Magnetic susceptibility of optimally doped HgBa${}_2$CuO${}_{4+\delta }$

The magnitude of the powder spin susceptibility of an optimally doped superconductor HgBa${}_2$CuO${}_{4+\delta }$ (Hg1201) in the normal state is found to be nearly the same as that of La${}_{2-x}$Sr${}_x$CuO${}_4$ near the optimally doped level. The Stoner enhancement factor of Hg1201 is larger than that of La${}_{2-x}$Sr${}_x$CuO${}_4$. The magnitude correlation of the Stoner enhancement factor is inconsistent with the effect of the recent theoretical Coulomb repulsion between 3$d$ electrons and that of the superexchange intereraction of a charge transfer type.