Study of the dynamics of lattice of copper selenide by the NMR method

The article presents the results of investigations of copper selenide Cu1.75Se using the NMR method. The 77Se NMR spectrum for Cu1.75Se is a single line with full width at half maximum (FWHM) of 4 kHz at the temperature of 250 K. Within the temperature range of 200–450 K, the rates of transverse and longitudinal relaxation are equal. This phenomenon is mainly typical of a liquid, where the homonuclear dipole-dipole interaction is effectively averaged due to the Brownian motion of molecules. In this case, the main mechanism that averages the dipole-dipole interaction is the motion of copper ions. Below 200 K, copper ions are partially localized due to the phase transition, and the behavior of the spin-spin and spin-lattice relaxation rates (as well as their values) are different.