Similar to the high temperature superconducting compounds, Ba2Cu3O4Cl2
has the two dimensional Cu-O plane. We investigated the magnetic prop
erties of this compound. It shows the antiferromagnetic behaviors with
a canted spin structure below 335K and another magnetic transition li
ke a spin glass phenomena at 33K. With replacing the Cu ion by a small
amount of Ni, the magnetic transition at 335K was depressed.