Observation of Magnetization Distribution in Soft Underlayer of Perpendicular Magnetic Recording Media by Electron Holography

The magnetic properties of the soft underlayer (SUL) of perpendicular recording media affect the recording performance significantly. We visualized and quantified the distribution and magnitude of magnetic flux in the recording layer and SULs of perpendicular recording media by electron holography. Pseudo-SULs with different permeability were deposited on the slider of perpendicular recording heads. The SUL with higher permeability produced higher write magnetic flux (B_y) as compared to the SUL with lower permeability, which results higher overwrite performance. Further, the magnitude profile of B_x in the SUL thickness direction was different for the two SULs; the magnitude of magnetic flux in SUL is related to the occurrence of adjacent track erasure.