Current-driven domain wall motion in artificial magnetic domain structures
We report progress towards optimisation of artificial magnetic domain structures for efficient spin transfer torque domain wall (DW) motion. Co/Pt multilayer samples have been sputtered on (100) Si/SiO2 substrates and perpendicular magnetic anisotropy confirmed using polar magneto-optical Kerr effect (MOKE) measurements. The influence of the thickness of Co and Pt layers on the coercivity and switching behaviour was systematically investigated and the conditions established for realising well-suited structures with medium coercivity (∼100 Oe) and sharp switching fields. Optimised Co/Pt multilayer films have been lithographically patterned into nanowire devices for time-resolved extraordinary Hall effect (EHE) measurements. Our devices are based on 50 Ω coplanar waveguides incorporating single and double Hall cross structures. The coercivity of the region surrounding the Co/Pt Hall crosses was reduced by local focussed ion beam (FIB) irradiation allowing the controlled nucleation of domain walls at the edges of these regions by application of an appropriate field sequence. We describe polar MOKE experiments that show how DC currents lead to asymmetric switching of these artificial domains due to current-assisted DW motion across them.
KeywordsDomain wall motion Coercivity control Extraordinary hall effect
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- S. S. P. Parkin, US Patents Nos. 6.834.005, 6.898.132,6.920.062, 7.031.178 & 7.236.386 (2004–2007).Google Scholar