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The synchrotron radiation technique of nuclear resonant inelastic X-ray scattering (NRIXS), also known as nuclear resonance vibrational spectroscopy or nuclear inelastic scattering, provides a wealth of information on the vibrational properties of solids. It has found applications in studies of lattice dynamics and elasticity, superconductivity, heme biochemistry, seismology, isotope geochemistry and many other fields. It involves probing the vibrational modes of solids by using the nuclear resonance of Mössbauer isotopes such as 57Fe, 83Kr, 119Sn, 151Eu and 161Dy. After data reduction, it provides the partial phonon density of states of the Mössbauer isotope that is investigated, as well as many other derived quantities such as the mean force constant of the chemical bonds and the Debye velocity. The data reduction is, however, not straightforward and involves removal of the elastic peak, normalization and Fourier–Log transformation. Furthermore, some of the quantities derived are highly sensitive to details in the baseline correction. A software package and several novel procedures to streamline and hopefully improve the reduction of the NRIXS data generated at sector 3ID of the Advanced Photon Source have been developed. The graphical user interface software is named SciPhon and runs as a Mathematica package. It is easily portable to other platforms and can be easily adapted for reducing data generated at other beamlines. Several tests and comparisons are presented that demonstrate the usefulness of this software, whose results have already been used in several publications. Here, the SciPhon software is used to reduce Kr, Sn, Eu and Dy NRIXS data, and potential implications for interpreting natural isotopic variations in those systems are discussed.

The development of a novel experimental capability of nuclear resonant inelastic X-ray scattering at high pressure and low temperature is presented. The new capability is demonstrated by studying the Fe-specific phonon density of states and magnetism in Eu57Fe2As2., A new synchrotron radiation experimental capability of coupling nuclear resonant inelastic X-ray scattering with the cryogenically cooled high-pressure diamond anvil cell technique is presented. The new technique permits measurements of phonon density of states at low temperature and high pressure simultaneously, and can be applied to studies of phonon contribution to pressure- and temperature-induced magnetic, superconducting and metal–insulator transitions in resonant isotope-bearing materials. In this report, a pnictide sample, EuFe2As2, is used as an example to demonstrate this new capability at beamline 3-ID of the Advanced Photon Source, Argonne National Laboratory. A detailed description of the technical development is given. The Fe-specific phonon density of states and magnetism from the Fe sublattice in Eu57Fe2As2 at high pressure and low temperature were derived by using this new capability.

This study demonstrates the use of monochromatic synchrotron X-ray radiation of 40 keV for high-precision equation-of-state studies on sets of single crystals analysed individually in the same diamond-anvil pressure cell. Angle-dispersive zone-axis diffraction patterns were obtained from crystals of wustite-Fe0.93O and magnesiowüstite-(Mg0.73Fe0.27)O to 51 GPa in a hydrostatic helium pressure medium. The rhombohedral phase of Fe0.93O was observed above 23 GPa, and its isothermal bulk modulus (K0) was determined to be 134 (+/-4) GPa, assuming K'=4. The rhombohedral phase of Fe(0.93)O is more compressible than B1-structured Fe0.93O, with K0=146 (+/-2) GPa. Magnesiowüstite-(Mg0.73Fe0.27)O remains cubic over the experimental pressure range, and has a bulk modulus of 154 (+/-3) GPa with K'=4.0 (+/-0.1).

Synchrotron-based X-ray emission spectroscopy (XES) is well suited to probing the local electronic structure of 3d transition metals such as Fe and Mn in their host phases. The laser-heated diamond anvil cell technique is uniquely capable of generating ultra-high static pressures and temperatures in excess of 100 GPa and 3000 K. Here X-ray emission spectroscopy and X-ray diffraction have been interfaced with the laser-heated diamond cell for studying the electronic spin states of iron in magnesiowüstite-(Mg0.75,Fe0.25)O and its crystal structure under lower-mantle conditions. X-ray emission spectra of the ferrous iron in a single crystal of magnesiowüstite-(Mg0.75,Fe0.25)O indicate that a high-spin to low-spin transition of ferrous iron occurs at 54 to 67 GPa and 300 K and the ferrous iron remains in the high-spin state up to 47 GPa and 1300 K. This pilot study points to the unique capability of the synchrotron-based XES and X-ray diffraction techniques for addressing the issue of electronic spin transition or crossover in 3d transition metals and compounds under extreme high-P-T conditions.