Improved GMR characteristics of specular spin valves by nano-oxide layer formation with mixed gases

Abstract

Summary form only given. The enhanced MR ratio of over 10% and good thermal stability are strongly required for spin valve (SV) used in a read head in order to realize ultrahigh magnetic recording density beyond 40 Gbit/in/sup 2/. Recently, very applicable SVs with a pinned layer containing a nano-oxide layer (NOL) were suggested as a new technology for the improvement of MR ratio, where NOL enhances specular electron scattering. Several oxidation methods for NOL have been studied on the NOL interface control and MR improvement. Of these, plasma oxidation and ion beam oxidation can be hard to control the formation rate of very thin NOL. Accordingly natural oxidation is a good way to control the formation rate because of low oxidation rate. However, we found that natural oxidation in pure O/sub 2/ atmosphere did have a good reproducibility in our experiments. In order to improve the reproducibility of uniform NOL, we have investigated the natural oxidation conditions by mixed gases (O/sub 2//N/sub 2/ and O/sub 2//Ar) for the NOL formation. The SV samples used have the structure of Ta(5 nm)/NiFe(2.5 nm)/IrMn(7 nm)/CoFe(2.5 nm)/NOL/CoFe(1.5 nm)/Cu(2.6 nm)/CoFe(1.5 nm)/NiFe(4.5 nm)/Ta(5 nm).