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71.
J.D. Pedarnig J. Heitz T. Stehrer B. Praher R. Viskup K. Siraj A. Moser A. Vlad M.A. Bodea D. Bäuerle N. Hari Babu D.A. Cardwell 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
Multi-component oxide ceramics and epitaxial oxide thin films are analyzed by laser-induced breakdown spectroscopy (LIBS). Furthermore, pulsed-laser deposition (PLD) of thin films is investigated by long-term monitoring of the optical plasma emission. Both nano-composite high-temperature superconductors (HTS) consisting of YBa2Cu3O7 − δ bulk and Y2Ba4MCuOx (M-2411, M = Ag, Nb) nano-particles, and semiconducting ZnO doped with Aluminum and Lithium are ablated by nano-second laser pulses. The plasma emission is recorded using grating spectrometers with intensified gated detectors. The LIBS signals of nano-particles correlate with the nominal content of the M-2411 phase (0–15 mol%) and reveal a strong signal of Ytterbium impurity (3–35 ppm). In situ monitoring of the PLD process shows element signals that are stable for more than 10,000 laser pulses for both HTS and ZnO ceramics. The relative concentration of elements in thin films and ceramics as determined by LIBS is almost the same. 相似文献
72.
D.C. Cabra A. Honecker P. Pujol 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):55-73
We analyze the phase diagram of a system of spin-1/2 Heisenberg antiferromagnetic chains interacting through a zig-zag coupling,
also called zig-zag ladders. Using bosonization techniques we study how a spin-gap or more generally plateaux in magnetization
curves arise in different situations. While for coupled XXZchains, one has to deal with a recently discovered chiral perturbation, the coupling term which is present for normal ladders
is restored by an external magnetic field, dimerization or the presence of charge carriers. We then proceed with a numerical
investigation of the phase diagram of two coupled Heisenberg chains in the presence of a magnetic field. Unusual behaviour
is found for ferromagnetic coupled antiferromagnetic chains. Finally, for three (and more) legs one can choose different inequivalent
types of coupling between the chains. We find that the three-leg ladder can exhibit a spin-gap and/or non-trivial plateaux
in the magnetization curve whose appearance strongly depends on the choice of coupling.
Received 11 February 1999 and Received in final form 16 June 1999 相似文献
73.
M.A. Garcia-Bach 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(3):439-448
For w-legged antiferromagnetic spin-1/2 Heisenberg ladders, a long-range spin pairing order can be identified which enables the
separation of the space spanned by finite-range (covalent) valence-bond configurations into w
+1 subspaces. Since every subspace has an equivalent counter subspace connected by translational symmetry, twofold degeneracy,
breaking translational symmetry is found except for the subspace where the ground state of w = even belongs to. In terms of energy ordering, (non)degeneracy and the discontinuities introduced in the long-range spin
pairing order by topological spin defects, the differences between even and odd ladders are explained in a general and systematic
way.
Received 19 July 1999 and Received in final form 8 October 1999 相似文献
74.
T. Henning B. Starmark T. Claeson P. Delsing 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(4):627-633
Models generalizing the su
(2) XX spin-chain were recently introduced. These XXC models also have an underlying su
(2) structure. Their construction method is shown to generalize to the chains based on the fundamental representations of the
Am Lie algebras. Integrability of the new models is shown in the context of the quantum inverse scattering method. Their R-matrix is found and shown to yield a representation of the Hecke algebra. The diagonalization of the transfer matrices is
carried out using the algebraic Bethe Ansatz. I comment on eventual generalizations and possible links to reaction-diffusion
processes.
Received: 24 June 1998 / Received in final form: 8 September 1998 / Accepted: 10 September 1998 相似文献
75.
76.
A schlieren method was used to generate time-resolved images of the tunneling ionization front produced when an ultrashort
high-power laser pulse irradiates He gas. By superimposing sequential schlieren images, we obtained information about the
laser propagation and found that the ionization front propagated farther with decreasing density of the target gas. Ray-tracing
suggested that this density dependence is a result of the spatial distribution of the laser intensity.
Received: 20 May 1999 / Revised version: 19 August 1999 / Published online: 27 January 2000 相似文献
77.
Deconfined quantum phase transition from Néel phase to valence bond crystal state in 2D Heisenberg model is under debate nowadays. One crucial issue is the suppression of Haldane's instanton on quantum critical point which drives the spinon deconfined. In this Letter, by making use of the ?-mapping topological current theory, we reexamine the Haldane's instanton in an alternative way along the direction of topology. We find that the monopole events are space-time singularities of Néel field , the corresponding topological charges are the wrapping number of around the singularities which can be expressed in terms of the Hopf indices and Brouwer degrees of ?-mapping. The suppression of the monopole events can only be guaranteed when the ?-field possesses no zero points. Moreover, the quadrapolarity of monopole events in the Heisenberg model due to the Berry phase is also reproduced in this topological argument. 相似文献
78.
Y. J. Wang C. M. Leung S. W. Or X. Y. Zhao H. S. Luo X. K. Lv Z. D. Zhang 《Applied Physics A: Materials Science & Processing》2009,97(1):201-204
We report an extrinsic magnetoelectric effect in composite laminates made by sandwiching one thickness-polarized 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN–PT) piezoelectric single crystal plate between two length-magnetized, polymer-based pseudo-1–3 (Tb0.3Dy0.7)0.5Pr0.5Fe1.55 magnetostrictive composite plates. The laminates exhibit large magnetoelectric voltage coefficients (α
V
) of ∼0.17 V/Oe with a flat response for frequencies in excess of 40 kHz and of ∼2.97 V/Oe at the natural resonance frequency
of ∼65 kHz. The distinct advantages of the laminates include high magnetic field sensitivity, low Joule heating loss, wide
operating bandwidth, and low cost. 相似文献
79.
L. S. Lima A. S.T. Pires 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(3):335-342
In this paper we study the dynamics of the two-dimensional XY model with single-ion anisotropy, and spin S = 1, in the large
D phase, and low temperatures, using the bond operator formalism. The in-plane structure factor is a delta function. The out
of plane shows a three peak structure, which merges in a single peak at the Brillouin zone boundary. We analyze also spin
currents generated by a magnetic field gradient. The spin conductivity is calculated, at finite temperature, using the Kubo
formula. The model shows unconventional ballistic spin transport at finite temperature. The computed spin conductivity exhibits
a nonzero Drude weight at finite temperature. For ω< 2m, where m is the energy gap, the spin conductivity is described solely
by the Drude weight. There is a regular contribution to the spin conductivity for ω> 2m, which persist in the zero temperature
limit. The conductivity at the critical point, and for small frequencies, is (gμB)2/ħ times a universal scaling function of ħω/kB T. 相似文献
80.