R. Cubitt

Direct Evidence for an Intrinsic Square Vortex Lattice in the Overdoped High- Tc Superconductor La1.83Sr0.17CuO4+δ

We report here the first direct observations of a well ordered vortex lattice in the bulk of a La(2-x)Sr(x)CuO(4+delta) single crystal (slightly overdoped, x = 0.17). Our small angle neutron scattering investigation of the mixed phase reveals a crossover from triangular to square coordination with increasing magnetic field. The existence of an intrinsic square vortex lattice has never been observed in high-temperature superconductors and is indicative of the coupling of the vortex lattice to a source of anisotropy, such as those provided by a d-wave order parameter or the presence of stripes.

Reconstruction from Small-Angle Neutron Scattering Measurements of the Real Space Magnetic Field Distribution in the Mixed State of Sr2RuO4

We have measured the diffracted neutron scattering intensities from the square magnetic flux lattice in the perovskite superconductor Sr2RuO4, which is thought to exhibit p-wave pairing with a two-component order parameter. The relative intensities of different flux lattice Bragg reflections over a wide range of field and temperature have been shown to be inconsistent with a single component Ginzburg-Landau theory but qualitatively agree with a two-component p-wave Ginzburg-Landau theory.

correction: Observation of a square flux-line lattice in the unconventionalsuperconductor Sr 2 RuO 4

This corrects the article DOI: 10.1038/24335

FLUX-LINE LATTICE STRUCTURES IN UNTWINNED YBA2CU3O7-DELTA

A small angle neutron scattering study of the flux-line lattice in a large single crystal of untwinned YBa2Cu3O is presented. In fields parallel to the c-axis, diffraction spots are observed corresponding to four orientations of a hexagonal lattice, distorted by the a-b anisotropy. A value for the anisotropy, the penetration depth ratio, of 1.18(2) was obtained. The high quality of the data is such that second order diffraction is observed, indicating a well ordered FLL. With the field at 33 degrees to c a field dependent re-orientation of the lattice is observed around 3T.

Using small-angle neutron scattering to probe the local magnetic structure of perpendicular magnetic recording media

Small-angle neutron scattering SANS has been used to measure the local magnetic structure of perpendicular media consisting of granular CoCrPt– SiOx thin films. The dimensions of the magnetic structures determined by SANS are consistent with the physical grain sizes suggested by transmission electron microscopy measurements, but yield additional information on magnetic structure within the grains, including the existence of a much smaller magnetic core. The results are similar to those recently obtained on longitudinal magnetic recording media, but with the addition of strong interference terms due to the narrower distribution of grain sizes in these samples.

Unconventional angular dependence of the microscopic magnetic field distribution in single crystal Bi2Sr2CaCu2O8 from muon-spin rotation studies

Abstract The angular dependence of the microscopic magnetic field distribution in single-crystal Bi 2 Sr 2 CaCu 2 O 8 has been measured for a range of applied fields using the muon-spin rotation technique. The results show significant deviations from the predictions of the anisotropic 3D model, which may reflect the extremely anisotropic, quasi-2D nature of the flux structure. The temperature dependence of the field distribution at 400 mT has also been measured for a range of orientations, showing disagreement with the predictions of a simple two-fluid model.

Magnetic-field-induced nonlocal effects on the vortex interactions in twin-free YBa_{2}Cu_{3}O_{7}

The vortex lattice (VL) in the high-κ superconductor YBa2Cu3O7, at 2 K and with the magnetic field parallel to the crystal c axis, undergoes a sequence of transitions between different structures as a function of applied magnetic field. However, from structural studies alone, it is not possible to determine precisely the system anisotropy that governs the transitions between different structures. To address this question, here we report new small-angle neutron scattering measurements of both the VL structure at higher temperatures and the field and temperature dependence of the VL form factor. Our measurements demonstrate how the influence of anisotropy on the VL, which in theory can be parameterized as nonlocal corrections, becomes progressively important with increasing magnetic field, and suppressed by increasing the temperature toward Tc. The data indicate that nonlocality due to different anisotropies plays an important role in determining the VL properties.

Measuring the penetration depth anisotropy in MgB{sub 2} using small-angle neutron scattering

Using small-angle neutron scattering, we have measured the misalignment between an applied field of

Small-angle scattering from the vortex lattice in high-Tc and other superconductors

4\phantom{\rule{0.3em}{0ex}}\mathrm{kOe}

Recent upgrades of the neutron reflectometer D17 at ILL

and the flux-line lattice in