169 research outputs found
Transport properties of Ag5Pb2O6: a three-dimensional electron-gas-like system with low-carrier-density
We report normal-state transport properties of the single-crystalline samples
of the silver-lead oxide superconductor Ag5Pb2O6, including the electrical
resistivity, magnetoresistance, and Hall coefficient. From the Hall coefficient
measurement, we confirmed that the carrier density of this oxide is as low as
5x10^{21} cm^{-3}, one order of magnitude smaller than those for ordinary
alkali metals and noble metals. The magnetoresistance behavior is well
characterized by the axial symmetry of the Fermi surface and by a single
relaxation time. The T^2 term of the resistivity is scaled with the specific
heat coefficient, based on the recent theory for the electron-electron
scattering. The present results provide evidence that Ag5Pb2O6 is a
low-carrier-density three-dimensional electron-gas-like system with enhanced
electron-electron scatterings.Comment: 7 pages, 4 figures. Accepted for publication in Phys. Rev.
Field-Induced Transition on Triangular Plane in the Spin Ice Compound Dy2Ti2O7
The origin of the lowest-temperature anomaly reported several years ago using
a polycrystalline sample of the spin ice compound Dy2Ti2O7 had remained
unresolved. Here we finally clarify its origin by susceptibility measurements
down to 65 mK using single crystals under accurate control of the magnetic
fields in two independent directions. We demonstrate that the transition is
induced under a subtle field combination that precisely cancel the
nearest-neighbor spin interactions acting on the spins on the triangular
lattice within the pyrochlore structure. Contrary to the other two fieldinduced
transitions, this transition is driven only by the interactions beyond the
nearest neighbors. Our observation thus provides the first qualitative evidence
for the essential importance of the dipolar interaction beyond the nearest
neighbors in the spin ice.Comment: submitted to PR
Non-linear Temperature Dependence of Resistivity in Single Crystalline AgPbO
We measured electrical resistivity, specific heat and magnetic susceptibility
of single crystals of highly conductive oxide Ag_5Pb_2O_6, which has a layered
structure containing a Kagome lattice. Both the out-of-plane and in-plane
resistivity show T^2 dependence in an unusually wide range of temperatures up
to room temperature. This behavior cannot be accounted for either by electron
correlation or by electron-phonon scattering with high frequency optic phonons.
In addition, a phase transition with a large diamagnetic signal was found in
the ac susceptibility, which strongly suggests the existence of a
superconducting phase below 48 mK.Comment: 5 pages, 5 figures; accepted for publication in Physcal Review B;
Revised version: small correction in the caption of Fig.
First-Order Superconducting Transition of Sr2RuO4
By means of the magnetocaloric effect, we examine the nature of the
superconducting-normal (S-N) transition of Sr2RuO4, a most promising candidate
for a spin-triplet superconductor. We provide thermodynamic evidence that the
S-N transition of this oxide is of first order below approximately 0.8 K and
only for magnetic field directions very close to the conducting plane, in clear
contrast to the ordinary type-II superconductors exhibiting second-order S-N
transitions. The entropy release across the transition at 0.2 K is 10% of the
normal-state entropy. Our result urges an introduction of a new mechanism to
break superconductivity by magnetic field.Comment: 13 pages (Main text: 5 pages; Supplemental Material: 8 pages). To be
published in Physical Review Letter
Ferromagnetism Induced by Uniaxial Pressure in the Itinerant Metamagnet Sr3Ru2O7
We report a uniaxial-pressure study on the magnetisation of single crystals
of the bilayer perovskite Sr3Ru2O7, a metamagnet close to a ferromagnetic
instability. We observed that the application of a uniaxial pressure parallel
to the c-axis induces ferromagnetic ordering with a Curie temperature of about
80 K and critical pressures of about 4 kbar or higher. This value for the
critical pressure is even higher than the value previously reported (~ 1 kbar),
which might be attributed to the difference of the impurity level. Below the
critical pressure parallel to the c-axis, the metamagnetic field appears to
hardly change. We have also found that uniaxial pressures perpendicular to the
c-axis, in contrast, do not induce ferromagnetism, but shift the metamagnetic
field to higher fields.Comment: Accepted for publication in Proc of 24th Int. Conf. on Low
Temperature Physics (LT24); 2 page
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