Write field measurements of a perpendicular head on a soft underlayer film

We demonstrate a technique to measure the field of a perpendicular head on a soft underlayer. We built a current-perpendicular-to-the-plane giant magnetoresistive sensor deposited on a soft underlayer and placed it on the write-read contact tester. Scanning a perpendicular head over the device with sub-nm resolution allowed us to map the field spatially and by changing the writer current, obtain saturation curves of both the main pole and the return pole.