Magnetic properties of uniaxial synthetic antiferromagnetic films

A study of the properties of uniaxial synthetic antiferromagnetic films with the structure Si(100)/Ta(5 nm)/Co(a)/NM(b)/Co(c)/Ta(10 nm) prepared by oblique sputtering is reported. Easy axis and hard axis hysteresis loops show a strong uniaxial anisotropy. The structural origin of the anisotropy is revealed by atomic force microscopy. The magnetization switching process was measured by polarized neutron reflectometry. The system exhibits biquadratic coupling, since the experimental remanence differs from that calculated by a model considering only bilinear coupling. The dependence of the critical fields on top ferromagnetic layer thickness is measured. A fit including both bilinear and biquadratic coupling qualitatively agrees with the results. (C) 2004 American Institute of Physics.