Switching field distribution of planar-patterned CrPt3 nanodots fabricated by ion irradiation

Planar-patterned CrPt3 ordered L12 nanodots with various bit sizes (D) from 220 to 55 nm were fabricated by the local irradiation of 30 keV of Kr+ ions not by conventional physical etching. Patterned nanodots with bit size ≤ 65 nm show either dark or bright contrast, suggesting that they have single domain structure. Switching field distribution of nanodots was studied by taking magnetic force microcopy images, in the progress of the magnetization reversal. As-prepared CrPt3 film exhibited perpendicular hysteresis loop with the coercivity of 5.5 kOe. Compared with the as-prepared film, the average switching field (Hsf) of the CrPt3 nanodots increased as 6.5, 8.5, and 9.2 kOe while the switching field distribution (ΔHsf) decreased as 6.8, 3.6, and 2.8 kOe, for the patterned nanodots with bit sizes of 220, 150, 65 nm, respectively. We found that the small ΔHsf/Hsf is possible in the high density planar bit patterned media fabricated by ion irradiation.