Perpendicular magnetic recording performance of double-layer media

Perpendicular magnetic recording performance for double-layer (Co-Cr,Ni-Fe) media was analyzed, with a simple magnetization model, in comparison with single-layer media. The calculated output voltage from a ring-shaped reproducing head shows good agreement with experimental data. It is shown theoretically and empirically that the Co-Cr layer thickness can be reduced without sacrificing the output amplitude, if the Ni-Fe layer is placed underneath it to perform as a "flux sink" to extinguish the rear surface charge on the Co-Cr layer.