Magnetotransport Properties of Perpendicular [Pt/Co]/Cu/[Co/Pt] Pseudo-Spin-Valves

We studied the giant magnetoresistance (GMR) effect in [Co/Pt]₄/Co/Cu/Co/[Co/Pt]₄ pseudo-spin-valves with perpendicular magnetic anisotropy (PMA) and analyzed the impact of the Cu spacer layer thickness as well as the Co layer thickness at the Cu/Co interface. The magnetotransport measurements were carried out by a four-point probe method in current-in-plane geometry at room temperature and additionally by the van der Pauw method at low temperatures. The GMR ratio at room temperature can be almost doubled to ~1.5% by increasing the Co layer thickness to 10 Å at each side of the Cu spacer layer, while keeping all other thicknesses constant. Due to this relatively large single Co layer thickness, which reduces the perpendicular magnetic anisotropy, the magnetic reversal is driven by magnetostatic interactions, leading to the formation of vertically correlated magnetic domains. In addition, by tuning the PMA of both [Co/Pt] multilayers, the formation of magnetic domains in the soft layer can be achieved without affecting the hard layer, which stays uniformly magnetized, resulting in a GMR ratio of up to 1.6% at room temperature. Upon formation of vertically correlated domains, the GMR ratio will be reduced again.