Electron holography and HRTEM study of the magnetic microstructure of L10 FePt epitaxial thin film grown on MgO-substrate

Perpendicular epitaxial film of L10 FePt, showing the c-axis normal to the film plane, was successfully grown on top of MgO substrate using DC-magnetron co-sputtering technique. The electron holography study showed that a columnar epitaxial film displayed only a weak stray-field signal due to the presence of columnar boundaries. The growth of a continuous (full) epitaxial film however revealed characteristic LTEM images for the perpendicular magnetic domains. The electron hologram indicated the presence of the stray-field of induction originating from the perpendicular magnetizations. The reconstructed phase-image displayed a characteristic contrast-fringes pattern, indicating the presence of perpendicular magnetic domain walls. From the phase-shift measurement, the perpendicular magnetic induction strength was estimated to be about 0.27T, which was low. The low induction strength was because the film was weakly ordered due to a low substrate temperature.