Publications

98. Pressure dependence of the optical properties of the charge-density-wave compound LaTe2
M. Lavagnini, A. Sacchetti, L. Degiorgi, E. Arcangeletti, L. Baldassarre, P. Postorino, S. Lupi, A. Perucchi, K. Y. Shin and I. R. Fisher,
Phys. Rev. B 77, 165132 (2008).

ABSTRACT
We report the pressure dependence of the optical response of LaTe2, which is deep in the charge-density-wave (CDW) ground state even at 300 K. The reflectivity spectrum is collected in the midinfrared spectral range at room temperature and at pressures between 0 and 7 GPa. We extract the energy scale due to the single-particle excitation across the CDW gap and the Drude weight. We establish that the gap decreases upon compressing the lattice while the Drude weight increases. This signals a reduction in the quality of nesting upon applying pressure, therefore inducing a lesser impact of the CDW condensate on the electronic properties of LaTe2. The consequent suppression of the CDW gap leads to a release of additional charge carriers, manifested by the shift of weight from the gap feature into the metallic component of the optical response. On the contrary, the power-law behavior, seen in the optical conductivity at energies above the gap excitation and indicating a weakly interacting limit within the Tomonaga-Luttinger liquid scenario, seems to be only moderately dependent on pressure.

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97. Charge density wave formation in R2Te5 (R = Nd, Sm, Gd)
K. Y. Shin, J. Laverock, Y. Q. Wu, C. L. Condron, M.F. Toney, S. B. Dugdale, M. J. Kramer and I. R. Fisher,
Phys. Rev. B 77, 165101 (2008).

ABSTRACT
The rare earth (R) tellurides R2Te5 have a crystal structure intermediate between that of RTe2 and RTe3, consisting of alternating single and double Te planes sandwiched between RTe block layers. We have successfully grown single crystals of Nd2Te5, Sm2Te5, and Gd2Te5 from a self-flux and we describe here evidence for charge density wave formation in these materials. The superlattice patterns for all three compounds are relatively complex, consisting at room temperature of at least two independent wave vectors. Consideration of the electronic structure indicates that, to a large extent, these wave vectors are separately associated with sheets of the Fermi surface which are principally derived from the single and double Te layers.

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96. Effect of chemical pressure on the charge density wave transition in rare-earth tritellurides RTe3
N. Ru, C. L. Condron, G. Y. Margulis, K. Y. Shin, J. Laverock, S. B. Dugdale, M. F. Toney, and I. R. Fisher,
Phys. Rev. B 77, 035114 (2008).

ABSTRACT
The charge density wave transition is investigated in the bilayer family of rare-earth tritelluride RTe3 compounds (R=Sm, Gd, Tb, Dy, Ho, Er, and Tm) via high-resolution x-ray diffraction and electrical resistivity. The transition temperature increases monotonically with increasing lattice parameter from 244(3) K for TmTe3 to 416(3) K for SmTe3. The heaviest members of the series, R=Dy, Ho, Er, and Tm, are observed to have a second transition at a lower temperature, which marks the onset of an additional charge density wave with wave vector almost equal in magnitude to the first, but oriented in the perpendicular direction.

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95. Reply to Comment on “Extrinsic origin of the insulating behavior of polygrain icosahedral Al-Pd-Re quasicrystals”
J. Dolinsek, P. J. McGuiness, M. Klanjsek, I. Smiljanic, A. Smontara, E. S. Zijlstra, S. K. Bose, I. R. Fisher, M. J. Kramer and P. C. Canfield,
Phys. Rev. B 76, 216202 (2007).

ABSTRACT
We clarify issues raised in the preceding Comment regarding the viewpoint that the highly porous and oxidized arc-melted polygrain i-Al-Pd-Re samples could reveal intrinsic electrical transport properties of this icosahedral family. Flux-grown single-grain i-Al-Pd-Re samples of superior structural quality do not show insulatinglike behavior, and their transport properties are on common ground with all other Al-based icosahedral families.

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94. Nuclear magnetic resonance evidence for a strong modulation of the Bose-Einstein condensate in BaCuSi2O6
S. Krämer R. Stern, M. Horvatic, C. Berthier, T. Kimura, and I. R. Fisher
Phys. Rev. B 76, 100406(R) (2007).

ABSTRACT
We present a 63,65Cu and 29Si NMR study of the quasi-2D coupled spin 1/2 dimer compound BaCuSi2O6 in the magnetic field range 13–26 T and at temperatures as low as 50 mK. NMR data in the gapped phase reveal that below 90 K different intradimer exchange couplings and different gaps (B/A=1.16) exist in every second plane along the c axis, in addition to a planar incommensurate (IC) modulation. 29Si spectra in the field induced magnetic ordered phase reveal that close to the quantum critical point at Hc1=23.35 T the average boson density of the Bose-Einstein condensate is strongly modulated along the c axis with a density ratio for every second plane A/B5. An IC modulation of the local density is also present in each plane.

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93. STM Studies of TbTe3: Evidence for a Fully Incommensurate Charge Density Wave
A. Fang, N. Ru, I. R. Fisher and A. Kapitulnik
Phys. Rev. Lett 99, 046401 (2007).

ABSTRACT
We observe unidirectional charge density wave (CDW) ordering on the quasi-2D material TbTe3 with a scanning tunneling microscope at ~6 K. Our analysis indicates that the CDW is fully incommensurate, with wave vector q_CDW ~ 0.71×2pi/c. By imaging at various tip-sample voltages, we highlight effects of the subsurface layer and its effect on the CDW. We also observe an additional (possibly surface) dimerization and 0.68×2pi/a ordering perpendicular to the CDW.

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92. Ferromagnetism in the Mott Insulator Ba2NaOsO6
A. S. Erickson, S. Misra, G. J. Miller, R. R. Gupta, Z. Schlesinger, W. A. Harrison, J. M. Kim, and I. R. Fisher
Phys. Rev. Lett 99, 016404 (2007).

ABSTRACT
Results are presented of single crystal structural, thermodynamic, and reflectivity measurements of the double-perovskite Ba2NaOsO6. These characterize the material as a 5d1 ferromagnetic Mott insulator with an ordered moment of ~0.2µ_B per formula unit and T_C=6.8(3) K. The magnetic entropy associated with this phase transition is close to Rln2, indicating that the quartet ground state anticipated from consideration of the crystal structure is split, consistent with a scenario in which the ferromagnetism is associated with orbital ordering.

