On the growth of icosahedral Al-Pd-Mn quasicrystals from the ternary melt

Author： Fisher I. R. Kramer M. J. Wiener T. A. Islam Z. Ross A. R. Lograsso T. A. Kracher A. Goldman A. I. Canfield P. C.

Publisher： Taylor & Francis Ltd

ISSN： 1463-6417

Source： Philosophical Magazine B, Vol.79, Iss.10, 1999-10, pp. : 1673-1684

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Abstract

Icosahedral Al71Pd21Mn8 quasicrystals have been grown from the ternary melt via a 'self-flux' technique. The nucleation is exceptionally well controlled, and individual grains can have masses of up to almost 30 g (limited only by the dimensions of the growth crucible). The quasicrystals grown by this technique are readily separated from the melt by decanting and clearly manifest a dodecahedral morphology with pentagonal facets. X-ray and electron-diffraction data indicate a remarkably well-ordered structure, with a correlation length of over 1000 A. The magnetic susceptibility has a temperature-independent diamagnetic component and a temperature-dependent paramagnetic term. For temperatures greater than approximately 60 K, the paramagnetic term follows a Curie-Weiss temperature dependence characterized by an average effective moment of 0:62 0:02muB/Mn and a Weiss temperature of- 12:8 0:1 K. Deviations from the Curie-Weiss temperature dependence for temperatures less than approximately 60 K may be due to the formation of local (short range) magnetic correlations. The electrical resistivity has a broad maximum at approximately 90 K and a room-temperature value of 1:57 0:05 m cm. We note that the previously observed empirical trend that a very high resistivity is associated with the highest quality Al-Pd-Mn quasicrystals does not seem to be in general true and that these high-quality (as demonstrated by X-ray and electron diffraction) 'flux-grown' samples have a relatively low room-temperature resistivity. In addition to the ternary icosahedral Al-Pd-Mn quasicrystals, a novel pseudo-quaternary icosahedral quasicrystal, Al67Ga4Pd21Mn8, is described.