Effects of Ni buffer layer on giant magnetoresistance in Co/Cu/Co sandwich

Abstract

Listen

Translate article

In order to increase the sensitivity of Co/Cu/Co sandwiches, different thickness Ni layers were used as buffer layer. It was found that in the Co 55 Å/Cu 35 Å/Co 55 Å sandwiches with different thickness Ni buffer layers, MR ratios between 3.5% and 5.6% could be obtained, and the coercive forces were about 12 Oe. Hence, the maximum field sensitivity could be enhanced to about 1%/Oe. Further investigation from the results of atomic force microscopy showed the improvement of the interfacial flatness in the sandwiches with Ni buffer layer. The microstructure observed by high-resolution electron microscope demonstrated the different structure of the two Co layers in the Ni buffered sandwich, which directly determined the small saturation field of the sandwich. This was confirmed by the magnetic behaviors of the two Co layers calculated from the experimental hysteresis loops. All these showed that the usage of a Ni buffer layer could result in interfacial improvement, different crystalline structure, and small saturation field in the Co/Cu/Co sandwich. These enhanced the electron spin scattering at the Co–Cu interfaces and finally enlarged the giant magnetoresistance and the sensitivity in the sandwich.