biostudies-literatureLee MHNational Research Foundation of KoreaSamsung Electronics21081https://www.ebi.ac.uk/biostudies/studies/S-EPMC8548299biostudies-literatureUnknown11(1)Quantifying the spin-orbit torque (SOT) efficiency with changing the layer thickness is crucial for understanding the physical background of SOT. This study investigates the Nb-thickness-dependent SOT efficiency of two types of layered heterostructures: Ta/Nb/CoFeB and Pt/Nb/CoFeB. We find that the Nb thickness dependence of the SOT efficiency in the two samples is quite different. In the Pt/Nb series, the SOT sign changes according to the thickness variation because Pt and Nb have different spin-orbit coupling signs. We observe the resulting reversal in switching polarity through current-induced SOT switching experiments. However, due to the same spin-orbit coupling signs of Ta and Nb, no such polarity reversal was observed in Ta/Nb series. Further, we extract the spin diffusion length of Nb in each heterostructure. These results provide a systematic understanding of the material- and thickness-dependent SOT characteristics.Scientific reportsSpin-orbit torques in normal metal/Nb/ferromagnet heterostructures.PMC85482992020M3F3A2A010825912021R1A6A3A130457162015M3D1A1070465IO201211-08104-01Lee MHKim TKim GWKim YKKim YJCha IHLee KJGo GfalseSpin-orbit torques in normal metal/Nb/ferromagnet heterostructures.Quantifying the spin-orbit torque (SOT) efficiency with changing the layer thickness is crucial for understanding the physical background of SOT. This study investigates the Nb-thickness-dependent SOT efficiency of two types of layered heterostructures: Ta/Nb/CoFeB and Pt/Nb/CoFeB. We find that the Nb thickness dependence of the SOT efficiency in the two samples is quite different. In the Pt/Nb series, the SOT sign changes according to the thickness variation because Pt and Nb have different spin-orbit coupling signs. We observe the resulting reversal in switching polarity through current-induced SOT switching experiments. However, due to the same spin-orbit coupling signs of Ta and Nb, no such polarity reversal was observed in Ta/Nb series. Further, we extract the spin diffusion length of Nb in each heterostructure. These results provide a systematic understanding of the material- and thickness-dependent SOT characteristics.2021-01-01T00:00:00Z2021 Oct2025-04-19T15:33:39.632Z2025-04-19T15:33:39.632ZS-EPMC85482993470294310.1038/s41598-021-99745-4