Bridgman-grown i-Al68.9Pd21.6Mn9.5 quasicrystal: Comparison of α, CP, Ï..., and Ï⁄ with those for flux-grown samples

Thermal expansivity (α, 1–300 K), heat capacity (CP, 1–108 K), electrical conductivity (σ, 1–300 K) and magnetic susceptibility (χ, 1–300 K) data have been obtained for a Bridgman-grown single grain iAl68.9Pd21.6Mn9.5 quasicrystal (BR) for direct comparison with data previously published for a flux-grown single grain sample [ Phys. Rev. B 65 184206 (2002)], and present σ, χ and CP data for a second flux-grown sample described in an earlier publication [ Philos. Mag. B 79 1673 (1999)]. Fortuitously, comparative analyses show these samples to have essentially the same composition. At all temperatures, σ and χ for BR are, respectively, approximately one-third and one-quarter those for PRB. The CP’s are the same (±1%) down to 30 K, below which the BR CP decreases more rapidly to one-half that for PRB at 1 K. The α’s agree to ±2% from 300 to 40 K, with a more rapid decrease for BR below 30 K, eventually to 0.6 αPRB below 4 K. The total Grüneisen parameters are similar at all temperatures. The two methods for sample growth differ primarily in a quenching of the flux-grown sample to room temperature after growth, while the Bridgman-grown sample cools very slowly, resulting in slightly different phases, and magnetic properties which are associated with lattice defects. An attempt to convert the single grain flux-grown sample to the phase of the Bridgman sample using an 800°C anneal and a slow cool to room temperature was not successful, with the appearance of second phase inclusions. These inclusions are ascribed to slightly different compositions for the two phases [ Boissieu et al. Philos. Mag. A 78 305 (1998)]. This suggests that a single grain flux-grown sample with an Mn composition near 9% cannot be converted by annealing and slow cooling into a single grain LT phase, and vice versa. These considerations may not apply to samples with Mn compositions closer to 8%. Disciplines Condensed Matter Physics | Metallurgy Comments This article is from Physical Review B 70 (2004): 094201, doi:10.1103/PhysRevB.70.094201. This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/ameslab_pubs/90 Bridgman-grown i-Al68.9Pd21.6Mn9.5 quasicrystal: Comparison of a, CP, s, and x with those for flux-grown samples C. A. Swenson,* T. A. Lograsso, N. E. Anderson, Jr., and A. R. Ross† Ames Laboratory, Iowa State Unversity, Ames, Iowa 50011, USA (Received 23 February 2004; published 17 September 2004) Thermal expansivity (a, 1–300 K), heat capacity (CP, 1–108 K), electrical conductivity (s, 1–300 K) and magnetic susceptibility (x, 1–300 K) data have been obtained for a Bridgman-grown single grain i-Al68.9Pd21.6Mn9.5 quasicrystal (BR) for direct comparison with data previously published for a flux-grown single grain sample [Phys. Rev. B 65, 184206 (2002); PRB], and present s , x and CP data for a second flux-grown sample described in an earlier publication [Philos. Mag. B 79, 1673 (1999); PM]. Fortuitously, comparative analyses show these samples to have essentially the same composition. At all temperatures, s and x for BR are, respectively, approximately one-third and one-quarter those for PRB. The CP’s are the same s±1%d down to 30 K, below which the BR CP decreases more rapidly to one-half that for PRB at 1 K. The a’s agree to ±2% from 300 to 40 K, with a more rapid decrease for BR below 30 K, eventually to 0.6 aPRB below 4 K. The total Grüneisen parameters are similar at all temperatures. The two methods for sample growth differ primarily in a quenching of the flux-grown sample to room temperature after growth, while the Bridgmangrown sample cools very slowly, resulting in slightly different phases, and magnetic properties which are associated with lattice defects. An attempt to convert the single grain flux-grown sample to the phase of the Bridgman sample using an 800°C anneal and a slow cool to room temperature was not successful, with the appearance of second phase inclusions. These inclusions are ascribed to slightly different compositions for the two phases [see Boissieu et al., Philos. Mag. A 78, 305 (1998)]. This suggests that a single grain flux-grown sample with an Mn composition near 9% cannot be converted by annealing and slow cooling into a single grain LT phase, and vice versa. These considerations may not apply to samples with Mn compositions closer to 8%. DOI: 10.1103/PhysRevB.70.094201 PACS number(s): 61.44.Br, 62.20.Dc, 65.40.Ba, 65.40.De