Jiangsu Aoli New Materials Co.,Ltd , https://www.jsaolimaterials.com
Research progress on high spin Hall conductance of Dirac semi-metallic thin films
[ Instrument R & D of Instrument Network ] The spin orbit torque (SOT) effect of current in a strong spin orbit coupling material provides an ultra-fast and efficient way to manipulate the magnetic moment. It is to develop the next generation of spin logic and spin storage Important foundation. To apply this effect to current spintronics metal multilayer film devices, it is necessary to find materials with both large spin Hall angles and high electrical conductivity (ie, high spin Hall conductance).
Compared with the traditionally used Pt, W and other heavy metals, two-dimensional transition metal chalcogenide materials (TMDs) have more crystalline phases, symmetry, conductance, spin-orbit coupling strength, and energy band topological characteristics. Adjustable space has recently become an emerging system for studying the conversion between charge and spin (and pseudo-spin) degrees of freedom. Although many studies have found that materials such as MoS2 and WTe2 have large spin Hall angles, their relatively large resistance and difficulties in large-scale preparation of films with controllable thickness limit the practical application of the system. Dirac semi-metallic materials with high conductivity and spin-momentum locked topological surface states may overcome the above problems, but their spin orbital moment (SOT) effect has not been reported.
Recently, Xu Hongjun, a postdoctoral fellow in the M02 research group of the State Key Laboratory of Magnetism, Institute of Physics, Chinese Academy of Sciences / National Research Center for Condensed Matter Physics, Beijing, specially appointed researcher Yu Guoqiang, researcher Han Xiufeng and others successfully prepared large areas, high Controlled PtTe2 thin films and the first study of the spin-orbit torque effect of this second type of Dirac semimetal. Drawing on the preparation method of PtSe2 thin film, Pt thin films with different thicknesses can be transformed into [001] oriented PtTe2 thin films by annealing in tellurium vapor. Similar to the single-crystal PtTe2 nanoflakes reported in the literature, these PtTe2 thin films have high conductivity (~ 106 S / m) at room temperature. Because of the relative stability of PtTe2 in the atmosphere, a uniform, flat, and large-area PtTe2 thin film can be transferred to magnetron sputtering equipment to prepare spintronics devices. The systematic spin torque-ferromagnetic resonance measurement of the PtTe2 / Py heterojunction revealed that the PtTe2 film has a large spin orbital torque effect: Ignoring the loss of interface spin, the spin hall of PtTe2 at 5 nm The angle is in the range of 0.09-0.15, which is 1.5 to 2 times that of 4 nm Pt in the control experiment. From the experimental results of the non-monotonic change of spin orbit torque efficiency of PtTe2 with thickness, it can be speculated that the spin orbit torque generated by PtTe2 has two different sources of bulk state and surface state. Because of its high conductivity and large spin Hall angle, the spin Hall conductance of PtTe2 (0.2-1.6 × 105? / 2e Ω-1m-1) is the largest of the currently reported TMDs, and can even be compared with typical The topological insulator Bi2Se3 is comparable. Further vertical magnetic moment flip experiments also confirmed that PtTe2 has higher current-spin current conversion efficiency than Pt. The study shows that PtTe2 and Dirac semimetals are promising for low-power spin-orbit torque devices and other spintronics devices. This work also reveals the large-scale preparation, research, and application of 2D and topologies similar to PtTe2. Possibility of materials [HJ Xu, JW Wei, HG Zhou, JF Feng, T. Xu, HF Du, CL He, Y. Huang, JW Zhang, YZ Liu, H.-C. Wu, CY Guo, X. Wang , Y. Guang, HX Wei, Y. Peng, WJ Jiang, GQ Yu, * and XF Han, High Spin Hall Conductivity in Large-Area Type-II Dirac Semimetal PtTe2, Adv. Mater. 10 (2020) 2000513].
The research was supported by the Ministry of Science and Technology (Project No. 2017YFA0206200), the National Natural Science Foundation of China (Project Fund Nos. 11874409, 11674373, 51801087, 11804380) and the Chinese Academy of Sciences Key Frontier Science Research Program (Project No. QYZDJ-SSW-SLH016).