The development of the magnetic excitation spectra of MnF2 with increasing temperature

摘要: The changes in the magnetic excitation spectra of MnF2 produced by increasing temperature range 0.75 TN to 1.2 have been studied neutron inelastic scattering techniques. discrete spin-wave observed a previous experiment at 4.2 °K Low et al. suffer line broadening and an energy decrease as is raised; also continuous component appears. These three effects are small about 50 (0.75 TN) but develop rapidly with temperature. However, total seen be independent up highest value used TN. Theoretical calculations dynamical interactions between spin waves found fit dispersion within 10%, 62 (similar 0.9 TN). Beyond this well-defined soon no longer recognizable spectra. At large wave vectors assume paramagnetic-like character just below Neel point, show marked raised through transition point. abrupt critical observed. Significant differences vector dependence these near 100 001 reciprocal lattice points demonstrate effect anisotropy transverse correlations. parameter reasonable agreement 30%) theoretical predictions Moriya Tomita.