Low-temperature lattice excitation of icosahedral Al-Mn-Pd quasicrystals

Abstract

We suggest a theoretical method for dealing with the contribution of phasons to the lattice vibration of quasicrystals. Based on this, we derive the density of vibrational states ͑DOVS͒ and specific-heat expressions of the icosahedral Al-Mn-Pd quasicrystal, and obtain corresponding numerical solutions which are in agreement with the experimental data measured by Wälti et al. ͓Phys. Rev. B 57, 10 504 ͑1998͔͒. This consistency shows that the contribution of the phasons to either the DOVS or specific heat cannot be neglected at low temperature. Our theory would be also helpful to study further the thermal conductivity of the icosahedral quasicrystal.

Tuning of the superconducting and ferromagnetic transitions by Cu doping for Ru in GdSr2RuCu2O8

“…The formal valence of Ru has been taken to be 5+ in most of the previous Rietveld analyses. Recent 18 for the magnetic order in this compound. Thus, the precise nature of magnetic order in this compound still remains controversial and needs to be explored.…”

Observation of two-dimensional spin fluctuations in the bilayer ruthenateSr3Ru2O

“…At a temperature ≈20 K, there is a peak in the magnetic susceptibility (a), and and also in the susceptibility close to a ferromagnetic position measured by neutron scattering (b). The antiferromagnetic fluctuations (c) fall away rapidly with increasing temperature and this is reflected in the change in sign of the longitudinal magnetoresistance (d) [7]. It is not clear what causes this dramatic change in magnetic correlations, but it may be related to a loss in c-axis electronic coherence, which reveals itself as a steep rise in the c-axis resistivity in this temperature region [6].…”

“…The experimental observation of low energy incommensurate 2D spin fluctuations in Sr 2 RuO 4 [3,4] has raised the question of the relevance of spin fluctuations to the mechanism producing p-wave pairing in this material. The closest relative of Sr 2 RuO 4 , the bilayer Sr 3 Ru 2 O 7 , is a paramagnet where ferromagnetic and antiferromagnetic correlations may be in competition, and ferromagnetism can be induced by pressure or impurities [5][6][7][8][9][10]. In highquality single crystals of Sr 3 Ru 2 O 7 , the resistivity exhibits a Fermi-liquid T 2 temperature dependence below 10 K [6,11].…”

Extremely compact soft X-ray lasers based on capillary discharges

“…The alignment of the interferometer was done with an 824 nm laser diode on a second set of ARTICLE IN PRESS rulings on the gratings. In the elongated plasma columns generated by the capillary discharge, gain guiding and strong refractive anti-guiding results in the rapid buildup of spatial coherence [6]. This intrinsic mode selection mechanism makes it possible to achieve a very high degree of spatial coherence, which in turn allows for the generation of high-visibility interferograms.…”

“…The peak-to-peak divergence was measured to be about 4.6 mrad for all capillary lengths between 18 and 34.5 cm. Recent measurements of the spatial coherence indicate that full spatial coherence is approached with the longest capillaries and that the peak spectral brightness is about 2 Â 10 25 photons/(s mm 2 mrad 2 0.01% bandwidth) [6]. The possibility of extending these capillary discharge laser sources to shorter wavelengths is currently under investigation [7].…”