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 inves tigated by magnetic force microscopy (MFM) and Lorentz transmission electro n microscopy (LTEM). For most defocusing distances, the observed signal con trast is greatest at the track edges where the magnetization is antiparalle l to the dc-erased intertrack regions. Head-on type "walls'' at the transit ions show limited contrast indicating small amplitude deviations in the zig zag transition as observed by MFM. Results are markedly different from earl ier work on recording media which revealed large zigzag amplitude and or vo rtex formation at the transition. LTEM images suggest an increase in the tr ack-edge noise and a reduction in the effective track width with density, p resumably due to flux leakage of the head field at the pole edges. (C) 1999 American Institute of Physics. [S0021-8979(99)62808-0].