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91. Geometric frustration and dimensional reduction at a quantum critical point
C. D. Batista, J. Schmalian, N. Kawashima, P. Sengupta, S. E. Sebastian, N. Harrison, M. Jaime and I. R. Fisher
Phys. Rev. Lett 98, 257201 (2007).

ABSTRACT
We show that the spatial dimensionality of the quantum critical point associated with Bose-Einstein condensation at T=0 is reduced when the underlying lattice comprises layers coupled by a frustrating interaction. Our theoretical predictions for the critical behavior correspond very well with recent measurements in BaCuSi2O6 [ S. E. Sebastian et al., Nature (London) 441, 617 (2006)].

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90. Optical properties of the Ce and La ditelluride charge density wave compounds
M. Lavagnini, A. Sacchetti, L. DeGiorgi, K. Y. Shin and I. R. Fisher
Phys. Rev. B 75, 205133 (2007).

ABSTRACT
The La and Ce ditellurides LaTe2 and CeTe2 are deep in the charge-density-wave (CDW) ground state even at 300 K. We have collected their electrodynamic response over a broad spectral range from the far infrared up to the ultraviolet. We establish the energy scale of the single particle excitation across the CDW gap. Moreover, we find that the CDW collective state gaps a large portion of the Fermi surface. Based on the observation of a power-law behavior in the optical conductivity, similar to that found for the related rare-earth tritellurides but over a reduced frequency range, we suggest that interactions and umklapp processes may play a role in the onset of the CDW broken-symmetry ground state.

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89. Pressure Dependence of the Charge-Density-Wave Gap in Rare-Earth Tritellurides
A. Sacchetti, E. Arcangeletti, A. Perucchi, L. Baldassarre, P. Postorino, S. Lupi, N. Ru, I. R. Fisher and L. Degiorgi
Phys. Rev. Lett. 98, 026401 (2007).

ABSTRACT
We investigate the pressure dependence of the optical properties of CeTe3, which exhibits an incommensurate charge-density-wave (CDW) state already at 300 K. Our data are collected in the midinfrared spectral range at room temperature and at pressures between 0 and 9 GPa. The energy for the single particle excitation across the CDW gap decreases upon increasing the applied pressure, similarly to the chemical pressure by rare-earth substitution. The broadening of the bands upon lattice compression removes the perfect nesting condition of the Fermi surface and therefore diminishes the impact of the CDW transition on the electronic properties of RTe3.

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88. Multiple Magnon Modes and Consequences for the Bose-Einstein Condensed Phase in BaCuSi2O6
Ch. Rüegg, D. F. McMorrow, B. Normand, H. M. Ronnow, S. E. Sebastian, I. R. Fisher, C. D. Batista, S. Gvasaliya, Ch. Niedermayer, J. Stahn
Phys. Rev. Lett. 98, 017202 (2007).

ABSTRACT
The compound BaCuSi2O6 is a quantum magnet with antiferromagnetic dimers of S=1/2 moments on a quasi-2D square lattice. We have investigated its spin dynamics by inelastic neutron scattering experiments on single crystals with an energy resolution considerably higher than in an earlier study. We observe multiple magnon modes, indicating clearly the presence of magnetically inequivalent dimer sites. The more complex spin Hamiltonian revealed in our study leads to a distinct form of magnon Bose-Einstein condensate phase with a spatially modulated condensate amplitude.

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87. Bose-Einstein condensation in BaCuSi2O6
N. Harrison, S. E. Sebastian, C. D. Batista, M. Jaime, L. Balicas, P. A. Sharma, N. Kawashima and I. R. Fisher
J. Phys.: Conf. Ser. 51, 9-14 (2006).

ABSTRACT
BaCuSi2O6 is a model spin dimer system in which a BEC QCP is realised. Universal BEC power law scaling is experimentally observed, with 3d critical behaviour above 0.5 K, but a crossover to 2d BEC critical scaling down to 30 mK. Here we briefly review and expand on the results presented in the recent Nature paper.

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86. Role of anisotropy in the spin-dimer compound BaCuSi2O6
S. E. Sebastian, P. Tanedo, P. A. Goddard, S.-C. Lee, A. Wilson, S. Kim, S. Cox, R. D. McDonald, S. Hill, N. Harrison, C. D. Batista and I. R. Fisher
Phys. Rev. B. 74, 180401(R) (2006).

ABSTRACT
We present results of magnetization and electron paramagnetic resonance experiments on the spin dimer system BaCuSi2O6. Evidence indicates that the origin of anisotropic terms in the spin Hamiltonian lies in magnetic dipolar interactions. Axial symmetry breaking is on a very small energy scale of < 11 mK, confirming Bose Einstein condensation critical scaling over an extended temperature range in the vicinity of the quantum critical point.

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85. Type II superconducting parameters of Tl-doped PbTe determined from heat capacity and electronic transport measurements
Y. Matsushita, P. Wianicki, A. T. Sommer, T. H. Geballe and I. R. Fisher
Phys. Rev. B. 74, 134512 (2006).

ABSTRACT
Tl-doped PbTe (Pb_{1-x}Tl_{x}Te) is an anomalous superconductor with a remarkably high maximum T_c value given its relatively low carrier concentration. Here, we present results of systematic measurements of superconducting parameters for this material, for Tl concentrations up to x=1.4%. We find that it is a Type II, weak-coupled BCS superconductor in the dirty limit and discuss implications for the applicability of the charge Kondo model recently proposed to account for superconductivity in this system.

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84. Extrinsic origin of the insulating behavior of polygrain icosahedral Al-Pd-Re quasicrystals
J. Dolinsek, P. J. McGuiness, M. Klanjsek, I. Smiljanic, A. Smontara, E. S. Zijlstra, S. K. Bose, I. R. Fisher, M. J. Kramer and P. C. Canfield
Phys. Rev. B. 74, 134201 (2006).

