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Invited article: High-pressure techniques for condensed matter physics at low temperature.
MedLine Citation:
PMID:  20441318     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Condensed matter experiments at high pressure accentuate the need for accurate pressure scales over a broad range of temperatures, as well as placing a premium on a homogeneous pressure environment. However, challenges remain in diamond anvil cell technology, including both the quality of various pressure transmitting media and the accuracy of secondary pressure scales at low temperature. We directly calibrate the ruby fluorescence R1 line shift with pressure at T=4.5 K using high-resolution x-ray powder diffraction measurements of the silver lattice constant and its known equation of state up to P=16 GPa. Our results reveal a ruby pressure scale at low temperatures that differs by 6% from the best available ruby scale at room T. We also use ruby fluorescence to characterize the pressure inhomogeneity and anisotropy in two representative and commonly used pressure media, helium and methanol:ethanol 4:1, under the same preparation conditions for pressures up to 20 GPa at T=5 K. Contrary to the accepted wisdom, both media show equal levels of pressure inhomogeneity measured over the same area, with a consistent DeltaP/P per unit area of +/-1.8 %/(10(4) microm(2)) from 0 to 20 GPa. The helium medium shows an essentially constant deviatoric stress of 0.021+/-0.011 GPa up to 16 GPa, while the methanol:ethanol mixture shows a similar level of anisotropy up to 10 GPa, above which the anisotropy increases. The quality of both pressure media is further examined under the more stringent requirements of single crystal x-ray diffraction at cryogenic temperature. For such experiments we conclude that the ratio of sample-to-pressure chamber volume is a critical parameter in maintaining sample quality at high pressure, and may affect the choice of pressure medium.
Yejun Feng; R Jaramillo; Jiyang Wang; Yang Ren; T F Rosenbaum
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Review of scientific instruments     Volume:  81     ISSN:  1089-7623     ISO Abbreviation:  Rev Sci Instrum     Publication Date:  2010 Apr 
Date Detail:
Created Date:  2010-05-05     Completed Date:  2010-07-27     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0405571     Medline TA:  Rev Sci Instrum     Country:  United States    
Other Details:
Languages:  eng     Pagination:  041301     Citation Subset:  -    
The Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
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