Study of the reversal mechanism in longitudinal hard disk media:: The role of K2/K1

The validity of the coherent rotations mechanism of reversal in CoCrPtB longitudinal hard disk media is probed. The proposed method is based on a comparison between the K-2/K-1 ratios (K-1 and K-2 being the first and second order anisotropy constants) measured by a hard axis loop method, and that estimated using in-plane isothermal remanent magnetization and dc-demagnetization processes in the hypothesis of coherent reversal. The disagreement between the two values of K-2/K-1, noticed for all the investigated samples, indicates an incoherent reversal mechanism. The origin of this mechanism is believed to be the grain coupling. The high values of the switching field at pi/2 angle between the applied field and the easy axis H-SW(psi=pi/2), measured by hard axis loop, can be larger than the writing field. This may explain the experimentally noticed degradation of signal/noise ratio with increasing H-SW(psi=pi/2). (C) 2002 American Institute of Physics.