ABSTRACT
Polygrain icosahedral i-Al-Pd-Re quasicrystals are known to exhibit dramatically different electronic transport properties to other Al-based quasicrystals. By performing comparative experimental and theoretical studies of the electronic transport and electronic structure of polygrain and monocrystalline i-Al-Pd-Re samples, we show that the extraordinarily high electrical resistivity and the metal-to-insulator transition in the polygrain material are not intrinsic properties of the quasiperiodic lattice, but are of extrinsic origin due to the high porosity and the oxygen-rich weakly insulating regions in the material. We also compare theoretical electronic structures and experimental electrical resistivities of monocrystalline i-Al-Pd-Re and i-Al-Pd-Mn quasicrystals and show that there are no significant differences between these two isomorphous compounds, suggesting that i-Al-Pd-Re is on common ground with other Al-based quasicrystals. We present a structural model of i-Al-Pd-Re.

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83. Chemical pressure and hidden one-dimensional behavior in rare earth tri-telluride charge density wave compounds
A. Sacchetti, L. Degiorgi, T. Giamarchi, N. Ru and I. R. Fisher,
Phys. Rev. B. 74, 125115 (2006).

ABSTRACT
We report on the first optical measurements of the rare-earth tri-telluride charge-density wave systems. Our data, collected over an extremely broad spectral range, allow us to observe both the Drude component and the single-particle peak, ascribed to the contributions due to the free charge carriers and to the charge-density wave gap excitation, respectively. The data analysis displays a diminishing impact of the charge-density wave condensate on the electronic properties with decreasing lattice constant across the rare-earth series. We propose a possible mechanism describing this behavior and we suggest the presence of a one-dimensional character in these two-dimensional compounds. We also envisage that interactions and umklapp processes might play a relevant role in the formation of the charge-density wave state in these compounds.

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82. Comment on “Bose-Einstein condensation of magnons in Cs2CuCl4”
S. E. Sebastian, V. S. Zapf, N. Harrison, C. D. Batista, P. A. Sharma, M. Jaime, I. R. Fisher and A. Lacerda
Phys. Rev. Lett. 96, 189703 (2006).


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81. Use of periodic approximants in a dynamical LEED study of the quasicrystalline tenfold surface of decagonal Al-Ni-Co
K. Pussi, N. Ferralis, M. Mihalkovic, M. Widom, S. Curtarolo, M. Gierer, C. J. Jenks, P. C. Canfield, I. R. Fisher and R. D. Diehl
Phys. Rev. B. 73, 184203 (2006).

ABSTRACT
The determination of quasicrystal (QC) surface structures is a challenge to current surface structure techniques. Low-energy electron diffraction (LEED) is the primary technique for the determination of periodic surface structures, but application of dynamical LEED to quasicrystals requires the use of many approximations. In this study, two different approaches were used to apply dynamical LEED to the structure of the tenfold surface of decagonal Al73Ni10Co17. One method (method 1) involves the use of a quasicrystalline model along with approximations that average over the composition and local geometries. The other method (method 2) uses periodic models that approximate the actual local QC structure (approximants) in more exact, atomistic calculations. Although the results using the two methods were consistent, the results of the approximant analysis (method 2) suggested a different way to apply the approximations in method 1, resulting in a better fit between experimental and calculated beams. Thus, periodic approximant structure models can provide a simpler and more efficient method for the determination of local geometries in QC surfaces, and may also facilitate analyses using quasicrystal models.

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80. Dimensional reduction at a quantum critical point
S. E. Sebastian, N. Harrison, C. D. Batista, L. Balicas, M. Jaime, P. A. Sharma, N. Kawashima and I. R. Fisher
Nature vol. 441, number 7093, pp 617-620 (June 1st 2006).

ABSTRACT
Competition between electronic ground states near a quantum critical point (QCP) — the location of a zero-temperature phase transition driven solely by quantum-mechanical fluctuations — is expected to lead to unconventional behaviour in low-dimensional systems. New electronic phases of matter have been predicted to occur in the vicinity of a QCP by two-dimensional theories, and explanations based on these ideas have been proposed for signifi- cant unsolved problems in condensed-matter physics, such as non-Fermi-liquid behaviour and high-temperature superconductivity. But the real materials to which these ideas have been applied are usually rendered three-dimensional by a finite electronic coupling between their component layers; a two-dimensional QCP has not been experimentally observed in any bulk threedimensional system, and mechanisms for dimensional reduction have remained the subject of theoretical conjecture. Here we show evidence that the Bose–Einstein condensate of spin triplets in the three-dimensional Mott insulator BaCuSi2O6 provides an experimentally verifiable example of dimensional reduction at a QCP. The interplay of correlations on a geometrically frustrated lattice causes the individual two-dimensional layers of spin-1/2 Cu2+ pairs (spin dimers) to become decoupled at the QCP, giving rise to a two-dimensional QCP characterized by linear power law scaling distinctly different from that of its three-dimensional counterpart. Thus the very notion of dimensionality can be said to acquire an ‘emergent’ nature: although the individual particles move on a three-dimensional lattice, their collective behaviour occurs in lower-dimensional space.

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79. Low temperature structural phase transition and incommensurate lattice modulation in the spin gap compound BaCuSi2O6
E. C. Samulon, Z. Islam, S. E. Sebastian, P. B. Brooks, M. K. McCourt Jr., J. Ilavsky and I. R. Fisher
Phys. Rev. B. 73, 100407(R) (2006).

ABSTRACT
Results of high resolution x-ray diffraction experiments are presented for single crystals of the spin gap compound BaCuSi2O6 in the temperature range from 16 to 300 K. The data show clear evidence of a transition from the room temperature tetragonal phase into an incommensurately modulated orthorhombic structure below ~100 K. This lattice modulation is characterized by a resolution-limited reduced wavevector q=(0,0.129+/-0.001,0) (reciprocal lattice units) referred to the orthorhombic lattice, and its 2nd and 3rd harmonics. The phase transition is first order and exhibits considerable hysteresis. This observation implies that the spin Hamiltonian representing the system is more complex than originally thought.

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78. Scanning Hall probe imaging of ErNi2B2C
H. Bluhm, S. E. Sebastian, J. W. Guikema, I. R. Fisher and K. A. Moler
Phys. Rev. B. 73, 014514 (2006).

