The DX centre
T.N. Morgan
Semiconductor Science and Technology
The excitation spectrum of the ferromagnetic s=12 Ising-Heisenberg chain as probed by dynamic form factors is studied. Exact results are presented for zero temperature, and the modifications introduced by thermally induced transitions are elucidated by finite-chain calculations. A particularly interesting result is the occurrence of a thermally induced resonance around zero frequency for an Ising-like model. Its origin is traced back to transitions involving magnon bound states. The resonance structure of the dynamic form factors associated with a Heisenberg-like system turns out to be less spectacular, because the contributions of different induced transitions nearly overlap on the frequency scale; so that rather broad resonance structures result. Our findings have an important bearing on related models with s>12, such as CsNiF3, and on the soliton aspect of the classically treated systems. © 1982 The American Physical Society.
T.N. Morgan
Semiconductor Science and Technology
Michiel Sprik
Journal of Physics Condensed Matter
David B. Mitzi
Journal of Materials Chemistry
Mark W. Dowley
Solid State Communications