Use of room-temperature bias sputtering to decrease intergranular coupling in magnetic media deposited on polymeric substrates

CoCrPt thin films sputter-deposited on polymeric substrates without explicit heating were investigated as a function of substrate bias. The coercivity and the coercive squareness in the CoCrPt films were strongly dependent on bias voltage. A significant reduction in the coercive squareness S^* from a value near unity was observed with increasing bias voltage, implying a decrease in the degree of intergranular exchange coupling. With the addition of explicit substrate heating, S^* was further reduced, and was associated with a significant improvement of coercivity. This paper presents a possible approach to achieve media with acceptably low exchange coupling deposited at temperatures well below the glass transition temperature of polymeric substrates.