Direct magnetic patterning of nonferromagnetic Co-C thin films by electron-beam radiation

Non-ferromagnetic Co-C thin films were magnetically patterned by electron-beam direct writing. Co₅₀C₅₀ films with thickness of 30-60 nm were prepared by alternately sputtering Co and C films onto C-buffered glass substrates. The as-deposited Co₅₀C₅₀ films are amorphous and nonferromagnetic. Magnetic patterning of the as-deposited Co₅₀C₅₀ film was realized by subjecting it to electron-beam radiation using a focused 30kev beam with a current of 6.6 nA and a dwell time per dot of 3.8 s and longer. The smallest magnetic dot diameter produced by a dwell time per dot of 3.8 s is about 270 nm. The magnetic dot diameter increases linearly with the square root of dwell time per dot, which implies that the magnetic dots are produced by heat-conduction-induced phase change in the film. The magnetic measurements show that the dots are magnetically soft. The present nanolithography is potentially a flexible alternative to fabricate patterned magnetic nanostructures for submicrometer magnetic devices.