Magnetic Properties of Co/Pt Multilayer Dots.

We fabricated submicron Co/Pt multilayer circular dot arrays using the electron beam lithography and the lift-off technique. Perpendicular anisotropy (K1eff) of these dot arrays was controlled in the range of 6.0 to -2.0 × 106 erg/cc. We then investigated domain structures and switching processes of these dots using MFM and PMOKE. The domain structures of the dot array with K1eff = 6.0 × 106 erg/cc ( tCo = 0.5 nm) change from multi-domain to single-domain state as decreasing dot diameter to the domain size. The single-domain dots can take only two stable states (spin-up or -down) during the magnetization process, indicating that domain size in the continuous film is a key factor for designing bi-stable memory arrays and, moreover, that Co/Pt dots are good candidates as patterned memory elements.