engleski

Anisotropic transport properties of single-crystalline d-Al-Ni-Co decagonal quasicrystal

The crystallographic-direction-dependent transport measurements were performed on large single crystals [1] of d-Al-Ni-Co with the exact composition Al69.7Co10.0Ni20.3. The measurements were performed along three orthogonal directions which are: [00001] direction (periodic one, and that of the 10-fold axis of d-phase), and [10-00] and [10000] directions which are the of two different 2-fold axes in the quasiperiodic plane. Anisotropic electrical resistivity, ρ, thermopower, S, and thermal conductivity, κ, were measured from 2 to 300 K and the Hall coefficient, RH, was measure from 90 to 379 K. As expected, the anisotropy of the electrical resistivity, thermopower and thermal conductivity measured along 2-fold axes is small or negligible, and the anisotropy of RH for magnetic field, B, along 2-fold axes is within the experimental error. At the same time there is a significant anisotropy in ρ, S, and κ values obtained for 2-fold axes and those measured for the periodic [00001] direction. In the Hall effect this anisotropy corresponds to the anisotropy of RH for B parallel to [00001] (RH < 0) and for B parallel to 2-fold axes (RH > 0). The results agree well with the previous results for d-QCs [2-4] which are either performed on samples of the lesser quality or are incomplete in the sense that are not performed for the two distinct 2-fold axes. Also, there is correlation of the anisotropy in the transport properties of d-QCs and the anisotropy in Al13TM4 class of the approximants to decagonal quasicrystals [5-7].References: [1] B. Bauer, et al., Phil. Mag. 86 (2006) 317-322. [2] S. Martin, et. al., Phys. Rev. Lett. 67 (1991) 719. [3] Y.P. Wang et al., Phys. Rev. B 48 (1993) 10542-10545. [4] A.D.Bianchi et al., Phys. Rev. B 58 (1998) 3046-3056. [5] A. Smontara, et al., Phys. Rev. B, 78 (2008) 104204. [6] J. Dolinšek, et al., Phys. Rev. B, 79 (2009) 184201. [7] P. Popčević, et al., Phys. Rev. B, 81 (2010) 184203.

d-Al-Ni-Co ; electrical resistivity ; thermopower ; Hall coefficient ; thermal conductivity ; anisotropy

The paper was presented at the First European Integrated Center for the Development of New Metallic Alloys and Compounds Days (C-MAC) as a talk by Ana Smontara. This work was done within the activities of the European Integrated Center for the Development of New Metallic Alloys and Compounds - C-MAC.