Electrical Resistivity of an Al-Re-Si Cubic Approximant Phase and Role of Local Environment in Electronic Transport
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Electrical Resistivity of an Al-Re-Si Cubic Approximant Phase and Role of Local Environment in Electronic Transport Ryuji Tamura, Takayuki Asao, Mutsuhiro Tamura, and Shin Takeuchi Department of Materials Science and Technology, Science University of Tokyo, Noda, Chiba 278-8510, Japan ABSTRACT In order to gain an insight into the role of the local atomic environment in the electronic transport of the icosahedral quasicrystal, the electrical resistivity of α-AlReSi, which is the (1/1,1/1,1/1) approximant of the icosahedral phase, has been investigated. Very high resistivity and its pronounced negative temperature dependence have been observed, indicating that the electronic states of the 1/1 cubic approximant are quite similar to those of icosahedral phases. In order to further elucidate which structural entity is responsible for such anomalous transport, a comparison of the electrical resistivity between (1/1,1/1,1/1) and (1/0,1/0,1/0) approximants has been made. The typical transport behavior of icosahedral phases which is also seen in 1/1 and higher-order approximants was not observed in any of the studied 1/0 cubic approximants. The result can be regarded as an implication that the intercluster distance between the TM clusters plays a significant role in the confinement of electronic states.
INTRODUCTION The electrical resistivity of approximants has been classified in terms of the approximation degree, or the lattice constant, based on the results of the many alloy systems[1] and it has been shown that, in general, approximants with unit cell larger than 2 nm possess similar electronic properties to icosahedral phases (i-phases) whereas those with unit cell smaller than 2 nm show both similar and dissimilar behaviors depending on the alloy composition; for instance, 1/1-cubic approximants in the Mg-Zn-(Ga,Al)[2,3], the Al-Li-Cu[4] and the Al-Cu-Ru[5] systems reveal dissimilar transport whereas those in the Al-Mn-Si[6] and Al-Cu-Fe-Si[7] systems show a similar character. As far as higher-order approximants are concerned, Berger et al.[8] have found that in the Al-Cu-Fe system temperature dependences of the resistivity of three different approximants with lattice parameter larger than 2 nm are exactly the same as that of the corresponding i-phase up to 1000 K. Such a result implies that there is no essential difference in the electronic transport between approximants and quasicrystals provided that the approximation degree is as large as 2/1 or larger. The situation is somewhat subtle in the case of the 1/1 cubic approximant. However, the large resistance ratio ρ(4.2K)/ρ(300K) ~ 2 observed in the α-AlMnSi[6] seems to be an indication that there is a key to understand the anomalous transport of i-phases in the local structure of the 1/1 cubic approximant. K13.3.1
Recently, a single phase of a well-ordered 1/1 cubic approximant in the Al-Re-Si system has been produced and its electrical resistivity was investigated[9]. By an analogy with α-AlMnSi[10], the atomic structure of α-AlReSi is considered to have a body-
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