Affiliation:
1. State Key Laboratory of Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 China
2. College of Materials Science and Opto‐Electronic Technology University of Chinese Academy of Sciences Beijing 100049 China
3. Cornell University Ithaca NY 14850 USA
4. Beijing National Laboratory for Condensed Matter Physics Institute of Physics University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing 100190 China
Abstract
AbstractSpin currents of perpendicularly polarized spins (z spins) have received blooming interest for the potential in energy‐efficient spin–orbit torque switching of perpendicular magnetization in the absence of a magnetic field. However, generation of z spins is limited mainly to magnetically or crystallographically low‐symmetry single crystals that are hardly compatible with the integration to semiconductor circuits. This work reports efficient generation of z spins in sputter‐deposited polycrystalline heavy metal devices via a new mechanism of broken electric symmetries in both the transverse and perpendicular directions. Both the damping‐like and field‐like spin–orbit torques of z spins can be tuned significantly by varying the degree of the electric asymmetries via the length, width, and thickness of devices as well as by varying the type of the heavy metals. The presence of z spins also enables deterministic, nearly‐full, external‐magnetic‐field‐free switching of a uniform perpendicularly magnetized FeCoB layer, the core structure of magnetic tunnel junctions, with high coercivity at a low current density. These results establish the first universal, energy‐efficient, integration‐friendly approach to generate z‐spin current by electric asymmetry design for dense and low‐power spin‐torque memory and computing technologies and will stimulate investigation of z‐spin currents in various polycrystalline materials.
Funder
National Key Research and Development Program of China
National Natural Science Foundation of China
U.S. Department of Energy