Resolution Enhancement by Applying MFM Under UHV Conditions

The enhancement in signal-to-noise ratio and lateral resolution in MFM in going from ambient pressure to UHV is demonstrated. The performance of several cantilevers is evaluated using a patterned 50 nm thick permalloy film, with cross-tie as well as 90 domain walls, and a 200 nm thick permalloy film with perpendicular magnetization. The increase in the quality factor of the cantilever oscillation in UHV improves the sensitivity, consequently allowing less magnetic material on the tip to achieve the same signal-to-noise ratio. This reduction in magnetic volume sharpens the lateral resolution. We also demonstrate that the magnetic interaction can be so weak that a magnetic contrast is visible only under UHV conditions.