300 research outputs found
Samarium Magnetism Studied on SmPd2Al3 Single Crystal
In this paper, specific features of Sm magnetism in an intermetallic compound
have been studied. For this purpose, a high-quality single crystal of SmPd2Al3
was grown and subjected to detailed measurements of specific heat,
magnetization, ac susceptibility, and electrical resistivity with respect to
temperature and a magnetic field applied along the principal crystallographic
directions. SmPd2Al3 magnetism was found to be strongly anisotropic with the
easy-magnetization direction along the c axis where the main magnetic features
are concentrated. The a-axis response remains weak, paramagneticlike, even in
the magnetically ordered state. Ferromagnetism with TC=12.4 K has been
indicated by all the measured physical properties. At lower temperatures, three
successive order-order phase transitions have been observed on the temperature
dependence of the specific heat as three anomalies: at 3.4, 3.9, and 4.4 K,
respectively. The low-temperature magnetization data can be understood within a
scenario that considers the antiferromagnetic ground state as being gradually
destroyed through a series of four metamagnetic transitions at 0.03, 0.35, 0.5,
and 0.75 T, as detected in the 1.8 K magnetization data. The experimental data
are discussed together with the results of electronic-structure and
crystal-field calculations from first principles, which were performed as an
important part of the study for comprehension and explanation of the observed
behavior of the SmPd2Al3 compound
Coupling between magnon and ligand-field excitations in magnetoelectric Tb3Fe5O12 garnet
The spectra of far-infrared transmission in Tb3Fe5O12 magnetoelectric single
crystals have been studied in the range between 15 and 100 cm-1, in magnetic
fields up to 10 T, and for temperatures between 5 and 150 K. We attribute some
of the observed infrared-active excitations to electric-dipole transitions
between ligand-field split states of Tb3+ ions. Anticrossing between the
magnetic exchange excitation and the ligand-field transition occurs at the
temperature between 60 and 80 K. The corresponding coupling energy for this
interaction is 6 cm-1. Temperature-induced softening of the hybrid IR
excitation correlates with the increase of the static dielectric constant. We
discuss the possibility for hybrid excitations of magnons and ligand-field
states and their possible connection to the magnetoelectric effect in
Tb3Fe5O12.Comment: submitted to Phys. Rev. B on May 15th, 201
Oxide phosphors for light upconversion; Yb3+ and Tm3+ co-doped Y2BaZnO5
Copyright 2011 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Journal of Applied Physics 109, 063104 (2011) and may be found at
Combined local-density and dynamical mean field theory calculations for the compressed lanthanides Ce, Pr, and Nd
This paper reports calculations for compressed Ce (4f^1), Pr (4f^2), and Nd
(4f^3) using a combination of the local-density approximation (LDA) and
dynamical mean field theory (DMFT), or LDA+DMFT. The 4f moment, spectra, and
the total energy among other properties are examined as functions of volume and
atomic number for an assumed face-centered cubic (fcc) structure.Comment: 15 pages, 9 figure
Tourism policy and destination marketing in developing countries: the chain of influence
Tourism marketers including destination marketing organisations (DMOs) and international tour operators play a pivotal role in destination marketing, especially in creating destination images. These images, apparent in tourist brochures, are designed to influence tourist decision-making and behaviour. This paper proposes the concept of a “chain of influence” in destination marketing and image-making, suggesting that the content of marketing materials is influenced by the priorities of those who design these materials, e.g. tour operators and DMOs. A content analysis of 2,000 pictures from DMO and tour operator brochures revealed synergies and divergence between these marketers. The brochure content was then compared to the South African tourism policy, concluding that the dominant factor in the chain of influence in the South African context is in fact its organic image
Efficient quantum key distribution scheme with nonmaximally entangled states
We propose an efficient quantum key distribution scheme based on
entanglement. The sender chooses pairs of photons in one of the two equivalent
nonmaximally entangled states randomly, and sends a sequence of photons from
each pair to the receiver. They choose from the various bases independently but
with substantially different probabilities, thus reducing the fraction of
discarded data, and a significant gain in efficiency is achieved. We then show
that such a refined data analysis guarantees the security of our scheme against
a biased eavesdropping strategy.Comment: 5 Pages, No Figur
Spectral line shape of resonant four-wave mixing induced by broad-bandwidth lasers
We present a theoretical and experimental study of the line shape of resonant four-wave mixing induced by broad-bandwidth laser radiation that revises the theory of Meacher, Smith, Ewart, and Cooper (MSEC) [Phys. Rev. A 46, 2718 (1992)]. We adopt the same method as MSEC but correct for an invalid integral used to average over the distribution of atomic velocities. The revised theory predicts a Voigt line shape composed of a homogeneous, Lorentzian component, defined by the collisional rate Γ, and an inhomogeneous, Doppler component, which is a squared Gaussian. The width of the inhomogeneous component is reduced by a factor of √2 compared to the simple Doppler width predicted by MSEC. In the limit of dominant Doppler broadening, the width of the homogeneous component is predicted to be 4Γ, whereas in the limit of dominant homogeneous broadening, the predicted width is 2Γ. An experimental measurement is reported of the line shape of the four-wave-mixing signal using a broad-bandwidth, "modeless", laser resonant with the Q1 (6) line of the A2 Σ - X2 Π(0,0) system of the hydroxyl radical. The measured widths of the Voigt components were found to be consistent with the predictions of the revised theory
Spectroscopic analysis of LiTm F
The absorption spectra of Tm3+ in LiTmF4 have been measured at 2, 10, 30, and 50 K in the spectral interval 4000-25 000 cm-1. The energy levels of the ground-state configuration were calculated by diagonalizing the Hamiltonian of the electron-electron interaction, the spin-orbit coupling, and the crystal field in a basis of the whole configuration. The electrostatic parameter F2, the spin-orbit parameter ζ, and the crystal-field parameters Bkq were varied to obtain the best agreement with the experimentally observed levels. As the model does not account for configuration mixing and minor magnetic effects, it was necessary after optimizing F2 and ζ to match the centers of gravity for the multiplets before the final adjustment of the B parameters. When this was done, the standard deviation was lowered from 170 to 12 cm-1. The B parameters obtained for Tm3+ have been compared to those of Tb3+, Ho3+, and Er3+ in LiLnF4, and they follow a common trend. The intensities of the transitions from the ground state were calculated in the Judd-Ofelt scheme, fitting six complex intensity parameters A(kqλ) for best agreement with the experimentally observed intensities. The model was only able to give a rough estimate of the transition probabilities. The obtained relative standard deviation was 1.1. Contrary to what was found in the case of the energy calculations, it was important for the intensity calculations that the B parameters were allowed to take complex values. The imaginary part of the A parameters was not important to the intensities
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