NMR and NQR study of the electronic and structural properties of Al-Cu-Fe and Al-Cu-Ru quasicrystals

Journal Article · Thu Dec 01 00:00:00 EST 1994 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.50.15651· OSTI ID:6822546

Shastri, A; Borsa, F; Torgeson, D R; Shield, J E; Goldman, A I ^[1]

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1. Ames Laboratory, U.S. Department of Energy and Department of Physics Astronomy, Iowa State University, Ames, Iowa 50011 (United States)

[sup 27]Al and [sup 63,65]Cu NMR is reported for powdered stable Al-Cu-Fe and Al-Cu-Ru icosahedral quasicrystals and crystalline approximants, and for an Al-Pd-Mn single-grain quasicrystal. [sup 27]Al NQR spectra at 4.2 K were observed in Al-Cu-Fe and Al-Cu-Ru samples. From quadrupole-perturbed NMR spectra at different magnetic fields, and from zero-field NQR spectra, a wide distribution of local electric-field gradient (EFG) tensor components and principal-axis-system orientations was found at the Al site. A model EFG calculation based on a 1/1 Al-Cu-Fe approximant successfully explained the observed NQR spectra. The average local gradient is largely determined by the [ital p]-electron wave function at the Al site, while the width of the distribution is due to EFG lattice contribution. Comparison of [sup 63]Cu and [sup 27]Al NMR shows the EFG distribution at the two sites is similar, but the electronic contribution to the EFG is considerably smaller at the Cu site, in agreement with a more [ital s]-type wave function of the conduction electrons. Overall spread of EFG values is well reproduced by calculation based on the approximant. However, the experimental spectra indicate a much larger number of nonequivalent sites when compared with the simulated NQR spectra based on the 1/1 approximant. The short-range, local chemical order is well represented by the approximant, but differences in coordination must be included at intermediate range in the quasicrystal. Measured [sup 27]Al Knight shift, magnetic susceptibility, and nuclear spin-lattice relaxation time as a function of temperature indicate reduced density of states at the Fermi level by a factor of 7 or 8 from the value in Al metal, consistent with the notion of a pseudogap for these quasicrystals. No differences in measured parameters were detected as a function of composition of the quasicrystalline alloys.

• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 6822546
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 50:21; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM ALLOYS
ELECTRONIC STRUCTURE
COPPER ALLOYS
IRON ALLOYS
RUTHENIUM ALLOYS
ENERGY-LEVEL DENSITY
FERMI LEVEL
KNIGHT SHIFT
MAGNETIC SUSCEPTIBILITY
NMR SPECTRA
NUCLEAR QUADRUPOLE RESONANCE
POWDERS
SPIN-LATTICE RELAXATION
TEMPERATURE DEPENDENCE
TERNARY ALLOY SYSTEMS
ALLOY SYSTEMS
ALLOYS
ENERGY LEVELS
MAGNETIC PROPERTIES
PHYSICAL PROPERTIES
PLATINUM METAL ALLOYS
RELAXATION
RESONANCE
SPECTRA
360104* - Metals & Alloys- Physical Properties
665100 - Nuclear Techniques in Condensed Matter Physics - (1992-)