NMR in Magnetically Ordered SolidHe3

Magnetically ordered solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, produced by compressional cooling to $T\approx 1$ mK, has been studied by high-resolution NMR at fields up to 2.98 T. In the ordered solid, at low fields $B_0<~410$, mT, peaks in the spectrum above and below $\frac{\gamma B_0}{2\pi }$ characteristic of antiferromagnetic ordering, are observed. For $B_0>~430$ mT, there is a temperature-dependent shift of the resonance to higher frequencies and a large rapid growth in magnetization, beginning at the ordering temperature.