1,259 research outputs found
Studies on X-ray Thomson Scattering from Antiferroquadrupolar Order in TmTe
We study Thomson scattering from the antiferroquadrupole ordering phase in
TmTe. On the basis of the group theoretical treatment, we classify the
selection rules of the scattering intensity governed by the orientation of the
scattering vector G. Then, numerical verification is performed by invoking the
ground states which are deduced from a J=7/2 multiplet model. The obtained
intensity varies drastically depending on the magnitude and direction of G. We
also calculate the scattering intensities under the applied field for H//(001)
and (110). Their results behave differently when the orientation of G is
changed, which is ascribed to the difference of their primary order parameters;
O_{2}^{0} and O_{2}^{2} for H // (001) and (110), respectively. We make
critical comparisons between our results for TmTe and the experimental ones for
CeB_6. First, we assert that the intensities expected from TmTe at several
forbidden Bragg spots are sufficient enough to be experimentally detected.
Second, their intensities at (7/2,1/2,1/2) differ significantly and may be
attributed to the difference of the order parametersbetween the \Gamma_3-type
(O_{2}^{2} and O_{2}^{0}) and \Gamma_5-type (O_{yz}, O_{zx}, and O_{xy})
components, respectively.Comment: 18 pages, 3 figures, to be published in J. Phys. Soc. Jp
Antiferroquadrupolar Order in the Magnetic Semiconductor TmTe
The physical properties of the antiferroquadrupolar state occurring in TmTe
below TQ=1.8 K have been studied using neutron diffraction in applied magnetic
fields. A field-induced antiferromagnetic component k = (1/2,1/2,1/2) is
observed and, from its magnitude and direction for different orientations of H,
an O(2,2) quadrupole order parameter is inferred. Measurements below TN ~= 0.5
K reveal that the magnetic structure is canted, in agreement with theoretical
predictions for in-plane antiferromagnetism. Complex domain repopulation
effects occur when the field is increased in the ordered phases, with
discontinuities in the superstructure peak intensities above 4 T.Comment: 6 pages, 6 figures, Presented at the International Conference on
Strongly Correlated Electrons with Orbital Degrees of Freedom (ORBITAL 2001),
September 11-14, 2001 (Sendai, JAPAN). To appear in: Journal of the Physical
Society of Japan (2002
Self-Consistent Perturbation Theory for Thermodynamics of Magnetic Impurity Systems
Integral equations for thermodynamic quantities are derived in the framework
of the non-crossing approximation (NCA). Entropy and specific heat of 4f
contribution are calculated without numerical differentiations of thermodynamic
potential. The formulation is applied to systems such as PrFe4P12 with
singlet-triplet crystalline electric field (CEF) levels.Comment: 3 pages, 2 figures, proc. ASR-WYP-2005 (JAERI
Theory of Coupled Multipole Moments Probed by X-ray Scattering in CeB
A minimal model for multipole orders in CeB shows that degeneracy of the
quadrupole order parameters and strong spin-orbit coupling lead to peculiar
temperature and magnetic-field dependences of the X-ray reflection intensity at
superlattice Bragg points. Furthermore, the intensity depends sensitively on
the surface direction. These theoretical results explain naturally recent X-ray
experiments in phases II and III of CeB. It is predicted that under weak
magnetic field perpendicular to the (111) surface, the reflection intensity
should change non-monotonically as a function of temperature.Comment: 4 pages, 5 figure
Effects of Impurities with Singlet-Triplet Configuration on Multiband Superconductors
Roles of multipole degrees of freedom in multiband superconductors are
investigated in a case of impurities whose low-lying states consist of singlet
ground and triplet excited states, which is related to the experimental fact
that the transition temperature is increased by Pr substitution for
La in LaOsSb. The most important contribution to the
increase comes from the inelastic interband scattering of electrons coupled to
quadrupole or octupole moments of impurities. It is found that a magnetic field
modifies an effective pairing interaction and the scattering anisotropy appears
in the field-orientation dependence of the upper critical field
in the vicinity of , although a uniaxial anisotropic field is
required for experimental detection. This would be proof that the Pr internal
degrees of freedom are relevant to the stability of superconductivity in
(LaPr)OsSb.Comment: 10 pages, 5 figures, to appear in J. Phys. Soc. Jp
Effects of Transferable Skills Workshops on the Career Self-Efficacy of College Student-Athletes
This study was designed to investigate the effects of two types of transferable skills workshops on the career self-efficacy of intercollegiate student-athletes. Participants were 79 college student-athletes (45 males [30 football players and 15 basketball players] and 34 females [14 softball players and 20 soccer players]) enrolled at a small NCAA Division III institution. Student-athletes (N=79) were randomly assigned to one of three conditions: (a) a control condition that involved viewing a video on sports nutrition, (b) an unaugmented transferable skills workshop that was based on the model suggested by Petitpas and Schwartz (1989), and (c) an augmented transferable skills workshop similar to the unaugmented workshop but including completion of a self-report inventory designed to help athletes identify sport-related skills that can transfer to other domains. All participants completed the Career Decision Self-Efficacy Short-Form (COSE-SF; Betz & Taylor, 200 I) before and after the workshops. Analyses of covariance (ANCOVAs) with COSE-SF pretest scores as a covariate revealed that the augmented transferable skills workshop produced significantly greater increases in career self-efficacy than the unaugmented transferable skills workshop and the control condition. Paired samples t-tests indicated that both transferable skills workshops, but not the control condition, produced statistically significant gains in career self-efficacy. The results suggest that both transferable skills workshops can have a positive influence on the career self-efficacy of student-athletes and that a standardized transferable skills inventory can be a helpful tool in enhancing the ability of student-athletes to identify transferable skills that can increase their career self-efficacy. The career self-efficacy level of student-athletes who participated in the transferable
skills workshops increased significantly compared to that of the control group.
