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  1. Free, publicly-accessible full text available December 1, 2023
  2. The electric field manipulates the spin chirality and skyrmion motion direction in a magnetic heterostructure.
    Free, publicly-accessible full text available February 17, 2024
  3. Free, publicly-accessible full text available December 1, 2023
  4. Abstract

    Recent advances in using topological insulators (TIs) with ferromagnets (FMs) at room temperature have opened an innovative avenue in spin‐orbit torque (SOT) nonvolatile magnetic memory and low dissipation electronics. However, direct integration of TIs with perpendicularly magnetized FM, while retaining an extraordinary charge‐to‐spin conversion efficiency (>100%), remains a major challenge. In addition, the indispensable thermal compatibility with modern CMOS technologies has not yet been demonstrated in TI‐based structures. Here, high‐quality integration of a perpendicularly magnetized CoFeB/MgO system with TI through a Mo insertion layer is achieved and efficient current‐induced magnetization switching at ambient temperature is demonstrated. The calibrated energy efficiency of TIs is at least 1 order magnitude larger than those found in heavy metals. Moreover, it is demonstrated that the perpendicular anisotropy of the integrated CoFeB/MgO system and the current‐induced magnetization switching behavior are well‐preserved after annealing at>350 °C, offering a wide temperature window for thermal treatments. This thermal compatibility with the modern CMOS back‐end‐of‐line process achieved in these TI‐based structures paves the way toward TI‐based low‐dissipation spintronic applications.

  5. Abstract

    Magnetic skyrmions are topologically nontrivial chiral spin textures that have potential applications in next‐generation energy‐efficient and high‐density spintronic devices. In general, the chiral spins of skyrmions are stabilized by the noncollinear Dzyaloshinskii–Moriya interaction (DMI), originating from the inversion symmetry breaking combined with the strong spin–orbit coupling (SOC). Here, the strong SOC from topological insulators (TIs) is utilized to provide a large interfacial DMI in TI/ferrimagnet heterostructures at room temperature, resulting in small‐size (radius ≈ 100 nm) skyrmions in the adjacent ferrimagnet. Antiferromagnetically coupled skyrmion sublattices are observed in the ferrimagnet by element‐resolved scanning transmission X‐ray microscopy, showing the potential of a vanishing skyrmion Hall effect and ultrafast skyrmion dynamics. The line‐scan spin profile of the single skyrmion shows a Néel‐type domain wall structure and a 120 nm size of the 180° domain wall. This work demonstrates the sizable DMI and small skyrmions in TI‐based heterostructures with great promise for low‐energy spintronic devices.