164 research outputs found
Probing the superconducting ground state of the rare-earth ternary boride superconductors RuB ( = Lu,Y) using muon-spin rotation and relaxation
The superconductivity in the rare-earth transition metal ternary borides
RuB (where = Lu and Y) has been investigated using muon-spin
rotation and relaxation. Measurements made in zero-field suggest that
time-reversal symmetry is preserved upon entering the superconducting state in
both materials; a small difference in depolarization is observed above and
below the superconducting transition in both compounds, however this has been
attributed to quasistatic magnetic fluctuations. Transverse-field measurements
of the flux-line lattice indicate that the superconductivity in both materials
is fully gapped, with a conventional s-wave pairing symmetry and BCS-like
magnitudes for the zero-temperature gap energies. The electronic properties of
the charge carriers in the superconducting state have been calculated, with
effective masses and in the Lu
and Y compounds, respectively, with superconducting carrier densities
() m and ()
m. The materials have been classified according to the
Uemura scheme for superconductivity, with values for
of and , implying that
the superconductivity may not be entirely conventional in nature.Comment: 8 pages, 8 figure
Static magnetic moments revealed by muon spin relaxation and thermodynamic measurements in quantum spin ice YbTiO
We present muon spin relaxation (SR) and specific-heat versus
temperature measurements on polycrystalline and single-crystal samples
of the pyrochlore magnet YbTiO. exhibits a sharp peak at a
of 0.21 and 0.26~K for the single-crystal and polycrystalline
samples respectively. For both samples, the magnetic entropy released between
50~mK and 30~K amounts to per Yb. At temperatures below
we observe a steep drop in the asymmetry of the zero-field SR time spectra
at short time scales, as well as a decoupling of the muon spins from the
internal field in longitudinal magnetic fields of ~T for both the
polycrystalline and single-crystal samples. These muon data are indicative of
static magnetic moments. Our results are consistent with the onset of
long-range magnetic order in both forms of YbTiO.Comment: 6 pages, 4 figures, accepted to PR
Structure and superconductivity of two different phases of Re3W
Two superconducting phases of Re(3)W have been found with different physical properties. One phase crystallizes in a noncentrosymmetric cubic (alpha-Mn) structure and has a superconducting transition temperature T(c) of 7.8 K. The other phase has a hexagonal centrosymmetric structure and is superconducting with a T(c) of 9.4 K. Switching between the two phases is possible by annealing the sample or remelting it. The properties of both phases of Re(3)W have been characterized by powder neutron diffraction, magnetization, and resistivity measurements. The temperature dependences of the lower and upper critical fields have been measured for both phases. These are used to determine the penetration depths and the coherence lengths for these systems
Using negative muons as a probe for depth profiling silver Roman coinage
Debasement of silver Roman coins is a well-known phenomenon and understanding the quality of ancient silver coinages can provide an idea about the underlying fiscal condition of the issuing states. These coins are made from a silver-copper alloy, the surfaces of which were deliberately enhanced at the mints by a process of surface-enrichment to give them the appearance of being made of pure silver. Therefore, any surface analysis would provide a composition of the silver-copper alloy that would not be representative of the original alloy from which the coin blank was made; the result would be too high in silver. However, the bulk of the sample, the interior, should provide a composition that is true to the original alloy. Elemental analysis using negative muons has been used to provide a depth dependent compositional, completely non-destructive analysis of a silver-copper alloy denarius of the empress Julia Domna datable to 211–217 CE. The composition of the coin, beyond the surface enrichment layer, is 51 ± 1.8 % copper and 49 ± 1.9% silver, taken at a muon depth of 402 ± 61 µm. The surface enrichment layer is approximately 190 µm thick
Gapless spin-liquid state in the structurally disorder-free triangular antiferromagnet NaYbO
We present the structural characterization and low-temperature magnetism of
the triangular-lattice delafossite NaYbO. Synchrotron x-ray diffraction and
neutron scattering exclude both structural disorder and crystal-electric-field
randomness, whereas heat-capacity measurements and muon spectroscopy reveal the
absence of magnetic order and persistent spin dynamics down to at least 70\,mK.
Continuous magnetic excitations with the low-energy spectral weight
accumulating at the -point of the Brillouin zone indicate the formation of a
novel spin-liquid phase in a triangular antiferromagnet. This phase is gapless
and shows a non-trivial evolution of the low-temperature specific heat. Our
work demonstrates that NaYbO practically gives the most direct experimental
access to the spin-liquid physics of triangular antiferromagnets.Comment: 6 pages, 4figure
The low-temperature highly correlated quantum phase in the charge-density-wave 1T-TaS_2 compound
A prototypical quasi-2D metallic compound, 1T-TaS_2 has been extensively
studied due to an intricate interplay between a Mott-insulating ground state
and a charge density-wave (CDW) order. In the low-temperature phase, 12 out of
13 Ta_{4+} 5\textit{d}-electrons form molecular orbitals in hexagonal
star-of-David patterns, leaving one 5\textit{d}-electron with \textit{S} = 1/2
spin free. This orphan quantum spin with a large spin-orbit interaction is
expected to form a highly correlated phase of its own. And it is most likely
that they will form some kind of a short-range order out of a strongly
spin-orbit coupled Hilbert space. In order to investigate the low-temperature
magnetic properties, we performed a series of measurements including neutron
scattering and muon experiments. The obtained data clearly indicate the
presence of the short-ranged phase and put the upper bound on ~ 0.4
\textit{\mu}_B for the size of the magnetic moment, consistent with the
orphan-spin scenario.Comment: 11 pages, 4 figures + supplemental material. Accepted by npj Quantum
Material
Negative muon spin rotation and relaxation on superconducting MgB2
The internal nuclear magnetic field in a superconducting MgB2 powder sample was studied with a μ- SR technique. Although the past μ +SR study on MgB2 reported the appearance of a dynamic behavior even below Tc due to μ + diffusion, μ- SR shows a static behavior in the whole temperature range measured, as expected. The ZF-μ- SR spectra do not suggest any appearance of additional magnetic field below Tc within the experimental accuracy. Considering the small asymmetry of the μ- SR signal, it is a challenge to detect the appearance of an internal magnetic field below Tc caused by the time reversal symmetry breaking
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