4,887 research outputs found
Observed distribution functions of H, He, C, O, and Fe in corotating energetic particle streams: Implications for interplanetary acceleration and propagation
Distribution functions for H, He, C, O, and Fe derived from our IMP 8 measurements of approximately 0.15 to approximately 8 MeV/nucleon particles in three corotating streams observed near earth are shown to have a simple exponential dependence on the particle speed. The e-folding speed, v sub o, is typically 0.01c, is found to be the same for the distribution functions of all elements examined, and varies little from one corotating event to the next. The relative abundances of energetic particles in these events resemble most closely the solar coronal composition and, thus, presumably that of the solar wind. These results may imply that the acceleration of these particles, which occurs in corotating interaction regions at several AU from the sun, is by a statistical process
Superconductivity without Fe or Ni in the phosphides BaIr2P2 and BaRh2P2
Heat capacity, resistivity, and magnetic susceptibility measurements confirm
bulk superconductivity in single crystals of BaIrP (T=2.1K) and
BaRhP (T = 1.0 K). These compounds form in the ThCrSi (122)
structure so they are isostructural to both the Ni and Fe pnictides but not
isoelectronic to either of them. This illustrates the importance of structure
for the occurrence of superconductivity in the 122 pnictides. Additionally, a
comparison between these and other ternary phosphide superconductors suggests
that the lack of interlayer bonding favors superconductivity. These
stoichiometric and ambient pressure superconductors offer an ideal playground
to investigate the role of structure for the mechanism of superconductivity in
the absence of magnetism.Comment: Published in Phys Rev B: Rapid Communication
Unconventional Metallic Magnetism in LaCrSb{3}
Neutron-diffraction measurements in LaCrSb{3} show a coexistence of
ferromagnetic and antiferromagnetic sublattices below Tc=126 K, with ordered
moments of 1.65(4) and 0.49(4) Bohr magnetons per formula unit, respectively
(T=10 K), and a spin reorientation transition at ~95 K. No clear peak or step
was observed in the specific heat at Tc. Coexisting localized and itinerant
spins are suggested.Comment: PRL, in pres
Wilson ratio in Yb-substituted CeCoIn5
We have investigated the effect of Yb substitution on the Pauli limited,
heavy fermion superconductor, CeCoIn. Yb acts as a non-magnetic divalent
substituent for Ce throughout the entire doping range, equivalent to hole
doping on the rare earth site. We found that the upper critical field in
(Ce,Yb)CoIn is Pauli limited, yet the reduced (H,T) phase diagram is
insensitive to disorder, as expected in the purely orbitally limited case. We
use the Pauli limiting field, the superconducting condensation energy and the
electronic specific heat coefficient to determine the Wilson ratio (),
the ratio of the specific heat coefficient to the Pauli susceptibility in
CeCoIn. The method is applicable to any Pauli limited superconductor in the
clean limit.Comment: 5 pages, 1 table, 4 figure
A New Heavy-Fermion Superconductor CeIrIn5: Relative of the Cuprates?
CeIrIn5 is a member of a new family of heavy-fermion compounds and has a
Sommerfeld specific heat coefficient of 720 mJ/mol-K2. It exhibits a bulk,
thermodynamic transition to a superconducting state at Tc=0.40 K, below which
the specific heat decreases as T2 to a small residual T-linear value.
Surprisingly, the electrical resistivity drops below instrumental resolution at
a much higher temperature T0=1.2 K. These behaviors are highly reproducible and
field-dependent studies indicate that T0 and Tc arise from the same underlying
electronic structure. The layered crystal structure of CeIrIn5 suggests a
possible analogy to the cuprates in which spin/charge pair correlations develop
well above Tc
Direct observation of the quantum critical point in heavy fermion CeRhSi
We report on muon spin rotation studies of the noncentrosymmetric heavy
fermion antiferromagnet CeRhSi. A drastic and monotonic suppression of the
internal fields, at the lowest measured temperature, was observed upon an
increase of external pressure. Our data suggest that the ordered moments are
gradually quenched with increasing pressure, in a manner different from the
pressure dependence of the N\'eel temperature. At \unit{23.6}{kbar}, the
ordered magnetic moments are fully suppressed via a second-order phase
transition, and is zero. Thus, we directly observed the quantum
critical point at \unit{23.6}{kbar} hidden inside the superconducting phase
of CeRhSi
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