Improvement of signal to noise ratio for Co/Pd multilayer perpendicular magnetic recording media by the addition of an underlayer

Signal and noise characteristics of Co/Pd multilayer perpendicular magnetic recording media are discussed based upon MFM analysis. The noise of the Co /Pd multilayer media is originated mainly from irregularities in the magnet ic transition regions, and can be drastically suppressed by increasing the thickness of the carbon underlayer although a large number of reversed magn etic domains between the magnetic transitions still exist. The fine magneti c clusters formed in the medium with a thick carbon underlayer result in cl ear magnetic transition boundaries of recorded bits in the high recording d ensity region. By examining the profile of the M-H loops. the decrement in the x value, which is defined as the slope of M-H loop at the value of coer civity, improves the signal to noise (S/N) ratio for the Co/Pd multilayer m edia. (C) 2001 Elsevier Science B.V. All rights reserved.