ABSTRACT
We report scanning Hall probe imaging of ErNi2B2C in the superconducting, antiferromagnetic and weakly ferromagnetic regimes in magnetic fields up to 20 Oe, well below Hc1, with two results. First, imaging isolated vortices shows that they spontaneously rearrange on cooling through the antiferromagnetic transition temperature TN = 6 K to pin on twin boundaries, forming a striped pattern. Second, a weak, random magnetic signal appears in the ferromagnetic phase below TWFM = 2.3 K, and no spontaneous vortex lattice is present down to 1.9 K. We conclude that ferromagnetism coexists with superconductivity either by forming small ferromagnetic domains or with oscillatory variation of the magnetization on sub-penetration depth length scales.

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77. Thermodynamic and transport properties of YTe3, LaTe3 and CeTe3
N. Ru and I. R. Fisher
Phys. Rev. B. 73, 033101 (2006).

ABSTRACT
Measurements of heat capacity, susceptibility and electrical resistivity are presented for single crystals of the charge density wave compounds YTe3, LaTe3 and CeTe3. The materials are metallic to low temperatures, but have a small density of states due to the charge density wave gapping large portions of the Fermi surface. CeTe3 is found to be a weak Kondo lattice, with an antiferromagnetic groundstate and T_N = 2.8 K. The electrical resistivity of all three compounds is highly anisotropic, confirming the weak dispersion perpendicular to Te planes predicted by band structure calculations.

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76. Characteristic BEC scaling close to Quantum Critical Point in BaCuSi2O6
S. E. Sebastian, P. A. Sharma, M. Jaime, N. Harrison, V. Correa, L. Balicas, N. Kawashima, C. D. Batista and I. R. Fisher
Phys. Rev. B. 72, 100404(R) (2005).

ABSTRACT
We report an experimental determination of the phase boundary approaching the quantum critical point separating a quantum paramagnetic state and the proposed spin Bose-Einstein condensate of triplons in the spin dimer compound BaCuSi2O6. The ordering temperature is related to the proximity to a quantum critical point at the lower critical magnetic field Hc1 = 23.52 +/- 0.03 T by a power law parameterized by critical exponent nu. We obtain an experimental estimate of nu = 0.63 +/- 0.03 down to a temperature of 0.61 K, which is in good agreement with the mean field prediction of nu = 2/3 for the 3D Bose-Einstein condensation universality class.

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75. Evidence for charge Kondo effect in superconducting Tl-doped PbTe
I. R. Fisher, Y. Matsushita, H. Bluhm and T. H. Geballe
Proc. SPIE Vol. 5932, 59321Y (Aug. 30, 2005).

ABSTRACT
We report results of low temperature thermodynamic and transport measurements of Pb(1-x)Tl(x)Te single crystals for Tl concentrations up to the solubility limit of approximately 1.5 %. The material superconducts for x > 0.3 %, with a maximum Tc of 1.5 K for the highest Tl concentrations. All superconducting samples exhibit an anomalous resistivity upturn at low temperatures, whereas non-superconducting samples (x < 0.3%) do not. The temperature and field dependence of this resistivity upturn are consistent with a charge Kondo effect involving degenerate Tl valence states differing by two electrons, with a characteristic Kondo temperature TK ~ 6 K. The observation of such an effect supports an electronic pairing mechanism for superconductivity in this material and may account for the anomalously high Tc values.

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74. Electronic structure and charge density wave formation in LaTe1.95 and CeTe2.00
K. Y. Shin, V. Brouet, N. Ru, Z. X. Shen and I. R. Fisher
Phys. Rev. B. 72, 085132 (2005).

ABSTRACT
Results are presented of complementary measurements that probe the electronic structure and charge density wave (CDW) modulation in the quasi-2D compounds LaTe1.95 and CeTe2. Transmission electron micrographs show that the modulation wave vectors associated with the CDW are different for the two materials, and in both cases are incommensurate with the underlying lattice. These wavevectors are shown to correspond to nesting features of a simplified model of the Fermi surface. Angle Resolved PhotoEmission Spectroscopy is used to reveal the electronic structure and Fermi surface topology in the CDW state. The data indicate a large CDW gap that varies in magnitude around the Fermi surface rather differently for the two compounds. Differences in the volume of the original Fermi surface are related to the doping effect of Te vacancies. Heat capacity measurements at low temperatures indicate a very small electronic density of states, consistent with the electrical resistivity, which appears to be semiconducting or semimetallic.

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73. Magnetic structure of GdCo2Ge2
W. Good, J. Kim, A.I. Goldman, D. Wermeille, P. C. Canfield, Z. Islam, J. C. Lang, G. Srajer and I. R. Fisher,
Phys. Rev. B. 71, 224427 (2005).

ABSTRACT
Resonant and nonresonant magnetic x-ray scattering studies of GdCo2Ge2 were performed to determine its magnetic structure at low temperature. This compound orders in an incommensurate antiferromagnetic (AF) structure characterized by a propogation wave vector t=(0,0,tz). The value of tz is temperature dependent and approaches 0.930 reciprocal lattice units well below TN = 33.25 K. A peak corresponding to 3tz was also observed, indicating either a squaring up of the magnetic structure or the presence of a noncollinear amplitude modulated structure below TN. Fitting the angular dependence of the magnetic scattering integrated intensities to the relevant resonant and nonresonant scattering cross sections revealed that the moment direction lies primarily in the tetragonal basal plane. Scattering measurements at the Co K-edge failed to detect any resonant signal, consistent with the absence of a magnetic moment on the Co sites.

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72. High-field behavior of the spin-gap compound Sr2Cu(BO3)2
S.E. Sebastian, D. Yin, P. Tanedo, N. Harrison, G. Jorge, M. Jaime, Y. Moyzerov, G. Miller and I. R. Fisher,
Phys. Rev. B. 71, 212405 (2005).

ABSTRACT
We report magnetization and heat capacity measurements of single crystal samples of the spin gap compound Sr2Cu(BO3)2. Low-field data show that the material has a singlet ground state comprising dimers with intradimer coupling J = 100 K. High field data reveal the role of weak interdimer coupling. For fields that are large compared to the spin gap, triplet excitations are observed for significantly smaller fields than predicted for isolated dimers, indicating that weak inter-dimer coupling leads to triplet delocalization. High field magnetization behavior at low temperatures suggests additional cooperative effects.

