Anisotropic physical properties of the Taylor-phaseT-Al72.5Mn21.5Fe6.0com

Abstract

We have investigated anisotropic physical properties ͑the magnetic susceptibility, the electrical resistivity, the thermoelectric power, the Hall coefficient and the thermal conductivity͒ of the single-crystalline Taylorphase T-Al 72.5 Mn 21.5 Fe 6.0 complex intermetallic that is an orthorhombic approximant to the d-Al-Mn-Pd decagonal quasicrystal. The measurements were performed along the a, b, and c directions of the orthorhombic unit cell, where ͑a , c͒ atomic planes are stacked along the perpendicular b direction. The T-Al 72.5 Mn 21.5 Fe 6.0 shows spin-glass behavior below the spin-freezing temperature T f Ϸ 29 K with a small anisotropy in the magnetic susceptibility. The anisotropic electrical resistivities are rather large and show negative temperature coefficient. The resistivity is lowest along the stacking direction, which appears to be a common property of the decagonal-approximant phases with a stacked-layer structure. The temperature-dependent resistivity was theoretically reproduced by the quantum transport theory of slow charge carriers. The thermopower is positive for all three crystallographic directions, indicating that holes are the majority charge carriers, and no anisotropy can be claimed within the experimental precision. The same conclusion on the holes being the dominant charge carriers follows from the Hall-coefficient measurements, which is a sum of the ͑positive͒ normal Hall coefficient and the anomalous term, originating from the magnetization. The anisotropy of the thermal conductivity is practically negligible. The T-Al 72.5 Mn 21.5 Fe 6.0 Taylor phase can be considered as a "close-to-isotropic" complex intermetallic. The relation of the anisotropic physical properties of the Taylor phase to other families of decagonal-approximant phases with the stacked-layer structure is discussed.

Magnetic and transport properties of i- R -Cd icosahedral quasicrystals (R=Y,Gd-Tm)

“…Interestingly, despite several theoretical predictions [3][4][5], no longrange magnetic ordering has yet been discovered in momentbearing quasicrystals [6]. Until recently, this lack of long-range magnetic ordering also extended to quasicrystal approximants [7][8][9], which can be viewed as quasicrystalline clusters sitting on a periodic lattice that possesses a translational symmetry. Recently, two exceptions have been identified: ferromagnetic Gd-Au-Si(Ge) [10] and antiferromagnetic RCd 6 [11][12][13][14][15].…”

Anisotropic transport properties of the Al13TM4 and T-Al–Mn–Fe complex metallic alloys

“…The second is the orthorhombic o-Al 13 Co 4 compound [3], belonging to the same class of decagonal approximants with four atomic layers within one periodic unit comprising 102 atoms. The third is the orthorhombic Taylor (T) phase of the Al-Mn-(Pd/Fe) CMAs with composition T-Al 72.5 Mn 21.5 Fe 6.0 [4], which is an approximant to the decagonal phase with six atomic layers in a periodic unit and 156 atoms in a giant unit cell. The above selection of samples allowed us to consider the evolution of anisotropic transport properties of the stacked-layer CMAs with increasing structural complexity and unit cell size.…”

Thermal transport properties of decagonal quasicrystals and their approximants

“…Their structure can be viewed as stacking of pseudotenfold layers along the direction that corresponds to the tenfold direction in decagonal phase. We have studied Y-Al-Co-Ni [10] phase with two stacking layers, o-Al 13 Co 4 [7], m-Al 13 Fe 4 and its ternary extension m-Al 13 (Fe,Ni) 4 [11] with four stacking layers and Taylor phase T-Al-Mn-Fe [12] with six stacking layers. Finally we correlated their transport properties to those of decagonal d-Al 70 Co 10 Ni 20 [13] with two stacking layers.…”