Sensitivity-enhanced electron holography and its application to magnetic recording investigations

The sensitivity for electron-phase measurement in electron holography has been improved to better than 2π/100 by the application of digital interferometry at the optical reconstruction stage. This enables quantitative measurement of magnetic flux as small as (1/100)(h/e)(=4.1×10−17 Wb), hitherto undetectable, with high spatial resolution. With this technique, we have observed the distribution of leakage magnetic field from a thin cross section of a perpendicularly magnetized recording film (cobalt-chromium) with a recording density as high as 300 kFCI (85 nm bit length), the highest density ever directly observed.