  Using a recently developed variational quantum Monte Carlo method, magnetic
properties of high-$T_{\rm C}$ superconductors are studied at zero temperature
($T$), by numerical simulations on the 2D t-J model. Our focus here is to
explore the difference in the properties of $p$-type and $n$-type cuprates as a
function of the carrier concentrations close to half filling. As observed
experimentally, it is found that the antiferromagnetically ordered phase
persists even for a small, yet finite amount of carrier doping, and that this
phase is more robust in the electron doped case.
