Analysis of the Current-Confined-Paths in the Film Plane for CPP-GMR Films

Nanostructure of current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) films with a current-confined-path nano-oxide layer (CCP-NOL) is analyzed by high-resolution transmission electron microscope (HRTEM) and three-dimensional atom probe (3DAP). By HRTEM analysis, it is found that the CCP is formed on the center of the grain of a pinned layer. By 3DAP analysis, the grain size of a free layer can be visually detected and its size is about 5-10 nm. The grain of a free layer is well aligned with a CCP, suggesting that the decrease of the grain size of a pinned layer is effective for increasing the number of the CCPs per unit area. Moreover, by using a 3DAP image, the density of the CCPs per unit area can be derived. As a result, it is clearly shown that the density of the CCPs per unit area increases with decreasing resistance area product (RA) , which cannot be obtained from HRTEM analysis. By combining HRTEM result and 3DAP result, the nanostructure of the CCP can be clarified, and the decrease of the grain size of a pinned layer and the decrease of RA are preferable for an extremely small element size for a higher-density recording head.