Magnetic field dependence of the proton zeeman relaxation in (NH4)2PbCl6

The magnetic field dependence of the proton Zeeman relaxation in polycrystalline (NH₄)₂ PbCl₆ was studied at 20 K and 43 K. The relaxation rate versus resonance frequency curve exhibited tunneling maxima at 22 MHz and 44 MHz for T = 20 K and at 21 MHz for T = 43 K. The interpretation of the time dependence of the magnetization as a sum of two exponentials showed that the time constants differed from each other much more at 20 K than at 43 K. The results were compared with a recent theory based on a common Zeeman spin temperature.