Topological insulators (TI) and magnetic topological insulators (MTI) can apply highly efficient spin‐orbit torque (SOT) and manipulate the magnetization with their unique topological surface states (TSS) with ultrahigh efficiency. Here, efficient SOT switching of a hard MTI, V‐doped (Bi,Sb)2Te3(VBST), with a large coercive field that can prevent the influence of an external magnetic field, is demonstrated. A giant switched anomalous Hall resistance of 9.2 kΩ is realized, among the largest of all SOT systems, which makes the Hall channel a good readout and eliminates the need to fabricate complicated magnetic tunnel junction (MTJ) structures. The SOT switching current density can be reduced to 2.8 × 105 A cm−2, indicating its high efficiency. Moreover, as the Fermi level is moved away from the Dirac point by both gate and composition tuning, VBST exhibits a transition from edge‐state‐mediated to surface‐state‐mediated transport, thus enhancing the SOT effective field to (1.56 ± 0.12) × 10−6 T A−1 cm2and the interfacial charge‐to‐spin conversion efficiency to 3.9 ± 0.3 nm−1. The findings establish VBST as an extraordinary candidate for energy‐efficient magnetic memory devices.
Giant spin-orbit torque (SOT) from topological insulators (TIs) provides an energy efficient writing method for magnetic memory, which, however, is still premature for practical applications due to the challenge of the integration with magnetic tunnel junctions (MTJs). Here, we demonstrate a functional TI-MTJ device that could become the core element of the future energy-efficient spintronic devices, such as SOT-based magnetic random-access memory (SOT-MRAM). The state-of-the-art tunneling magnetoresistance (TMR) ratio of 102% and the ultralow switching current density of 1.2 × 105 A cm−2have been simultaneously achieved in the TI-MTJ device at room temperature, laying down the foundation for TI-driven SOT-MRAM. The charge-spin conversion efficiency
- Award ID(s):
- 1935362
- NSF-PAR ID:
- 10307011
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 12
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Many key electronic technologies (e.g., large‐scale computing, machine learning, and superconducting electronics) require new memories that are at the same time fast, reliable, energy‐efficient, and of low‐impedance, which has remained a challenge. Nonvolatile magnetoresistive random access memories (MRAMs) driven by spin–orbit torques (SOTs) have promise to be faster and more energy‐efficient than conventional semiconductor and spin‐transfer‐torque magnetic memories. It is reported that the spin Hall effect of low‐resistivity Au0.25Pt0.75thin films enables ultrafast antidamping‐torque switching of SOT‐MRAM devices for current pulse widths as short as 200 ps. If combined with industrial‐quality lithography and already‐demonstrated interfacial engineering, an optimized MRAM cell based on Au0.25Pt0.75can have energy‐efficient, ultrafast, and reliable switching, for example, a write energy of <1 fJ (<50 fJ) for write error rate of 50% (<10−5) for 1 ns pulses. The antidamping torque switching of the Au0.25Pt0.75devices is ten times faster than expected from a rigid macrospin model, most likely because of the fast micromagnetics due to the enhanced nonuniformity within the free layer. The feasibility of Au0.25Pt0.75‐based SOT‐MRAMs as a candidate for ultrafast, reliable, energy‐efficient, low‐impedance, and unlimited‐endurance memory is demonstrated.
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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 (
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We offer a perspective on the prospects of ultrafast spintronics and opto-magnetism as a pathway to high-performance, energy-efficient, and non-volatile embedded memory in digital integrated circuit applications. Conventional spintronic devices, such as spin-transfer-torque magnetic-resistive random-access memory (STT-MRAM) and spin–orbit torque MRAM, are promising due to their non-volatility, energy-efficiency, and high endurance. STT-MRAMs are now entering into the commercial market; however, they are limited in write speed to the nanosecond timescale. Improvement in the write speed of spintronic devices can significantly increase their usefulness as viable alternatives to the existing CMOS-based devices. In this article, we discuss recent studies that advance the field of ultrafast spintronics and opto-magnetism. An optimized ferromagnet–ferrimagnet exchange-coupled magnetic stack, which can serve as the free layer of a magnetic tunnel junction (MTJ), can be optically switched in as fast as ∼3 ps. Integration of ultrafast magnetic switching of a similar stack into an MTJ device has enabled electrical readout of the switched state using a relatively larger tunneling magnetoresistance ratio. Purely electronic ultrafast spin–orbit torque induced switching of a ferromagnet has been demonstrated using ∼6 ps long charge current pulses. We conclude our Perspective by discussing some of the challenges that remain to be addressed to accelerate ultrafast spintronics technologies toward practical implementation in high-performance digital information processing systems.
