Direct observation of oscillatory interlayer exchange coupling in sputtered wedges using circularly polarized x rays

Oscillations in the magnetic exchange coupling between two ferromagnetic layers separated by Ru are directly observed in magnetron sputtered wedged sandwiches using x-ray magnetic circular dichroism. The magnetization of the lower magnetic layer in the sandwich is saturated in zero field by exchange biasing it to an antiferromagnetic layer of Fe60Mn40. The oscillatory exchange coupling through the Ru wedge causes the direction of the magnetic moment of the upper magnetic layer to rotate back and forth along the wedge and this is directly observed from variations in the intensity of absorption of circularly polarized x rays. Five oscillations in absorption intensity with a period corresponding to ≂11 Å were observed in a Ni81Fe19/Ru/Ni70Co30 wedge.