A double-quantum-well model of the exchange coupling in Fe/ZnSe/Fe

In this letter, we investigate the interlayer exchange coupling between two finitely thick ferromagnets (FM), separated by a non-metallic spacer, taking into account the contributions from double-well states. It is found that the negative temperature coefficient of the exchange coupling can be explained by the resonant tunnelling between two FM wells, whereas the positive temperature coefficient for the antiferromagnetic coupling can be attributed to non-resonant tunnelling. Our calculation of the electronic structure indicates that this temperature dependence is related to the relative magnitudes of the densities of states close to the Fermi surface for the cases of parallel and antiparallel alignments of the FMs. Also, the present model provides us with a new physical explanation for recent experimental observations.