Effect of the repeat number and Co layer thickness on the magnetization reversal process in [Pt/Co( x )] N multilayers

Magnetic properties, domain morphology and magnetization reversal processes were investigated for two sets of [Pt/Co(x)]N multilayers with various (Co/Pt) bilayer repeat numbers (N) and Co layer thicknesses (x) using hysteresis loops, magnetic force microscopy (MFM), and the first-order reversal curve method. When N ranges from 7 to 20, the effective anisotropy, Keff, of the multilayers increases from 0.86 × 106 erg cc−1 to 1.48 × 106 erg cc−1 and the coercivity (Hc) is maintained at approximately 290 Oe. Moreover, when x increases, Keff drops from 0.52 × 106 erg cc−1 to 0.09 × 106 erg cc−1 and Hc decreases from 285 Oe to 75 Oe. According to the switching field distribution, evidence has been found that the magnetization switching is gradually dominated by the reversible process and the portion of the irreversible switching process declines from 86% to 40% and 58% to 10% when N and x are increased, respectively.