Controlling the angle between magnetic moments of Co layers in Co|RuCo|Co

Abstract

Spintronic devices would greatly benefit from a noncollinear alignment between magnetizations of adjacent ferromagnetic layers for maximum performance and reliability. We demonstrate that such an alignment can be created and controlled by coupling two ferromagnetic layers across a magnetic spacer layer consisting of a nonmagnetic material, Ru, alloyed with a ferromagnetic element, Co. Changing the composition and thickness of the spacer layer enables the control of the relative angle between the magnetizations of the ferromagnetic layers between 0° and 180°. The onset of noncollinear alignment between the ferromagnetic layers coincides with the advent of magnetic order in the spacer layer. This study maps the concentration and thickness ranges of RuCo spacer layers that give rise to noncollinearity between ferromagnetic Co layers. The experimental results are successfully reproduced by simulating our structures with an atomistic model. This model assumes that Co atoms in the RuCo spacer layer have magnetic moments and that neighboring Co atoms are ferromagnetically coupled, while Co atoms separated by one or more Ru atoms are antiferromagnetically coupled.