Fabrication of FePt type exchange coupled composite bit patterned media by block copolymer lithography

We fabricated exchange coupled composite (ECC) L1(0) ordered, (001) oriented FePt (5nm)/Fe (5 nm) bit patterned media over a large area by diblock copolymer lithography. We formed the dot arrays of the copolymer directly on the magnetic film and used them as the etching mask. The average size of the ECC FePt/Fe pillars was about 32 nm, with a center to center distance of about 35 nm and a size distribution of about 8%. The perpendicular coercivity (H-c) of the ECC FePt/Fe patterned structures was about 4.3 kOe. Both the coercivity and the saturation field of the ECC FePt/Fe patterned structure were reduced by about 50% due to the exchange coupling between FePt and Fe in the FePt/Fe patterned structure compared to the FePt patterned structure with similar dot size and distribution. The thermal stability and gain factor of the FePt/Fe ECC structure were about 260 k(B)T and 1.35, respectively. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3562453]