engleski

Intrinsic anisotropic magnetic, electrical and thermal transport properties of d-Al-Co-Ni decagonal quasicrystal

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 have 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 the 27Al NMR spectroscopy. The measurements were performed along the 10-fold periodic direction of the structure and along 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 periodic directions. d-Al-Co-Ni is an anisotropic diamagnet with stronger diamagnetism for the magnetic field along the periodic direction. Electrical and thermal transport is strongly metallic along the periodic crystalline direction, but is 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 non-periodic lattice. The third-rank Hall-coefficient tensor shows sign-reversal anisotropy related to the direction of the magnetic field, when applied along the periodic 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.

decagonal quasycristals; transport properties; anisotropy

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