27Al NMR study in ZrNiAl |
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Authors: | Nowak B Hayashi S |
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Institution: | W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroc?aw. bnowak@int.pan.wroc.pl |
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Abstract: | We have studied the microscopic properties of the hexagonal ZrNiAl, a model compound for a wide family of intermetallic compounds crystallizing in this type of structure, by using 27Al NMR spectroscopy. We have investigated the lineshape of static and MAS NMR spectra as a function of magnetic field strength (4.7–9.4 T) and temperature (5–300 K). Our data indicate that the 27Al NMR spectra result from a combined effect of quadrupole and anisotropic shift interactions. The 27Al nuclei are in an environment characterized by the quadrupole coupling constant e2qQ/h of 3.3 MHz, asymmetry parameter ηQ of 0.42, isotropic shift δiso of 393 ppm, shift anisotropy δanis = δzz ? (δxx + δyy)/2 of 150 ppm, and asymmetry factor ηS of 0.5. They are found to be temperature independent. The spin–lattice relaxation rate measured at 7.05 T is proportional to the temperature with T1T = 135 s K. The mechanisms responsible for observed values of δiso, δanis, T1T, and the enhanced Korringa constant are discussed. |
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Keywords: | intermetallics ZrNiAl 27Al static and MAS NMR quadrupole interaction shift anisotropy spin–lattice relaxation |
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