Magnetic resonance and relaxation in NH4ClO4

The proton spin‐lattice relaxation, second moment, and magnetization of NH₄ClO₄ have been investigated between 1.5 and 100°K, using pulse NMR techniques. The system has a T₁ minimum at 29°K and, below 20°K, evidences nonexponential recovery with a relatively weak temperature dependence. The second moment gradually increases from 1.3 G² to $\text{∞ 4\hspace{0.17em}}{\mathrm{G}}^2$ at 2°K. Spin conversion is observed below 4°K. The data are interpreted with reference to the possible hindered rotor levels of the ${\mathrm{NH}}_4^{+}$ ion.