C. Ager

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

This corrects the article DOI: 10.1038/24335

μSR studies of the flux vortex phases in a BEDT-TTF superconductor

μSR has been used to probe the structure and stability of the flux vortex array in the organic superconductor κ-(BEDT-TTF) 2 Cu(SCN) 2 . At temperatures below 5 K and fields below 5 mT the internal field distribution is found to closely match that expected for a three dimensional (3D) Abrikosov flux line lattice (FLL). Careful studies in this 3D-FLL regime have enabled an improved measurement of the temperature dependence of the superconducting penetration depth to be made. A linear term is found in the temperature dependence of the penetration depth, suggesting the presence of line nodes in the gap parameter and d-wave pairing.

Evidence for a square vortex lattice in Sr2RuO4 from muon-spin-rotation measurements

A muon-spin-rotation study of the flux-line lattice in Sr 2RuO4 is presented. For the field parallel to the crystallographic c-direction, the observed field distribution strongly indicates a square symmetry of the vortex lattice. We determine the value of the coherence length from the upper critical field and the Ginzburg-Landau parameter which is found to be D 1:2.1/ from the field distribution. This gives a value for the penetration depth of D 185.15/ nm. The temperature dependence of the penetration depth is measured.

Stability of the vortex lattice in ET superconductors studied by μSR

Abstract Muon-spin rotation (μSR) measurements have been used to study the vortex lattice and its instabilities in the organic superconductors κ-ET 2 Cu(SCN) 2 and β-ET 2 IBr 2 . We ascribe the field- and temperature-dependent destruction of the vortex lattice to the large anisotropy found in these materials.

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

Small-angle neutron scattering (SANS) is an extremely powerful probe of the vortex state in type II superconductors. The technique may be further enhanced by the use of polarised neutrons and the application of the neutron spin-echo method. We discuss some recent applications of these techniques to the study of both conventional and unconventional superconducting materials, and describe the unique information which SANS can provide on the vortex state. ( 2000 Elsevier Science B.V. All rights reserved.

BEDT-TTF superconductors studied by μSR

Muon-spin rotation (μSR) measurements have been used to study the superconducting vortex properties of the organic superconductors κ-(BEDT-TTF)2Cu(SCN)2, α-(BEDT-TTF)2NH4Hg(SCN)4 and β-(BEDT-TTF)2IBr2. These materials all have highly anisotropic structures consisting of metallic layers of BEDT-TTF molecules alternating with less well conducting anion layers. Varying the anion gives rise to a change in the anisotropy of the superconductivity and also to changes in the superconducting transition temperature. We have used both transverse and longitudinal magnetic fields to study the three-dimensional flux line lattice that is present at low temperatures and fields and to study also the loss of flux lattice order that occurs on increasing the temperature and field.

Muon-spin rotation (μSR) measurements on Bi2Sr2CaCu2O8+δ in the presence of columnar defects

Abstract We present muon-spin rotation measurements on the cuprate superconductor Bi2Sr2CaCu2O8+δ, in the presence of columnar defects. The results are compared to measurements on the pristine material, and indicate a strong suppression of thermal fluctuations of the vortex positions in the irradiated material.

Angular-dependent muon-spin rotation on the mixed state of the organic superconductor K-(BEDT-TTF)2CU(SCN)2

Abstract We have performed muon-spin rotation (μSR) measurements on the organic superconductor K-(BEDT-TTF) 2 CU(SCN) 2 as a function of the angle between the applied field and the superconducting planes. The measurements are found to have much in common with those on the anisotropic cuprate superconductor Bi 2 Sr 2 CaCu 2 O 8 + δ .

Vortex studies in heavy-ion irradiated Bi2.15Sr1.85CaCu2O8+δ probed by μSR and small-angle neutron scattering

μSR and small-angle neutron scattering (SANS) have been used to probe the vortex arrangement in single crystals of the high-Tc superconductor Bi2.15Sr1.85CaCu2O8+δ which have been irradiated with heavy ions to produce columnar defects. The influence of these pinning sites on the spatial arrangement of the vortices is discussed, and the results are compared with numerical simulations.