3,250 research outputs found
Evolution of transport properties of BaFe2-xRuxAs2 in a wide range of isovalent Ru substitution
The effects of isovalent Ru substitution at the Fe sites of BaFe2-xRuxAs2 are
investigated by measuring resistivity and Hall coefficient on high-quality
single crystals in a wide range of doping (0 < x < 1.4). Ru substitution
weakens the antiferromagnetic (AFM) order, inducing superconductivity for
relatively high doping level of 0.4 < x < 0.9. Near the AFM phase boundary, the
transport properties show non-Fermi-liquid-like behaviors with a
linear-temperature dependence of resistivity and a strong temperature
dependence of Hall coefficient with a sign change. Upon higher doping, however,
both of them recover conventional Fermi-liquid behaviors. Strong doping
dependence of Hall coefficient together with a small magnetoresistance suggest
that the anomalous transport properties can be explained in terms of
anisotropic charge carrier scattering due to interband AFM fluctuations rather
than a conventional multi-band scenario.Comment: 7 pages, 6 figures, submitted to Phys. Rev.
A cascade of magnetic field induced spin transitions in LaCoO3
We present magnetization and magnetostriction studies of the insulating
perovskite LaCoO3 in magnetic fields approaching 100 T. In marked contrast with
expectations from single-ion models, the data reveal two distinct first-order
spin transitions and well-defined magnetization plateaux. The magnetization at
the higher plateau is only about half the saturation value expected for spin-1
Co3+ ions. These findings strongly suggest collective behavior induced by
strong interactions between different electronic -- and therefore spin --
configurations of Co3+ ions. We propose a model of these interactions that
predicts crystalline spin textures and a cascade of four magnetic phase
transitions at high fields, of which the first two account for the experimental
data.Comment: 5 pages + supplementary materials, 5 figure
The nature of the continuum limit in the 2D gauge model
The RP(2) gauge model is studied in 2D. We use Monte-Carlo renormalization
techniques for blocking the mean spin-spin interaction, , and the mean gauge
field plaquette, . The presence of the O(3) renormalized trajectory is
verified and is consistent with the known three-loop beta-function. The
first-order `vorticity' transition observed by Solomon et al. is confirmed, and
the location of the terminating critical point is established. New scaling
flows in (,) are observed associated with a large exponent kappa in the
range 4~5. The scaling flows give rise to a strong cross-over effect between
regions of high and low vorticity and are likely to induce an apparent signal
for scaling in the cross-over region which we propose explains the scaling
observed for RP(2), RP(3) and SO(4)-matrix models. The signal for this `pseudo'
scaling will occur for the RP(2) spin model in the cross-over region which is
the region in which computer simulations are done. We find that the RP(2) spin
model is in the same universality class as the O(3) spin model but that it is
likely to require a very large correlation length before the true scaling of
this class sets in. We conjecture that the scaling flows are due either to the
influence of a nearby new renormalized trajectory or to the ghost of the
Kosterlitz-Thouless trajectory in the associated XY model.Comment: 29 pages, LATEX2e, 10 figures, uses styles[epsfig,latexsym
The METCRAX II Field Experiment: A Study of Downslope Windstorm-Type Flows in Arizona\u2019s Meteor Crater
The second Meteor Crater Experiment (METCRAX II) was conducted in October 2013 at Arizona\u2019s Meteor Crater. The experiment was designed to investigate nighttime downslope windstorm 12type flows that form regularly above the inner southwest sidewall of the 1.2-km diameter crater as a southwesterly mesoscale katabatic flow cascades over the crater rim. The objective of METCRAX II is to determine the causes of these strong, intermittent, and turbulent inflows that bring warm-air intrusions into the southwest part of the crater. This article provides an overview of the scientific goals of the experiment; summarizes the measurements, the crater topography, and the synoptic meteorology of the study period; and presents initial analysis results
Justifications-on-demand as a device to promote shifts of attention associated with relational thinking in elementary arithmetic
Student responses to arithmetical questions that can be solved by using arithmetical structure can serve to reveal the extent and nature of relational, as opposed to computational thinking. Here, student responses to probes which require them to justify-on-demand are analysed using a conceptual framework which highlights distinctions between different forms of attention. We analyse a number of actions observed in students in terms of forms of attention and shifts between them: in the short-term (in the moment), medium-term (over several tasks), and long-term (over a year). The main factors conditioning students´ attention and its movement are identified and some didactical consequences are proposed
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