S. J. Lister

Paul Scherrer Institut, Aargau, Switzerland

Are you S. J. Lister?

Claim your profile

Publications (9)50.42 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Muon-spin rotation has been used to observe directly the spatial variation of the magnetic flux density near the ferromagnetic-superconducting interface in a permalloy-niobium trilayer. Above the superconducting transition temperature Tc the profile of the induced magnetic flux density within the niobium layer has been determined. Below Tc there is a significant reduction of the induced flux density, predominantly near the ferromagnetic-superconducting interfaces. We are uniquely able to determine the magnitude and spatial variation of this reduction in induced magnetization due to the presence of the Cooper pairs, yielding the magnitude and length scale associated with this phenomenon. Both are inconsistent with a simple Meissner screening and indicate the existence of another mechanism, the influence of which is localized within the vicinity of the ferromagnetic interface.
    01/2014; 89(5).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The unusual magnetic behaviour of a Pd/Nb67Ti33/Pd heterostructure was investigated using polarised neutron reflectivity technique. On application of a large in-plane magnetic field, Stoner enhanced paramagnet Pd was found to influence the magnetic state of the Nb67Ti33 layer both above and below the superconducting transition temperature Tc significantly. Unlike the case of a conventional proximity effect for a superconductor/metallic heterostructure, the pair correlation in the superconducting state has been found to be more stable in the higher field limit compared to its low field counterpart, possibly signaturing a ‘novel’ coupled state in the system. The superconducting state in Nb67Ti33 has been found to be diamagnetic in nature at all the fields that can be fitted using a Meissner kind of behaviour in the high field limit. The magnetic properties of Pd and Nb67Ti33 are in excellent agreement with those measured using bulk magnetisation measurements.
    Physica C Superconductivity 04/2013; 487:67–71. · 0.72 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Muon-spin rotation measurements, performed on the mixed state of the classic anisotropic superconductor Bi_{2.15}Sr_{1.85}CaCu_{2}O_{8+δ}, obtain quantities directly related to two- and three-body correlations of vortices in space. A novel phase diagram emerges from such local probe measurements of the bulk, revealing an unusual glassy state at intermediate fields which appears to freeze continuously from the equilibrium vortex liquid but differs both from the lattice and the conventional high-field vortex glass state in its structure.
    Physical Review Letters 03/2013; 110(10):107004. · 7.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Polarized small-angle neutron scattering has been used to measure the magnetic structure of a CoCrPt – SiO <sub> x </sub> thin-film data storage layer, contained within a writable perpendicular recording media, at granular (<10 nm ) length scales. The magnetic contribution to the scattering is measured as the magnetization is reversed by an external field, providing unique spatial information on the switching process. A simple model of noninteracting nanomagnetic grains provides a good description of the data and an analysis of the grain-size dependent reversal provides strong evidence for an increase in magnetic anisotropy with grain diameter.
    Applied Physics Letters 10/2010; · 3.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Polarized small-angle neutron scattering has been used to measure the local magnetic structure of writable thin-film perpendicular media with a granular CoCrPt-SiO <sub>x</sub> recording layer. By exploiting the cross terms between the nuclear and magnetic scattering, we are able to probe simultaneously both the grain structure and the subgranular magnetic structure of the recording layer, which has a thickness of only 15 nm and which is embedded within a full perpendicular media structure including soft underlayer. Two models are used to analyze the data, one analytical and the other a numerical approach based on transmission electron microscopy measurements of the grains. Both models show that the recording layer consists of ferromagnetically ordered core regions that are smaller in extent than the corresponding grains and allow a direct, quantitative comparison of these two length scales.
    Journal of Applied Physics 10/2009; · 2.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Spin-polarized neutron-reflectivity measurements have been performed on superconducting Pb films. For fields applied in the plane of the film we are able to determine the magnetic field profile across the thickness of the film in the superconducting state. This allows the direct observation of distinct mesoscopic ground states in this geometry, from Meissner expulsion to a double row of vortices, which occur as a function of film thickness and external magnetic field. The data can be compared directly with solutions of the time-dependent Ginzburg-Landau equations, where we demonstrate good agreement between data and simulation. This provides a powerful demonstration of this widely applicable experimental technique to study mesoscopic ground states and a useful validation of this theoretical approach.
    Physical review. B, Condensed matter 10/2009; · 3.77 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In principle, a complex assembly of strongly interacting electrons can self-organize into a wide variety of collective states, but relatively few such states have been identified in practice. We report that, in the close vicinity of a metamagnetic quantum critical point, high-purity strontium ruthenate Sr3Ru2O7 possesses a large magnetoresistive anisotropy, consistent with the existence of an electronic nematic fluid. We discuss a striking phenomenological similarity between our observations and those made in high-purity two-dimensional electron fluids in gallium arsenide devices.
    Science 02/2007; 315(5809):214-7. · 31.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The magnetic phase diagram of high-temperature superconductors can contain many exotic vortex phases not observed in conventional superconducting materials. For example, the familiar vortex lattice may melt at high temperatures into a vortex liquid. The influence of defects, which pin the vortices, is of particular interest from both a theoretical and an experimental point of view. We have used small angle neutron scattering (SANS) to probe the order of the vortex system on a microscopic scale and have succeeded, for the first time, to measure a well-ordered vortex lattice (VL) structure at all doping regimes of La2−xSrxCuO4. In the optimally to overdoped regime a field-induced transition from hexagonal to square coordination is reported. The possible connections of our SANS results to photoemission data, as well as the implications for various competing theoretical models will be discussed.
    Physica B Condensed Matter 11/2006; · 1.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The magnetic phase diagram of high-temperature superconductors can contain many exotic vortex phases not observed in conventional superconducting materials. For example, the familiar vortex lattice may melt at high temperatures into a vortex liquid. The influence of defects, which pin the vortices, is of particular interest from both a theoretical and an experimental point of view. We have used a combination of small angle neutron scattering (SANS) and muon-spin rotation to probe the order of the vortex system on a microscopic scale and have succeeded, for the first time, to measure a well-ordered vortex lattice (VL) structure at all doping regimes of LSCO. In the optimally to overdoped regime a field-induced transition from hexagonal to square coordination is reported. The possible connections of our neutron results to photoemission data, as well as the implications for various competing theoretical models will be discussed. In the underdoped regime we observe, as a function of applied magnetic field, a transition from an ordered vortex state to a vortex glass phase that results from the presence of random pinning. Finally, recent measurements of the VL on electron doped high-temperature superconductors are presented.
    Proceedings of the SPIE - The International Society for Optical Engineering. 01/2005; 5932:59322D-1-8.

Publication Stats

122 Citations
50.42 Total Impact Points

Institutions

  • 2014
    • Paul Scherrer Institut
      • Laboratory for Muon Spin Spectroscopy (LMU)
      Aargau, Switzerland
  • 2006–2013
    • University of St Andrews
      • School of Physics and Astronomy
      Saint Andrews, SCT, United Kingdom
  • 2007
    • Scottish Universities Physics Alliance
      Glasgow, Scotland, United Kingdom