Magnetic properties of antiferromagnetically coupled antidots of Co/Pd multilayers

Antidots of Co/Pd multilayers with 3-bilayers [(Co/Pd) _x3] that were antiferromagnetically coupled(AFC) to (Co/Pd) _x10 were fabricated and their magnetic properties were investigated. The thickness of Co in (Co/Pd) _x3 was varied from 0.4 to 0.8 nm. Samples with a Co thickness of ₀.8 nm in the bilayer showed a perpendicular magnetic anisotropy (PMA) when antiferromagnetically coupled to (Co/Pd) _x10. On the other hand, the magnetization direction of single Co/Pd multilayers with thick Co (0.8 nm) as a reference structure (without AFC) was observed to be in plane, indicating that the PMA in (Co/Pd) _x3 films with thicker Co is due to the antiferromagnetic coupling. We also carried out a systematic study on this set of thin films patterned in antidot array fabricated using nanoimprint lithography. It was found that the AFC is helpful to induce a perpendicular magnetic anisotropy in both thin film and antidot form. Such a result is interesting both from a fundamental viewpoint and also from their potential applications in spintronics devices and patterned magnetic medium.