411 research outputs found
Susceptibility Inhomogeneity and Non-Fermi-Liquid Behavior in Ce(Ru_{0.5}Rh_{0.5})_2Si_2
Magnetic susceptibility and muon spin rotation (\muSR) experiments have been
carried out to study the effect of structural disorder on the non-Fermi-liquid
(NFL) behavior of the heavy-fermion alloy Ce(Ru_{0.5}Rh_{0.5})_2Si_2. Analysis
of the bulk susceptibility in the framework of disorder-driven Griffiths-phase
and Kondo-disorder models for NFL behavior yields relatively narrow
distributions of characteristic spin fluctuation energies, in agreement with
\muSR linewidths that give the inhomogeneous spread in susceptibility. \muSR
and NMR data both indicate that disorder explains the "nearly NFL" behavior
observed above \sim2 K, but does not dominate the NFL physics found at low
temperatures and low magnetic fields.Comment: 6 pages, 4 figures, REVTeX, submitted to Phys. Rev.
NMR investigation of vortex dynamics in Ba(Fe0.93Rh0.07)2As2 superconductor
75As NMR spin-lattice relaxation (1/T1) and spin-echo decay (1/T2) rate
measurements were performed in a single crystal of Ba(Fe0.93Rh0.07)2As2
superconductor. Below the superconducting transition temperature Tc, when the
magnetic field H is applied along the c axes, a peak in both relaxation rates
is observed. Remarkably that peak is suppressed for H || ab. Those maxima in
1/T1 and 1/T2 have been ascribed to the flux lines lattice motions and the
corresponding correlation times and pinning energy barriers have been derived
on the basis of an heuristic model. Further information on the flux lines
motion was derived from the narrowing of 75As NMR linewidth below Tc and found
to be consistent with that obtained from 1/T2 measurements. All the
experimental results are described in the framework of thermally activated
vortices motions.Comment: 8 pages, 11 figure
Magneto-Transport Properties of Doped RuSrGdCuO
RuSrGdCuO, in which magnetic order and superconductivity coexist
with , is a complex material which poses new and
important questions to our understanding of the interplay between magnetic and
superconducting (SC) order. Resistivity, Hall effect and thermopower
measurements on sintered ceramic RuSrGdCuO are presented, together
with results on a broad range of substituted analogues. The Hall effect and
thermopower both show anomalous decreases below which may be
explained within a simple two-band model by a transition from localized to more
itinerant behavior in the RuO layer at .Comment: 10 pages, 7 figures, submitted to Phys. Rev. B., correspondence to
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The Synthesis, Structure and Physical Properties of the Layered Ruthenocuprates RuSr2GdCu2O8 and Pb2Sr2Cu2RuO8Cl
Studies of the structure and physical properties of the layered rutheno- cuprates RuSr2GdCu2O8 and Pb2Sr2Cu2RuO8Cl are reviewed. RuSr2GdCu2O8 is a weak ferromagnetic superconductor and doping studies have shown that it is possible to tune the magnetic and superconducting transitions simultaneously. The average crystal structure of RuSr2GdCu2O8 is tetragonal at both 10 and 295 K (space group P4/mmm), but a sq.root2a x sq.root2a x c superstructure resulting from coherent rotations of the RuO6 octahedra within subdomains of 50-200 ºA is observed by selected area electron distraction (SAED). The same tilts and rotations of the RuO6 octahedra are observed in semiconducting Pb2Sr2Cu2RuO8Cl, which has strikingly similar magnetic properties to RuSr2GdCu2O8. Antiferromagnetic order is observed in the 10 K neutron diffraction pattern with a Ru moment of 1.1(1) B, but a spin-flop transition is observed above a field of 0.5 T
Penetration depth, multiband superconductivity, and absence of muon-induced perturbation in superconducting PrOsSb
Transverse-field muon spin rotation (SR) experiments in the
heavy-fermion superconductor PrOsSb ( K) suggest that
the superconducting penetration depth is temperature-independent
at low temperatures, consistent with a gapped quasiparticle excitation
spectrum. In contrast, radiofrequency (rf) inductive measurements yield a
stronger temperature dependence of , indicative of point nodes in
the gap. This discrepancy appears to be related to the multiband structure of
PrOsSb. Muon Knight shift measurements in PrOsSb
suggest that the perturbing effect of the muon charge on the neighboring
Pr crystalline electric field is negligibly small, and therefore is
unlikely to cause the difference between the SR and rf results.Comment: 10 pages, 7 figure
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