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Author (up) Blanco, M.C.; Franco, D.G.; Jalit, Y.; Pannunzio Miner, E.V.; Berndt, G.; Paesano Jr., A.; Nieva, G.; Carbonio, R.E. url  openurl
  Title Synthesis, magnetic properties and Mössbauer spectroscopy for the pyrochlore family Bi2BB′O7 with B=Cr and Fe and B′=Nb, Ta and Sb Type Journal Article
  Year 2012 Publication Physica B: Condensed Matter Abbreviated Journal Frontiers of Condensed Matter V (FCM 2010)  
  Volume 407 Issue 16 Pages 3078-3080  
  Keywords Pyrochlores; Crystal structure; Magnetism; Mösbauer spectroscopy; Displacive disorder  
  Abstract The samples Bi2BB′O7, with B=Cr and Fe and B′=Nb, Ta and Sb were prepared by solid state method. The crystallographic structure was investigated on the basis of X-ray powder diffraction data. Rietveld refinements show that the crystal structure is cubic, space group Fd-3m. The Bi3+ cation on the eight-coordinate pyrochlore A-site shows displacive disorder, as a consequence of its lone pair electron configuration. There is also a considerable A-site disorder shown by Rietveld Analysis and confirmed in the case of the iron containing samples with Mössbauer spectroscopy. The magnetic measurements show paramagnetic behavior at all temperatures for the Cr oxides. The Fe pyrochlores show antiferromagnetic order around 10 K.  
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  ISSN 0921-4526 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ hernan @ Serial 647  
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Author (up) Encina, S.; Pedrazzini, P.; Sereni, J.G.; Geibel, C. url  doi
openurl 
  Title Low temperature thermopower and magnetoresistance of Sc-rich CeSc1-xTixGe Type Journal Article
  Year 2018 Publication Physica B: Condensed Matter Abbreviated Journal Physica B  
  Volume 536 Issue Pages 133-136  
  Keywords CeScGe; CeTiGe; Antiferromagnetism; Transport properties; Low temperatures; Magnetic field  
  Abstract In CeSc1-xTixGe, Ti-alloying reduces the record-high antiferromagnetic (AFM) ordering temperature found in CeScGe at TN=46K and induces ferromagnetism for x≥0.5. In this work we focus on the AFM side, i.e. Sc-rich samples, and study their thermopower S(T) and magnetoresistance ρ(H,T). The measured S(T) is small in comparison with the thermopower of other Ce-systems and shows some features that are compatible with a weak hybridization between the 4f and band states. This is a further hint pointing to the local character of magnetism in this alloy. Magnetic fields up to 16T have a minor effect on the electrical resistivity of stoichiometric CeScGe. On the other hand, for x=0.65, we find that fields above 4T suppress the hump in ρ(T). Furthermore, the 4.2K magnetoresistance displays a strong decrease in the same field range, also in coincidence with magnetization results from the literature. Our results indicate that ρ(T,H) is a proper tool to assess the H−T phase diagram of this system.  
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  ISSN 0921-4526 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 765  
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Author (up) Fasano, Y.; Szabó, P.; Kačmarčík, J.; Pribulová, Z.; Pedrazzini, P.; Samuely, P.; Correa, V.F. url  doi
openurl 
  Title Unconventional superconductivity in the strong-coupling limit for the heavy fermion system CeCoIn5 Type Journal Article
  Year 2018 Publication Physica B: Condensed Matter Abbreviated Journal Physica B  
  Volume 536 Issue Pages 798-802  
  Keywords Heavy fermion superconductors; Scanning tunneling spectroscopy; Superconducting phase; Pseudogap phase  
  Abstract We present scanning tunneling spectroscopy measurements of the local quasiparticles' excitation spectra of the heavy fermion CeCoIn5 between 440mK and 3K in samples with a bulk Tc=2.25K. The spectral shape of our low-temperature tunneling data, quite textbook nodal-Δ conductance, allow us to confidently fit the spectra with a d-wave density of states considering also a shortening of quasiparticles' lifetime term Γ. The Δ(0) value obtained from the fits yields a BCS ratio 2Δ/kTc=7.73 suggesting that CeCoIn5 is an unconventional superconductor in the strong coupling limit. The fits also reveal that the height of coherence peaks in CeCoIn5 is reduced with respect to a pure BCS spectra and therefore the coupling of quasiparticles with spin excitations should play a relevant role. The tunneling conductance shows a depletion at energies smaller than Δ for temperatures larger than the bulk Tc, giving further support to the existence of a pseudogap phase that in our samples span up to T*∼1.2Tc. The phenomenological scaling of the pseudogap temperature observed in various families of cuprates, 2Δ/kT*∼4.3, is not fulfilled in our measurements. This suggests that in CeCoIn5 the strong magnetic fluctuations might conspire to close the local superconducting gap at a smaller pesudogap temperature-scale than in cuprates.  
