Magnetic anisotropy and reversal mechanisms in dual layer exchanged coupled perpendicular media

We report the magnetic properties of perpendicular media with a layered structure in which a high anisotropy, segregated, granular CoCrPt-oxide base layer is capped by a lower anisotropy CoCrPt-based film. Anisotropy field (Hk) data show that for the thickness of oxide media studied here, the measured value of Hk remains constant as cap thickness increases. This provides strong evidence that the anisotropy of the composite grain is controlled by the hard oxide layer and is not a simple average of the anisotropy of the oxide and cap layers. The reversal mechanism is explored by determining the angle dependent switching as a function of cap thickness. In the absence of a cap layer, the media show a Stoner-Wohlfarth-like reversal which becomes more Kondorsky-like [1cos (θ)] when a critical cap thickness is reach, which we interpret as indicating greater lateral exchange coupling. © 2008 American Institute of Physics.