Abstract

An intrinsic mechanism of the biquadratic term in the interlayer coupling energy is analysed numerically within the spin-polarized free-electron approximation for ferromagnetic films and free-electron approximation for non-magnetic spacers. The corresponding coupling parameter does not vanish in the limit of flat interfaces, contrary to Slonczewski's mechanism (Phys. Rev. Lett. 67 (1991) 3172) which gives a non-zero contribution only in the presence of interface roughness (steps). The coupling parameter oscillates with the interlayer thickness and the oscillation period is equal to half of the corresponding period for bilinear term. The dependence of the coupling parameter on thickness of the magnetic films is also analysed.

Correspondence to: Prof. J. Barna, Magnetism Theory Division, Institute of Physics, A. Mickiewicz University, ul Matejki 48/49, 60-769 , Pozna, , Poland.