engleski

Magnetic, transport and thermoelectric properties of giant-unit-cell Xi'-Al-Pd-Mn complex metallic alloy

The Xi'-Al-Pd-Mn family of intermetallics is representative of a new class of materials, named "Complex Metallic Alloys" (CMA), whose crystal structures are based on giant unit cells containing up to more than a thousand atoms per cell. CMA systems are characterized by two substantially different physical length scales-Xi one defined by the quasiperiodic short-range atomic order within the cluster substructure and the other by the periodic long-range order-Xi so that the competition between these two scales influences physical properties of the material. The investigation of magnetic, transport and thermoelectric properties of three Xi'-Al-Pd-Mn high-quality monocrystals (one in a Psi-superstructure state with 1500 atoms in the unit cell, the other two in a mixed basic Xi' phase (360 atoms/unit cell) and the Psi phase) has shown that the samples are diamagnets with a tiny paramagnetic Curie-like magnetization and an estimated fraction of magnetic Mn atoms about 100 ppm. The electrical resistivity between 300 and 4 K exhibits temperature variation of less than 2 %. The origin of this temperature-compensated resistivity is analyzed in terms of the spectral conductivity model. The thermal conductivity of the Xi'-Al-Pd-Mn samples is small and can be described by a sum of electronic and lattice contributions that are of comparable size at room temperature. The lattice contribution can be reproduced by the sum of Debye (long-wavelength phonons) and hopping of localized vibrations terms. The thermoelectric power is small and negative, compatible with low concentration of electrons as the majority charge carriers. The studied physical properties of the giant-unit-cell Xi'-Al-Pd-Mn CMA material are in many respects intermediate to those of regular metals and quasicrystals, suggesting that both the short-scale quasiperiodicity and the large-scale periodicity influence the physical properties of the material.

Xi'-Al-Pd-Mn; magnetic; transport and thermoelectric properties

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