Abstract
The oscillatory perpendicular interlayer-coupling field and strength as a function of Ru spacer thickness were studied for samples of the [CoPt]5 CoRuCoTbCo 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 CoTbCo bilayers was enhanced because the CoPt multilayers stabilized the magnetization direction of CoTbCo. Consequently, oscillatory coercivity of CoTbCo 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 CoPt multilayers can be varied accordingly while keeping the same Ru thickness. © 2007 American Institute of Physics.