Crystal dynamics of nickel–iron and copper–zinc alloys

Abstract

Using inelastic scattering of slow neutrons, the frequency-wavevector dispersion relations for the lattice vibrations in the face-centered cubic alloys Ni3Fe, Ni0.5Fe0.5, Ni0.3Fe0.7, and Cu3Zn have been measured at 296 °K. Measurements were also made at 573 °K for the Ni0.3Fe0.7 alloy. The results for the nickel–iron alloys are very similar to those for nickel, with mean frequency ratios (alloy/nickel) of 0.990, 0.950, 0.953 for the Ni3Fe, Ni0.5Fe0.5, and Ni0.3Fe0.7 alloys respectively. Significant deviations of the limiting slopes of the dispersion curves for Ni0.3Fe0.7 from velocities reported by Alers et al. from ultrasonic measurements are thought to be caused by magnetic contributions which are small at the frequencies measured here. The temperature dependence of the frequencies for Ni0.3Fe0.7 is consistent with that observed for nickel. For Cu3Zn, the results are similar to those for copper; except that the mean frequency ratio (alloy/copper) is 0.932. A neutron diffraction method was used to characterize the homogeneity and composition of the alloys. Born – von Kármán fits to the data, the frequency distributions, and Debye temperature vs. temperature relations are also given.