| Current perpendicular to plane giant magnetoresistance (CPP-GMR) read heads may be a viable candidate for the future generation 1 terabit/in 2 magnetic recording that requires read heads with the magnetoresistance (MR) ratio over 5 percent and the resistance-area (RA) product in the range of 0.1∼1 ohm mum2. CPP-GMR read heads, however, have two major drawbacks: first, the noise caused by the spin torque, and second, a small change in the resistance. Use of a symmetrically arranged, dual-CPP-GMR structure with a current confined path (CCP) may alleviate these drawbacks. Thus, the main objective of this study was to develop such a dual-CPP-GMR structure and materials for the structure that have been specifically designed to address these drawbacks. Accordingly, the dual-CPP-GMR spin valves were fabricated using electron beam lithography and Cu nanoclusters and MgO spacer for the CCP structure was also developed. Interestingly, in this study, we found unexpected switching behaviors that related to the vortex-like domains generated by the Oersted field. Our experimental data suggested that the switching was assisted by an additional mechanism attributable to the current induced switching from the spin torque, which further suggested the susceptible nature of the dual-CPP-GMR spin valve to the spin torque noise. The experimental data, which differentiated from the theoretical prediction, indicated that currently available models of the spin torque are incomplete, and transmission and reflection of the spin current are not identical in the generation of the spin torques. |
