Low-frequency lattice dynamics in Ba1-xKxBiO3 oxides according to 39K NMR data

The spin-lattice relaxation times T-1 in Ba1-xKxBiO3 (x=0.3, 0.4,0.5) were measured in the normal temperature range (20-300 K). A substantial contribution to the spin-lattice relaxation rate from dynamic local distortions of the crystal lattice near potassium atoms is found. The activation energy of this process increases with decreasing potassium concentration, and the frequency of lattice excitations decreases. The nature of the low-frequency lattice dynamics is discussed. (C) 1999 American Institute of Physics. [S0021-3640(99)00617-9].