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71. Evidence for charge Kondo effect in superconducting Tl-doped PbTe
Y. Matsushita, H. Bluhm, T. H. Geballe and I. R. Fisher,
Phys. Rev. Lett., 94, 157002 (2005).

ABSTRACT
We report results of low-temperature thermodynamic and transport measurements of Pb_{1-x}Tl_{x}Te single crystals for Tl concentrations up to the solubility limit of approximately x = 1.5%. For all doped samples, we observe a low-temperature resistivity upturn that scales in magnitude with the Tl concentration. The temperature and field dependence of this upturn are consistent with a charge Kondo effect involving degenerate Tl valence states differing by two electrons, with a characteristic Kondo temperature T_K ~ 6 K. The observation of such an effect supports an electronic pairing mechanism for superconductivity in this material and may account for the anomalously high Tc values.

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70. Fermi surface nesting and charge-density wave formation in rare-earth tritellurides
J. Laverock, S. B. Dugdale, Zs. Major, M. A. Alam, N. Ru, I. R. Fisher, G. Santi, and E. Bruno,
Phys. Rev. B. 71, 085114 (2005).

ABSTRACT
The Fermi surface of rare earth tritellurides (RTe3) is investigated in terms of the nesting-driven charge- density wave formation using positron annihilation and first-principles linear muffin-tin orbital calculations. Fermi surface nesting is revealed as a strong candidate for driving charge density wave formation in these compounds. The nesting vector obtained from positron annihilation experiments on GdTe3 is determined to be q = (0.28+/-0.02,0,0)a* (a* = 2pi/a), in excellent agreement with previous experimental and theoretical studies.

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69. Magneto-optic spectrum and electronic structure of single-crystal MnBi
D. P. Brammeier, J.-M. Park, C. G. Olsen, I. R. Fisher and D. W. Lynch,
J. Magnetism and Magnetic Materials, 283, 95-102 (2004).
ABSTRACT
Single crystals of MnBi were used for magneto-optic Kerr-angle spectroscopy and photoelectron spectroscopy. The Kerr-angle peak at 3.35 eV was observed for our nearly oxygen-free bulk samples, but the role of the oxide overlayer, demonstrated by Auger spectroscopy, as a possible origin of this peak cannot be fully assessed. The energy bands from photoelectron spectroscopy were in general agreement with calculated band structures, but were not extensive enough, due to sample cleavage properties, to distinguish reliably between band-structure calculations that disagree.

68. Fermi surface reconstruction in the CDW state of CeTe3 observed by photoemission
V. Brouet, W. L. Yang, X. J. Zhou, Z. Hussain, N. Ru, K. Y. Shin, I. R. Fisher and Z. X. Shen,
Phys. Rev. Lett, 93, 126405 (2004).

ABSTRACT
CeTe3 is a layered compound where an incommensurate charge density wave (CDW) opens a large gap (~400 meV) in optimally nested regions of the Fermi surface (FS), whereas other sections with poorer nesting remain ungapped. Through angle-resolved photoemission, we identify bands back-folded according to the CDW periodicity. They define FS pockets formed by the intersection of the original FS and its CDW replica. Such pockets illustrate very directly the role of nesting in the CDW formation but they could not be detected so far in a CDW system. We address the reasons for the weak intensity of the folded bands, by comparing different foldings coexisting in CeTe3.

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67. An STM and SXPS study of the interaction of C60 with the ten-fold surface of the Al72Ni11Co17 quasicrystal
E.J. Cox, J. Ledieu, V.R. Dhanak, S.D. Barrett, C.J. Jenks, I. R. Fisher, and R. McGrath,
Surface Science, 566-568, 1200-1205 (2004).

66. Structure of the ten-fold d-AlNiCo quasicrystal surface
N. Ferralis, K. Pussi, E.J. Cox, M. Gierer, J. Ledieu, I. R. Fisher, C. J. Jenks, M. Lindroos, R. McGrath, and R.D. Diehl,
Phys. Rev. B, 69, 153404 (2004).

65. Magnetic properties of single grain R-Mg-Cd primitive icosahedral quasicrystals (R = Y, Gd, Tb, Dy)
S. E. Sebastian, T. Huie, I. R. Fisher, K. W. Dennis and M. J. Kramer
Phil. Mag. B 84, 1029-1037 (2004).

ABSTRACT
The growth and characterization of single grains of the primitive icosahedral quasicrystal R-Mg-Cd (R = Y, Gd, Tb or Dy) are described. From the thermodynamic properties, it is confirmed that the system is a spin glass exhibiting the characteristic spin-freezing transition of such systems. There is no evidence for two distinct freezing transitions previously observed for polygrain samples. The bulk magnetic properties and the effect of crystalline electric fields on the spin-freezing temperature are found to be very similar to those of the face-centred icosahedral quasicrystal R-Mg-Zn.

64. Low energy electron diffraction study of Xe adsorption on the ten-fold decagonal Al-Ni-Co quasicrystal surface
N. Ferralis, R.D. Diehl, K. Pussi, M. Lindroos, I. Fisher, and C.J. Jenks,
Phys. Rev. B. 69, 075410 (2004).

63. Phonon dispersion curve of Mg-Zn-Y quasicrystals
R. A. Brand, J. Voss, F. Hippert, M. Krisch, R. Sterzel, W. Assmus and I. R. Fisher,
Journal of noncrystalline solids, 334&335, 207-209 (2004).

62. Degree of structural perfection of icosahedral quasicrystalline grainsinvestigated by synchrotron x-ray diffractometry and imaging techniques
J. Gastaldi, S. Agliozzo, A. Letoublon, J. Wang, L. Mancini, H. Klein, J. Hartwig, J. Baruchel, I. R. Fisher, T. Sato, A. P. Tsai and A. M. de Boissieu,
Phil. Mag. 83, 1-29 (2003).

61. Surface structures of approximant phases in the Al-Pd-Mn system
V. Fournee, A. R. Ross, T. A. Lograsso, J. W. Anderegg, C. Dong, K. Kramer, I.R. Fisher, P. C. Canfield, and P. A. Thiel,
Phys. Rev. B. 66, 165423 (2002).

