Anisotropic physical properties of theAl13Fe4complex intermetallic and its ternary derivativeAl13(Fe,Ni)4

Abstract

We have investigated the magnetic susceptibility, the electrical resistivity, the specific heat, the thermoelectric power, the Hall coefficient, and the thermal conductivity of the ${\text{Al}}_{13}{\text{Fe}}_{4}$ and ${\text{Al}}_{13}{(\text{Fe},\text{Ni})}_{4}$ monoclinic approximants to the decagonal quasicrystal. While the ${\text{Al}}_{13}{\text{Fe}}_{4}$ crystals are structurally well ordered, the ternary derivative ${\text{Al}}_{13}{(\text{Fe},\text{Ni})}_{4}$ contains substitutional disorder and is considered as a disordered version of the ${\text{Al}}_{13}{\text{Fe}}_{4}$. The crystallographic-direction-dependent measurements were performed along the ${a}^{\ensuremath{\ast}}$, $b$, and $c$ directions of the monoclinic unit cell, where the $({a}^{\ensuremath{\ast}},c)$ atomic planes are stacked along the $b$ direction. The electronic transport and the magnetic properties exhibit significant anisotropy. The stacking $b$ direction is the most conducting direction for the electricity and heat. The effect of substitutional disorder in ${\text{Al}}_{13}{(\text{Fe},\text{Ni})}_{4}$ is manifested in the large residual resistivity $\ensuremath{\rho}(T\ensuremath{\rightarrow}0)$ and significantly reduced thermal conductivity of this compound, as compared to the ordered ${\text{Al}}_{13}{\text{Fe}}_{4}$. Specific-heat measurements reveal that the electronic density of states at the Fermi level of both compounds is high. The anisotropic Hall coefficient ${R}_{H}$ reflects complex structure of the anisotropic Fermi surface that contains electronlike and holelike contributions. Depending on the combination of directions of the current and the magnetic field, electronlike $({R}_{H}l0)$ or holelike $({R}_{H}g0)$ contributions may dominate, or the two contributions compensate each other $({R}_{H}\ensuremath{\approx}0)$. Similar complicated anisotropic behavior was observed also in the thermopower. The anisotropic Fermi surface was calculated ab initio using the atomic parameters of the refined ${\text{Al}}_{13}{\text{Fe}}_{4}$ structural model that is also presented in this work.