<p>Current-induced spin-orbit torque at heavy metal/ferromagnet interfaces plays a critical role in modern spintronics. The challenges in relevant research are to enhance the conversion efficiency and generate unconventional torque components. Here, we propose a simple protocol to meet such demands by engineering symmetrical structures, specifically by a wedge-shaped topological material interface in Bi<sub>2</sub>Te<sub>3</sub>/CoFeB heterostructures. The symmetry of the topological interface is manipulated to lead to unconventional emergences of both the out-of-plane and in-plane spin polarizations. Torque measurements show that these polarizations have conversion efficiencies up to 10%, characterized by the nonreciprocal ferromagnetic resonance spectra and the distinctive torque profile. The observed enhancement in the unconventional spin-orbit torque is attributed to the wedge-oriented symmetry reduction of the spin-momentum locking structure of interfacial Dirac fermions. This advance opens avenues for designing geometrically characteristic spintronics devices, demonstrating the potential of using multidirectional spin-orbit torques for forthcoming nanotechnological applications.</p>

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Symmetry-reduced topological interface for unleashing a multidirectional spin-orbit torque

  • Satoshi Sugimoto,
  • Yasufumi Araki,
  • Yukiko K. Takahashi,
  • Jun’ichi Ieda,
  • Shinya Kasai

摘要

Current-induced spin-orbit torque at heavy metal/ferromagnet interfaces plays a critical role in modern spintronics. The challenges in relevant research are to enhance the conversion efficiency and generate unconventional torque components. Here, we propose a simple protocol to meet such demands by engineering symmetrical structures, specifically by a wedge-shaped topological material interface in Bi2Te3/CoFeB heterostructures. The symmetry of the topological interface is manipulated to lead to unconventional emergences of both the out-of-plane and in-plane spin polarizations. Torque measurements show that these polarizations have conversion efficiencies up to 10%, characterized by the nonreciprocal ferromagnetic resonance spectra and the distinctive torque profile. The observed enhancement in the unconventional spin-orbit torque is attributed to the wedge-oriented symmetry reduction of the spin-momentum locking structure of interfacial Dirac fermions. This advance opens avenues for designing geometrically characteristic spintronics devices, demonstrating the potential of using multidirectional spin-orbit torques for forthcoming nanotechnological applications.