60. Quasicrystal surfaces: potential as templates for molecular adsorption
R. McGrath, J. Ledieu, E. J. Cox, S. Haq, R. D. Diehl, C. J. Jenks, I. R. Fisher, A. R. Ross and T. A. Lograsso,
Journal of Alloys and Compounds 342, 432 (2002).

59. Transport properties of icosahedral quasicrystal Al72Pd19.5Mn8.5
A. Bilusic, Z. Budrovic, A. Smontara, J. Dolinsek, P. C. Canfield, and I. R. Fisher,
Journal of Alloys and Compounds 342, 413-415 (2002).

58. The local atomic structure of R-Mg-Zn (R=Y, Gd, Dy and Tb)
M. J. Kramer, S. T. Hong, P. C. Canfield, I. R. Fisher, J. D. Corbett, Y. Zhu, and A. I. Goldman,
Journal of Alloys and Compounds 342, 82-86 (2002).

57. The electrical conductivity of single-grain Al-Pd-Re quasicrystals
I. R. Fisher, X. P. Xie, I. Tudosa, C. W. Gao, C. Song, P. C. Canfield, A. Kracher, K. Dennis, D. Abanoz and M.J. Kramer
Phil. Mag. B 82, 1089 (2002).

ABSTRACT
Systematic electrical transport data are presented for single quasicrystals in the Al-Pd-Re family across the accessible width of formation. The temperature dependence of the electrical conductivity can be accounted for in terms of weak localization and electron-electron interactions for all compositions studied, in contrast to previous studies of cast and annealed polygrain material. These results indicate that the conductivity mechanism in the Al-Pd-Re system is not dramatically different from that of other quasicrystal families.

56. Surface preparation and characterization of the icosahedral Al-Ga-Pd-Mn quasicrystal
M. Heinzig, C. J. Jenks, M. Van Hove, I. R. Fisher, P. C. Canfield and P. A. Thiel,
J. Alloys and Compounds 338, 248-252 (2002).

55. The ten-fold surface of the decagonal Al72Ni11Co17 quasicrystal studied by LEED, SPA-LEED, AES and STM
E. J. Cox, J. Ledieu, R. McGrath, R. D. Diehl, C. J. Jenks, and I. R. Fisher,
Materials Research Society Symposium Proceedings (2001), 643, K11.3.1-K11.3.6 (2002).

54. The thermal stability of a single-grain Mg-Zn-Y icosahedral quasicrystal
Z. P. Luo, Y. L. Tang, D. J. Miller, M. J. Kramer, I. R. Fisher, and P. C. Canfield,
Materials Research Society Symposium Proceedings (2001), 643, K9.4.1-K9.4.6 (2002).

53. The influence of growth rate on porosity in icosahedral Al-Pd-Mn quasicrystals,
A. R. Ross, I. R. Fisher, P. C. Canfield and T. A. Lograsso,
Materials Research Society Symposium Proceedings (2001), 643, K1.5.1-K1.5.5. (2002).

52. Icosahedral quasicrystal Al-Pd-Mn and its xsi' approximant: linear expansivity, specific heat, magnetic susceptibility, electrical resistivity and elastic constants
C. Swenson, I. R. Fisher, N. E. Anderson Jr., P. C. Canfield and A. Migliori,
Phys. Rev. B. 65, 184206 (2002).

51. Microwave conductivity and penetration depth in the heavy fermion superconductor CeCoIn5
R. J. Ormeno, A. Sibley, C. E. Gough, S. Sebastian and I. R. Fisher,
Phys. Rev. Lett. 88, 047005 (2002).

50. Infrared and optical properties of pure and cobalt doped LuNi2B2C
M. Windt, J. J. McGuire, T. Room, A. Pronin, T. Timusk, I. R. Fisher, and P. C. Canfield,
Phys. Rev. B. 65, 064506/1-064506/9 (2002).

49. High-temperature solution growth of single crystals and quasicrystals
P. C. Canfield and I. R. Fisher,
J. Crystal Growth, 225, 155-161 (2001).

48. Observation of a spin reorientation in TbCu2Ge2 from resonant and non-resonant x-ray scattering
C. Song, D. Johnson, D. Wermeille, A. I. Goldman, S. L. Bud'ko, I. R. Fisher, and P. C. Canfield,
Phys. Rev. B 64, 224414 (2001).

47. Unusual spin glass phase in icosahedral Tb-Mg-Zn quasicrystals
J. Dolinsek, Z. Jaglicic, M. A. Chernikov, I. R. Fisher, and P. C. Canfield,
Phys. Rev. B 64, 224209 (2001).

46. Reentrant behavior in the temperature dependence of metamagnetic transitions in single crystal Nd6Fe13-xAl1+x
R. W. McCallum, I. R. Fisher, N. E. Anderson, P. C. Canfield, M. J. Kramer and K. W. Dennis
IEEE Transactions on Magnetics 37(4, Pt. 1), 2147 (2001).

45. R9Mg34Zn57 icosahedral quasicrystals: The tuning of a model spin glass
P.C. Canfield and I.R. Fisher,
J. Alloys and Compounds 317-318, 443-447 (2001).

44. Structure and physical properties of the new Pseudo-binary intermetallic compound Ti11(Sb,Sn)8
H. Kim, M.M. Olmstead, J.Y. Chan, P.C. Canfield, I.R. Fisher, R.W. Henning, A.J. Schultz and S.M. Kauzlarich,
J. Solid State Chemistry 157, 225-232 (2001).

43. Investigation of the effect of Ga doping on the thermoelectric properties of the A1PdMn quasicrystalline system.
D.W. Winkler, A.L. Pope, T.M. Tritt, I.R. Fisher, T.A. Wiener and P.C. Canfield,
Proc. 18th Int. Conf. Thermoelectr. 398-401 (1999).

42. Plasticity of icosahedral Zn-Mg-Dy single quasicrystals
M. Heggen, P. Schall, M. Feuerbacher, H. Klein, I. R. Fisher, P.C. Canfield and K. Urban,
Materials Science and Engineering A 294-296, 781-785 (2000).

41. Heat capacities of icosahedral and hexagonal phases of Zn-Mg-Y system
A. Inaba, H. Takakura, A. P. Tsai, I. R. Fisher, and P. C. Canfield,
Materials Science & Engineering, A 294-296 723-726 (2000).