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  ISSN 0921-4526 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 766  
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Author (up) Kappler, J.P.; Besnus, M.J.; Haen, P.; Sereni, J.G. doi  openurl
  Title Ce ground state in CePd1-xNix Type Journal Article
  Year 1997 Publication Physica B: Condensed Matter Abbreviated Journal Physica B  
  Volume 230-232 Issue Pages 162-164  
  Keywords  
  Abstract Alloying ferromagnetic CePd (Tc = 6.5 K) with the intermediate valence compound CeNi compresses the lattice, though the ferromagnetic order is present up to x = 0.94 in CePd1−xNix. We report here the competition of magnetic order and Kondo effect, through specific heat, magnetization and resistivity measurements. Detailed results gathered on the x = 0.95 sample show several features suggesting a non-Fermi liquid behaviour which may be due to the proximity to magnetic order: ϱ = ϱ0 + AT1.1 (3 < T ⩽ 30 K) and C/T ∝ − ln T(T ⩾ 0.9 K). At lower temperatures C/T tends to saturate at a value of 0.225 J/K2 mol, about three times the value observed for CeNi.  
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  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 688  
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Author (up) Kappler, J.P.; Besnus, M.J.; Herr, A.; Meyer, A.; Sereni, J.G. doi  openurl
  Title Crossover between intermediate valence and magnetic order in CeRh1-xPdx Type Journal Article
  Year 1991 Publication Physica B: Condensed Matter Abbreviated Journal Physica B  
  Volume 171 Issue 1-4 Pages 346-349  
  Keywords  
  Abstract Magnetic, resistivity and specific-heat measurements on the system CeRh1-xPd(x) are presented. The results indicate a continuous decrease of the hybridization when substituting Pd for Rh in the intermediate-valence compound CeRh. The transition to a magnetically ordered state occurs near x = 0.4. The experimental data suggest the coexistence of Kondo effect and magnetic order for Pd contents around 40-50 at.%. The present results show evidence for a crossover from an IV state with full degeneracy through Kondo-lattice behaviour to a local-moment magnetic state.  
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  ISSN 0921-4526 ISBN Medium  
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  Notes ISI:A1991FU47000065 Approved no  
  Call Number BT @ hernan @ Serial 121  
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Author (up) López, D.; Rodríguez, E.; Nieva, G.; de la Cruz, F.; Cheong, S. W. openurl 
  Title Three-dimensional vortex flux flow in LSCO and YBCO through pseudo dc flux transformer measurements Type Journal Article
  Year 1994 Publication Physica B: Condensed Matter Abbreviated Journal Physica B  
  Volume 194-196 Issue 2 Pages 1977-1978  
  Keywords  
  Abstract A pseudo dc flux transformer configuration shows that the flux flow in La2−xSrxCuO4 (x=0.075) and YBa2Cu3O7 single crystals is due to the movement of 3-D vortices across the sample. We show that the loss of c-axis long range vortex correlation is achieved either by thermal fluctuations or by an inhomogeneus Lorentz force acting on the vortices.  
