MAGNETIC EXCHANGE-COUPLING EFFECTS IN ASYMMETRIC TRILAYER STRUCTURES OF MBE-GROWN CO CR/FE/

We present results of anisotropy and exchange-coupling studies of asym metric Co/Cr/Fe trilayers and superlattices grown by molecular beam ep itaxy on Cr(001)/Mg(001) buffers and substrates. The magnetic properti es have been investigated using both the longitudinal magneto-optical Kerr effect and ferromagnetic resonance. The hysteresis data obtained from the trilayer system were fit to a theoretical model which contain s both bilinear and biquadratic coupling. The effective in-plane aniso tropy was found to be of fourfold symmetry with the same easy-axis ori entation for both the Fe and Co layers. An analysis of the easy-axis h ysteresis loops indicates long-period oscillatory coupling and also su ggests a short periodic coupling. We show that weakly antiferromagneti cally coupled asymmetric films might serve as potential candidates for improved spin-valve systems.