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In a recent study, Professor Gang Xiao and his collaborators have explored the potential of emergent magneto-inductance (EML) in the context of miniaturizing magnetic devices without compromising their performance. By focusing on thin films of Permalloy deposited on polycarbonate substrates, they have identified a stepwise magnetic field-induced EML effect that shows promise for practical applications.

Their observations at room temperature reveal a notable inductance variation in these materials, exceeding 1 microhenry (µH). Interestingly, the inductance exhibits a reversal near zero magnetic field, a finding that could have intriguing applications in the design of magnetic devices.

The study investigates how the EML effect varies with changes in frequency, magnetic field steps, and the width of the film. These variations align with theoretical predictions based on the spin motive force, suggesting that the transient motion of domain walls may play a key role in this phenomenon.

This work represents a step toward enhancing the flexibility and efficiency of magnetic devices, opening up a venue into the future possibilities that lie at the intersection of fundamental physics and technological innovation.

Recently, the Xiao Group has made a pivotal breakthrough in understanding the electronic noise of a single skyrmion, a microscopic swirling magnetic texture with potential for next-generation computing technologies. The study, published in Physical Review B, delves into how skyrmions interact with materials disorder and external perturbations, revealing distinct noise signatures across different pinning regimes. This insight is crucial for developing low-noise, reliable skyrmion-based devices, marking a significant step towards harnessing skyrmions for advanced applications in data storage, logic circuits, and beyond.

The Xiao Group has recently published an insightful Perspective article in APL Materials, exploring the fascinating realm of spin textures in synthetic antiferromagnets (SAFs).

Spin textures, including magnetic domain walls and skyrmions, hold immense promise for revolutionizing electronic devices by encoding information bits.

While ferromagnetic films have shown potential in device prototypes, their widespread implementation has been hindered by material-related limitations. However, antiferromagnetic spin textures present a viable solution to many of these challenges, offering a pathway to faster, smaller, more energy-efficient, and robust electronics.

Synthetic antiferromagnets, characterized by multiple magnetic layers separated by spacers, serve as a platform for manipulating the functionality of spin textures using different materials and interface engineering techniques.

In the Perspective article, the authors extensively examine the challenges and opportunities associated with spin textures in synthetic antiferromagnets. They propose potential directions for future research in this exciting field, shedding light on the advantages of spin textures in SAFs compared to their ferromagnetic counterparts. Notably, they highlight the benefits of smaller size, higher mobility, and the vanishing skyrmion Hall effect. The researchers also discuss the potential of utilizing magnetic multilayers that combine both interfacial and interlayer Dzyaloshinskii-Moriya interactions (DMIs), which present a promising avenue for constructing three-dimensional spin textures. Furthermore, they delve into the incorporation of significant interlayer DMIs in SAFs, which can enhance their nontrivial responses to external stimuli.

The authors believe that spin textures possess the potential to revolutionize the landscape of next-generation beyond-CMOS data storage, logic, probabilistic computing, and neuromorphic computing devices. The ongoing advancements in spin textures within SAFs are poised to significantly broaden the scope of spintronic applications.

This Perspective article provides valuable insights and paves the way for future developments in spin textures and their transformative impact on electronic technologies.

This work is supported by the National Science Foundation under Grant No. DMR-2202514.

The 2023 edition of IMPACT Research at Brown magazine describes recent research on magnetic skyrmions from the Xiao Group on P. 45.

“Physics department interim chair Gang Xiao, professor of physics and engineering, is building devices that generate skyrmions—disk-like magnetic swirls in two-dimensional metallic films—that can change their polarity, motion, and size when exposed to a magnetic field or an electric current. Xiao is already using skyrmions to generate truly random numbers, which might be useful in cybersecurity and encryption, yet he has his sights set higher. Arrays and networks of skyrmions, he said, could form the basis for tiny yet incredibly efficient computers.

“If you built a silicon computer that mimics the human brain, you’d need a nuclear power plant to run it. But humans only need about ten watts of energy to power our brains. Skyrmions could bring us a lot closer to that sort of fast, low-power computation”, said Xiao.

IMPACT, an annual publication from the Office of the Vice President for Research at Brown University, illuminates the trailblazing work of researchers who are pushing boundaries in their respective fields. This sixth issue of IMPACT continues its tradition of spotlighting influential research contributing to global advancement.

In a recent gathering of the Physics Department, faculty, staff and students came together to express their heartfelt appreciation for Professor Gang Xiao, who will be stepping down as the Interim Chair of the department on June 30, 2023. The gathering served as an opportunity to recognize Professor Xiao’s exceptional service following the untimely passing of the department’s former chair, Professor Meenakshi Narain. The presence of Brown’s Interim Provost, Professor Lawrence Larson, further highlighted the significance of Professor Xiao’s leadership and service during this challenging period.

Amidst the gathering, Professor Xiao humbly conveyed his sincere gratitude to the entire physics community. He emphasized the vital role played by every member of the department in ensuring a smooth transition after the tragic loss of the department’s beloved Chair Narain. Their dedication and collaboration were pivotal in upholding the department’s mission.