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  Notes Approved no  
  Call Number BT @ gnieva @ Serial 442  
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Author (up) Núñez Regueiro, M; Castello, D.; Jaime, M. url  doi
openurl 
  Title Thermal conductivity of high temperature superconductors Type Journal Article
  Year 1991 Publication Physica B: Condensed Matter Abbreviated Journal Physica B  
  Volume 169 Issue 1-4 Pages 631-632  
  Keywords  
  Abstract We have measured the thermal conductivity of Tl1Ba2Cu3O9 and of the related compounds CuO and La2CuO4. For the superconducting sample we observe the characteristic T2 behaviour at low temperatures, that does not appear in the non-superconducting samples. The superconducting transition and the antiferromagnetic ordering are detected by our measurements.  
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  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 582  
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Author (up) Pedrazzini, P.; Jaccard, D. doi  openurl
  Title The critical pressure of chromium Type Journal Article
  Year 2008 Publication Physica B: Condensed Matter Abbreviated Journal Physica B  
  Volume 403 Issue 5-9 Pages 1222-1224  
  Keywords Chromium; Quantum phase transitions; High pressure; Resistivity  
  Abstract We present first results of high-pressure resistivity measurements on pure chromium. Two pieces of evidence show that spin density wave magnetism is suppressed at a critical pressure pc?10GPa, namely, the evolution of the ordering temperature TN(p) and the rapid decrease of the residual resistivity close to pc. Our discussion profits from the comparison between pressurized-Cr and the Cr1-xVx alloy, for which a large amount of information on its electronic properties is available.  
  Address  
  Corporate Author DPMC, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland Thesis  
  Publisher Elsevier Place of Publication Editor  
  Language English Summary Language Original Title  
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  ISSN 0921-4526 ISBN Medium  
  Area Expedition Conference International Conference on Strongly Correlated Electron Systems  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 429  
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Author (up) Pedrazzini, P.; Jaccard, D.; Deppe, M.; Geibel, C.; Sereni, J.G. url  doi
openurl 
  Title Multiprobe high-pressure experiments in CePd0.6Rh0.4 and CePd3 Type Journal Article
  Year 2009 Publication Physica B: Condensed Matter Abbreviated Journal Physica B  
  Volume 404 Issue 19 Pages 2898-2903  
  Keywords Ce compounds; Ferromagnetism; Quantum phase transition; High pressure; Resistivity; Seebeck coefficient; Specific heat  
  Abstract Results of recent multiprobe high-pressure experiments on ferromagnetic CePd0.6Rh0.4 and intermediate-valent CePd3 are presented. Simultaneous resistivity (ρ), thermopower (S), and ac heat capacity measurements show that the long-range ferromagnetic state of CePd0.6Rh0.4 vanishes in the proximity of a sharp valence-crossover pressure , i.e. before reaching a quantum critical point. However, a magnetic signal that is progressively suppressed is still detected at higher pressures. For CePd3, the results of simultaneous ρ(T,p) and S(T,p) measurements up to and down to the mK temperature range show a surprisingly weak pressure dependence.  
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  Notes Approved no  
  Call Number BT @ jsereni @ Serial 561  
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Author (up) Sereni, J.G. url  doi
openurl 
  Title Role of entropy in the ground state formation of frustrated systems Type Journal Article
  Year 2018 Publication Physica B: Condensed Matter Abbreviated Journal Physica B  
  Volume 536 Issue Pages 397-400  
  Keywords Entropy; Frustrated systems; Nernst postulate  
  Abstract The absence of magnetic order in Rare Earth-based frustrated compounds allows to recognize the action of the third law of thermodynamics in the low temperature behavior of those systems. One of the most relevant findings is the appearance of a coincident specific heat Cm/T|T→0≈7J/molK2 ‘plateau’ in six Yb systems. This characteristic feature occurs after a systematic modification of the thermal trajectory of their entropies Sm(T) in the range of a few hundred milikelvin degrees. Such behavior is explained by the formation of an entropy-bottleneck imposed by the third law constraint (Sm|T→0≥0), that drives the system into alternative ground states. Based in these finding, three possible approaches to the Sm|T→0 limit observed in real systems are analyzed in terms of the ∂2Sm/∂T2 dependencies.  
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  ISSN 0921-4526 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 768  
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