156 research outputs found
The effect of Cr impurity to superconductivity in electron-doped BaFe2-xNixAs2
We use transport and magnetization measurements to study the effect of
Cr-doping to the phase diagram of the electron-doped superconducting
BaFe2-xNixAs2 iron pnictides. In principle, adding Cr to electron-doped
BaFe2-xNixAs2 should be equivalent to the effect of hole-doping. However, we
find that Cr doping suppresses superconductivity via impurity effect, while not
affecting the normal state resistivity above 100 K. We establish the phase
diagram of Cr-doped BaFe2-x-yNixCryAs2 iron pnictides, and demonstrate that
Cr-doping near optimal superconductivity restore the long-range
antiferromagnetic order suppressed by superconductivity.Comment: 10 pages, 5 figure
Longitudinal spin excitations and magnetic anisotropy in antiferromagnetically ordered BaFe2As2
We report on a spin-polarized inelastic neutron scattering study of spin
waves in the antiferromagnetically ordered state of BaFe2As2. Three distinct
excitation components are identified, with spins fluctuating along the c-axis,
perpendicular to the ordering direction in the ab-plane, and parallel to the
ordering direction. While the first two "transverse" components can be
described by a linear spin-wave theory with magnetic anisotropy and inter-layer
coupling, the third "longitudinal" component is generically incompatible with
the local moment picture. It points towards a contribution of itinerant
electrons to the magnetism already in the parent compound of this family of
Fe-based superconductors.Comment: 4 pages, 4 figures, plus Supplemental Materia
Growth and post-annealing studies of La-Bi2201 single crystals
BiSrLaCuO (01.00) single crystals
with high-quality have been grown successfully using the travelling-solvent
floating-zone technique. The patterns of X-ray diffraction suggest high
crystalline quality of the samples. After post-annealing in flowing oxygen at
600 C, the crystals show sharp superconducting transitions revealed by AC
susceptibility. The hole concentration is deduced from superconducting
transition temperature (), which exhibits a linear relation with La doping
level . It ranges from the heavily overdoped regime ( 0.2) to the
extremely underdoped side ( 0.08) where the superconductivity is
absent. Comparing with the superconducting dome in
BiSrCuO system, the effects from out-of-plane
disorders show up in our samples. Besides the La doping level , the
superconductivity is also sensitive to the content of oxygen which could be
tuned by post-annealing method over the whole doping range. The post-annealing
effects on and for each La doping level are studied, which give some
insights on the different nature between overdoped and underdoped regime.Comment: 6 pages, 6 figure
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