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 mn. 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.