NUCLEAR-SPIN DYNAMICS OF NUCLEAR-ORDERED SOLID HE-3 IN THE LOW-FIELD PHASE

Pulsed NMR was used to investigate nuclear spin dynamics of nuclear-or dered solid He-3 in the low field phase. The nuclear spill motion beca me unstable under certain conditions. Under stable conditions the spin motion can be described by the OCF equations. Tile tipping-angle-depe ndent frequency shift and multiple spin echoes were observed, which ar e similar to the case of superfluid He-3. The onset of the instability of spin motion is attributed to the stimulated emission mechanism thr ough the three-magnon relaxation process, which is similar to the Suhl instability in electronic magnetism. We derived tile magnon life time from the analysis of the instability. During the instability, a large negative frequency shift was observed. This negative shift is explain ed by the extension of Fomin-Ohmi's theory to include the state of dec ayed magnon and this explanation is consistent with the instability mo del.