Streuung an Kristallen mit Ionenspin-Gitter-Kopplung

The dependence of the Heisenberg exchange interaction on the ion positions couples the lattice with the ion spins. The resulting phonon damping depends on the magnetic order of the crystal. We calculate the Phonon Greens Function (PGF) by solving the equation of motion of the coupled spin-phonon system. The scattering functionsS(q,ω) andS(q) of the crystal can be determined with the PGF. In the region of great spin fluctuations an additional diffuse scattering intensity appears. This determines spin-lattice coupling parameters at least in the case of scattering of X-rays which do not interact directly with magnetism. The ordering temperature is assumed to be small compared to the Debye temperature. The magnetic influence on the diffuse scattering intensity is then of the order of a few per cent.