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In this talk, we present enhanced spin and orbital torque efficiencies in well-engineered artificial heterostructures and alloy thin films, including topological insulator BiSb/Ti/NiFe heterostructures and nonequilibrium RuMo alloy thin films.
We investigated the effect of the Ti insertion layer on the torque efficiency of two series of samples, BiSb/NiFe and BiSb/Ti/NiFe, under as-deposited, room-temperature aging and annealing conditions. Samples with the Ti layer showed a multifold increase in torque efficiency compared to those without Ti insertion. Atomic resolution microstructural analysis clearly illustrates the interfacial chemistry where Ti effectively prevents the interdiffusion of Ni and Sb. This interfacial chemistry near Ti at the interface of BiSb/NiFe significantly enhances torque efficiency. On the other hand, epitaxial thin films of fully nonequilibrium hcp-Ru50Mo50(0001) nanoalloys were prepared as chemically disordered alloys with an expected negligible intrinsic SHE. Structural analysis confirmed epitaxial growth and atomic-scale alloying of the thin films. Unlike the modest torque efficiency (~0.4%) observed for Ru50Mo50/CoFeB, the torque efficiency for the Ru50Mo50/Ni bilayers reached approximately 30% with a long-range relaxation length. The observed large variation in torque efficiency with the ferromagnetic layer could be attributed to the OHE. Interestingly, a small torque efficiency was observed for Ru/Ni, indicating that the nonequilibrium Ru50Mo50 composition enhances the OHE. Furthermore, inserting a Ru layer between the Ru50Mo50 and Ni layers maintains and improves torque efficiency, indicating orbital transport through Ru. These results not only show the significance of artificially engineered heterostructures and nanoalloy thin films for potential applications in spin and orbital torque technologies., but also contribute to the understanding of the intricate relationships between nanostructures and spin-orbitronics.

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  ©公益社団法人 日本磁気学会 (The Magnetics Society of Japan)

Keyword: Spin-Orbit Torques, Artificial alloy thin films

Conference: 第48回日本磁気学会学術講演会 (2024-09-24 - 2024-09-27)

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Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.5079

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Updated at: 2024-12-03 16:31:01 +0900

Published on MDR: 2024-12-03 16:31:01 +0900