The oscillatory perpendicular interlayer-coupling field and strength as a function of Ru spacer thickness were studied for samples of the [Co/Pt]5/Co/Ru/Co/TbCo structure. For Ru thickness in the range of 0.5–1 nm, a strong antiferromagnetic (AF) coupling (J∼0.38 erg/cm2) was observed. When AF coupling existed, the coercivity of Co/TbCo bilayers was enhanced because the Co/Pt multilayers stabilized the magnetization direction of Co/TbCo. Consequently, oscillatory coercivity of Co/TbCo with Ru thickness was also observed. Since the magnetization direction of the Co sublattice in TbCo can be tuned by adjusting composition or measuring temperature, the direction of the shifted minor loop of Co/Pt multilayers can be varied accordingly while keeping the same Ru thickness.