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High Pressure Spectroscopies at HPCAT. Yuming Xiao. Outline. Introduction X-ray Emission Spectroscopy (R/XES) Nuclear Resonant Scattering (NRIXS/NFS) Inelastic X-ray Scattering (IXS/XRS) Future Developments. Synchrotron Spectroscopies under High Pressure. Challenges:

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Presentation Transcript
outline
Outline
  • Introduction
  • X-ray Emission Spectroscopy (R/XES)
  • Nuclear Resonant Scattering (NRIXS/NFS)
  • Inelastic X-ray Scattering (IXS/XRS)
  • Future Developments
synchrotron spectroscopies under high pressure
Synchrotron Spectroscopies under High Pressure
  • Challenges:
  • small samples (~a few tens µm in diameter and thickness)
  • background scattering from other DAC components

Spectroscopic methods already applied to HP studies:

XFS XAS(XANES, EXAFS) XMCD

R/XES HERIX MERIX IXSXRS

SAXS NRS (NRIXS, NFS) XPCS

DAC (Diamond Anvil Cell)

  • Strategies at 16 ID-D:
  • variable focused sizes depending on experimental requirements (large 1-meter long KB mirrors to maximize flux at sample position or portable 200mm long KB mirrors to minimize beam size)
  • increase solid angle collection (mini-XES, polycap-XES, 17-element system for XRS)
  • post-sample collimation (tweezers slit, polycapillary lens for IXS)
x ray emission spectroscopy

A dedicated XES/RXES setup coupled to the main 2.7 m spectrometer

X-ray Emission Spectroscopy

One 4-inch analyzer

Amptek Si SSD

Low temperature (down to ~10k)

online ruby

membrane control

Rueff & Shukla, Rev.Modern. Phys., 2011

xes of ce across the vollume collapse transition
XES of Ce across the γ-αVollume Collapse Transition
  • satellite structure of cerium : the exchange interaction of the 4f with the 4d level
  • comparison with the very weak structure of CeO2 at ambient conditions shows that cerium’s moment reduces by approximately 30 % across the volume collapse.
  • the data lend further support to the Kondo volume collapse model
  • a general experimental methodology to study relevant strongly correlated f-electron systems

Lipp et al. Phys. Rev. Lett., 109, 195705 (2012)

hp evolution of fe 2 o 3 electronic structure revealed by pfy xas
HP Evolution of Fe2O3 Electronic Structure Revealed by PFY-XAS
  • High-spin insulator to low-spin metal transition was reflected in the pre-edge of XAS spectra.
  • Crystal-field splitting energy was found to increase monotonically with pressure up to 48GPa
  • Ligand hybridization significantly reduces the critical high-spin/low-spin transition pressure

Wang et al. Phys. Rev. B 82, 144428 (2010)

swd xes and p olycapillary xes
SWD XES and Polycapillary XES

Pacoldet al. J. Syn.Rad.,19,245-251 (2012)

Bradley et al. Phys. Rev. B., 85, 100102 (2012)

Mortensen et al. unpublished

nuclear resonant scattering
Nuclear Resonant Scattering

NRIXS

density of states (DOS):vibrational kinetic energy, vibrational entropy, Debye temperature, and Debye sound velocity

NFS

hyperfine interactions parameters: valence, spin state and magnetic ordering

pressure induced invar behavior in pd 3 fe
Pressure-Induced Invar Behavior in Pd3Fe
  • The NFS revealed a collapse of the 57Fe magnetic moment between 8.9 and 12.3 GPa at 300 K, coinciding with a transition in bulk modulus found by XRD
  • Heating the sample at 7GPa showed negligible thermal expansion from 300 to 523K

Winterrose et al. PRB 83, 134304 (2011)

Winterrose et al. PRL 102, 237202 (2009)

fese under high pressure
FeSe under High Pressure

tetragonal P4/nmm

hexagonal P63/mmc

LT orthorhombic Cmma

HP orthorhombic Pbnm

Kumar et al. APL, 2011

Kumar et al. J.Phys.Chem. B, 2010

inelastic x ray scattering
Inelastic X-ray Scattering

Back scattering energy 9.886keV

17 2-inch Si ( 5 5 5) analyzers

Amptek Si SSD

Energy resolution 1eV

XRS

light element (C, B, N, etc.) K –edge XAS under high pressure

IXS

electronic band structure, excitons, plasmons and their dispersion under high pressure

amorphous diamond a high pressure superhard carbon allotrope
Amorphous Diamond: A High Pressure Superhard Carbon Allotrope
  • observed a new carbon allotrope with a fully sp3-bonded amorphous structure and diamond-like strength by compressing glassy carbon above 40 GPa
  • XRS revealed a continuous pressure induced sp2-to-sp3 bonding change
  • XRD confirmed the perseverance of non-crystallinity
  • transition was reversible upon releasing pressure

Lin et al. Phys. Rev. Lett. 107, 175504 (2011)

electronic structure of crystalline 4 he under hp
Electronic Structure of Crystalline 4He under HP
  • rich electron excitation spectrum
  • a sharp excitation peak showing linear volume dependence
  • determined electronic dispersion along h00 direction and provided a quantitative picture of helium exciton beyond the simplified Wannier-Frenkel description

Mao et al. Phys. Rev. Lett. 105, 186404 (2010)

polycapillary collimation for ixs
Polycapillary Collimation for IXS
  • focus length ~3.5mm
  • focus size ~20µm
  • exit focus size ~150µm
  • exit cone ~2.5°

secondary focus source to IXS analyzer

future developments
Future Developments
  • Better beam focus
  • 5x5µm regularly, special case for 1 (V) x 5 (H)µm or even 1x1µm
  • ~100meV IXS
  • multi-analyzer XES
  • in-line HRM
  • Integration
acknowledgements
Acknowledgements
  • HPCAT
    • Paul Chow
    • Genevieve Boman
    • Eric Rod
    • Curtis Kenny-Benson
    • Arun Bommannavar
    • Guoyin Shen

HPCAT 16 ID-D Users

HPCAT is supported by CIW, CDAC, UNLV and LLNL through funding from DOE-NNSA, DOE-BES and NSF. APS is supported by DOE-BES, under Contract No. DE-AC02-06CH11357.