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Radiation hardness of 3HF-tile/O2-WLS-fiber calorimeter

Description: The radiation hardness of a 3HF-tile/O2-WLS-fiber calorimeter with two different tile/fiber patterns has been studied. Two calorimeter modules were irradiated up to 10 Mrad with the BEPC 1.3 GeV electron beam. The radiation damage of these modules is compared with our previous measurements from SCSN81-tile/BCF91A-WLS-fiber modules. The longitudinal damage profiles are fitted as a function of depth.
Date: November 1, 1993
Creator: Han, S. W.; Hu, L. D. & Liu, N. Z.
Partner: UNT Libraries Government Documents Department

Temperature-dependent x-ray diffraction study of Pd/Cu site interchange in non-Fermi liquid UCu(4)Pd

Description: A pair distribution function (PDF) analysis of temperature-dependent x-ray diffraction measurements from UCu{sub 4}Pd is presented. Fits to the displacement parameters (u{sup 2}'s) with a Debye model show better agreement with a model that includes 25% of the Pd atoms on 16$e$ (Cu) sites. In addition, significant non-thermal disorder is observed in the Cu environment, in contrast to previous measurements of local order in the U-Cu pairs.
Date: June 1, 2002
Creator: Han, S.-W.; Booth, C.H.; Bauer, E.D. & Maple, M.B.
Partner: UNT Libraries Government Documents Department

Lattice disorder and size-induced Kondo behavior in CeAl2 andCePt2+x

Description: When the particle size of CeAl{sub 2} and CePt{sub 2+x} samples is reduced to the nanometer scale, antiferromagnetism is suppressed and Kondo behavior dominates. We find that the Kondo temperature T{sub K} can either decrease (CeAl{sub 2}) or increase (CePt{sub 2+x}) in the nanoparticles relative to the bulk. Extended x-ray absorption fine-structure data show that the Ce-Al and Ce-Pt environments are significantly distorted in the nanoparticles. While such distortions should strongly affect magnetic and electronic properties, we find they cannot explain the observed changes in T{sub K}. Changes in the conduction density of states or other parameters must, therefore, play a significant role.
Date: March 14, 2006
Creator: Han, S.-W.; Booth, C.H.; Bauer, E.D.; P.H., Huang; Chen, Y.Y. & Lawrence, J.M.
Partner: UNT Libraries Government Documents Department

Lattice disorder and magnetism in f-electron intermetallics

Description: Real materials can have real differences compared to ideal systems. For instance, non-Fermi liquid (NFL) behavior was initially thought to be due to chemical disorder, since the first such materials were all substituted. Although several nominally well-ordered NFL's have been discovered and extensively studied, the effect of disorder on the magnetic properties of f-electron intermetallic systems remains poorly understood. Disorder in NFL systems is reviewed from an experimental, local structure point of view, including a discussion of results on the nominally ordered U{sub 3}Ni{sub 3}Sn{sub 4} and CeCoIn{sub 5} systems, and the chemically disordered UCu{sub 4}Pd and CeRhRuSi{sub 2} systems.
Date: July 29, 2004
Creator: Booth, C.H.; Han, S.-W.; Skanthakumar, S. & Sarrao, J.L.
Partner: UNT Libraries Government Documents Department

Perturbing the superconducting planes in CeCoIn5 by Snsubstitution

Description: In contrast to substitution on the Co or Ce site, Sn substitution has a remarkably strong effect on superconductivity in CeCoIn{sub 5-x}Sn{sub x}, with T{sub c} {yields} 0 beyond only {approx}3.6% Sn. Instead of being randomly distributed on in-plane and out-of-plane In sites, extended x-ray absorption fine structure measurements show the Sn atoms preferentially substitute within the Ce-In plane. This result highlights the importance of the In(1) site to impurity scattering and clearly demonstrates the two-dimensional nature of superconductivity in CeCoIn{sub 5}.
Date: January 11, 2005
Creator: Daniel, M.; Bauer, E.D.; Han, S.-W.; Booth, C.H.; Cornelius,A.L.; Pagliuso, P.G. et al.
Partner: UNT Libraries Government Documents Department

Local structure around Sn in CeCoIn{sub 5-x}Sn{sub x}

Description: The local structure around Sn dopants in CeCoIn{sub 5-x}Sn{sub z} has been probed by extended x-ray absorption fine structure (EXAFS) technique. The fit results for both x = 0.12 and x = 0.18 clearly indicate the dopant Sn atoms predominantly occupying the planar In(1) site. These results are consistent with the quasi-two-dimensional electronic properties of CeCoIn{sub 5} and is discussed in relation to the observed bulk properties.
Date: June 16, 2004
Creator: Daniel, M.; Han, S.-W.; Booth, C.H.; Cornelius, A.L.; Bauer, E.D. & Sarrao, J.L.
Partner: UNT Libraries Government Documents Department

X-ray absorption studies of the local structure and f-level occupancy in CeIr(1-x)Rh(x)In(5)

Description: The CeIr{sub 1-x}Rh{sub x}In{sub 5} series exhibits a range of interesting phenomena, including heavy-fermion superconductivity, non-Fermi liquid behavior, and concomitant antiferromagnetism (AF) and superconductivity (SC). In the low-Rh concentration range (0.1 {ge} x {ge} 0.5), specific heat measurements show a broad anomaly, suggestive of gross phase separation. We have performed x-ray absorption experiments at the Ce L{sub III}, Ir L{sub III}, and Rh K-edges as a function of Rh concentration and temperature. X-ray absorption near-edge structure (XANES) measurements indicate that cerium is close to trivalent in this system, with no measurable change with temperature from 20-300 K, consistent with a heavy-fermion material. Extended x-ray absorption fine structure (EXAFS) measurements as a function of temperature from all measured edges indicate the local crystal structure of all samples is well ordered, with no gross phase separation observed, even for samples with x = 0.125 and x = 0.25. These results therefore suggest that the anomalous specific heat behavior in the 0.1 {ge} x {ge} 0.5 range have some other explanation, and some possibilities are discussed.
Date: April 15, 2004
Creator: Daniel, M.; Han, S.-W.; Booth, C.H.; Cornelius, A.L.; Pagliuso, P.G.; Sarrao, J.L. et al.
Partner: UNT Libraries Government Documents Department