Magnetic force microscopy studies of DC erasure in a 5 Gbit/in2 medium [CoCrPtTa/CrMo]

The DC erasure process in a 5 Gbits/in² medium is investigated using magnetic force microscopy (MFM). 50 to 250 kfci patterns were imaged in the remanent state after application of in situ magnetic fields perpendicular H_⊥ and parallel H_| to the tracks. Degradation of bits is observed to start at the track edges and the transitions. Decay at the transition tends to occur locally at many places and propagates into the bits with opposing magnetization relative to H_|. For H_⊥, decay occurs on both sides of the transition and the written bits persist at higher fields compared to the application of H_|. For the H _| case, the averaged MFM signal for 50 to 250 kfci patterns fits the bulk DC demagnetization curve suggesting the reduced effect of demagnetizing fields