Investigation of spin wave relaxation in antiferromagnet s with strong hyperfine interaction

Parametric excitation and relaxation of electron spin waves (ESW) with a frequency νsub(k) appriximately 15 GHz aere investigated experimentally in antiferromagnetic CsMnCl3 and RbMnCl3 (in the spin-flop phase) at T=1.2-4.2 K. At low temperatures the relaxation parameter is mainly determined by the term Δνsub(mn) which does not depend on the temperature and is proportional to the wave vector of the ESW. By appropriate treatment of the expe-- rimental data it has been possible to separate out a similar contribution to the ESW attenuation in the antiferromagnets MnCO3 and CsMnF3 studied previously. Within the experimental errors for all four compounds the magnitude and functional dependences of Δνsub(mn) correspond to the theoretically calculated relaxation parameter (15) which is related to the scattering of ESW by the paramagnetic system of 55Mn nuclei. Thus the existence of the abovementioned relaxation mechanism in antiferromagnets with srtrong hyperfine interaction is confirmed. For RbMnCl3 the attenuation connected with magnon-phonon interaction is also determined. On the basis of the value of the attenuation the corresponding magnetoelastic constant is estimated to be THETA approximately 10 K