EXCHANGE COUPLING IN MAGNETIC MULTILAYERS - A QUANTUM-SIZE EFFECT

The long-wavelength oscillations observed in magnetic multilayers axe explained by an indirect Ruderman-Kittel-Kasuya-Yosida-like (RKKY) exchange interaction. A perturbative theory of the RKKY-like exchange coupling between two ferromagnetic layers separated by a nonmagnetic slab is derived. The approach includes a realistic description of the multilayer one-electron states, whose wave functions satisfy matching conditions at the ferromagnetic-nonmagnetic interfaces. The quantum-size effects exhibited by the electron transmission coefficient give rise to a distinct multilayer wavelength lambda. which provides the measured long periods.