title: Spin-torque generator engineered by natural oxidation of Cu.
abstract: The spin Hall effect is a spin-orbit coupling phenomenon, which enables electric generation and detection of spin currents. This relativistic effect provides a way for realizing efficient spintronic devices based on electric manipulation of magnetization through spin torque. However, it has been believed that heavy metals are indispensable for the spin-torque generation. Here we show that the spin Hall effect in Cu, a light metal with weak spin-orbit coupling, is significantly enhanced through natural oxidation. We demonstrate that the spin-torque generation efficiency of a Cu/Ni81Fe19bilayer is enhanced by over two orders of magnitude by tuning the surface oxidation, reaching the efficiency of Pt/ferromagnetic metal bilayers. This finding illustrates a crucial role of oxidation in the spin Hall effect, opening a route for engineering the spin-torque generator by oxygen control and manipulating magnetization without using heavy metals.
authors.affiliation: Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan.
authors.forename: Hongyu
authors.initials: H
authors.lastname: An
authors.affiliation: Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan.
authors.forename: Yuito
authors.initials: Y
authors.lastname: Kageyama
authors.affiliation: Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kanno
authors.affiliation: Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan.
authors.forename: Nagisa
authors.initials: N
authors.lastname: Enishi
authors.affiliation: Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan.|PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Ando