JMMM 121 (1993) 326-329

On the biquadratic interlayer coupling in layered magnetic structures

J. Barnas and P. Grunberg

New mechanisms contributing to a biquadratic term in the phenomenological expressino for 
the interlayer coupling energy are proposed and analysed theoretically. One of them takes 
into account excange coupling not only between the two magnetic atomic planes which are 
adjacent to the interlayer, but also coupling between further atomic planes. The second 
mechanism is based on the fact that the wavefunctions corresponding to the electronic 
states responsible for the coupling depend on the relative orientation of the film 
magnetization. Both mechanisms give nonvanishing terms for ideally flat interfaces, 
contrary to the Slonczwewski;s (Phys. Rev. Lett. 67 (1991) 3172) mechanism which works 
only in the presence of interface roughness (steps).