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.
Comment: 4 pages, 3 figures