Enhancement of spin-orbit torque efficiency in <italic>B</italic>2-CoGa(Pt)/<italic>L</italic>1<sub>0</sub>-MnAl bilayers for high-density MRAM

<sec><p indent="0mm">Magnetic random-access memory (MRAM) has emerged as a leading candidate for next-generation storage technology, offering high speed, high density, non-volatility, low power consumption, and radiation resistance. MRAM has evolved through three generations: field-driven toggle MRAM, spin-transfer torque (STT)-MRAM, and the experimental spin-orbit torque (SOT)-MRAM. The current commercial MRAM products primarily rely on STT-MRAM, which is based on Ta/CoFeB/MgO multilayers with the interfacial perpendicular magnetic anisotropy (PMA). However, STT-MRAM performance deteriorates at sub<sc>-10 nm</sc> size due to thermal instability. In contrast, the tetragonal Mn-based binary alloys exhibit stable bulk PMA and enhanced properties for sub<sc>-10 nm</sc> tunnel junction devices. Previous research has demonstrated the potential of these alloys for high-density MRAM, with magnetization switching achieved via SOT without the need for external magnetic fields. Among Mn-based binary alloys, <italic>L</italic>1₀-MnAl stands out due to its strong PMA, high spin polarization, and low magnetic damping, making it a promising material for next-generation MRAM. On the other side, the <italic>B</italic>2-CoGa alloy serves as both an ideal buffer layer and a spin current source for the epitaxial growth of PMA <italic>L</italic>1₀-MnAl thin films on GaAs substrates. Our study demonstrates that doping <italic>B</italic>2-CoGa with Pt significantly enhances the SOT efficiency in (CoGa)_{1−<italic>x</italic>}Pt<italic>_x</italic>/<italic>L</italic>1₀-MnAl bilayers while preserving the excellent PMA properties of <italic>L</italic>1₀-MnAl. </sec><sec> Experimental results show that Pt doping up to <italic>x</italic> = 0.1 keeps the PMA characteristics while simultaneously reducing the critical current density required for magnetization switching from <sc>4.63×10⁷ A/cm²</sc> to <sc>2.59×10⁷ A/cm².</sc> SOT efficiency increases from 0.042 to 0.080. This enhancement is attributed to the increased resistivity of the (CoGa)_{1−<italic>x</italic>}Pt<italic>_x</italic> layer, which does not compromise its effective spin Hall conductivity. The optimized bilayer, with <italic>x</italic> = 0.075, supports magnetic tunnel junctions with lateral size as small as <sc>8.09 nm,</sc> reducing power consumption by 37%. The SOT effect utilizes spin currents generated by phenomena such as the spin Hall effect to switch local magnetization in adjacent ferromagnetic layers. The damping-like SOT efficiency (<italic>ξ</italic>_DL), a crucial parameter for reducing device power consumption, is influenced by both spin Hall conductivity and resistivity of the material. The introduction of Pt impurities into (CoGa)_{1−<italic>x</italic>}Pt<italic>_x</italic> bilayers optimizes this balance, significantly enhancing <italic>ξ</italic>_DL. Compared to traditional heavy metals used as buffer layers, the (CoGa)_{1−<italic>x</italic>}Pt<italic>_x</italic> layer provides better lattice matching with Mn-based binary alloys, preserving their crystalline quality and PMA. This work systematically investigates the structural, magnetic, and SOT-driven magnetization switching properties of epitaxially grown (CoGa)_{1−<italic>x</italic>}Pt<italic>_x</italic>/<italic>L</italic>1₀-MnAl bilayers, focusing on the dependence of magnetization switching on Pt concentration. Deterministic SOT-induced switching is achieved for <italic>x</italic> ≤ 0.1, with optimal PMA and SOT performance observed at <italic>x</italic> = 0.075. These results demonstrate the feasibility of incorporating Pt-doped CoGa layers into MRAM designs to enhance performance and scalability. This study provides valuable insights into improving SOT efficiency in Mn-based MRAM structures by incorporating Pt-doped CoGa buffer layers. These findings contribute to the development of high-density, high-performance MRAM devices with reduced power consumption. </sec>