Ferromagnetic interlayer coupling and switching process of exchange coupled composite media

The ferromagnetic coupling effects in the exchange coupled composite (ECC) magnetic recording media were studied by varying the interlayer thickness and the saturation magnetization (Ms) of the soft layer. A minimum coercivity was observed at a certain interlayer thickness for the ECC media with a low Ms soft layer. When the Ms of the soft layer was increased (700 emu cm3 in this work), no interlayer was needed to get the lowest coercivity for the ECC media, which makes the ECC media practical for a manufacturing process. A method to characterize the ferromagnetic coupling strength for the ECC media was quantitatively proposed. The switching process of the ECC media was observed to consist of the reversible switching of the soft layer and the irreversible switching of the hard layer.