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Articles 1 - 7 of 7
Full-Text Articles in Physics
Low‐Temperature Phase Diagram Of Ybbipt, R. Movshovich, A. Lacerda, Paul C. Canfield, J. D. Thompson, Z. Fisk
Low‐Temperature Phase Diagram Of Ybbipt, R. Movshovich, A. Lacerda, Paul C. Canfield, J. D. Thompson, Z. Fisk
Paul C. Canfield
Resistivity measurements are reported on the cubic heavy‐fermion compound YbBiPt at ambient and hydrostatic pressures to ≊19 kbar and in magnetic fields to 1 T. The phase transition at T c =0.4 K is identified by a sharp rise in resistivity. That feature is used to build low‐temperature H‐T and P‐Tphase diagrams. The phase boundary in the H‐T plane follows the weak‐coupling BCS expression remarkably well from T c to T c /4, while small hydrostatic pressure of ≊1 kbar suppresses the low‐temperature phase entirely. These effects of hydrostatic pressure and magnetic field on the phase transition are consistent with …
Magnetic And Crystallographic Order In Α‐Manganese, A. C. Lawson, Allen C. Larson, M. C. Aronson, S. Johnson, Z. Fisk, Paul C. Canfield, J. D. Thompson, R. B. Von Dreele
Magnetic And Crystallographic Order In Α‐Manganese, A. C. Lawson, Allen C. Larson, M. C. Aronson, S. Johnson, Z. Fisk, Paul C. Canfield, J. D. Thompson, R. B. Von Dreele
Paul C. Canfield
We have made time‐of‐flight neutron diffractionmeasurements on α‐manganese metal. Powder diffraction measurements were made at 14 temperatures between 15 and 305 K, and single crystalmeasurements were made at 15 and 300 K. We found that the crystal structure of α‐Mn is tetragonal below its Néel point of 100 K, with crystal symmetryI4̄2m and magnetic (Shubnikov) symmetry P I 4̄21 c. In agreement with the earlier results of Yamada et al., there are six independent magnetic atoms, and we found that their moments are weakly temperature dependent. The onset of magnetic order causes slight changes in the atomic positions and in …
Resistivity Of The High-Temperature Metallic Phase Of Vo2, Werner W. Schulz, Philip B. Allen, Renate M. Wentzcovitch, Paul C. Canfield
Resistivity Of The High-Temperature Metallic Phase Of Vo2, Werner W. Schulz, Philip B. Allen, Renate M. Wentzcovitch, Paul C. Canfield
Paul C. Canfield
Measurements are reported on the electrical resistivity ρ(T) along the c axis of a single crystal of VO2, from the metal-insulator transition at T=333 K up to 840 K. The temperature dependence is very linear, and a fit to Bloch-Grüneisen theory gives a residual resistivity ρ0=65 μΩ cm and a ratio ρ(840 K)/ρ0=8. With the help of a local-density-approximation band-structure calculation, we further pursue the conventional (Bloch-Boltzmann) interpretation by extracting the electron-phonon coupling constant λ=1.1 and the mean free path l(800 K)=3.3 Å. The short mean free path implies that the conventional interpretation is internally inconsistent. The most likely explanation …
Doping And Pressure Studies On Ybbipt, A. Lacerda, R. Movshovich, M. F. Hundley, Paul C. Canfield, D. Arms, G. Sparn, J. D. Thompson, Z. Fisk, N. E. Philips, H.-R. Ott
Doping And Pressure Studies On Ybbipt, A. Lacerda, R. Movshovich, M. F. Hundley, Paul C. Canfield, D. Arms, G. Sparn, J. D. Thompson, Z. Fisk, N. E. Philips, H.-R. Ott
Paul C. Canfield
The compound YbBiPt exhibits an extremely large low‐temperature C/T (γ∼8 J K−2 mol−1/Yb) which, if due solely to a renormalized effective mass, would make this material the heaviest correlated electron system known to date. In the Kondo model, the very large γ corresponds to a small characteristic energy scale that is expected to be pressure dependent. We have studied the effect of chemical pressure on YbBiPt single crystals by heat‐capacity measurements on Y and Lu‐doped samples. We have also made preliminary low‐temperature measurements under hydrostatic pressure of the heat capacity (300 mK≤T≤2 K, up to 8 kbar) and resistance (30 …
Nqr Study Of Local Structure And Cooling Rate‐Dependent Superconductivity In La2cuo4+Δ, A. P. Reyes, E. T. Ahrens, P. C. Hammel, J. D. Thompson, Paul C. Canfield, Z. Fisk, R. H. Heffner, J. E. Schirber
Nqr Study Of Local Structure And Cooling Rate‐Dependent Superconductivity In La2cuo4+Δ, A. P. Reyes, E. T. Ahrens, P. C. Hammel, J. D. Thompson, Paul C. Canfield, Z. Fisk, R. H. Heffner, J. E. Schirber
Paul C. Canfield
Preliminary results of structural studies in oxygen‐annealed La2CuO4+δ(δ∼0.03) using 139La nuclear quadrupole resonance (NQR) spectroscopy are reported. Superconducting critical temperatures were found to depend on the rate of cooling through a narrow temperature range near 195 K. Analysis of the 139La NQR spectra reveal that lanthanum atoms in the oxygen‐rich metallic region occupy two sites having different local environments. One site has a structural configuration closely related to the stoichiometric oxygen‐poor compound. The second appears only below 200 K and exhibits a large shift and broad distribution of NQR frequency ν Q . Shifts in ν Q in the vicinity …
Novel Ce Magnetism In Cedipnictide And Di‐Ce Pnictide Structures, Paul C. Canfield, J. D. Thompson, Z. Fisk
Novel Ce Magnetism In Cedipnictide And Di‐Ce Pnictide Structures, Paul C. Canfield, J. D. Thompson, Z. Fisk
Paul C. Canfield
Results of electrical resistance and magnetic susceptibility measurements on Ce2Bi, Ce2Sb, CeScGe, CeScSi and CeSb2 are presented. Ce2Bi and Ce2Sb have antiferromagnetictransitions at low temperatures, while CeSb2, CeScGe and CeScSi have ferromagnetictransitions, CeScGe having a T c = 46 K. The data are analyzed with respect to the similarities of the two crystal structure groups that these materials fall into: CeSb2 having the LaSb2structure and the other materials all having the La2Sb structure.
Magnetism And Heavy Fermion‐Like Behavior In The Rbipt Series, Paul C. Canfield, J. D. Thompson, W. P. Beyermann, A. Lacerda, M. F. Hundley, E. Peterson, Z. Fisk, H. R. Ott
Magnetism And Heavy Fermion‐Like Behavior In The Rbipt Series, Paul C. Canfield, J. D. Thompson, W. P. Beyermann, A. Lacerda, M. F. Hundley, E. Peterson, Z. Fisk, H. R. Ott
Paul C. Canfield
Members of the RBiPt (R=Ce–Lu with the exceptions of Pm and Eu) series have been grown as single crystals.Magnetic susceptibility and electrical resistance have been measured on all members of the series, and specific heatmeasurements have been performed on representatives. The high temperature resistance uniformly changes from that of a small‐gap semiconductor or semimetal seen in NdBiPt to that of a heavy‐fermion metal seen in YbBiPt, which shows a linear coefficient of specific heat at low temperatures of 8 J/K2 mole. Further, the lighter rare earth members show an unusually sharp increase in their resistance associated with antiferromagnetic ordering at …