In addition, participants who completed the TSI as part of their transferable skills
workshop showed higher levels of career self-efficacy than student-athletes who did
not complete the TSI
Multipole tensor analysis of the resonant x-ray scattering by quadrupolar and magnetic order in DyB2C2
Resonant x-ray scattering (RXS) experiment has been performed for the (3 0
1.5) superlattice reflection in the antiferroquadrupolar and antiferromagnetic
phase of DyB2C2. Azimuthal-angle dependence of the resonance enhanced
intensities for both dipolar (E1) and quadrupolar (E2) resonant processes has
been measured precisely with polarization analysis. Every scattering channel
exhibits distinctive azimuthal dependence, differently from the symmetric
reflection at (0 0 0.5) which was studied previously. We have analyzed the
results using a theory developed by Lovesey et al., which directly connects
atomic tensors with the cross-section of RXS. The fitting results indicate that
the azimuthal dependences can be explained well by the atomic tensors up to
rank 2. Rank 3 and rank 4 tensors are reflected in the data very little. In
addition, The coupling scheme among the 4f quadrupolar moment, 5d ortitals, and
the lattice has been determined from the interference among the Thomson
scattering from the lattice distortion and the resonant scatterings of E1 and
E2 processes. It has also been established from the RXS of the (3 0 1.5)
reflection that the canting of the 4f quadrupolar moments exists up to T_Q. We
also discuss a possible wavefunction of the ground state from the point-charge
model calculation.Comment: 9 pages, 10 figure
Multipole State of Heavy Lanthanide Filled Skutterudites
We discuss multipole properties of filled skutterudites containing heavy
lanthanide Ln from a microscopic viewpoint on the basis of a seven-orbital
Anderson model. For Ln=Gd, in contrast to naive expectation, quadrupole moments
remain in addition to main dipole ones. For Ln=Ho, we find an exotic state
governed by octupole moment. For Ln=Tb and Tm, no significant multipole moments
appear at low temperatures, while for Ln=Dy, Er, and Yb, dipole and
higher-order multipoles are dominant. We briefly discuss possible relevance of
these multipole states with actual materials.Comment: 5 pages, 3 figure
Quadrupolar Order in Isotropic Heisenberg Models with Biquadratic Interaction
Through Quantum Monte Carlo simulation, we study the biquadratic-interaction
model with the SU(2) symmetry in two and three dimensions. The zero-temperature
phase diagrams for the two cases are identical and exhibit an intermediate
phase characterized by finite quadrupole moment, in agreement with mean-field
type arguments and the semi-classical theory. In three dimensions, we
demonstrate that the model in the quadrupolar regime has a phase transition at
a finite temperature. In contrast to predictions by mean-field theories, the
phase transition to the quadrupolar phase turns out to be of the second order.
We also examine the critical behavior in the two marginal cases with the SU(3)
symmetry.Comment: 4 pages 5 figure
Detection of Neutron Scattering from Phase IV of Ce0.7La0.3B6: A Confirmation of the Octupole Order
We have performed a single crystal neutron scattering experiment on
Ce0.7La0.3B6 to investigate the order parameter of phase IV microscopically.
Below the phase transition temperature 1.5 K of phase IV, weak but distinct
superlattice reflections at the scattering vector (h/2,h/2,l/2) (h, l = odd
number) have been observed by neutron scattering for the first time. The
intensity of the superlattice reflections is stronger for high scattering
vectors, which is quite different from the usual magnetic form factor of
magnetic dipoles. This result directly evidences that the order parameter of
phase IV has a complex magnetization density, consistent with the recent
experimental and theoretical prediction in which the order parameter is the
magnetic octupoles Tbeta with Gamma5 symmetry of point group Oh. Neutron
scattering experiments using short wavelength neutrons, as done in this study,
could become a general method to study the high-rank multipoles in f electron
systems.Comment: 4 pages, 4 figure
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