As Professor Xiao concludes his tenure as Interim Chair, he looks forward to dedicating himself to research and teaching. His passion for scientific exploration and discovery, coupled with his commitment to training future scientists and engineers, will be the driving force behind his endeavors moving forward.

Junhang Duan, a talented master student researcher from Professor Xiao’s Group, has been recognized with the ScM Research Excellence Award by the Physics department. Her research on the physics of magnetic skyrmion and domain wall motion, conducted under the guidance of Professor Gang Xiao, has earned her this well-deserved recognition.

Upon completing her master’s studies, Junhang will continue her academic journey as a PhD student at Northwestern University, beginning this Fall semester.

Congratulations to Junhang on this significant achievement, and we wish her the best of luck in her future research endeavors at Northwestern!

Professor Xiao gave a lecture for the “Frontiers of Condensed Matter Physics” (FCMP) Columbia 2023 Spring Series on April 3rd, 2023. The lecture, titled “Generating true random numbers with single skyrmions: exploring local dynamics and skyrmion interactions”, is part of a lecture series featuring leading CMP-AMO researchers sharing their latest findings and insights.

About FCMP: Since 2011, Columbia University has been hosting the “Frontiers of Condensed Matter Physics (FCMP) Lectures” to bring in leading CMP/AMO researchers and provide a platform for them to present their latest research to a diverse audience comprising graduate students, postdocs, and senior researchers. The lectures aim to be historically, pedagogically, and intuitively presented to enable even entry-level CMP graduate students to enjoy and gain valuable insights from them.

In response to the ongoing pandemic, the lectures have been moved fully online since 2020, and recordings of the lectures are made available to subscribed students and interested observers from the research community. The FCMP is organized by Professor Yasutomo Uemura of Columbia University. The 2023 Spring series is co-hosted by Professors Philip Kim (Harvard), Pengcheng Dai (Rice), Liuyan Zhao (Michigan), and Weiwei Xie (Michigan State), who circulate flyers among their groups and institutions and recommend speakers. The lecture series promises to be an exciting and informative event for all those interested in the latest developments in condensed matter physics.

On March 8, 2023, Professor Xiao gave an invited talk at the APS March Meeting 2023 in Las Vegas, NV. The talk was part of Session M44 on Topological Magnetic Textures and was titled “Single skyrmion true random number generator using local dynamics and interaction between skyrmions”.

During the talk, Professor Xiao discussed the creation of a single skyrmion true random number generator, which utilizes local dynamics, and a multi-skyrmion system whose dynamics is influenced by the interaction between skyrmions. This new physics could have implications for a range of fields, from cryptography to probabilistic computing.

The video recording of Professor Xiao’s talk is available till June 20, 2023 on APS March Meeting website. Access to the recording requires APS March Meeting registration.

This innovative research represents an exciting advancement in the field of topological magnetic textures, and we look forward to seeing how this technology will be utilized in the future.

The research was supported by the National Science Foundation (OMA-1936221).

Magnetic skyrmions are tiny magnetic swirls that hold great potential in innovative electronic devices owing to their desirable properties of long-term stability, small size, and highly efficient controllability by various external stimuli. In this recently published review, we address the fundamental physics of the static, global and local dynamic properties of skyrmions and provide an overview of recent advances in computational models that utilize these unique properties. A discussion on the challenges lying ahead is also provided.

For more information, click here.

A research group, including Brown University Professor of Physics and Engineering Gang Xiao, has successfully observed the world’s largest tunnel magnetocapacitance (TMC) ratio and explained its mechanism. In addition to Xiao, the international collaborative was comprised of Kenta Sato, a second-year master’s student at Keio University’s Graduate School of Science and Technology in Japan, Hideo Kaiju, Associate Professor at Keio University’s Faculty of Science and Technology, and colleagues including Hiroaki Sukegawa, Principal Researcher at the National Institute for Materials Science in Japan.

TMC is a phenomenon in which capacitance (electrical capacitance, or the amount of electricity that a system can store) changes based on a magnetic field. This phenomenon is observed in textured magnetic tunnel junctions (MTJs) with a thin insulating layer between two magnetic layers. Until now, the largest observed TMC ratio, a figure-of-merit on magnetic sensitivity, has been 332%. In this study, researchers achieved the world’s largest TMC ratio of 426% by using an insulation tunneling layer and applying voltage biasing. Furthermore, they explained the mechanism behind this phenomenon using dielectric theory, which incorporates quantum mechanics and statistical theory.

These results pave the way for creating new capacitance-detecting, high-performance magnetic sensors and magnetic memory devices. They are also expected to be applied in next-generation Internet of Things (IoT) technology—a major driver of the Digital Age—and to make significant contributions to the acquisition, accumulation, and analysis of big data. In the future, these findings are expected to be put to practical use not only in the Information Technology/Information and Communication Technology (IT/ICT) field but also in a wide range of other fields, including environmental energy, healthcare, health sciences, transportation, agriculture, and manufacturing.

The research results were published online in Scientific Reports (via Springer Nature Group) on May 16, 2022.