Nuclear Magnetic Resonance in Cubic Sodium Tungsten Bronzes

The nuclear magnetic resonances of ${\mathrm{W}}^{183}$ (natural abundance) have been studied in samples of cubic sodium tungsten bronzes (${\mathrm{Na}}_x\mathrm{W}{\mathrm{O}}_3$) with $x$ ranging from 0.56 to 0.89, in tungsten trioxide, and in tungsten metal. The bronze resonances exhibit appreciable diamagnetic shifts (∼0.3%) with respect to tungsten trioxide, the shift increasing with increasing $x$. The spin-lattice relaxation time for ${\mathrm{Na}}^{23}$ in ${\mathrm{Na}}_{0.89}$W${\mathrm{O}}_3$ was found to be 55 sec. These results provide evidence that the conduction band in the cubic sodium tungsten bronzes is based on tungsten $5d$ states.