Elastic tensor of YNi 2 B 2 C

Abstract The complete elastic tensor of YNi 2 B 2 C was determined by application of the resonant ultrasound spectroscopy technique to a single-crystal sample. Elastic constants were found to be in good agreement with partial results obtained from Ôtime-of-flightÕ measurements performed on samples cut from the same ingot. From the measured constants, the bulk modulus and Debye temperature are calculated. The discovery of superconductivity in the borocarbide quaternary intermetallic compounds [1] has generated a great deal of interest due to the observed interplay between superconductivity and magnetic order. Compounds in this family have formulae of the form RNi 2 B 2 C, where choice of the rare earth ion, R, strongly affects the physical properties, which range from superconducting with no magnetic ordering (R ¼ Y) to non-superconducting with a N e eel temperature of 19 Recent heat transport measurements on nonmagnetic borocarbides suggest that the superconductivity is very anomalous, with a gap that is either highly anisotropic [5]). As a first step towards measuring the attenuation of sound it is important to establish the full elastic tensor of the material. The second-order elastic constants relate stresses placed on a material along various directions to the resulting deformations of the crystal lattice. As such, knowledge of a compoundÕs elastic constants can be useful when investigating a number of solid state properties, such as interatomic potentials, equations of state, phonon spectra, the Debye temperature, and the bulk modulus. In the most general case, a highly anisotropic solid can have 21 independent second-order elastic constants, but the crystal structure for all compounds in the RNi 2 B 2 C group is body-centered-tetragonal (space group I4=mmm), consisting of R-C planes separated by Ni 2 B 2 layers stacked along the c-axis In this article, the elastic constants of YNi 2 B 2 C are determined at room temperature via tw