Interlayer magnetic coupling: The torque method

We present ab initio calculations of the interlayer exchange coupling between two, in general noncollinearly aligned magnetic slabs embedded in a nonmagnetic spacer. Based on a surface Green's function formalism, two equivalent but formally and physically different approaches are examined and discussed. For the Co/Cu/Co(001) system we demonstrate the usefulness of the concept of infinitesimal rotations in order to calculate the coupling for a finite relative angle theta, in particular for theta=pi, between the corresponding spin directions in the magnetic slabs. The temperature and layer dependence of the interlayer exchange coupling is examined and the possibility for noncollinear coupling is investigated.