Phonon Excitations in Pd40Ni40P20 Bulk Metallic Glass by Inelastic X-Ray Scattering
To clarify microscopic elastic properties of a Pd40Ni40P20 bulk metallic glass, inelastic X-ray scattering (IXS) experiments were carried out using high-resolution IXS spectrometer installed at BL35XU/SPring-8. Clear longitudinal acoustic (LA) excitation modes are observed in the whole momentum transfer Q range up to ~22 nm-1. The microscopic sound velocity of the LA modes obtained from the Q → 0 limit of the dispersion relation is about 12% faster than the macroscopic value, suggesting the microscopic heterogeneity in the elastic properties of this BMG. In addition, transverse acoustic (TA) modes can be deduced from a detailed analysis of the IXS spectra. The microscopic Poisson’s ratio obtained from the ratio of the excitation energies of the TA and LA modes is 0.47 ± 0.04, larger than the macroscopic value of 0.40. Thus, the fragile nature of this BMG already found in the macroscopic sense is much enhanced in the microscopic view.
C. Sommitsch, M. Ionescu, B. Mishra, E. Kozeschnik and T. Chandra
S. Hosokawa et al., "Phonon Excitations in Pd40Ni40P20 Bulk Metallic Glass by Inelastic X-Ray Scattering", Materials Science Forum, Vol. 879, pp. 767-772, 2017