Magnetic and magnetoresistive characterization of a top-pinned spin-valve with a multilayer with perpendicular-to-plane anisotropy deposited on top

Abstract

In this work, we have performed a first-order reversal curve study of the magnetization process of a top-pinned spin valve when a Pt/Co multilayer with perpendicular to plane anisotropy is deposited on top of the structure, near the pinned layer. We find that the magnetostatic interaction with the Pt/Co multilayer largely alters the magnetization process of both the pinned and the free layer of the spin valve, giving their magnetization a perpendicular-to-plane component, although some areas remain pinned in the plane. With this complex multilayer set, we fabricated nanostrips using a patterned Pt/Co multilayer on top of the spin valve as a pinning point for the magnetic domain wall traveling through the free layer. The Pt/Co feature on top of the spin valve strip pins the domain wall, although only in the return branch of the free layer magnetoresistance loop. The transport measurements show that the associated depinning field of the Pt/Co pinning feature is relatively weak. Nevertheless, the strong influence of the Pt/Co multilayer on the spin valve, visible in the magnetic characterization, indicates that this type of pinning defect may well be a good alternative in some spintronic devices, where the application requires adjusting the pinning strength of the local defects.