Nuclear spin dynamics of nuclear-ordered solid3He in the low field phase

Abstract

Pulsed NMR was used to investigate nuclear spin dynamics of nuclear-ordered solid3He in the low field phase. The nuclear spin motion became unstable under certain conditions. Under stable conditions the spin motion can be described by the OCF equations. The tipping-angle-dependent frequency shift and multiple spin echoes were observed, which are similar to the case of superfluid3He. The onset of the instability of spin motion is attributed to the stimulated emission mechanism through the three-magnon relaxation process, which is similar to the Suhl instability in electronic magnetism. We derived the magnon life time from the analysis of the instability. During the instability, a largenegative frequency shift was observed. This negative shift is explained by the extension of Fomin-Ohmi's theory to include the state of decayed magnon and this explanation is consistent with the instability model.