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

Abstract

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 ${H}_{c}\ensuremath{\approx}\frac{7.3\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{J}}{{\ensuremath{\mu}}_{e}}$, where $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{J}$ is the motionally averaged exchange interaction. For an fcc crystal at 50 ${\mathrm{cm}}^{3}$/mole, ${H}_{c}\ensuremath{\approx}{10}^{6}$ G. Similar considerations apply to the fluid state where the relevant parameter is again $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{J}$ which is proportional to the density in the low-density limit.