Tailoring of switching field in GdCo-based spin valves by inserting Co layer

Abstract GdCo(35 nm)/Co(1 ÷ 7 nm)/Cu(4 nm)/Co(7 nm) spin valves were prepared by magnetron sputtering. The Gd 23 Co 77 alloy with rare earth rich composition used in this study has a magnetization compensation temperature above room temperature. The effective composition of GdCo/Co exchange coupled bilayers changes from rare earth rich to transition metal rich compositions with the increase of Co layer thickness, leading to the change of giant magnetoresistance sign. The coercivity of GdCo/Co composite layer also changes. Consequently, the coercivity and the switching field of ferrimagnetic layer can be tailored by the insertion of thin Co layers of different thickness between the GdCo and Cu layers. In the present case, the switching field of GdCo/Co composite layer varied from 40 to 400 Oe.