Superexchange Coupling and Spin Susceptibility Spectral Weight in Undoped Monolayer Cuprates

A systematic inelastic neutron scattering study of the superexchange interaction in three different undoped monolayer cuprates ( ${\mathrm{La}}_2{\mathrm{CuO}}_4$, ${\mathrm{Nd}}_2{\mathrm{CuO}}_4$, and ${\mathrm{Pr}}_2{\mathrm{CuO}}_4$) has been performed using conventional triple axis technique. We deduce the in-plane antiferromagnetic (AF) superexchange coupling $J$ which actually presents no simple relation versus crystallographic parameters. The absolute spectral weight of the spin susceptibility has been obtained and it is found to be smaller than expected even when quantum corrections of the AF ground state are taken into account.