[11p-E214-1~13] 10.1 Emerging materials in spintronics and magnetics (including fabrication and characterization methodologies)

3:30 PM - 3:45 PM JST(6:30 AM - 6:45 AM UTC)Presentation by Applicant for JSAP Young Scientists Presentation AwardEnglish Presentation

[11p-E214-8] A new half-Heusler topological semimetal for SOT – MRAM applications with improved spin Hall conductivity and low surface roughness

〇(M2)DaiHoangLong Trinh¹, HoangHuy Ho¹, NamHai Pham¹ (1.Science Tokyo)

Keywords:

half-Heusler alloy,Topological semimetal,Spin Hall effect

Ultrafast, ultralow-power spin-orbit torque (SOT) MRAM requires materials combining high electrical conductivity (σ), a large spin Hall angle (θ_SH), and CMOS back-end-of-line compatibility (withstanding up to 400°C). Highly conductive heavy metals (Ta, W, Pt) possess high thermal durability but insufficient θ_SH. Conversely, topological insulators like BiSb offer giant θ_SH and high σ, but melt at ~280°C. Topological semimetals like the half-Heusler alloy YPtBi endure up to 600°C and show a large θ_SH, but suffer from low σ. Simultaneous integration of large θ_SH, high σ, and sufficient thermal durability remains a key challenge.In this work, we study a new 3-element XYZ (Y ≠ Yttrium) half-Heusler topological semimetal featuring low surface roughness and improved spin Hall conductivity (σ_SH = θ_SH × σ). Single-phase (111) XYZ thin films with a 3.6 nm grain size were deposited at 400°C on sapphire substrates via co-sputtering. AFM confirmed an ultra-smooth surface, with an average roughness of just 0.3 nm for a 10-nm thick film.We evaluated the spin Hall angle and performed SOT magnetization switching using a c-plane Al₂O₃ substrate/XYZ(12.6 nm)/Pt(0.8 nm)/Co(0.8 nm)/Pt(0.8 nm) heterostructure. A large θ_SH = 4.3 was recorded, doubling that of YPtBi. Furthermore, we achieved SOT magnetization switching with a threshold current density of ~4.0 MA/cm² at 50 μs, which is at least an order of magnitude lower than conventional heavy metals.