9,409 research outputs found
Superconductivity in Ti-doped Iron-Arsenide Compound Sr4Cr0.8Ti1.2O6Fe2As2
Superconductivity was achieved in Ti-doped iron-arsenide compound
Sr4Cr0.8Ti1.2O6Fe2As2 (abbreviated as Cr-FeAs-42622). The x-ray diffraction
measurement shows that this material has a layered structure with the space
group of \emph{P4/nmm}, and with the lattice constants a = b = 3.9003 A and c =
15.8376 A. Clear diamagnetic signals in ac susceptibility data and
zero-resistance in resistivity data were detected at about 6 K, confirming the
occurrence of bulk superconductivity. Meanwhile we observed a superconducting
transition in the resistive data with the onset transition temperature at 29.2
K, which may be induced by the nonuniform distribution of the Cr/Ti content in
the FeAs-42622 phase, or due to some other minority phase.Comment: 3 pages, 3 figure
Transition of stoichiometricSr2VO3FeAs to a superconducting state at 37.2 K
The superconductor Sr4V2O6Fe2As2 with transition temperature at 37.2 K has
been fabricated. It has a layered structure with the space group of p4/nmm, and
with the lattice constants a = 3.9296Aand c = 15.6732A. The observed large
diamagnetization signal and zero-resistance demonstrated the bulk
superconductivity. The broadening of resistive transition was measured under
different magnetic fields leading to the discovery of a rather high upper
critical field. The results also suggest a large vortex liquid region which
reflects high anisotropy of the system. The Hall effect measurements revealed
dominantly electron-like charge carriers in this material. The
superconductivity in the present system may be induced by oxygen deficiency or
the multiple valence states of vanadium.Comment: 5 pages, 4 figure
Superconductivity at 15.6 K in Calcium-doped Tb_{1-x}Ca_xFeAsO: the structure requirement for achieving superconductivity in the hole-doped 1111 phase
Superconductivity at about 15.6 K was achieved in Tb_{1-x}Ca_xFeAsO by
partially substituting Tb^{3+} with Ca^{2+} in the nominal doping region x =
0.40 \sim 0.50. A detailed investigation was carried out in a typical sample
with doping level of x = 0.44. The upper critical field of this sample was
estimated to be 77 Tesla from the magnetic field dependent resistivity data.
The domination of hole-like charge carriers in the low-temperature region was
confirmed by Hall effect measurements. The comparison between the calcium-doped
sample Pr_{1-x}Ca_xFeAsO (non-superconductive) and the Strontium-doped sample
Pr_{1-x}Sr_xFeAsO (superconductive) suggests that a lager ion radius of the
doped alkaline-earth element compared with that of the rare-earth element may
be a necessary requirement for achieving superconductivity in the hole-doped
1111 phase.Comment: 7 pages, 7 figure
Automated Detection of Skin Tone Diversity in Visual Marketing Communication
Companies invest heavily in diversity, equity, and inclusion efforts. Specifically, the representation of people in visual marketing communication is often considered a manifestation of diversity policies. We propose a standard framework built on machine learning to create novel measures quantifying skin tone dynamics. We first use the Swin Transformer to extract skin pixels from images. Next, the K-means algorithm is deployed to classify skin tone components from the extracted skin pixels, accounting for multiple people with distinct skin colors in an image. Using images posted by 34 fashion brands on Instagram and Twitter, we demonstrate a useful application of the tool. The results highlight that, in the past two years, the fashion industry has slightly increased its diversity, represented by the increased variety of skin tones of people included in social media posts. Our method allows for automated detection of objective measures of skin-tone diversity in visual marketing communications
(Sr_3Sc_2O_5)Fe_2As_2 as a possible parent compound for FeAs-based superconductors
A new compound with the FeAs-layers, namely (Sr_3Sc_2O_5)Fe_2As_2
(abbreviated as FeAs-32522), was successfully fabricated. It has a layered
structure with the space group of I4/mmm, and with the lattice constants a =
4.069 and c = 26.876 . The in-plane Fe ions construct a square
lattice which is close to that of other FeAs-based superconductors, such as
REFeAsO (RE = rare earth elements) and (Ba,Sr)Fe_2As_2. However the inter
FeAs-layer spacing in the new compound is greatly enlarged. The temperature
dependence of resistivity exhibits a weak upturn in the low temperature region,
but a metallic behavior was observed above about 60 K. The magnetic
susceptibility shows also a non-monotonic behavior. Interestingly, the
well-known resistivity anomaly which was discovered in all other parent
compounds, such as REFeAsO, (Ba,Sr)Fe_2As_2 and (Sr,Ca,Eu)FeAsF and associated
with the Spin-Density-Wave (SDW)/structural transition has not been found in
the new system either on the resistivity data or the magnetization data. This
could be induced by the large spacing distance between the FeAs-planes,
therefore the antiferromagnetic correlation between the moments of Fe ions in
neighboring FeAs-layers cannot be established. Alternatively it can also be
attributed to the self-doping effect between Fe and Sc ions. The Hall
coefficient R_H is negative but strongly temperature dependent in wide
temperature region, which indicates the dominance of electrical conduction by
electron-like charge carriers and probably a multi-band effect or a spin
related scattering effect. It is found that the magnetoresistance cannot be
described by the Kohler's rule, which gives further support to above arguments.Comment: 5 pages, 5 figures, some contents added, and one figure adde
Superconductivity induced by doping Platinum in BaFe2As2
By substituting Fe with the 5d-transition metal Pt in BaFe2As2, we have
successfully synthesized the superconductors BaFe2-xPtxAs2. The systematic
evolution of the lattice constants indicates that the Fe ions were successfully
replaced by Pt ions. By increasing the doping content of Pt, the
antiferromagnetic order and structural transition of the parent phase is
suppressed and superconductivity emerges at a doping level of about x = 0.02.
At a doping level of x = 0.1, we get a maximum transition temperature Tc of
about 25 K. The synchrotron powder x-ray diffraction shows that the resistivity
anomaly is in good agreement with the structural transition. The
superconducting transitions at different magnetic fields were also measured at
the doping level of about x = 0.1, yielding a slope of -dHc2/dT = 5.4 T/K near
Tc. A phase diagram was established for the Pt doped 122 system. Our results
suggest that superconductivity can also be easily induced in the FeAs family by
substituting the Fe with Pt, with almost the similar maximum transition
temperatures as doping Ni, Co, Rh and Ir.Comment: 6 pages, 5 figure
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