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Rare earth and actinide f-electron materials often exhibit novel and interesting behavior such as structural, magnetic,
metal-insulator, and superconducting transitions. In addition, superconducting transitions in several compounds have been observed
in the vicinity of a magnetic quantum critical point (QCP) - a pressure, chemical substitution, or magnetic field at which a magnetic
ordering temperature in the system is suppressed to zero-temperature. While doping to affect chemical concentration introduces
defects, applying pressure or a magnetic field introduces no defects and is thus a “clean” parameter; for this reason,
ultra-high pressures and high magnetic fields are used to investigate the behavior of f-electron materials in the vicinity of
QCP’s.
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Attaining the pressures necessary to investigate some these novel materials requires the use of designer diamond anvil cells
(dDAC’s) that are capable of attaining pressures in the Mbar range, much higher than the pressures achievable in a piston-cylinder
pressure cell. Designer diamond anvils were developed and carefully fabricated by S.T. Weir's research group at of Lawrence Livermore National Laboratory and Y.K. Vohra's research group at the University of Alabama, Birmingham. Designer diamond anvils are capable of reliable and repeatable high-pressure measurements due to the encapsulation
of metal microprobes within a chemically deposited layer on the diamond; they can be fabricated for use as resistivity, Hall effect,
or magnetic susceptibility probes. In addition to high pressures, the thorough investigation of f-electron compounds often benefits
from the very low temperatures and high magnetic fields achieved in a dilution refrigerator equipped with a superconducting magnet.
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Ruby fluorescence is used to measure applied pressure in dDAC's. A blue (510 nm) laser shining on ruby chips in the pressure cell causes
the rubies to fluoresce. A spectrometer with a CCD detector analyzes the fluorescence spectrum, which is pressure-dependent. The Maple Laboratory at UCSD would like to especially thank Sam Weir, Damon Jackson, Chantel Aracne, and Reed Patterson for their invaluable assistance in the development of the Ultra High Pressure Facility.
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Our study of the pressure dependence of the
CeRh1-xCoxIn5 system is
an example of the research our pressure facility makes possible.
Research within the Ultra High Pressure Facility at UCSD is supported by the National Nuclear Security
Administration under the Stewardship Sciences Academic Alliance.
Selected References:
P.-C. Ho, W. M. Yuhasz, N. P. Butch, N. A. Frederick, T. A. Sayles, J. R. Jeffries, M. B. Maple, J. B. Betts, A. H. Lacerda,
P. Rogl, and G. Giester, "Ferromagnetism and possible heavy fermion behavior in single crystals of NdOs4Sb12," Phys. Rev. B 72, 094410 (2005).
J. R. Jeffries, N. A. Frederick, E. D. Bauer, H. Kimura, V. S. Zapf, K.-D. Hof, T. A. Sayles, and M. B. Maple, "Superconductivity
and non-Fermi liquid behavior near antiferromagnetic quantum critical points in CeRh1-xCoxIn5,"
Phys. Rev. B 72, 024551 (2005).
N. P. Butch, W. M. Yuhasz, P.-C. Ho, J. R. Jeffries, N. A. Frederick, T. A. Sayles, X. G. Zheng, M. B. Maple, J. B. Betts,
A. H. Lacerda, F. M. Woodward, J. W. Lynn, P. Rogl, and G. Geister, "Ordered Magnetic State in PrFe4Sb12 Single Crystals,"
Phys. Rev. B 71, 214417 (2005).
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