Pt-based multilayers toward energy-efficient spin–orbit torque devices

Abstract

The 5d transition metal Pt is widely recognized as a spin Hall material for generating spin–orbit torques (SOTs) in Pt/ferromagnetic (FM) heterostructures. Despite its low resistivity, it exhibits a damping-like SOT efficiency (ξDL) significantly lower than other well-studied SOT materials, such as W and Ta, limiting its practical applications. In this study, systematic investigations are conducted on the incorporation of various insertion layers, including oxides (NiO, MgO), transition metals (Ta, W, Nb), and FM materials (Co, CoFeB), to enhance ξDL without the need for co-sputtered alloy engineering. Notably, MgO insertion exhibits the most pronounced impact, offering a broad tuning window for the spin current source resistivity (ρSCS) ranging from 49.7 to 215.4 μΩ cm. An optimized ξDL of approximately 0.52 is achieved in the [Pt(0.6)/MgO(0.4)]5/Pt/Co/Pt configuration. Utilizing tilted anisotropy as a field-free solution, this multilayer design demonstrates a significantly reduced zero-thermal critical switching current density (Jc0 = 4.28 × 1010 A/m2) compared to pure Pt (Jc0 = 6.20 × 1011 A/m2), underscoring its potential for practical applications. The combination of high ξDL, moderate ρSCS, and low Jc0 collectively enhances energy efficiency and performance in SOT magnetic random-access memory and next-generation spintronic applications.