362 research outputs found
High-field irreversible moment reorientation in the antiferromagnet FeTe
Magnetization measurements have been performed on single-crystalline
FeTe in pulsed magnetic fields up to 53 T
and temperatures from 4.2 to 65 K. At K, a non-reversible reorientation
of the antiferromagnetic moments is observed at T as the pulsed
field is on the rise. No anomaly is observed at during the fall of the
field and, as long as the temperature is unchanged, during both rises and falls
of additional field pulses. The transition at is reactivated if the
sample is warmed up above the N\'{e}el temperature K and cooled
down again. The magnetic field-temperature phase diagram of FeTe in
is also investigated. We present the temperature
dependence of , as well as that of the antiferromagnetic-to-paramagnetic
borderline in temperatures above 40 K.Comment: 5 pages, 4 figure
Antiferromagnetism and hot spots in CeIn
Enormous mass enhancement at ''hot spots'' on the Fermi surface (FS) of
CeIn has been reported at strong magnetic field near its antiferromagnetic
(AFM) quantum critical point [T. Ebihara et al., Phys. Rev. Lett. 93, 246401
(2004)] and ascribed to anomalous spin fluctuations at these spots. The ''hot
spots'' lie at the positions on FS where in non-magnetic LaIn the narrow
necks are protruded. In paramagnetic phase CeIn has similar spectrum. We
show that in the presence of AFM ordering its FS undergoes a topological change
at the onset of AFM order that truncates the necks at the ''hot spots'' for one
of the branches. Applied field leads to the logarithmic divergence of the dHvA
effective mass when the electron trajectory passes near or through the neck
positions. This effect explains the observed dHvA mass enhancement at the ''hot
spots'' and leads to interesting predictions concerning the spin-dependence of
the effective electron mass. The (T,B)-phase diagram of CeIn, constructed
in terms of the Landau functional, is in agreement with experiment.Comment: 4 pages, 1 figur
Ferromagnetism and Lattice Distortions in the Perovskite YTiO
The thermodynamic properties of the ferromagnetic perovskite YTiO are
investigated by thermal expansion, magnetostriction, specific heat, and
magnetization measurements. The low-temperature spin-wave contribution to the
specific heat, as well as an Arrott plot of the magnetization in the vicinity
of the Curie temperature K, are consistent with a
three-dimensional Heisenberg model of ferromagnetism. However, a magnetic
contribution to the thermal expansion persists well above , which
contrasts with typical three-dimensional Heisenberg ferromagnets, as shown by a
comparison with the corresponding model system EuS. The pressure dependences of
and of the spontaneous moment are extracted using thermodynamic
relationships. They indicate that ferromagnetism is strengthened by uniaxial
pressures and is weakened by uniaxial
pressures and hydrostatic pressure.
Our results show that the distortion along the - and -axes is further
increased by the magnetic transition, confirming that ferromagnetism is favored
by a large GdFeO-type distortion. The c-axis results however do not fit
into this simple picture, which may be explained by an additional
magnetoelastic effect, possibly related to a Jahn-Teller distortion.Comment: 12 pages, 13 figure
Avpr1a variant associated with preschoolers' lower altruistic behavior
10.1371/journal.pone.0025274PLoS ONE69
Superconductivity mediated by a soft phonon mode: specific heat, resistivity, thermal expansion and magnetization of YB6
The superconductor YB6 has the second highest critical temperature Tc among
the boride family MBn. We report measurements of the specific heat,
resistivity, magnetic susceptibility and thermal expansion from 2 to 300 K,
using a single crystal with Tc = 7.2 K. The superconducting gap is
characteristic of medium-strong coupling. The specific heat, resistivity and
expansivity curves are deconvolved to yield approximations of the phonon
density of states, the spectral electron-phonon scattering function and the
phonon density of states weighted by the frequency-dependent Grueneisen
parameter respectively. Lattice vibrations extend to high frequencies >100 meV,
but a dominant Einstein-like mode at ~8 meV, associated with the vibrations of
yttrium ions in oversized boron cages, appears to provide most of the
superconducting coupling and gives rise to an unusual temperature behavior of
several observable quantities. A surface critical field Hc3 is also observed.Comment: 29 pages, 5 tables, 17 figures. Accepted for publication in Phys.
