4 research outputs found
Magnetic Field Effects on Neutron Diffraction in the Antiferromagnetic Phase of
We discuss possible magnetic structures in UPt based on our analysis of
elastic neutron-scattering experiments in high magnetic fields at temperatures
. The existing experimental data can be explained by a single-{\bf q}
antiferromagnetic structure with three independent domains. For modest in-plane
spin-orbit interactions, the Zeeman coupling between the antiferromagnetic
order parameter and the magnetic field induces a rotation of the magnetic
moments, but not an adjustment of the propagation vector of the magnetic order.
A triple-{\bf q} magnetic structure is also consistent with neutron
experiments, but in general leads to a non-uniform magnetization in the
crystal. New experiments could decide between these structures.Comment: 5 figures included in the tex
Point-Contact Andreev-reflection Spectroscopy in the Fe-based superconductor LaFeAsO1-xFx
Point-contact Andreev-reflection (PCAR) spectroscopy measurements have been performed in the Fe-based superconductor LaFeAsO1−x F x in order to investigate the energy gaps. The Andreev spectra show clear and reproducible features that could be related to two nodeless gaps. Their values, as determined by fitting the conductance curves measured in junctions with local T c =27.3–28.6 K within the two-band BTK model, are Δ 1=2.75–3.8 meV for the small gap and Δ 2=7.9–10.2 meV for the larger one, respectively. The absence of zero-bias conductance peaks and considerations regarding the nonperfectly directional current injection in PCAR experiments and the polycrystalline nature of the samples rule out the possibility of nodal gaps in the superconductor. Moreover, the conductance curves show pseudogap-like features coexisting, at low temperature, with superconductivity and disappearing close to the Neel temperature of the parent compound, T N≈140 K