7Li and 31P NMR studies of monoclinic Li3In2(PO4)3

Fourier-transform NMR spectra and spin-lattice relaxation rates were studied for ⁷Li and ³¹P in a monoclinic modification of the Li₃In₂(PO₄)₃ superionic conductor over a wide temperature range of 240-575 K. The static magnetic susceptibility of the lithium subsystem of the compound and the ³¹P NMR line shape exhibit anomalous changes with increasing temperature. Quadrupole structure of the ⁷Li NMR spectrum is observed under fast motion of the lithium ions in the superionic phase. In this phase the temperature behavior of the spin-lattice relaxation rates is different for ⁷Li and ³¹P nuclei. The results are discussed taking into account the preceding NMR data on monoclinic Li₃Sc₂(PO₄)₃ and rhombohedral Li₃In₂(PO₄)₃ compounds.