I will summarize our recent studies of magnetic excitations in the electron-doped copper oxide Pr_0.88LaCe_0.12CuO₄. As a function of annealing condition, this copper oxide can be tuned from a long-range ordered antiferromagnet into a high-T_c superconductor with T_c=24 K. Compared with electron-doped superconductor Nd_2-xCe_xCuO₄, where long-range static antiferromagnetic order co-exists with superconductivity at all dopings, the unique advantage of Pr_0.88LaCe_0.12CuO₄ is that this material is phase-pure at optimal doping (so that no other phase coexists with superconductivity).  I describe our systematic investigation of this material as it is tuned from a long-range ordered antiferromagnet to an optimally doped superconductor. I compare our results with that of hole-doped materials and summarize what is known about spin excitations in high-Tc superconductors.