71 research outputs found
Giant Vortices Below the Surface of NbSe Detected Using Low Energy -NMR
A low energy radioactive beam of polarized Li has been used to observe
the vortex lattice near the surface of superconducting NbSe. The
inhomogeneous magnetic field distribution associated with the vortex lattice
was measured using depth-resolved -detected NMR. Below one
observes the characteristic lineshape for a triangular vortex lattice which
depends on the magnetic penetration depth and vortex core radius. The size of
the vortex core varies strongly with magnetic field. In particular in a low
field of 10.8 mT the core radius is much larger than the coherence length. The
possible origin of these giant vortices is discussed.Comment: 5 pages, 3 figures. Submitted to Phys. Rev. Let
Local Magnetic Properties of a Monolayer of Mn12 Single Molecule Magnets
The magnetic properties of a monolayer of Mn12 single molecule magnets
grafted onto a Si substrate have been investigated using depth-controlled
-detected nuclear magnetic resonance. A low energy beam of spin
polarized radioactive 8Li was used to probe the local static magnetic field
distribution near the Mn12 monolayer in the Si substrate. The resonance
linewidth varies strongly as a function of implantation depth as a result of
the magnetic dipolar fields generated by the Mn12 electronic magnetic moments.
The temperature dependence of the linewidth indicates that the magnetic
properties of the Mn12 moments in this low dimensional configuration differ
from bulk Mn12.Comment: 6 pages, 4 figure
Vortex lattice disorder in YBCO probed using Beta-NMR
Beta-NMR has been used to study vortex lattice disorder near the surface of
the high-Tc superconductor YBCO. The magnetic field distribution from the
vortex lattice was detected by implanting a low energy beam of highly polarized
8Li into a thin overlayer of silver on optimally doped, twinned and detwinned
YBCO samples. The resonance in Ag broadens significantly below the transition
temperature Tc as expected from the emerging field lines of the vortex lattice
in YBCO. However, the lineshape is more symmetric and the dependence on the
applied magnetic field is much weaker than expected from an ideal vortex
lattice, indicating that the vortex density varies across the face of the
sample, likely due to pinning at twin boundaries. At low temperatures the
broadening from such disorder does not scale with the superfluid density.Comment: 10 pages, 6 figure
Absolute value and temperature dependence of the magnetic penetration depth in Ba(Co0.074Fe0.926)(2)As-2
The absolute value and temperature dependence of the in-plane magnetic penetration depth λ have been measured on a single crystal of Ba(Co0.074Fe0.926)2As2 using low-energy muon-spin rotation and microwave cavity perturbation. The magnetic field profiles in the Meissner state are consistent with a local London model beyond a depth of 15 nm. We determine the gap symmetry through measurements of the temperature dependence of the superfluid density which follows a two-gap s-wave model over the entire temperature range below Tc. While the intermediate to high temperature data is well fit by an energy gap model in the BCS-like (weak-coupling) limit, a second smaller gap becomes apparent at low temperatures
Zero-field spin depolarization of low-energy muons in ferromagnetic nickel and silver metal
We present zero-fieldmuon-spindepolarization measurements in nickel and silver performed using low-energymuon-spin relaxation technique.Ni or Ag are usually used in this depth-resolved technique as a backing material to enable background subtraction when studying small crystals or materials with weak magnetism. The depolarization rate of the asymmetry in silver and that of the slow relaxing part of the asymmetry in nickel are small(≤ 0.05 μs−1), and weakly temperature and energy-dependent
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