  We studied the hole concentration dependences of 63Cu Knight shifts in
single-CuO2-layer high-Tc cuprate superconductors HgBa2CuO4+d and double-layer
HgBa2CaCu2O6+d. We found that the spin Knight shift at room temperature as a
function of the hole concentration in the single-layer superconductor is
different from that in the double-layer superconductor. Two type relations
between the spin Knight shift and the hole doping level serve to estimate the
individual hole concentrations of the non-equivalent CuO2 planes in a unit
cell.
