Large area patterning of single magnetic domains with assistance of ion irradiation in ion milling

This study demonstrates a pronounced ion irradiation effect in ion milling of magnetic thin films. In fabrication of bit-patterned media, the ion irradiation could facilitate bit island isolation before complete removal of magnetic materials by ion milling. Combined with block copolymer lithography, sub-20 nm CoPt dots with uniaxial perpendicular anisotropy, resembling Stoner–Wohlfarth-like single domains, were achieved. X-ray diffraction demonstrates that the degradation of the magnetic film by ion irradiation is related to crystal structure damage.