Role of Cu Layer on the Enhancement of Spin-to- Charge Conversion in Py/Cu/Bi2Se3

Abstract The enhancement of spin-to-charge conversion in Py/Cu/Bi2Se3 is achieved when increasing the Cu layer thickness up to 7nm. The conversion rate is studied using spin pumping technique. The inverse IEE length λIEE is found to increase up to ∼2.7nm when 7nm Cu layer is introduced. Interestingly, maximized λIEE is obtained when the effective spin mixing conductance (and thus Js) is decreased due to the Cu insertion. Monotonic increase of λIEE with decreasing Js suggests that IEE relaxation time τ is enhanced due to additional tunnelling barrier (Cu) that limits the interface transmission rate. The results have shown the importance of interface engineering in Py/TI magnetic heterostructure, which is the key factor for optimizing spin-to-charge conversion efficiency.