25 research outputs found
First-Order Reorientation of the Flux-Line Lattice in CaAlSi
The flux line lattice in CaAlSi has been studied by small angle neutron
scattering. A well defined hexagonal flux line lattice is seen just above Hc1
in an applied field of only 54 Oe. A 30 degree reorientation of this vortex
lattice has been observed in a very low field of 200 Oe. This reorientation
transition appears to be of first-order and could be explained by non-local
effects. The magnetic field dependence of the form factor is well described by
a single penetration depth of 1496(1) angstroms and a single coherence length
of 307(1) angstroms at 2 K. At 1.5 K the penetration depth anisotropy is 2.7(1)
with the field applied perpendicular to the c axis and agrees with the
coherence length anisotropy determined from critical field measurements.Comment: 5 pages including 6 figures, to appear in Physical Review Letter
Direct observation of the quantum critical point in heavy fermion CeRhSi
We report on muon spin rotation studies of the noncentrosymmetric heavy
fermion antiferromagnet CeRhSi. A drastic and monotonic suppression of the
internal fields, at the lowest measured temperature, was observed upon an
increase of external pressure. Our data suggest that the ordered moments are
gradually quenched with increasing pressure, in a manner different from the
pressure dependence of the N\'eel temperature. At \unit{23.6}{kbar}, the
ordered magnetic moments are fully suppressed via a second-order phase
transition, and is zero. Thus, we directly observed the quantum
critical point at \unit{23.6}{kbar} hidden inside the superconducting phase
of CeRhSi
Magnetic-field-induced nonlocal effects on the vortex interactions in twin-free YBa2Cu3O7
The vortex lattice (VL) in the high-kappa 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 towards Tc. The data indicate that nonlocality due to different
anisotropies play important roles in determining the VL properties.Comment: To appear in Phys. Rev.
Switching of magnetic domains reveals evidence for spatially inhomogeneous superconductivity
The interplay of magnetic and charge fluctuations can lead to quantum phases
with exceptional electronic properties. A case in point is magnetically-driven
superconductivity, where magnetic correlations fundamentally affect the
underlying symmetry and generate new physical properties. The superconducting
wave-function in most known magnetic superconductors does not break
translational symmetry. However, it has been predicted that modulated triplet
p-wave superconductivity occurs in singlet d-wave superconductors with
spin-density wave (SDW) order. Here we report evidence for the presence of a
spatially inhomogeneous p-wave Cooper pair-density wave (PDW) in CeCoIn5. We
show that the SDW domains can be switched completely by a tiny change of the
magnetic field direction, which is naturally explained by the presence of
triplet superconductivity. Further, the Q-phase emerges in a common
magneto-superconducting quantum critical point. The Q-phase of CeCoIn5 thus
represents an example where spatially modulated superconductivity is associated
with SDW order
Professionalisation as development and as regulation: Adult education in Germany, the United Kingdom and India
Adult Education and Work Contexts: International Perspectives and Challenges
Il volume, un collettaneo, presenta differenti prospettive nel campo dell'employability in education analizzando in particolare:
1. Lifelong Learning Policies Targeting Employment Contexts
2. Trasnational Perspectives and Lifelong Learning Policies
3. Employment Perspectives and Professionalization in Adult Education.
I contributi raccolti sono stati sottopposti a peer review doppio ceco
Journal of educational sciences = Revista de stiinte ale educatiei : Special issue on professionalisation in adult education
Reflecting Teams als Seminarmethode
http://methodenpool.uni-koeln.de/download/reflectingteam.pd