The biogeochemical Fe cycle has controlled major nutrient cycles such as the C cycle throughout geological time. Iron sulfide minerals may have provided energy and surfaces for the first pioneer organisms on Earth. Banded iron formations document the evolution of oxygenic photosynthesis. To assess the potential habitability of planets other than Earth one looks for water, an energy source and a C source. On Mars, for example, Fe minerals have provided evidence for the past presence of liquid water on its surface and would provide a viable energy source. Here we present Mössbauer spectroscopy investigations of Fe and C cycle interactions in both ancient and modern environments. Experiments to simulate the diagenesis of banded iron formations indicate that the formation of ferrous minerals depends on the amount of biomass buried with ferric precursors rather than on the atmospheric composition at the time of deposition. Mössbauer spectra further reveal the mutual stabilisation of Fe-organic matter complexes against mineral transformation and decay of organic matter into CO. This corresponds to observations of a 'rusty carbon sink' in modern sediments. The stabilisation of Fe-organic matter complexes may also aid transport of particulate Fe in the water column while having an adverse effect on the bioavailability of Fe. In the modern oxic ocean, Fe is insoluble and particulate Fe represents an important source. Collecting that particulate Fe yields small sample sizes that would pose a challenge for conventional Mössbauer experiments. We demonstrate that the unique properties of the beam used in synchrotron-based Mössbauer applications can be utilized for studying such samples effectively. Reactive Fe species often occur in amorphous or nanoparticulate form in the environment and are therefore difficult to study with standard mineralogical tools. Sequential extraction techniques are commonly used as proxies. We provide an example where Mössbauer spectroscopy can replace sequential extraction techniques where mineralogical information is sought. Where mineral separation is needed, for example in the investigation of Fe or S isotope fractionation, Mössbauer spectroscopy can help to optimize sequential extraction procedures. This can be employed in a large number of investigations of soils and sediments, potentially even for mineral separation to study Fe and S isotope fractionation in samples returned from Mars, which might reveal signatures of biological activity. When looking for the possibility of life outside Earth, Jupiter's icy moon Europa is one of the most exciting places. It may be just in reach for a Mössbauer spectrometer deployed by a future lander to study the red streak mineral deposits on its surface to look for clues about the composition of the ocean hidden under the moon's icy surface. [ABSTRACT FROM AUTHOR]

The binding of the signal molecule nitric oxide (NO) to the NO transporter protein Nitrophorin 2 (NP2) from the bloodsucking insect Rhodnius prolixus has been characterized by Mössbauer spectroscopy as well as nuclear forward scattering (NFS) and nuclear inelastic scattering (NIS). A striking feature of the vibrational spectrum obtained from NP2-NO is a vibration at 594 cm. This mode is assigned to a Fe-NO stretching mode via simulation of the NIS data by density functional theory (DFT) coupled with molecular mechanics (MM) methods. At frequencies below 100 cm collective motions like heme doming occur which could explain spectroscopic features observed by NIS at these low energies. [ABSTRACT FROM AUTHOR]

Discusses an application of the nuclear inelastic scattering of synchrotron radiation to molecular dynamics. Mossbauer effect; Nuclear inelastic absorption measurements; Energy spectrum of absorption of synchrotron radiation.

The development of the new field of nuclear inelastic scattering is reviewed. The experimental technique and the variety of applications are illustrated by recent results obtained at the Nuclear Resonance beamline of the European Synchrotron Radiation Facility. [ABSTRACT FROM AUTHOR]

We explore alternative ways to Mössbauer spectroscopy such as nuclear forward scattering of synchrotron radiation, and synchrotron radiation perturbed angular correlation spectroscopy to reveal the elusive and long-sought hyperfine interactions in ε-Fe. We indicate that synchrotron radiation perturbed angular correlation spectroscopy is the most viable method. [ABSTRACT FROM AUTHOR]

We compare the atomic motions in a glass and in a relevant crystal using nuclear inelastic scattering, a technique that determines the exact number of vibrational states. The results show that around the boson peak, the number of states in a glass is exactly the same as the number of sound wave states in the crystal around the transverse acoustic (TA) van Hove singularity. Furthermore, increasing pressure causes the transformation of the boson peak of the glass towards the TA singularity of the crystal. Once corrected for the difference in the elastic medium, the boson peak matches the TA singularity in energy and height. This suggests the identical nature of the two features. [ABSTRACT FROM AUTHOR]