Effect of Inserted Ni layers on Magnetoresistance of Co/Cu Multilayers

The effect of the inserted Ni layers on the magnetoresistance(MR) of Co/Cu multilayers has been investigated. It was found that the insertion of Ni layer enhanced the MR ratio of the multilayers. The effect was investigated on sputter deposited Co(1nm)/Cu(2.3nm) multilayers which give one of the maximum MR ratios. The degree of the effect depends on the thickness of Ni layer, and the prominent effect was observed only when the thickness of Ni layer is 0.1-0.2 nm. The symmetric and asymmetric two types of insertion of Ni layer were carried out to see the effect of the interface on the magnetoresistance, since an interface plays a significant role in scattering of conduction electrons. MR ratio is strongly affected by the thickness of Ni layer itself and the total thickness of Co and Ni layers between two Cu layers. The two types of insertion of Ni layer yield little difference in MR ratio, showing that MR effect depends more on the electrical structure which the total thickness of ferromagnetic Co and Ni layers forms than on the morphological change or the interdiffusion at the interfaces due to the insertion of Ni layers.