Correlations between electric, magnetic, and galvanomagnetic quantities in stable icosahedral phases based on aluminum
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ICRYSTALS
Correlations between Electric, Magnetic, and Galvanomagnetic Quantities in Stable Icosahedral Phases Based on Aluminum A. F. Prekul and N. I. Shchegolikhina Institute of Metal Physics, Ural Division, Russian Academy of Sciences, ul. Sof’i Kovalevskoœ 18, Yekaterinburg, 620041 Russia e-mail: [email protected] Received September 4, 2006
Abstract—On the basis of the results of the experimental investigation of the correlations between the electric, magnetic, and galvanomagnetic properties, the nature of the electronic phenomena leading to the difference of icosahedral quasicrystals from typical metals and insulators (low conductivity and negative temperature coefficient of resistance, diamagnetism of the ground state and its decrease with increasing temperature, and existence of residual and thermally induced charge carriers) is discussed. PACS numbers: 71.23.Ft, 72.15.-v, 75.20.En, 72.20.My DOI: 10.1134/S1063774507060119
INTRODUCTION The purpose of this study is to analyze the unusual electronic properties of metal alloys with long-range aperiodic order on the basis of the results of determining the main parameters of charge carriers: concentration, mobility, effective mass, and sign. Until now, little attention has been paid to this problem. Descriptive approaches dominated, in which interpretation entirely and completely depends on the functional description of the response of a system to a particular external effect. As a result, a large number of contradictory and mutually exclusive opinions about the nature of the same experimental regularities have arisen. We can illustrate this statement by several examples. It is known that the conductivity of icosahedral (i) phases is anomalously low in magnitude. This fact can be related, on the one hand, to the extremely short relaxation time and low mobility and, on the other hand, to a low electron concentration. The conductivity increases with an increase in temperature, as in normal semiconductors and disordered systems. Figure 1 shows typical temperature behavior of the conductivity in the entire domain of existence of a homogeneous i phase. This behavior can be adequately described by both power-law [1] and exponential [2, 3] functions under the following necessary condition: the conductivity is a complex characteristic, which contains temperature-independent (σ0) and temperature-dependent (σt) components. Accordingly, both the band-structural models of a metal and a semiconductor (taking into account, respectively, different scattering mechanisms and thermal activation of carriers) and the models of electronic localization (taking into account the mechanisms of hopping conductivity) appear to be reliable.
Consider another example: Fig. 2 shows typical behavior of the magnetic susceptibility. Excluding the Curie– Weiss contribution in the low-temperature region (as a property that is not typical of i phases), one can clearly see components with similar meaning; the temperatureindependent component χ0 is diamagnetic. Within the assumption that the Fermi s
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