18 research outputs found
Absence of static magnetic order in lightly-doped Ti1-xScxOCl down to 1.7 K
Impurity-induced magnetic order has been observed in many quasi-1D systems
including doped variants of the spin-Peierls system CuGeO3. TiOCl is another
quasi-1D quantum magnet with a spin-Peierls ground state, and the magnetic Ti
sites of this system can be doped with non-magnetic Sc. To investigate the role
of non-magnetic impurities in this system, we have performed both zero field
and longitudinal field muSR experiments on polycrystalline Ti1-xScxOCl samples
with x = 0, 0.01, and 0.03. We verified that TiOCl has a non-magnetic ground
state, and we found no evidence for spin freezing or magnetic ordering in the
lightly-doped Sc samples down to 1.7 K. Our results instead suggest that these
systems remain non-magnetic up to the x = 0.03 Sc doping level.Comment: 5 pages, 4 figure
Absence of large nanoscale electronic inhomogeneities in the Ba(Fe1-xCox)2As2 pnictide
75As NMR and susceptiblity were measured in a Ba(Fe1-xCox)2As2 single crystal
for x=6% for various field H values and orientations. The sharpness of the
superconducting and magnetic transitions demonstrates a homogeneity of the Co
doping x better than +-0.25%. On the nanometer scale, the paramagnetic part of
the NMR spectra is found very anisotropic and very narrow for H//ab which
allows to rule out the interpretation of Ref.[6] in terms of strong Co induced
electronic inhomogeneities. We propose that a distribution of hyperfine
couplings and chemical shifts due to the Co effect on its nearest As explains
the observed linewidths and relaxations. All these measurements show that Co
substitution induces a very homogeneous electronic doping in BaFe2As2, from
nano to micrometer lengthscales, on the contrary to the K doping.Comment: 6 pages, 4 figure
Anomalous metamagnetism in the low carrier density Kondo lattice YbRh3Si7
We report complex metamagnetic transitions in single crystals of the new low
carrier Kondo antiferromagnet YbRh3Si7. Electrical transport, magnetization,
and specific heat measurements reveal antiferromagnetic order at T_N = 7.5 K.
Neutron diffraction measurements show that the magnetic ground state of
YbRh3Si7 is a collinear antiferromagnet where the moments are aligned in the ab
plane. With such an ordered state, no metamagnetic transitions are expected
when a magnetic field is applied along the c axis. It is therefore surprising
that high field magnetization, torque, and resistivity measurements with H||c
reveal two metamagnetic transitions at mu_0H_1 = 6.7 T and mu_0H_2 = 21 T. When
the field is tilted away from the c axis, towards the ab plane, both
metamagnetic transitions are shifted to higher fields. The first metamagnetic
transition leads to an abrupt increase in the electrical resistivity, while the
second transition is accompanied by a dramatic reduction in the electrical
resistivity. Thus, the magnetic and electronic degrees of freedom in YbRh3Si7
are strongly coupled. We discuss the origin of the anomalous metamagnetism and
conclude that it is related to competition between crystal electric field
anisotropy and anisotropic exchange interactions.Comment: 23 pages and 4 figures in the main text. 7 pages and 5 figures in the
supplementary materia
Magnetization and specific heat of the dimer system CuTe2O5
We report on magnetization and specific heat measurements on
single-crystalline CuTe2O5. The experimental data are directly compared to
theoretical results for two different spin structures, namely an alternating
spin-chain and a two-dimensional (2D) coupled dimer model, obtained by Das et
al. [Phys. Rev. B 77, 224437 (2008)]. While the analysis of the specific heat
does not allow to distinguish between the two models, the magnetization data is
in good agreement with the 2D coupled dimer model.Comment: 5 pages, 3 figure
The Psychological Science Accelerator’s COVID-19 rapid-response dataset
In response to the COVID-19 pandemic, the Psychological Science Accelerator coordinated three large-scale psychological studies to examine the effects of loss-gain framing, cognitive reappraisals, and autonomy framing manipulations on behavioral intentions and affective measures. The data collected (April to October 2020) included specific measures for each experimental study, a general questionnaire examining health prevention behaviors and COVID-19 experience, geographical and cultural context characterization, and demographic information for each participant. Each participant started the study with the same general questions and then was randomized to complete either one longer experiment or two shorter experiments. Data were provided by 73,223 participants with varying completion rates. Participants completed the survey from 111 geopolitical regions in 44 unique languages/dialects. The anonymized dataset described here is provided in both raw and processed formats to facilitate re-use and further analyses. The dataset offers secondary analytic opportunities to explore coping, framing, and self-determination across a diverse, global sample obtained at the onset of the COVID-19 pandemic, which can be merged with other time-sampled or geographic data
The Psychological Science Accelerator’s COVID-19 rapid-response dataset
In response to the COVID-19 pandemic, the Psychological Science Accelerator coordinated three large-scale psychological studies to examine the effects of loss-gain framing, cognitive reappraisals, and autonomy framing manipulations on behavioral intentions and affective measures. The data collected (April to October 2020) included specific measures for each experimental study, a general questionnaire examining health prevention behaviors and COVID-19 experience, geographical and cultural context characterization, and demographic information for each participant. Each participant started the study with the same general questions and then was randomized to complete either one longer experiment or two shorter experiments. Data were provided by 73,223 participants with varying completion rates. Participants completed the survey from 111 geopolitical regions in 44 unique languages/dialects. The anonymized dataset described here is provided in both raw and processed formats to facilitate re-use and further analyses. The dataset offers secondary analytic opportunities to explore coping, framing, and self-determination across a diverse, global sample obtained at the onset of the COVID-19 pandemic, which can be merged with other time-sampled or geographic data
Superfluid density and field-induced magnetism in Ba(Fe1-xCox)(2)As-2 and Sr(Fe1-xCox)(2)As-2 measured with muon spin relaxation
We report muon spin rotation (mu SR) measurements of single-crystal Ba(Fe1-xCox)(2)As-2 and Sr(Fe1-xCox)(2)As-2. From measurements of the magnetic field penetration depth lambda we find that for optimally and overdoped samples, 1/lambda(T -> 0)(2) varies monotonically with the superconducting transition temperature T-C. Within the superconducting state we observe a positive shift in the muon precession signal, likely indicating that the applied field induces an internal magnetic field. The size of the induced field decreases with increasing doping but is present for all Co concentrations studied.This article is published as Williams, T. J., A. A. Aczel, E. Baggio-Saitovitch, S. L. Bud’ko, P. C. Canfield, J. P. Carlo, T. Goko et al. "Superfluid density and field-induced magnetism in Ba (Fe 1− x Co x) 2 As 2 and Sr (Fe 1− x Co x) 2 As 2 measured with muon spin relaxation." Physical Review B 82, no. 9 (2010): 094512.
DOI: 10.1103/PhysRevB.82.094512.
Copyright 2010 American Physical Society.
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