Interlayer exchange coupling in multilayered Co/Os

Abstract

We have studied the interlayer exchange coupling (IEC) in Co/Osn/Co in trilayer geometry using the quantum well (QW) model, RKKY theory in the framework of ab-initio total energy calculation. Also we have used the phase accumulation model (PAM) to describe the thickness dependence of QW states energies. We predict the presence of a short period oscillation in Os with 3.5–4ML in addition to the long one of 7ML which has been measured experimentally. Our results of PAM relate the oscillation periods of 6.29ML and 3.69ML to Γ¯(k||=0) and M¯(k||≠0) direction, respectively. On the other hand, using our calculated Fermi surface including spin–orbit coupling of bulk Os we identified the two periods as the spanning vectors at Γ-centered nested electron surfaces e9, 6.86ML for long period, and inner hole ellipsoid h7, 3.80ML for short period. These periods are very comparable to those periods of 6.8ML and 3.7ML obtained by RKKY-fitting of the IEC. The principal behavior of the IEC found experimentally is reproduced by the theory. We have found in our calculations of IEC in the multilayer geometry Com/Osn a shift of the AF coupling peaks when we varied the thickness of the FM layers which might be interpreted as due to QW interactions.