Interlayer exchange coupling in multilayered Co/Os

Abstract We have studied the interlayer exchange coupling (IEC) in Co/Os n /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 3.5–4 ML in addition to the long one of 7 ML which has been measured experimentally. Our results of PAM relate the oscillation periods of 6.29 ML and 3.69 ML 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 e 9 , 6.86 ML for long period, and inner hole ellipsoid h 7 , 3.80 ML for short period. These periods are very comparable to those periods of 6.8 ML and 3.7 ML 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 Co m /Os n 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.