7,030 research outputs found
Electronic phase separation due to magnetic polaron formation in the semimetallic ferromagnet EuB - A weakly-nonlinear-transport study
We report measurements of weakly nonlinear electronic transport, as measured
by third-harmonic voltage generation , in the low-carrier density
semimetallic ferromagnet EuB, which exhibits an unusual magnetic ordering
with two consecutive transitions at \,K and \,K. Upon cooling in zero magnetic field through the ferromagnetic
transition, the dramatic drop in the linear resistivity at the upper transition
coincides with the onset of nonlinearity, and upon further cooling is
followed by a pronounced peak in at the lower transition
. Likewise, in the paramagnetic regime, a drop of the material's
magnetoresistance precedes a magnetic-field-induced peak in nonlinear
transport. A striking observation is a linear temperature dependence of
. We suggest a picture where at the upper transition
the coalescing MP form a conducting path giving rise to a strong
decrease in the resistance. The MP formation sets in at around \,K below which these entities are isolated and strongly fluctuating, while
growing in number. The MP then start to form links at , where
percolative electronic transport is observed. The MP merge and start forming a
continuum at the threshold . In the paramagnetic temperature regime
, MP percolation is induced by a magnetic field, and the
threshold accompanied by charge carrier delocalization occurs at a single
critical magnetization.Comment: to appear in J. Kor. Phys. Soc (ICM2012 conference contribution
Crystal structure and physical properties of EuPtIn intermetallic antiferromagnet
We report the synthesis of EuPtIn single crystalline platelets by the
In-flux technique. This compound crystallizes in the orthorhombic Cmcm
structure with lattice parameters \AA, \AA and
\AA. Measurements of magnetic susceptibility, heat capacity,
electrical resistivity, and electron spin resonance (ESR) reveal that
EuPtIn is a metallic Curie-Weiss paramagnet at high temperatures and
presents antiferromagnetic (AFM) ordering below K. In addition, we
observe a successive anomaly at K and a spin-flop transition at
T applied along the -plane. In the paramagnetic state, a
single Eu Dysonian ESR line with a Korringa relaxation rate of Oe/K is observed. Interestingly, even at high temperatures, both ESR
linewidth and electrical resistivity reveal a similar anisotropy. We discuss a
possible common microscopic origin for the observed anisotropy in these
physical quantities likely associated with an anisotropic magnetic interaction
between Eu 4 electrons mediated by conduction electrons.Comment: 5 pages, 5 figure
Assistive lighting for people with sight loss
This paper affirms the importance of lighting as a technology in the context of people with sight loss. Its importance lies in the ability of appropriate lighting interventions to support independent living and to reduce the likelihood of falls and accidents. The concept of “assistive lighting” is introduced with a set of tenets by which the merits of different lighting interventions can be considered. The tenets are derived from research on lighting and sight loss, including a thorough review of the literature; and consultation in the period from 2008 to 2010 with over 80 rehabilitation workers and occupational therapists in the United Kingdom. They affirm the need for lighting to be appropriate, sufficient, even, adjustable, sustainable and energy efficient, simple and adaptable. Examples of different lighting interventions are provided and these are considered in relation to the tenets. One of the key outcomes of the research was publication of a guide to good practice on lighting interventions for people with sight loss.
Implications for Rehabilitation
-Assistive lighting has important implications for rehabilitation in relation to people with sight loss.
-Simple lighting interventions carry the potential for improving the independence and quality of life of people with sight loss and can reduce the risk of accidents.
-The tenets by which options for lighting interventions can be considered can assist rehabilitation officers and occupational therapists in their work.
-Lighting can be considered as a factor of increasing importance within the broader context of universal design
Thermally activated exchange narrowing of the Gd3+ ESR fine structure in a single crystal of Ce1-xGdxFe4P12 (x = 0.001) skutterudite
We report electron spin resonance (ESR) measurements in the Gd3+ doped
semiconducting filled skutterudite compound Ce1-xGdxFe4P12 (x = 0.001). As the
temperature T varies from T = 150 K to T = 165 K, the Gd3+ ESR fine and
hyperfine structures coalesce into a broad inhomogeneous single resonance. At T
= 200 K the line narrows and as T increases further, the resonance becomes
homogeneous with a thermal broadening of 1.1(2) Oe/K. These results suggest
that the origin of these features may be associated to a subtle interdependence
of thermally activated mechanisms that combine: i) an increase with T of the
density of activated conduction-carriers across the T-dependent semiconducting
pseudogap; ii) the Gd3+ Korringa relaxation process due to an exchange
interaction, J_{fd}S.s, between the Gd3+ localized magnetic moments and the
thermally activated conduction-carriers and; iii) a relatively weak confining
potential of the rare-earth ions inside the oversized (Fe2P3)4 cage, which
allows the rare-earths to become rattler Einstein oscillators above T = 148 K.
We argue that the rattling of the Gd3+ ions, via a motional narrowing
mechanism, also contributes to the coalescence of the ESR fine and hyperfine
structure.Comment: 7 pages, 9 figures, accepted for publication in Phys Rev
Superconductivity without Fe or Ni in the phosphides BaIr2P2 and BaRh2P2
Heat capacity, resistivity, and magnetic susceptibility measurements confirm
bulk superconductivity in single crystals of BaIrP (T=2.1K) and
BaRhP (T = 1.0 K). These compounds form in the ThCrSi (122)
structure so they are isostructural to both the Ni and Fe pnictides but not
isoelectronic to either of them. This illustrates the importance of structure
for the occurrence of superconductivity in the 122 pnictides. Additionally, a
comparison between these and other ternary phosphide superconductors suggests
that the lack of interlayer bonding favors superconductivity. These
stoichiometric and ambient pressure superconductors offer an ideal playground
to investigate the role of structure for the mechanism of superconductivity in
the absence of magnetism.Comment: Published in Phys Rev B: Rapid Communication
Site specific spin dynamics in BaFe2As2: tuning the ground state by orbital differentiation
The role of orbital differentiation on the emergence of superconductivity in
the Fe-based superconductors remains an open question to the scientific
community. In this investigation, we employ a suitable microscopic spin probe
technique, namely Electron Spin Resonance (ESR), to investigate this issue on
selected chemically substituted BaFeAs single crystals. As the
spin-density wave (SDW) phase is suppressed, we observe a clear increase of the
Fe 3 bands anisotropy along with their localization at the FeAs plane. Such
an increase of the planar orbital content interestingly occurs independently on
the chemical substitution responsible for suppressing the SDW phase. As a
consequence, the magnetic fluctuations combined with the resultant particular
symmetry of the Fe 3 bands are propitious ingredients to the emergence of
superconductivity in this class of materials.Comment: 6 pages, 5 figure
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