With the Hamiltonian for linear magneto - elastic coupling proposed by Callen and Callen we deduced expressions for changes in the velocity of acoustic waves in terbium and dysprosium due to ferromagnetic ordering and the application of an external magnetic field. These calculations are in fair agreement with experimental results. We also examined the extent to which this simple picture may be used to explain the magnon - phonon interactions in terbium. The magneto - elastic contributions to the spin wave energies were considered in detail, and the "flexible lattice" calculations performed by Cooper were examined critically. Experimental measurements of the elastic constants of terbium as
functions of temperature are presented. Strong coupling between the lattice and the spin system is observed. Recent experimental results for ferromagnetic terbium obtained by means of inelastic neutron scattering show that the two-ion exchange interaction in the c-direction is highly anisotropic.
|Place of Publication||Roskilde, Denmark|
|Publisher||Risø National Laboratory|
|Number of pages||101|
|Publication status||Published - 1971|
|Series||Denmark. Forskningscenter Risoe. Risoe-R|
- Risø report 252