MICROSTRUCTURAL EVOLUTION WITH ORDERING ON CU3AU AND CUAU3 ALLOYS STUDIED BY NUCLEAR-MAGNETIC-RESONANCE MEASUREMENTS

Nuclear magnetic resonance (NMR) measurements have been carried out on Cu3Au and CuAu3 alloys at different degrees of ordering. Ths spin-ech o spectrum from the fully ordered Cu3Au alloy exhibits a characteristi c resonance line broadened owing to second-order quadrupole effects. O n the other hand, an intense narrow resonance line appears in the spin -echo spectra obtained from the disordered Cu3Au alloy as well as the ordered and disordered CuAu3 alloys. The spectra from the partially or dered Cu3Au alloys can be explained by the superposition of the broad line for the ordered state and the narrow line for the disordered stat e. From the fit of the experimental NMR spectra with theoretical NMR l ine-shape simulations, we have obtained information about the existenc e probabilities that the probe nuclei is in the same environment as th ose for the ordered structure. The results are discussed in comparison with the X-ray diffraction results.