Rev.
New Superconducting and Magnetic Phases Emerge on the Verge of Antiferromagnetism in CeIn
We report the discovery of new superconducting and novel magnetic phases in
CeIn on the verge of antiferromagnetism (AFM) under pressure () through
the In-nuclear quadrupole resonance (NQR) measurements. We have found a
-induced phase separation of AFM and paramagnetism (PM) without any trace
for a quantum phase transition in CeIn. A new type of superconductivity
(SC) was found in GPa to coexist with AFM that is magnetically
separated from PM where the heavy fermion SC takes place. We propose that the
magnetic excitations such as spin-density fluctuations induced by the
first-order magnetic phase transition might mediate attractive interaction to
form Cooper pairs.Comment: 4 pages, 4 EPS figures, submitted to J. Phys. Soc. Jp
High frequency magnetic oscillations of the organic metal -(ET)ZnBr(CHCl) in pulsed magnetic field of up to 81 T
De Haas-van Alphen oscillations of the organic metal
-(ET)ZnBr(CHCl) are studied in pulsed magnetic
fields up to 81 T. The long decay time of the pulse allows determining reliable
field-dependent amplitudes of Fourier components with frequencies up to several
kiloteslas. The Fourier spectrum is in agreement with the model of a linear
chain of coupled orbits. In this model, all the observed frequencies are linear
combinations of the frequency linked to the basic orbit and to the
magnetic-breakdown orbit .Comment: 6 pages, 4 figure
Pressure Evolution of the Magnetic Field induced Ferromagnetic Fluctuation through the Pseudo-Metamagnetism of CeRu2Si2
Resistivity measurements performed under pressure in the paramagnetic ground
state of CeRu2Si2 are reported. They demonstrate that the relative change of
effective mass through the pseudo metamagnetic transition is invariant under
pressure. The results are compared with the first order metamagnetic transition
due to the antiferromagnetism of Ce0.9La0.1Ru2Si2 which corresponds to the
"negative" pressure of CeRu2Si2 by volume expansion. Finally, we describe the
link between the spin-depairing of quasiparticles on CeRu2Si2 and that of
Cooper pairs on the unconventional heavy fermion superconductor CeCoIn5.Comment: 5 pages, 6 figures, accepted for publication in J. Phys. Soc. Jp
The Oxytocin Receptor (OXTR) Contributes to Prosocial Fund Allocations in the Dictator Game and the Social Value Orientations Task
Background: Economic games observe social decision making in the laboratory that involves real money payoffs. Previously we have shown that allocation of funds in the Dictator Game (DG), a paradigm that illustrates costly altruistic behavior, is partially determined by promoter-region repeat region variants in the arginine vasopressin 1a receptor gene (AVPR1a). In the current investigation, the gene encoding the related oxytocin receptor (OXTR) was tested for association with the DG and a related paradigm, the Social Values Orientation (SVO) task. Methodology/Principal Findings: Association (101 male and 102 female students) using a robust-family based test between 15 single tagging SNPs (htSNPs) across the OXTR was demonstrated with both the DG and SVO. Three htSNPs across the gene region showed significant association with both of the two games. The most significant association was observed with rs1042778 (p = 0.001). Haplotype analysis also showed significant associations for both DG and SVO. Following permutation test adjustment, significance was observed for 2–5 locus haplotypes (p,0.05). A second sample of 98 female subjects was subsequently and independently recruited to play the dictator game and was genotyped for the three significant SNPs found in the first sample. The rs1042778 SNP was shown to be significant for the second sample as well (p = 0.004, Fisher’s exact test). Conclusions: The demonstration that genetic polymorphisms for the OXTR are associated with human prosocial decisio
Kondo engineering : from single Kondo impurity to the Kondo lattice
In the first step, experiments on a single cerium or ytterbium Kondo impurity
reveal the importance of the Kondo temperature by comparison to other type of
couplings like the hyperfine interaction, the crystal field and the intersite
coupling. The extension to a lattice is discussed. Emphasis is given on the
fact that the occupation number of the trivalent configuration may be the
implicit key variable even for the Kondo lattice. Three phase
diagrams are discussed: CeRuSi, CeRhIn and SmS
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