engleski

Hall effect in single crystals of Al13TM4 complex metallic alloys

The Hall effect in Y-Al-Ni-Co (m-Al76Co22Ni2), o-Al13Co4, m-Al13Fe4 and m-Al13(Fe, Ni)4 (Al77Fe21Ni2) single crystals has been measured for all the combinations of the electrical current and magnetic field directions, and in the temperature interval from 90 to 370 K. Selected intermetallics have common structural characteristics and belong to the Al13TM4 group of decagonal approximants. In all these intemetallics the Hall coefficient RH exibits well defined anisotropy. In o-Al13Co4 and Y-Al-Ni-Co RH exibits only a weak temperature dependence, and changes from negative electron-like (in o-Al13Co4) or zero (in Y-Al-Ni-Co) to positive hole-like for different combinations of the current and field directions. The results for the anisotropy of RH are well correlated to the anisotropy in d-Al-Ni-Co and d-Al-Cu-Co quasicrystals. The investigated anisotropic RH was reproduced theoretically by ab-initio calculation using Boltzmann transport theory and the calculated anisotropic Fermi surface. In Al13Fe4 compound RH exhibits, in addition to the very large values (up to 7• 10­9 m3C­1) at the lower temperatures, unexpectedly large temperature dependence and, for one of the magnetic field directions, the change of the sign from positive to negative value with the increase of temperature. The results are well interpreted within a simple two-band model with anisotropic electron and hole masses and scattering times. RH results for Al13(FeNi)4 fall in between the results for Al13Fe4 and the results for o-Al13Co4 and Y-Al-Ni-Co.

complex metallic alloys; Hall effect

The paper was presented at the "1st International Conference on Complex Metallic Alloys and their Complexity" (04-07.10.2009, Nancy, Francuska) as a talk by Ana Smontara. This work was supported in part by the 6th Framework EU Network of Excellence 'Complex Metallic Alloys' (Contract No. NMP3-CT-2005-500140).