Effect of interface roughness on exchange coupling in synthetic antiferromagnetic multilayers

In this work, FeCo/Ru/FeCo synthetic antiferromagnetic multilayers were deposited at ambient temperature on glass substrates under two different dc magnetron sputtering conditions which significantly changed the interface roughness. Interface roughness was calculated from X-ray reflectivity measurements. Angular dependent torque curves and hysteresis loops were calculated from energy minimization for a simple domain model assuming both bilinear and biquadratic exchange and were fitted to the experimental data. The effect on the reversal process and in particular, on the apparent exchange couplings, was found to be significant.