Patterning of planar magnetic nanostructures by ion irradiation

We have investigated the ultrahigh resolution of light ion irradiation indu ced magnetic patterning. High aspect ratio silica masks on Co/Pt multilayer s were obtained by e-beam lithography and reactive ion etching with feature sizes down to 30 nm for lines and 20 nm for dots. He+ ion irradiation of t he magnetic layers through these masks was used to pattern the magnetic pro perties. We chose irradiation irradiation conditions such that patterned ar eas had a coercive force three times lower than the protected areas. After mask removal, we obtained high resolution and high density, planar magnetic nanostructures. Magnetization reversal processes in the line patterns are analyzed with numerical simulations. We suggest that this irradiation induc ed magnetic patterning technique is promising for both present magneto-opti cal storage devices and future near field recording. (C) 1999 American Vacu um Society. [S0734-211X(99)16306-6].