Intrinsic anisotropic magnetic, electrical, and thermal transport properties ofd-Al-Co-Ni decagonal quasicrystals

Abstract

To address the questions on the anisotropy of bulk physical properties of decagonal quasicrystals and the intrinsic physical properties of the d-Al-Co-Ni phase, we investigated the anisotropic magnetic susceptibility, the electrical resistivity, the thermoelectric power, the Hall coefficient, and the thermal conductivity of a d-Al-Co-Ni single crystal of exceptional structural quality. Superior structural order on the local scale of atomic clusters was confirmed by 27 Al nuclear magnetic resonance spectroscopy. The measurements were performed in the 10-fold periodic direction of the structure and in three specific crystallographic directions within the quasiperiodic plane, corresponding to the 2 and 2 twofold symmetry directions and their bisector. The specific heat, being a scalar quantity, was determined as well. The measurements of the second-rank bulk tensorial properties confirm the theoretical prediction that a solid of decagonal point group symmetry should exhibit isotropic physical properties within the quasiperiodic plane and anisotropy between the in-plane and the 10-fold directions. d-Al-Co-Ni is an anisotropic diamagnet with stronger diamagnetism for the magnetic field in the 10-fold direction. Electrical and thermal transport is strongly metallic in the 10-fold direction but largely suppressed within the quasiperiodic plane, the main reason being the lack of translational periodicity that hinders the propagation of electrons and phonons in a nonperiodic lattice. The third-rank Hall-coefficient tensor shows sign-reversal anisotropy related to the direction of the magnetic field when applied in the 10-fold direction or within the quasiperiodic plane. The observed anisotropy is not a peculiarity of quasicrystals but should be a general feature of solids with broken translational periodicity in two dimensions.

Impact of structural complexity and disorder on lattice dynamics and thermal conductivity in the o- Al13Co4 phase

“…Physical properties, measured in the range 2-300 K, display a significant anisotropy in electronic transport properties, whereas the lattice thermal conductivity is rather isotropic 9,10 . Similar to other CMA's the lattice thermal conductivity of the sample lies in the range 2 Wm −1 K −1 and depends only weakly on temperature (see Figure 13).…”

“…A similar behavior has been observed in different complex intermetallic alloys (CMAs) 7 , such as periodic quasicrystal approximants which share the same 'building blocks' as the parent quasicrystal 2, 6 . It is also interesting to point out that most CMAs have a 'glass like' thermal conductivity, with values of the order 1-4 Wm −1 K −1 at room temperature, and a weak temperature dependence in the 40-300K range, instead of the usual umklapp peak ob-served in simple systems [8][9][10] . This is very similar to what has been observed in skutterudites or Ge/Si clathrates 11 , systems that are also considered as CMA.…”

Electrical and thermal transport properties of icosahedral and decagonal quasicrystals

“…The application of the field along the 10-fold axis yields negative electronlike Hall coefficient with the value at 340 K of R 10 H E À6.2 Â 10 À10 m 3 C À1 and moderate temperature dependence. The values of both R Q H and 12 The index Q is conveniently used for the three investigated in-plane directions (2, 2 0 and bis). R 10 H are typical metallic.…”

“…(a) Temperature-dependent electrical resistivity r(T) of d-Al 69.7 Co 10.0 Ni 20.3 , measured along the 10, 2, 2 0 and bis directions 12. (b) The resistivities normalized to their 340 K values, r/r 340K .…”

Thermal transport properties of decagonal quasicrystals and their approximants

“…We have studied Y-Al-Co-Ni [10] phase with two stacking layers, o-Al 13 Co 4 [7], m-Al 13 Fe 4 and its ternary extension m-Al 13 (Fe,Ni) 4 [11] with four stacking layers and Taylor phase T-Al-Mn-Fe [12] with six stacking layers. Finally we correlated their transport properties to those of decagonal d-Al 70 Co 10 Ni 20 [13] with two stacking layers.…”