Rapid Decay Mechanisms for Bulk Spin-Aligned Atomic Hydrogen at T=0 K in Large Magnetic Fields

Solid spin-aligned atomic hydrogen is shown to be unstable against spontaneous magnon creation due to electronic dipole-dipole and hyperfine interactions even at T=0 K for magnetic fields less than Hc≈7.3J̃μe, where J̃ is the motionally averaged exchange interaction. For an fcc crystal at 50 cm3/mole, Hc≈106 G. Similar considerations apply to the fluid state where the relevant parameter is again J̃ which is proportional to the density in the low-density limit.