Spacer layer thickness and temperature dependence of interlayer exchange coupling in Co/Ru/Co trilayer structures

Abstract

In this paper, we measure the bilinear interlayer magnetic coupling ${J}_{1}$ between two Co layers coupled across a Ru spacer layer over a wide range of spacer layer thicknesses from 0.4 to 3.4 nm and temperatures from 5 to 300 K. These measurements are fit using the interface-reflection interlayer magnetic coupling model in order to determine coupling strengths and electron Fermi velocities within the spacer layer in the direction perpendicular to the film interface for each of the critical spanning vectors. We find that there is a significant contribution to ${J}_{1}$ from several different critical spanning vectors, all with different periods of oscillation with respect to the spacer layer thickness. The results indicate that there is likely no exponential superexchangelike contribution to coupling in our samples. The nonoscillatory antiferromagnetic coupling bias of ${J}_{1}$ seen in thinner Ru spacer layers can be explained solely by a linear combination of oscillatory Ruderman-Kittel-Kasuya-Yosida-like coupling from several different critical spanning vectors, all with different periods of oscillation. The experimentally determined electron Fermi velocities are found to be within the range expected from theoretical calculations. The results also indicate that the interface-reflection model is capable of describing the bilinear interlayer exchange coupling in our samples over the entire range of spacer layer thicknesses and temperatures measured in this paper.