Effect of thin oxide capping on interlayer coupling in spin valves

We controlled interlayer coupling from ferromagnetic to antiferromagnetic by appropriately capping spin valves with thin oxides. The interlayer coupling field was -16.6 Oe at a Cu-spacer thickness of 30 Å. The sign of coupling changed at a Cu-spacer thickness of 20 Å. The antiferromagnetic coupling achieved in this way allowed a reduction of thickness of the Cu spacer down to 20 Å without loss of good magnetic and electrical properties, and this led to a significant improvement in the MR response of the spin valves. The interlayer coupling field was only +8.6 Oe even at a Cu-spacer thickness of 20 Å. We attribute the improvement in MR response to less current shunting through the most conductive Cu layer and to enhanced specular scattering at the interface between the free and the oxide capping layer.