The Impact of NiO Interlayers and Annealing on Pt/Co for SOT-MRAM

In this work, the thickness dependence of NiO inserted at the Pt/Co interface was investigated. A detailed study of the magnetic, electric and structural properties with respect to annealing temperatures up to 400 °C was carried out. This annealing range is essential to ensure back-end-of-line (BEOL) compatibility for spin–orbit torque (SOT) magnetoresistive random-access memory (MRAM). Perpendicular magnetic anisotropy (PMA) was observed with a NiO interlayer and was further enhanced for all thicknesses by annealing. Upon annealing, intermixing between Co and NiO was observed, and the chemical roughness of this interface more than doubled. From SQUID magnetometry, the NiO appears superparamagnetic at room temperature. A four times increase in SOT efficiency was observed for annealed samples with 1.5–2.0 nm NiO insertions, where intermixing and increased interface roughness are present, thus introducing oxygen in Co. These findings highlight how oxygen-related interfacial chemistry strongly influences spin transport, which reflects the intricate nature of spin current behavior in multilayer systems. Altogether, the results demonstrate the importance of precisely controlling layer thickness, intermixing, interface roughness, and thermal treatment to optimize magnetic properties for applications such as SOT-MRAM.