Influence of the magnetic-layer thickness on the interlayer exchange coupling: Competition between oscillation periods

The oscillatory interlayer exchange coupling and its dependence on magnetic-layer thickness have been studied from first principles for (100) and (110) oriented Co/Cu/Co sandwiches. It is found that with increasing magnetic-layer thickness there is generally an important redistribution of weights among the different characteristic Ruderman-Kittel-Kasuya-Yosida-like oscillations. This effect is discussed in terms of the corresponding change in the electronic structure of the magnetic layers. The calculated exchange coupling energies for thicker cobalt layers are in excellent agreement with existing experiments.