1H and 39K spin–lattice relaxation, ionic motion and Raman processes in the proton conducting KHSeO4 single crystal

The spin–lattice relaxation rates of 1H and 39K nuclei in KHSeO4 crystals were studied in the temperature range 160–400 K. The spin–lattice relaxation recovery of 1H nucleus in this crystal can be represented with a single exponential function, and the relaxation T1−1 curve of 1H can be represented with the Bloembergen–Purcell–Pound (BPP) function. The relaxation process of 39K with dominant quadrupole relaxation can be described by a linear combination of two exponential functions. T1−1 for the 39K nucleus was found to have a very strong temperature dependence, T1−1=βT7. Rapid variations in relaxation rates are associated with critical fluctuations in the electronic spin system. The T7 temperature dependence of the Raman relaxation rate is shown here to be due to phonon–magnon coupling.