Conduction-band formation in metal layers intercalated in TaS2: Nuclear resonance of Sn, Hg, and Pb in TaS2

Metal layers of Sn, Hg, and Pb intercalated into Ta${\mathrm{S}}_2$ have been studied by nuclear magnetic resonance. The completely intercalated layers in ${\mathrm{Sn}}_{1.0}$Ta${\mathrm{S}}_2$, ${\mathrm{Hg}}_{1.0}$Ta${\mathrm{S}}_2$, and ${\mathrm{Pb}}_{1.0}$Ta${\mathrm{S}}_2$ have fully metallic nuclear-resonance frequency shifts $K$ with $K_{\parallel }$ and $K_{\perp }$ (parallel and perpendicular to normal to layers) (0.69 ± 0.02)% and (0.81 ± 0.03)% for ${\mathrm{Sn}}^{119}$ at 296 °K; (1.66 ± 0.10)% and (2.56 ± 0.10)% for ${\mathrm{Hg}}^{199}$ at 4.2 °K; and (1.28 ± 0.10)% and (1.54 ± 0.05)% for ${\mathrm{Pb}}^{207}$ at 296 °K. ${\mathrm{Sn}}_{1/3}$Ta${\mathrm{S}}_2$, which has an intercalated structure with one-third-filled Sn layers, yielded $K_{\parallel }=K_{\perp }=+(0.08\mathrm{}\pm 0.01)\%$ for ${\mathrm{Sn}}^{119}$ at 296 °K, suggesting a much smaller conduction-electron state density at the Fermi energy than in the fully filled layers. The ${\mathrm{Sn}}^{119}$ indirect nuclear-spin interaction through conduction electrons estimated from the measured $T_2$ values and calculated dipolar contribution was also weaker in ${\mathrm{Sn}}_{1/3}$ ${\mathrm{TaS}}_2$ than in ${\mathrm{Sn}}_{1.0}$Ta${\mathrm{S}}_2$. A decomposition of the susceptibility components of the compounds is made. The ${\mathrm{Sn}}^{119}$ Mössbauer-effect splitting previously observed in ${\mathrm{Sn}}_{1.0}$Ta${\mathrm{S}}_2$ is shown to be produced by quadrupole effects. Interpretation of the conduction-band formation in terms of a Mott criterion is proposed.