title: Elastic stiffness of the nuclear-spin system in tetragonal U2D2 nuclear-ordered solid (3)He.
abstract: We have measured temperature dependences of sound velocity for both longitudinal and transverse sound in nuclear-ordered U2D2 solid 3He with several crystal orientations along the melting curve. The sound velocity change was proportional to T4 for all sound modes and crystal orientations and was attributed to the nuclear-spin part of the internal energy. We extracted six-independent elastic stiffness of the nuclear-spin part and obtained Grüneisen constants of the spin wave velocity for four-independent strains. Grüneisen constants for compressional strain were larger than those for shear strain. Using the multiple-spin-exchange model, we explain the anisotropy of Grüneisen constants in tetragonal symmetry.
authors.affiliation: Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: S
authors.initials: S
authors.lastname: Sasaki
authors.forename: S G
authors.initials: SG
authors.lastname: Lee
authors.forename: Y
authors.initials: Y
authors.lastname: Sasaki
authors.forename: T
authors.initials: T
authors.lastname: Mizusaki