Linear giant magnetoresistance behavior of submicron scale Co/Cu multilayer strips with antiferromagnetic coupling

Linear magntoresistance (MR) response of Co/Cu multilayer strips with sub-μm width has been performed with a field sensitivity of sub-Oe. The orthogonal spin orientation for neighboring Co layers is initiated with an additional external field applied along the short axis of the strip. The thickness of the Cu layer was optimized to be 2.1 nm, at which the MR ratio of the as grown sample took a maximum value. The MR ratio of the as-grown film of [Co(2 nm)/Cu(2.1 nm)]₃/ Co(2 nm)/Cu(2 nm) was 12.4%. The multilayer was patterned into strips with the pattern width w down to 0.2 μm by means of electron beam lithography and Ar ion milling. The measured maximum MR ratio of the strips with w = 0.4 and 0.2 μm were 9.3% and 8.2%, respectively. The observed parabolic MR profile shows good agreement with the micromagnetic simulation assuming the symmetric scissors motion of the magnetization in the multilayer. A linear MR response was observed in a giant MR strip with 0.4 μm width by applying alternating external fields, ranged from 0.1 to 10 Oe, under a transverse bias field of 300 Oe.