Interlayer thickness dependence of the strong 90 degrees coupling in epitaxial CoFe/Mn/CoFe trilayers

Trilayers of CoFe/Mn/CoFe(001) have been prepared by molecular beam epitaxy and their magnetic properties measured by magnetometry and ferromagnetic resonance. Very strong near-90 degrees coupling between the CoFe layers, with no evidence for 180 degrees coupling, was found in all but the thickest Mn-Iayer samples. The coupling energy has the form suggested recently for the case when the interlayer itself is antiferromagnetic. An analysis of the ferromagnetic resonance data indicates that the magnitude of the coupling oscillates with the Mn thickness. (C) 1996 American Institute of Physics.