Maximizing the spin Hall ratio of Pt: Trade-off between intrinsic spin Hall conductivity and carrier lifetime

Spin Hall metals with high spin-torque efficiencies and relatively low resistivities are key for developing practical spin-orbit torque technologies (e.g. memories, oscillators, and logic). Pt-based spin Hall metals are the most attractive for such applications due to their relatively low resistivity, giant intrinsic spin Hall conductivity, easy growth, and ability to be readily integrated into experimental and/or manufacturing processes. This talk will report on an unambiguous determination of the intrinsic nature of spin Hall effect in Pt [1] and how the intrinsic spin Hall conductivity and spin Hall ratio of Pt varies with carrier lifetime, strain, and interruption of crystal order [2,3]. Based on this physical understanding, we have developed several low-resistivity spin Hall metals for spin-orbit torque technologies whose power consumption is estimated to be only 1% of that of the topological insulator Bi_xSe_1-x [4] based devices.
[1] L. Zhu et al., Sci Adv. 5, eaav8025 (2019).
[2] L. Zhu et al., Phys. Rev. Appl. 11, 061004 (2019).
[3] L. Zhu, R.A. Buhrman, Phys. Rev. Appl. (2019), in press. arXiv:1908.06528.
[4] M. DC et al., Nat. Mater. 17,800-807 (2018)