Quantized states are mapped in Ni/Cu/Ni(100) trilayer structures, which are taken as a more accurate rendering of spin valve devices than the bilayers studied previously. We find that an extra Ni overlayer affects the energy of quantized states in the Cu layer, explaining why the magnetic coupling is affected by the thickness of the magnetic layer, and how a phase difference may occur between magnetic coupling oscillations in trilayers and density of states oscillations in bilayers. The potential step that confines electrons to the Cu spacer is determined to be 0.9 eV. ©1995 American Institute of Physics.