Strongly enhanced spin current in topological insulator/ferromagnetic metal heterostructures by spin pumping

摘要

Spin pumping effect in Bi_2Se_3/Fe_3Si and Fe/Bi_2Te_3 heterostructures was studied. High quality films of Bi_2Se_3(001) on ferromagnetic Fe_3Si(111) layer and Fe(111) films on Bi_2Te_3(001) layer were grown epitaxially by molecular beam epitaxy. Using a microwave cavity source, large voltages due to the Inverse Spin Hall Effect (V_(ISHE)) were detected in Bi_2Se_3(001)/Fe_3Si(111) bi-layer at room temperature. V_(ISHE) of up to 63.4 ± 4.0 μV at 100 mW microwave power (P_(MW)) was observed. In addition, Fe(111)/Bi_2Te_3(001) bi-layer also showed a large V_(ISHE) of 3.0 ± 0.1 μV at P_(MW) of 25 mW. V_(ISHE) of both structures showed microwave linear power dependence in accordance with the theoretical model of spin pumping. The spin Hall angle was calculated to be 0.0053 ± 0.002 in Bi_2Se_3 and was estimated to be 0.0068 ± 0.003 in Bi_2Te_3. The charge current density (J_c) of Bi_2Se_3/Fe_3Si and Fe/Bi_2Te_3 structures are comparable and are about 2-5 times higher than the Fe_3Siormal metal and Fe_3Si/GaAs results. The significant enhancement of spin current in topological insulator/ferromagnetic metal (TI/FM) and FM/TI bilayers is attributed to strong spin-orbit coupling inherent of TIs and demonstrates the high potential of exploiting TI-based structures for spintronic applications.