Patent ID: 8940418
Filing Date: 2015-01-27
Classification: G11B

Abstract:
1. A perpendicular magnetic recording disk, comprising: a substrate; a first hard magnetic layer disposed above the substrate; a lower soft magnetic layer disposed between the substrate and the first hard magnetic layer, the first hard magnetic layer being disposed closer to the substrate than any other hard magnetic layer; a soft magnetic underlayer in contact with the lower soft magnetic layer and disposed between the substrate and the lower soft magnetic layer; a first exchange coupling layer disposed between the lower soft magnetic layer and the first hard magnetic layer; a middle soft magnetic layer disposed above the first hard magnetic layer; a second hard magnetic layer disposed above the middle soft magnetic layer; a second exchange coupling layer disposed between the first hard magnetic layer and the middle soft magnetic layer; a third exchange coupling layer disposed between the middle soft magnetic layer and the second hard magnetic layer; a fourth exchange coupling layer disposed above the second hard magnetic layer; and an upper soft magnetic layer disposed above the fourth exchange coupling layer.