Exchange coupling effects in CoCrPt-SiO2/FeCoTaCr composite media for perpendicular recording

The exchange coupled composite (ECC) media consisting of a magnetically hard CoCrPt-SiO2 layer and a magnetically soft FeCoTaCr layer were fabricated as an approach to improve writability. A nonmagnetic CoCr layer with different thickness was inserted between the hard and soft layers to adjust the exchange coupling strength. With proper CoCr thickness, a decrease of coercivity was observed. Transmission electron microscopy (TEM) revealed that the soft/hard stacked grains were magnetically isolated by SiO2 along grain boundaries. Magnetic properties were characterized by vibrating sample magnetometer (VSM). Angle-dependent coercivity indicated that the stacked magnetic grains switched magnetically in a coherent mode. Angle-dependent switching field demonstrated that ECC media had a better tolerance of the angle dispersion than perpendicular media. The switching field decreased with the increase in thickness of the soft magnetic layer. However, the thermal stability factor was kept almost constant (150) until the soft layer was over 3.3 nm