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

Pulsed NMR experiments have been performed on U2D2 solid He-3 with a s ingle domain in high fields. The free induction signal decayed rapidly under certain conditions. The rapid decay was attributed to the onset of an instability of uniform precession. We propose a model for the i nstability due to the self-induced emission from the upper-mode to low er-mode magnon branch, which is similar to the Suhl instability in ele ctronic ferromagnets. Under stable conditions of the spin notion, we o bserved the tipping angle-dependent frequency shift and multiple spin echoes, which agrees well with Namaizawa's theory.