86 research outputs found
Microscopic co-existence of superconductivity and magnetism in Ba1-xKxFe2As2
It is widely believed that, in contrast to its electron doped counterparts,
the hole doped compound Ba1-xKxFe2As2 exhibits a mesoscopic phase separation of
magnetism and superconductivity in the underdoped region of the phase diagram.
Here, we report a combined high-resolution x-ray powder diffraction and volume
sensitive muon spin rotation study of underdoped Ba1-xKxFe2As2 (0 \leq x \leq
0.25) showing that this paradigm is wrong. Instead we find a microscopic
coexistence of the two forms of order. A competition of magnetism and
superconductivity is evident from a significant reduction of the magnetic
moment and a concomitant decrease of the magneto-elastically coupled
orthorhombic lattice distortion below the superconducting phase transition.Comment: 4 pages, 4 figure
Electronic phase separation in the slightly underdoped iron pnictide superconductor Ba(1-x)K(x)Fe(2)As(2)
Here we present a combined study of the slightly underdoped novel pnictide
superconductor Ba(1-x)K(x)Fe(2)As(2) by means of X-ray powder diffraction,
neutron scattering, muon spin rotation (muSR), and magnetic force microscopy
(MFM). Commensurate static magnetic order sets in below Tm ~ 70 K as inferred
from the emergence of the magnetic (1 0 -3) reflection in the neutron
scattering data and from the observation of damped oscillations in the
zero-field-muSR asymmetry. Transverse-field muSR below Tc shows a coexistence
of magnetically ordered and non-magnetic states, which is also confirmed by MFM
imaging. We explain such coexistence by electronic phase separation into
antiferromagnetic and superconducting/normal state regions on a lateral scale
of several tens of nanometers. Our findings indicate that such mesoscopic phase
separation can be considered an intrinsic property of some iron pnictide
superconductors
Thermal and Optical Characterization of Undoped and Neodymium-Doped Y3ScAl4O12 Ceramics
Y3–3xNd3xSc1Al4O12 (x = 0, 0.01, and 0.02) ceramics were fabricated by sintering at high temperature under vacuum. Unit cell parameter refinement and chemical analysis have been performed. The morphological characterization shows micrograins with no visible defects. The thermal analysis of these ceramics is presented, by measuring the specific heat in the temperature range from 300 to 500 K. Their values at room temperature are in the range 0.81–0.90 J g1–K–1. The thermal conductivity has been determined by two methods: by the experimental measurement of the thermal diffusivity by the photopyroelectric method, and by spectroscopy, evaluating the thermal load. The thermal conductivities are in the range 9.7–6.5 W K–1 m–1 in the temperature interval from 300 to 500 K. The thermooptic coefficients were measured at 632 nm by the dark mode method using a prism coupler, and the obtained values are in the range 12.8–13.3 × 10–6 K–1. The nonlinear refractive index values at 795 nm have been evaluated to calibrate the nonlinear optical response of these materials.This work is supported by the Spanish Government under projects MAT2011-29255-C02-01-02, MAT2013-47395-C4-4-R, and the Catalan Government under project 2014SGR1358. It was also funded by the European Commission under the Seventh Framework Programme, project Cleanspace, FP7-SPACE-2010-1-GA No. 263044
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