Acquired Electronics360

Industrial Electronics

Researchers Develop Huge Breakthrough in Topological Insulator Based Devices

28 November 2017

The current-induced magnetization switching by spin-orbit torque (SOT) is an important ingredient for modern non-volatile magnetic devices, like magnetic random access memories and logic devices that are required for high-performance data storage and computing. Because of this, researchers around the world are actively searching for novel ways to reduce the present high switching current density in order to achieve highly efficient SOT-driven magnetization switching. Researchers from the National University of Singapore (NUS) have recently made a significant breakthrough in this field of research.

(A) Schematic diagram illustrating the Dirac cone of topological insulator and spin-momentum locking. (B) Topological insulator/ferromagnet (Bi2Se3/NiFe) spin-orbit torque devices. (C-E) Magneto-optic Kerr effect (MOKE) images of highly efficient spin-orbit torque driven magnetization switching in Bi2Se3/NiFe by a pulsed current at room temperature and zero-assistive magnetic field. Source: NUS(A) Schematic diagram illustrating the Dirac cone of topological insulator and spin-momentum locking. (B) Topological insulator/ferromagnet (Bi2Se3/NiFe) spin-orbit torque devices. (C-E) Magneto-optic Kerr effect (MOKE) images of highly efficient spin-orbit torque driven magnetization switching in Bi2Se3/NiFe by a pulsed current at room temperature and zero-assistive magnetic field. Source: NUS

Yang Hyunsoo, Associate Professor from the Department of Electrical and Computer Engineering and leader of the team, led this research to successfully demonstrate the first instance of room temperature magnetization switching driven by giant SOTs in topological insulator/conventional ferromagnetic (Bi2Se3/NiFe) heterostructures with a low current density. This can address the issue of scalability and high power consumption needed in modern spintronic devices.

Professor Yang said: “Our findings can solve the fundamental obstacle of a high switching current in present heavy metal based SOT applications, and this is a big step towards room temperature topological insulator based spintronic device applications with ultralow power dissipation and high integration density. We believe our work will greatly invigorate topological insulator-based global research activities from diverse disciplines."

Topological insulators are electronic materials that have a bulk band gap like an ordinary insulator, but also support conducting states on their surface, possessing a strong spin-orbit coupling and spin-momentum-locked topological surface states (TSS), on which the electron momentum and spin polarization directions are strongly locked.

"Due to spin-momentum-locked properties, as charge current flows in the TSS, all electron spins will be fully polarised in a perpendicular direction to the direction of the moving electron. Therefore, a very high efficient spin current generation and thus a giant SOT efficiency is expected in topological insulators," explained Dr. Zhu Dapeng, who is a co-first author of the study and a Research Fellow at the Department.

Taking advantage of TSS is a major part of realizing high-performance topological insulator based SOT devices. But in typical topological insulators like Bi2Se3, the parasitic bulk states and 2D electron gas can contaminate and/or wash out the high SOT efficiently in TSS dominated SOT effect in ultrathin Bi2Sefilms, exhibiting a large SOT efficiency up to 1.75 at room temperature, much larger than the values of ~0.01-0.3 in conventional used heavy metals.

In traditional heavy metal/ferromagnet SOT devices, the current density required for the magnetization switching is still high in the order of ~107-108 A/cm2 which hinders use in high-performance SOT applications.

The team demonstrated the high-efficient current-induced magnetization switching at room temperature using topological insulator Bi2Se3 with a conventional 3D ferromagnet NiFe (6nm), which is widely utilized in various industries.

"Our work successfully presents a significant reduction of switching current density for the magnetization switching by utilizing the giant SOT effect in Bi2Se3. The value is about 6×105A/cm2, which is almost two orders of magnitude smaller than that of heavy metals. This is a major milestone for the ultralow power consumption and high integration density SOT device applications. Moreover, our devices work robustly at room temperature, which breaks out the limit of ultralow working temperature in previous TI devices," said Dr. Wang Yi of the Department, who is the other co-first author of the study.

"Our magnetization switching scheme does not require an assistive magnetic field. This makes the topological insulator/ferromagnet material systems easy to integrate into the well-established industrial technology for magnetic devices," said Assoc Prof Yang.

From here on out, Yang and his team are conducting experiments to further decrease the switching current by further refining the materials and structures of the systems. They are also planning to incorporate and test the technology in core magnetic memory devices. The team hopes to work with industry partners to further explore various applications with the novel material systems.

The paper on this research was published in Nature Communications.

To contact the author of this article, email Siobhan.Treacy@ieeeglobalspec.com


Powered by CR4, the Engineering Community

Discussion – 0 comments

By posting a comment you confirm that you have read and accept our Posting Rules and Terms of Use.
Engineering Newsletter Signup
Get the Engineering360
Stay up to date on:
Features the top stories, latest news, charts, insights and more on the end-to-end electronics value chain.
Advertisement
Weekly Newsletter
Get news, research, and analysis
on the Electronics industry in your
inbox every week - for FREE
Sign up for our FREE eNewsletter
Advertisement

CALENDAR OF EVENTS

Date Event Location
23-27 Apr 2018 Oklahoma City, Oklahoma
10 May 2018 Pier 94
22-24 May 2018 Los Angeles, CA
04-07 Jun 2018 Boston, MA
06-08 Jun 2018 Los Angeles, CA
Find Free Electronics Datasheets
Advertisement