Perpendicular Head Structures to Improve the Corner Erasure Robustness

Data erasure can arise when a hard disk drive is exposed to a large external magnetic field. This has been raised as a particular concern for drives employing perpendicular recording. Flux tends to concentrate between the head and the soft-underlayer of the disk, especially around the edges and corners of the head where the data erasure is often most pronounced. In this paper, we use 3-D finite-element modeling to investigate the effects of head geometry on the fields that cause data erasure. An in-plane external field causes concentration of magnetic flux at the edges of the return pole (RP) and the upper and lower shields of the reader (USL/LSL). We found increasing the length (downtrack) of these structures is effective in reducing the erasure fields. Aligning the edges of the RP, USL, and LSL is also shown to be a practicable and effective way to reducing the erasure fields. These erasure fields are aggravated when the write element is active. The fields that arise during writing must be taken into consideration when assessing data erasure