Magnetic, electrical, thermal transport, and thermoelectric properties of theξ′andΨcomplex metallic alloy phases in the Al-Pd-Mn system

Abstract

The Al-Pd-Mn system of intermetallics contains complex metallic alloy ͑CMA͒ phases, whose crystal structures are based on giant unit cells comprising up to more than a thousand atoms per cell. We performed investigation of the magnetic, electrical, and thermal transport and thermoelectric properties of the Ј phase and the related ⌿ phase on single-crystalline samples grown by the Bridgman technique. 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 a 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 samples is small and can be described by the sum of the electronic and lattice contributions, which are of comparable size at room temperature. The lattice contribution can be reproduced by the sum of the Debye term ͑long-wavelength phonons͒ and the term due to hopping of localized vibrations. The thermoelectric power is small and negative, compatible with a low concentration of electrons as the majority charge carriers. The studied physical properties of the giant-unit-cell CMA phases in the Al-Pd-Mn system are in many respects intermediate between those of metals or simple intermetallics and quasicrystals, suggesting that both the polytetrahedral local atomic order and the large-scale periodicity influence the physical properties of the material.

Magnetic and transport properties of the giant-unit-cell Al3.26Mg2 complex metallic alloy

“…The thermal conductivity model appropriate to CMAs with the large-scale periodicity of the lattice and the small-scale atomic clustering structure has been described in detail in the previous investigation of the AlePdeMn system [7]. To summarize briefly, the total thermal conductivity parameter k(T ) is divided into three terms:…”

“…For the convenience of the fitting procedure, we rewrite t À1 sf ¼ Ax 2 T 2 (note that, since x 2 fT À2 , t À1 sf does not show an explicit temperature dependence). The second scattering mechanism is the umklapp processes, which we describe by a phenomenological form [7] t À1 um ¼ Bx a T 4 , where the exponent a (yielding a power-law dependence t À1 um fu a T 4Àa ) should be determined from the fit. The total scattering rate is then a sum t À1 ¼ t À1 sf þ t À1 um .…”

Thermal conductivity in complex metallic alloys: Beyond Wiedemann-Franz law

“…͑4͒, as reported in Ref. 23 ͑dashed line͒, we appreciate that some additional contribution coming from the lattice itself should be invoked in the temperature range of 100-300 K.…”

On the mechanical and tribological behavior of Al3Mg2 complex metallic alloys as bulk material and as coating

“…x ' -Al 74 Pd 22 Mn 4 with 258 atoms per unit cell and face centered orthorhombic atoms arranged in Mackay-type clusters [11,12], l-Al 4 Mn with 586 atoms/unit cell, and the heavy-fermion compound YbCu 4.5 with 7448 atoms in the super cell [13]. In this paper, the mechanical and tribological properties of a cubic b-Al 3 Mg 2 complex metallic alloy are investigated and compared to well-known engineering materials.…”