Magnetic and First-Order Reversal Curve Investigations of Antiferromagnetically Coupled Nanostructures of Co/Pd Multilayers

Magnetic properties of nanostructures of antiferromagnetically coupled (AFC) Co/Pd multilayers were studied using hysteresis loop and first order reversal curve (FORC) measurements. The thickness of Co sublayer in the stabilizing layer of the AFC was increased in order to reduce the anisotropy constant of the stabilizing layer. It was noticed that the (Co/Pd)_x3 multilayer stack showed a perpendicular magnetic anisotropy (PMA) even when the thickness of Co sublayer was increased to 1 nm. Antiferromagnetic coupling is explained to be the cause of such a PMA. The nanostructures do not show AFC at remanence for Co sublayer thickness below 0.8 nm. AFC at remanence was achieved for Co sublayer thickness of 1 nm. The FORC data indicated four peaks in the case of AFC structures, whereas a single peak was observed in single layered structures and samples where the stabilizing layers did not have a PMA. The observations are fundamentally interesting and useful in reducing switching field distribution in patterned media.