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.
Categories: cond-mat.supr-con cond-mat.str-el