CPP sensors with an enhanced MR using laminated FM layers

Abstract

Summary form only given. Current perpendicular to plane (CPP) GMR is being studied as the possible candidate for high density recording applications. One of the advantages of CPP GMR is that it allows the elimination of the insulating gap layer in the read head. However, the most recently reported MR ratio of CPP sensors is only about 2.3% even in specular spin-valves. The performance of the CPP spin-valves has to be increased substantially before it can be applied to read heads. One of the possible ways to increase the MR of CPP spin-valves is to confine the electrons at the active layers so that they will experience more spin-dependent scattering at the interface. This can be realized by either putting oxides at the outer boundary of the free and pinned layers or using metallic multiple layers. The former has already been explored in current in plane spin valves as the specular reflective layers. The latter is relatively new to metallic systems. If the surface of individual layers is sufficiently smooth, it should be possible to form highly reflective spin-dependent electron mirrors or Bragg reflectors. Based on this background, in this work, we have investigated the effect of using (CoFe/Cu)/sub N/ multilayers as a free layer in dual CPP spin-valves with nano-oxides as the specular reflection layers.