Magnetic force and Lorentz transmission electron microscopy analysis of bit transitions in longitudinal media

Written bits on a 3 kOe CoCrPtTa/Si longitudinal recording medium are investigated by magnetic force microscopy (MFM) and Lorentz transmission electron microscopy (LTEM). For most defocusing distances, the observed signal contrast is greatest at the track edges where the magnetization is antiparallel to the dc-erased intertrack regions. Head-on type "walls'' at the transitions show limited contrast indicating small amplitude deviations in the zigzag transition as observed by MFM. Results are markedly different from earlier work on recording media which revealed large zigzag amplitude and or vortex formation at the transition. LTEM images suggest an increase in the track-edge noise and a reduction in the effective track width with density, presumably due to flux leakage of the head field at the pole edges. (C) 1999 American Institute of Physics. [S0021-8979(99)62808-0].