Magnetic memory is at the very foundation of the magnetic recording industry. This memory has been extensively studied and exploited in many areas of technology such as magnetic recording media . However, despite this interest, a fully satisfactory microscopic understanding of magnetic memory is still lacking. We present the first real space microscopic study of return point memory (RPM) and complimentary point memory (CPM). Presented data were taken on a low temperature ultra high vacuum magnetic force microscope (MFM). By in-field MFM imaging [1] of a high defect density 185nm nickel film, we found a high RPM at the nucleation field with a correspondingly high CPM. Based on the visual inspection of the locations of domain nucleation and using appropriate statistical methods, we found that CPM is lower than RPM with a high confidence. This work addresses the open questions left by previous area averaging, fourier space studies of RPM and CPM [2,3], namely the role of defects in the RPM/CPM mechanism.
[1] Marioni M.A. Pilet, N.; Ashworth, T.V.; O'Handley, R.C. & Hug, H.J. Phys. Rev. Lett., 2006, 97, 027201
[2] Pierce, M.S.; Buechler, C.R.; Sorensen, L.B.; Turner, J.J.; Kevan, S.D.; Jagla, E.A.; Deutsch, J.M.; Mai, T.; Narayan, O.; Davies, J.E.; Liu, K.; Dunn, J.H.; Chesnel, K.M.; Kortright, J.B.; Hellwig, O. & Fullerton, E.E. Phys. Rev. Lett., 2005, 94, 017202
[3] Pierce, M.S.; G.Moore, R.; Sorensen, L.B.; Kevan, S.D.; Hellwig, O.; Fullerton, E.E. & Kortright, J.B. Phys. Rev. Lett., 2003, 90, 175502
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