OBSERVATION OF MAGNETIC-RESONANCE MODES OF FE LAYERS COUPLED VIA INTERVENING CR (INVITED)

Multiple-frequency (2-14 GHz) ferromagnetic resonance (FMR) has been used to directly observe the coupled resonance modes of a large set of single-crystal Fe/Cr/Fe(001) sandwiches grown by molecular-beam epitaxy. The FMR data reveal two resonance modes which have complicated frequency dependencies for those samples that show antialigned Fe layers in zero applied field. Such alignment is only found for samples with 12 Å<t(Cr)<25 Å. These samples also have dramatic discontinuities in their M-vs-H curves and magnetoresistance curves. Angle-dependent 35-GHz FMR was used to determine the anisotropy and effective magnetization of these samples when they were magnetically aligned. We show that the detailed FMR and M-vs-H behavior can be quantitatively explained by an AF coupling term of the form J M̂1·M̂ 2 and find that J has a t(Cr) dependence peaked about 16 Å.