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The sample manipulator has a cool down time of six hours. This long time constant is a result of the large thermal mass of the cold finger. The cryo head itself reaches a minimum temperature of ~10K in less than an hour under no load conditions. Temperature measurements with a calibrated GaAlAs diode mounted on the Ti-sample slug indicate a minimum sample temperature of ~18.5K. Another test investigated the impact radiative heating had on the minimum temperature, the difference between having the sample area shielded and unshielded was ~ 4K. Extrapolating the temperature versus heater power curve for the two permanent diodes to 10K provides an estimate of the heat load at the inner stage to be ~0.5 W. This heat loss includes all sources of head load on the inner stage such as radiative heat and heat leak from the outer to inner stage (titanium balls and worm gear interface). By engaging the worm shaft with a non-magnetic ball driver, the polar angle can be actuated while the sample is in measuring position at an azimuthal angle of ~0 degree. The ball driver is attached to a retractable externally mounted rotary-linear feed through. The additional thermal losses imposed by the ball driver are minimal. While engaged for longer time periods, the temperature increase at the sample was only ~0.2K. The functionality of the polar angle scan and the reproducibility of the mechanism were also tested in the photoemission chamber under UHV Figure 1 - Fermi Surface of BiSb alloy single crystal measured at a photon energy of 18 eV conditions. The improved thermal positional stability allowed photoemission measurements to be taken on a small sample (< 1 mm diameter) as it was heated from 18 to 280 K without the need to reposition the sample. The figure on the right shows a twodimensional photoemission intensity map of a Bi0.86Sb0.14 crystal near the Fermi energy which was measured at 50K utilizing the newly added polar angular axis. Acknowledgements The Synchrotron Radiation Center (SRC) is funded by the National Science Foundation (NSF) under Grant No. DMR-0884402.
ANGLE-RESOLVED PHOTOEMISSION OF UAsSe AND USb 2 E. Guziewicz 1 , T. Durakiewicz 1 , M.T. Butterfield 1 , C.G. Olson 2 , J.J. Joyce 1 , A.J. Arko 1 , J.L. Sarrao 1 , A. Wojakowski 3 , T. Cichorek 3,4 1 Los Alamos National Laboratory, Los Alamos, New Mexico, 87545 2 Ames Laboratory, Iowa State University, Ames IA, USA 3 Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw, Poland 4 Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany We have performed ARPES study on single crystals of UAsSe and USb 2 . Both compounds have tetragonal layered crystal structures and order magnetically along the c axis at low temperature. UAsSe shows ferromagnetic behavior below 116K, and USb 2 is an antiferromagnet below 203K. Magnetic behavior gives evidence for localization of the U5f states. However, the enhanced Sommerfeld coefficients (41 mJ/mol·K 2 for UAsSe and 26 mJ/mol·K 2 Figure 1: Angle-resolved normal photoemission spectra of USb 2 and UAsSe showing 3D character of these compounds. for USb 2 ) indicate some degree of hybridization between the U5f and conduction band electrons. We have investigated this problem of correlation between the U5f electrons and their hybridization with the conduction band using ARPES. Photoemission spectra were taken on the PGM beamline at the SRC in Wisconsin with an overall energy resolution for the lowest photon energies (h=20 eV) of 24 meV. Both uranium compounds display a similar electronic structure within 100 meV of the Fermi edge, where a very narrow 5f character peak is found. The intensity of this peak does not follow a simple photoionization cross-section dependence for the U5f electrons, indicating a considerable degree of hybridization with the conduction band. In both UAsSe and USb 2 we have found a dispersion of the peak near the Fermi edge of about 10 meV and 20 meV, respectively, which is additional evidence of hybridization. The dispersion in normal incidence spectra (Fig. 1) provides evidence that neither UAsSe nor USb 2 have purely 2D electronic structure and thus require treatment as 3D or quasi-2D materials. The narrow bands in these U-based magnetic materials are reminiscent of the band magnetism found in
Page 2 and 3: Welcome to the 36 th SRC Users’ M
Page 4 and 5: 12:20 - 1:10 Lunch 1:10 -1:45 Poste
Page 6 and 7: Administration Executive Director D
Page 8 and 9: STATUS OF THE SRC BEAMLINES AND INS
Page 10 and 11: ACCELERATOR DEVELOPMENTS Ken Jacobs
Page 12 and 13: HIGH ENERGY RESEARCH POSSIBILITIES
Page 14 and 15: ATOMICALLY UNIFORM THIN FILMS ON SI
Page 16 and 17: calculated binding energies of the
Page 18 and 19: MANY-ELECTRON EFFECTS ON THE XE 5S
Page 20 and 21: PHOTOELECTRON SPECTROMETRY OF ATOMI
Page 22 and 23: PHOTOEMISSION STUDY OF USb AND UTe
Page 24 and 25: CANADIAN SYNCHROTRON RADIATION FACI
Page 26 and 27: SELF-ASSEMBLY OF BLOCK COPOLYMERS O
Page 28 and 29: A B S T R A C T S
Page 30 and 31: Photoemission spectra, a.u. -0.3 -0
Page 32 and 33: THE INITIAL AND FINAL STATE BANDS I
Page 34 and 35: TRANSITION LAYERS AT BURIED FERROMA
Page 36 and 37: LOW-DIMENSIONAL ELECTRONS AT SILICO
Page 38 and 39: SUBCELLULAR DISTRIBUTION OF MOTEXAF
Page 40 and 41: LINEAR POLARIZATION MEASUREMENTS OF
Page 42 and 43: Fig.1: Photoemission spectra of opt
Page 46 and 47: Cr and Fe but for these U systems t
Page 48 and 49: [4] G. -H. Gweon, J. W. Allen, and
Page 50 and 51: References [1] S. Cho, Y. Kim, A. D
Page 52 and 53: [3] D. L. Mills, Physical Review B
Page 54 and 55: CHARACTERIZATION OF SULPHATE INTERA
Page 56 and 57: in the data acquisition chamber. Th
Page 58 and 59: spatially resolved chemistry of the
Page 60 and 61: THE RELATIONSHIP BETWEEN PHOSPHATE
Page 62 and 63: PHOTOEMISSION STUDIES OF QUANTUM WE
Page 64 and 65: Ag surface state such that it moves
Page 66 and 67: HIGH-RESOLUTION STUDY OF THE LITHIU
Page 68 and 69: RELATIVE PARTIAL CROSS SECTIONS AND
Page 70 and 71: Christian Ast Max-Planck Institute
Page 72 and 73: David L. Huber Physical Sciences La
Page 74 and 75: Tom Miller University of Illinois a
Page 76 and 77: Eric Wiedemann University of Wiscon
Page 78 and 79: Pete Hagen Phone: (608) 877-2154 Em
Page 80: NOTES

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