Tuning interlayer coupling and domain structure in [Co/Pd]nCo/Ru[Co/Pd(x)]m multilayer by controlling the thickness x of the weak-ferromagnetic Pd layers in the lower Co/Pd multilayer

Abstract

Interlayer coupling has been studied in a series of perpendicular antiferromagnetically coupled multilayers with asymmetric structures Pd(20 Å)/[Pd(15.7 Å)/Co(3.6 Å)]5/Ru(4.1 Å)/Co(3.6 Å)/[Pd(x Å)/Co(3.6 Å)]3/Pd(50 Å)/Si substrate. The coupling oscillates between antiferromagnetic and ferromagnetic as a function of x in the bottom sublayers. The strong antiferromagnetic coupling with a maximum value of 2430 Oe, which was determined by the minor-loop shift, was obtained. The pinning direction of the antiferromagnetic coupling also changes with the variation in x. The oscillatory behavior can be attributed to multiple reflections of electron waves at the Co/Pd interfaces and their interference. Micromagnetic structure evolves with a variety of interlayer couplings are observed by magnetic force microscopy. An antiferrostripe domain without a ferromagnetic shift is observed at the as-deposited state. Stray-field induced ferromagnetic domains appear in multilayers with weak antiferromagnetic coupling.