40. Electrical resistivity, thermopower, and thermal conductivity of single-grained (Y, Tb, Ho, Er)-Mg-Zn icosahedral quasicrystals.
K. Gianno, A.V. Sologubenko, M.A. Chernikov, H.R. Ott, I. R. Fisher and P.C. Canfield,
Materials Science and Engineering A 294-296, 715-718 (2000).

39. Diffusion of 57Co in decagonal Al-Ni-Co quasicrystals
C. Khoukaz, R. Galler, H. Mehrer, P.C. Canfield, I.R. Fisher and M. Feuerbacher
Materials Science and Engineering A 294-296, 697-701 (2000).

38. Phason strain and structural perfection in the R-Mg-Zn icosahedral phases
A. Letoublon, I.R. Fisher, T.J. Sato, M. de Boissieu, M. Boudard, S. Agliozzo, L. Mancini, J. Gastaldi, P.C. Canfield, A.I Goldman and A.P. Tsai,
Materials Science and Engineering A 294-296, 127-130 (2000).

37. Formation and morphological development of porosity in icosahedral Al-Pd-Mn alloys.
A. R. Ross, T.A. Wiener, I.R. Fisher, P.C. Canfield and T.A. Lograsso,
Materials Science and Engineering A 294-296, 53-56 (2000).

36. Growth of large single-grain quasicrystals from high-temperature metallic solutions
I.R. Fisher, M.J. Kramer, Z. Islam, T.A. Wiener, A. Kracher, A.R. Ross, T.A. Lograsso, A.I. Goldman and P.C. Canfield,
Materials Science and Engineering A 294-296, 10-16 (2000).

35. Design of a metallic Ising spin glass in the Y1-xTbxNi2Ge2 system
T.A. Wiener, I. R. Fisher, S.L. Bud'ko, A. Kracher and P.C. Canfield,
Phys. Rev. B. 62, 15056-15066 (2000).

34. Nonlocal effects in magnetization of high-kappa superconductors
V.G. Kogan, S.L. Bud'ko, I. R. Fisher and P.C. Canfield,
Phys. Rev. B. 62, 9077-9082 (2000).

33. Observation of a metamagnetic phase transition in an itinerant 4f system via the magneto-optic Kerr effect: Ce(Fe1-xCox)2
R.J. Lange, I.R. Fisher, P.C. Canfield, V.P. Antropov, S.J. Lee, B.N. Harmon and D.W. Lynch,
Phys. Rev. B. 62, 7084-7092 (2000).

32. Yb14ZnSb11: charge balance in Zintl compounds as a route to intermediate Yb valence
I.R. Fisher, S.L. Bud'ko, C. Song, P.C. Canfield, T.C. Ozawa and S.M. Kauzlarich,
Phys. Rev. Lett. 85, 1120-1123 (2000).

31. Low-temperature thermal conductivity of a single-grain Y-Mg-Zn icosahedral quasicrystal
K. Giannò, A.V. Sologubenko, M.A. Chernikov, H.R. Ott, I.R. Fisher, and P.C. Canfield,
Phys. Rev. B 62, 292-300 (2000).

30. Low-temperature transport, thermal and optical properties of single-grain quasicrystals of icosahedral phases in the Y-Mg-Zn and Tb-Mg-Zn alloy systems
M.A. Chernikov, S. Paschen, E. Felder, P. Vorburger, B. Ruzicka, L. Degiorgi, H.R. Ott, I.R. Fisher, and P.C. Canfield,
Phys. Rev. B 62, 262-272 (2000).

29. Non-locality and the flux line lattice square to hexagonal symmetry transition in the borocarbide superconductors
M.R. Eskildsen, I.R. Fisher, P.L. Gammel, D.J. Bishop, N.H. Andersen, K. Mortensen and P.C. Canfield,
Physica C 332, 320-326 (2000).

28. The magnetic characteristics of the Tb(Ni1-xCox)2Ge2 system
T.A. Wiener, I.R. Fisher and P.C. Canfield,
J. Alloys and Compounds 303-304, 289-292 (2000).

27. Magnetic properties of icosahedral R-Mg-Zn quasicrystals
I.R. Fisher, Z. Islam J. Zarestky, C. Stassis, M.J. Kramer, A.I. Goldman and P.C. Canfield,
J. Alloys and Compounds 303-304, 223-227 (2000).

26. Recent advances in the study of quasicrystals
I.R. Fisher, M.J. Kramer and A.I. Goldman,
Micron 31, 469-473 (2000).

25. Interwoven magnetic and flux line structures in single crystal (Tm,Er)Ni2B2C
P.L. Gammel, D. Lopez, D.J. Bishop, M.R. Eskildsen, N.H. Andersen, K. Mortensen, I.R. Fisher, K.O. Cheon and P.C. Canfield
Journal of Applied Physics 87, 5544-5548 (2000).

24. A comparison of structural stabilities of the three high-symmetry surfaces of Al-Pd-Mn bulk quasicrystals using LEED
Z. Shen, W. Raberg, M. Heinzig, C.J. Jenks, V. Fournée, M.A. Van Hove, T.A. Lograsso, D. Delaney, T. Cai, P.C. Canfield, I.R. Fisher, A.I. Goldman, M.J. Kramer, and P.A. Thiel
Surface Science 450, 1-11 (2000).

23. Optical properties and electronic structure of single crystals of LuAl2 and YbAl2
S.J. Lee, S.Y. Hong, I.R. Fisher, P.C. Canfield, B.N. Harmon and D.W. Lynch
Phys. Rev. B 61, 10076-10083 (2000).

22. Plastic deformation of icosahedral Zn-Mg-Dy single quasicrystals
M. Heggen, M. Feuerbacher, P. Schall, H. Klein, I.R. Fisher, P.C. Canfield and K. Urban
Phil. Mag. Letters, 80, 129-136 (2000).

21. Nesting properties and anisotropy of the Fermi surface of LuNi2B2C
S.B. Dugdale, M.A. Alam, I. Wilkinson, R.J. Hughes, I.R. Fisher, P.C. Canfield, T. Jarlborg and G. Santi,
Phys. Rev. Lett. 83, 4824-4827 (1999).

