3,342 research outputs found
Muon spin rotation and relaxation in the superconducting ferromagnet UCoGe
We report zero-field muon spin rotation and relaxation measurements on the
superconducting ferromagnet UCoGe. Weak itinerant ferromagnetic order is
detected by a spontaneous muon spin precession frequency below the Curie
temperature K. The precession frequency persists below the
bulk superconducting transition temperature K, where it measures
a local magnetic field T. The amplitude of the SR signal
provides unambiguous proof for ferromagnetism present in the whole sample
volume. We conclude ferromagnetism coexists with superconductivity on the
microscopic scale.Comment: 4 pages, 3 figures, accepted for publication in PR
Magnetic quantum critical point and superconductivity in UPt3 doped with Pd
Transverse-field muon spin relaxation measurements have been carried out on
the heavy-fermion superconductor UPt3 doped with small amounts of Pd. We find
that the critical Pd concentration for the emergence of the large-moment
antiferromagnetic phase is ~0.6 at.%Pd. At the same Pd content,
superconductivity is completely suppressed. The existence of a magnetic quantum
critical point in the phase diagram, which coincides with the critical point
for superconductivity, provides evidence for ferromagnetic spin-fluctuation
mediated odd-parity superconductivity, which competes with antiferromagnetic
order.Comment: 4 pages (includes 3 figures); postscript fil
Magnetic quantum critical point and superconductivity in UPt3 doped with Pd
Transverse-field muon spin relaxation measurements have been carried out on
the heavy-fermion superconductor UPt3 doped with small amounts of Pd. We find
that the critical Pd concentration for the emergence of the large-moment
antiferromagnetic phase is ~0.6 at.%Pd. At the same Pd content,
superconductivity is completely suppressed. The existence of a magnetic quantum
critical point in the phase diagram, which coincides with the critical point
for superconductivity, provides evidence for ferromagnetic spin-fluctuation
mediated odd-parity superconductivity, which competes with antiferromagnetic
order.Comment: 4 pages (includes 3 figures); postscript fil
Muon-spin-rotation measurements of the penetration depth in Li_2Pd_3B
Measurements of the magnetic field penetration depth in the ternary
boride superconductor LiPdB ( K) have been carried out by
means of muon-spin rotation (SR). The absolute values of , the
Ginzburg-Landau parameter , and the first and the second
critical fields at T=0 obtained from SR were found to be
nm, , mT, and
T, respectively. The zero-temperature value of the
superconducting gap 1.31(3) meV was found, corresponding to the
ratio . At low temperatures saturates and
becomes constant below , in agreement with what is expected for
s-wave BCS superconductors. Our results suggest that LiPdB is a s-wave
BCS superconductor with the only one isotropic energy gap.Comment: 6 pages, 7 figure
Macroscopic phase segregation in superconducting K0.73Fe1.67Se2 as seen by muon spin rotation and infrared spectroscopy
Using muon spin rotation (\muSR) and infrared spectroscopy we investigated
the recently discovered superconductor K0.73Fe1.67Se2 with Tc = 32 K. We show
that the combined data can be consistently described in terms of a
macroscopically phase segregated state with a matrix of ~88% volume fraction
that is insulating and strongly magnetic and inclusions with a ~12% volume
fraction which are metallic, superconducting and non-magnetic. The electronic
properties of the latter, in terms of the normal state plasma frequency and the
superconducting condensate density, appear to be similar as in other iron
selenide or arsenide superconductors.Comment: 22 pages, 8 figures. (citation list correction.
Magnetic order in double-layer manganites (La(1-z)Pr(z))1.2Sr1.8Mn2O7: intrinsic properties and role of the intergrowths
We report on an investigation of the double-layer manganite series
(La(1-z)Pr(z))1.2Sr1.8Mn2O7 (0 <= z <= 1), carried out on single crystals by
means of both macroscopic magnetometry and local probes of magnetism (muSR,
55Mn NMR). Muons and NMR demonstrate an antiferromagnetically ordered ground
state at non-ferromagnetic compositions (z >= 0.6), while more moderate Pr
substitutions (0.2 <= z <= 0.4) induce a spin reorientation transition within
the ferromagnetic phase.
A large magnetic susceptibility is detected at {Tc,TN} < T < 250K at all
compositions. From 55Mn NMR spectroscopy, such a response is unambiguously
assigned to the intergrowth of a ferromagnetic pseudocubic phase
(La(1-z)Pr(z))(1-x)Sr(x)MnO3, with an overall volume fraction estimated as
0.5-0.7% from magnetometry. Evidence is provided for the coupling of the
magnetic moments of these inclusions with the magnetic moments of the
surrounding (La(1-z)Pr(z))1.2Sr1.8Mn2O7 phase, as in the case of finely
dispersed impurities. We argue that the ubiquitous intergrowth phase may play a
role in the marked first-order character of the magnetic transition and the
metamagnetic properties above Tc reported for double-layer manganites.Comment: 11 pages, 9 figures. Submitted to Phys. Rev.
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
Evidence for a two component magnetic response in UPt3
The magnetic response of the heavy fermion superconductor UPt_3 has been
investigated on a microscopic scale by muon Knight shift studies. Two distinct
and isotropic Knight shifts have been found for the field in the basal plane.
While the volume fractions associated with the two Knight shifts are
approximately equal at low and high temperatures, they show a dramatic and
opposite temperature dependence around T_N. Our results are independent on the
precise muon localization site. We conclude that UPt_3 is characterized by a
two component magnetic response.Comment: 5 pages, 4 figure
Muon spin rotation study of the magnetic penetration depth in the intercalated graphite superconductor CaC6
We report temperature- and magnetic field-dependent bulk muon spin rotation
measurements in a c-axis oriented superconductor CaC6 in the mixed state. Using
both a simple second moment analysis and the more precise analytical
Ginzburg-Landau model, we obtained a field independent in-plane magnetic
penetration depth {\lambda}ab (0) = 72(3) nm. The temperature dependencies of
the normalized muon spin relaxation rate and of the normalized superfluid
density result to be identical, and both are well represented by the clean
limit BCS model with 2\Delta/kB Tc = 3.6(1), suggesting that CaC6 is a fully
gapped BCS superconductor in the clean limit regime.Comment: Accepted for publication in PR
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