20. On the growth of icosahedral Al-Pd-Mn quasicrystals from the ternary melt
I.R. Fisher, M.J. Kramer, T.A. Wiener, Z. Islam, A.R. Ross, T.A. Lograsso, A. Kracher, A.I. Goldman and P.C. Canfield,
Phil. Mag. B 79, 1673-1684 (1999).

19. Critical doping in overdoped high-Tc superconductors: a quantum critical point?
J.L. Tallon, J.W. Loram, G.V.M. Williams, J.R. Cooper, I.R. Fisher, J.D. Johnson, M.P. Staines and C. Bernhard,
Physica Status Solidi B 215, 531-540 (1999).

18. Anisotropy and metamagnetism in the RNi2Ge2 (R = Y, La-Nd, Sm-Lu) series
S.L. Bud'ko, Z. Islam, T.A. Wiener, I.R. Fisher, P.C. Canfield and A.H. Lacerda
J. Magn. Magn. Mat. 205, 53 - 78 (1999).

17. Systematic study of anisotropic transport and magnetic properties of RAgSb2 (R = Y, La-Nd, Sm, Gd-Tm)
K.D Myers, S.L. Bud'ko, I.R. Fisher, Z. Islam, H. Kleinke, P.C. Canfield and A.H. Lacerda,
J. Magn. Magn. Mat. 205, 27 - 52 (1999).

16. Magnetic and transport properties of single-crystal R2Cu2In (R = Gd-Tm, Lu)
I.R. Fisher, Z. Islam and P.C. Canfield,
J. Magn. Magn. Mat. 202, 1-10 (1999).

15. Thermodynamic and Transport Properties of Single-Crystal Yb14MnSb11
I.R. Fisher, T. A. Wiener, S. L. Bud'ko P. C. Canfield, J. Y. Chan and S. M. Kauzlarich,
Phys. Rev. B 59, 13829-13834 (1999).

14. Systematic studies of the square-hexagonal flux line lattice transition in Lu(Ni1-xCox)2B2C: the role of non-locality
P.L. Gammel, D.J. Bishop, M.R. Eskildsen, K. Mortensen, N.H. Andersen, I.R. Fisher, K.O. Cheon, P.C. Canfield and V.G. Kogan,
Phys. Rev. Lett. 82, 4082-4085 (1999).

13. On the growth of decagonal Al-Ni-Co quasicrystals from the ternary melt
I.R. Fisher, M.J. Kramer, Z. Islam, A.R. Ross, A. Kracher, T. Wiener, M.J. Sailer, A.I. Goldman and P.C. Canfield,
Phil. Mag. B 79, 425-434 (1999).

12. Boron isotope effect in single-crystal YNi2B2C and LuNi2B2C superconductors
K.O. Cheon, I.R. Fisher and P.C. Canfield,
Physica C 312, 35-39 (1999).

11. Magnetic and transport properties of single-grain R-Mg-Zn icosahedral quasicrystals [R = Y, (Y1-xGdx), (Y1-xTbx), Tb, Dy, Ho and Er]
I.R. Fisher, K.O. Cheon, A.F. Panchula, P.C. Canfield, M. Chernikov, H.R. Ott, and K. Dennis,
Phys. Rev. B 59, 308-321 (1999).

10. Resistivity and magnetic susceptibility of single-crystal Lu(Ni1-xCox)2B2C
K.O. Cheon, I.R. Fisher, V.G. Kogan, P.C. Canfield, P. Miranovic and P.L. Gammel,
Phys. Rev. B 58, 6463-6467 (1998).

9. Reinvestigation of long-range magnetic ordering in icosahedral Tb-Mg-Zn
Z. Islam, I.R. Fisher, J. Zarestky, P.C. Canfield, C. Stassis and A.I. Goldman
Phys. Rev. B 57, R11047-R11050 (1998).

8. Growth of large-grain R-Mg-Zn quasicrystals from the ternary melt (R = Y, Er, Ho, Dy and Tb)
I.R. Fisher, Z. Islam, A.F. Panchula, K.O. Cheon, M.J. Kramer, P.C. Canfield and A.I. Goldman,
Phil. Mag. B 77, 1601-1615 (1998).

7. Anisotropic resistivity and normal-state magnetoresistance of RNi2B2C (R = Y, Lu, Er, Ho)
I.R. Fisher, J.R. Cooper and P.C. Canfield,
Phys. Rev. B 56, 10820-10823 (1997).

6. Angular dependence of the c-axis normal-state magnetoresistance in single-crystal Tl2Ba2CuO6
N.E. Hussey, J.R. Cooper, J.M. Wheatley, I.R. Fisher, A. Carrington, A.P. Mackenzie, C.T. Lin and O. Milat,
Phys. Rev. Lett. 76, 122-125 (1996).

5. Angular dependence of the c-axis normal-state magnetoresistance in single-crystal Tl2Ba2CuO6
N.E. Hussey, J.R. Cooper, I.R. Fisher, A.P. Mackenzie and J.M. Wheatley,
Proc. 10th Anniv HTS Workshop Phys., Mater. Appl., (Ed. B. Batlogg, World Scientific, Singapore) p330-331 (1996).

4. Normal-state properties of RNi2B2C (R = Y, Ho, La) and anisotropic resistivity of single-crystal RNi2B2C (R = Lu, Er, Ho)
I.R. Fisher, J.R. Cooper, K.R. Locherer, R.J. Cava and P.C. Canfield
J. Low T. Phys. 105, Nos. 5/6, 1623-1628 (1996).

3. Effect of sample density on the resistivity and Hall coefficient of polycrystalline La1.83Sr0.17CuO4
I.R. Fisher and J.R. Cooper,
Physica C 272, 125-130 (1996).

2. Normal-state transport and magnetic properties of RNi2B2C (R = Y, Ho, La)
I.R. Fisher, J.R. Cooper and R.J. Cava,
Phys. Rev. B 52, 15086-15089 (1995).

1. Hall effect and thermoelectric power of Y0.9Ca0.1Ba2Cu3O7-delta
I.R. Fisher, P.S.I.P.N. de Silva, J.W. Loram, J.L. Tallon, A. Carrington and J.R. Cooper,
Physica C 235-240, 1497-1498 (1994).

Fisher Research Group
Geballe Laboratory for Advanced Materials
Dept. of Applied Physics
Stanford University
CA 94305-4045
 Last updated: April 30th 2008