Article
Chemistry, Physical
Xiaoxiao Duan, Xuemei Chen, Dingzhang Wu, Chunjiang Lu, Xinpeng He, Shuming Ye, Feng Lin, Rongfei Wang, Chong Wang
Summary: Dilute magnetic MnGe quantum dots (QDs) have been widely studied for their potential applications in spintronics. However, their practical use at room temperature is limited due to the relatively low Curie temperature. In this study, Te-doped Mn0.064Ge0.895Te0.041/Si QDs were successfully prepared using the ion beam composite target sputtering technique. The growth temperature and deposition thickness were found to affect the density and magnetic properties of the QDs. The Te-doped QDs exhibited higher Curie temperature and magnetization due to the enhanced exchange coupling between holes and Mn atoms.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Nanoscience & Nanotechnology
Jin Wang, Yongkang Xu, Shuanghai Wang, Xingze Dai, Pengfei Yan, Jian Zhou, Ruifeng Wang, Yongbing Xu, Liang He
Summary: This research focuses on investigating the magneto-transport properties of 2D material CrTe2 and uncovers the mechanism behind its ferromagnetism, providing a theoretical foundation for its applications.
ADVANCED ELECTRONIC MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Weiyuan Wang, Jiyu Fan, Hao Liu, Huan Zheng, Chunlan Ma, Lei Zhang, Yunbin Sun, Caixia Wang, Yan Zhu, Hao Yang
Summary: The 2D layered Cr4Te5 epitaxial films prepared by pulsed laser deposition technique exhibit ferromagnetic ordering state up to 300 K and easily achieve epitaxial growth along a single orientation of the hexagonal Al2O3 (0001) substrate.
Article
Chemistry, Multidisciplinary
Jiyang Huang, Daichi Oka, Yasushi Hirose, Masamichi Negishi, Tomoteru Fukumura
Summary: We grew thin films of Ti0.95Co0.05O2-δ, a room-temperature ferromagnetic semiconductor, on rigid and flexible glass substrates using TiO2 seed layers. The thin films exhibited a preferred (101) orientation and large crystallographic domains of around 50 μm in lateral size, showing clear ferromagnetic hysteresis loops at 300 K. The films also had high electrical conductivity and transparency, allowing for electrical and optical detection of the ferromagnetic signal through the anomalous Hall effect and magneto-optical effect, respectively. Interestingly, flatter films with larger domains were obtained on flexible glass substrates, leading to higher conductivity and larger anomalous Hall signals comparable to epitaxial thin films.
Article
Materials Science, Multidisciplinary
Petter Strom, Sagar Ghorai, Tuan T. Tran, Daniel Primetzhofer
Summary: Ferromagnetic thin films were synthesized by implanting Fe ions into polycrystalline Pd, demonstrating the ability to engineer magnetic properties through controlling Fe concentration depth profiles. In-plane magnetic moments were measured under different sample temperature and applied magnetic field conditions, showing that all samples exhibited ferromagnetism at sufficiently low temperatures.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Chemistry, Physical
Yow-Jon Lin, Hsing-Cheng Chang, C. Y. Chuang, Ping-En Lu, Jing-Shiuan Huang
Summary: This study investigates the effect of graphene addition on the electrical and ferromagnetic properties of ZnO thin films. The results show that graphene doping increases the hole concentration in the thin film and enhances the intensity of the ferromagnetic signal.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Materials Science, Multidisciplinary
H. J. Waring, Y. Li, C. Moutafis, I. J. Vera-Marun, T. Thomson
Summary: Researchers have found that synthetic ferromagnets have a unique layer structure, where the dynamic response of the ferromagnetic layers is closely related to the difference in magnetization and interlayer coupling. Experimental results demonstrate that conventional acoustic and optical descriptions do not fully capture the complexities of synthetic ferromagnets' dynamics.
Article
Chemistry, Physical
Nalin Prashant Poddar, J. Arout Chelvane, N. D. Vara Prasad, M. Manivel Raja
Summary: In this paper, the relationship between the structure-magnetic microstructure and magnetic properties of sputtered Fe-Co-Al thin films at different thicknesses is investigated. The results show that the crystallinity and particle size of the films increase with the increase in film thickness. The magnetic properties, including saturation magnetization and coercivity, change with the film thickness due to the observed changes in the magnetic microstructure. Evaluation: 8/10.
SURFACES AND INTERFACES
(2023)
Article
Physics, Applied
Andrew W. Forbes, Niraj Bhattarai, Christopher Gassen, Raghad S. H. Saqat, Ian L. Pegg, John Philip
Summary: Thin films of ferromagnet Fe2Ge were successfully grown via molecular beam epitaxy, and their magnetic and electrical properties were measured experimentally. The material showed strong spin polarization, as indicated by the observed high-temperature maximum in the longitudinal resistivity and the suppression of electron-magnon scattering at low temperatures. Measurements of the Hall resistivity revealed contributions from both the ordinary and anomalous Hall effects, providing information about the charge carrier concentration and mobility. Additionally, small negative magnetoresistance was observed in both longitudinal and transverse geometries. Fe2Ge holds promise as a spintronic material due to its compatibility with semiconductors.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Multidisciplinary Sciences
David S. Knoche, Matthias Steimecke, Yeseul Yun, Lutz Muehlenbein, Akash Bhatnagar
Summary: This study investigates the evolution of bulk photovoltaic effect in BiFeO3 thin films under different polarization conditions, revealing anomalous characteristics in open-circuit voltages under circularly polarized light. Spatially-resolved Raman measurements further analyze the interaction between light and different domains.
NATURE COMMUNICATIONS
(2021)
Article
Nanoscience & Nanotechnology
Imran Khan, Javed Ahmad, Muhammad Ehsan Mazhar, Jisang Hong
Summary: By utilizing the magnetic proximity effect and biaxial strain, the magnetic ground state, band gap enhancement, and valley polarization in WSe2/CrSnSe3 heterostructures can be controlled. Different magnetic anisotropy and Curie temperatures were observed in pristine and strained structures. Strain also enhanced valley splittings, providing a potential method to tune the valley splitting in the heterostructures.
Article
Nanoscience & Nanotechnology
S. Azzawi, A. Umerski, L. C. Sampaio, S. A. Bunyaev, G. N. Kakazei, D. Atkinson
Summary: Previous theory suggested that different monolayers within transition metal ferromagnet thin-films contribute different amounts to the total ferromagnetic damping. This study aimed to investigate if electronic engineering of the higher damping regions through localized doping could reduce the thin-film damping. Theoretical analysis and experimental results for sputtered Co thin-films with locally doped upper and lower surface regions with Cr were presented, showing a reduction in damping with increasing local doping up to 30% Cr, and a further decrease in damping with higher local doping potentially due to changes in the film structure. This work paves the way for the creation of low-damping magnetic thin-films.
Article
Chemistry, Multidisciplinary
Shanquan Chen, Jhong-Yi Chang, Qinghua Zhang, Qiuyue Li, Ting Lin, Fanqi Meng, Haoliang Huang, Yangyang Si, Shengwei Zeng, Xinmao Yin, My Ngoc Duong, Yalin Lu, Lang Chen, Er-Jia Guo, Hanghui Chen, Chun-Fu Chang, Chang-Yang Kuo, Zuhuang Chen
Summary: The spin state of Co ions in epitaxial LaCoO3 thin films under tensile strain has been determined to have mixed high-spin and low-spin states, while it is practically a low-spin state under compressive strain. The identification of this spin state ratio explains the origin of ferromagnetism in LaCoO3 films. This study highlights the importance of spin state degrees of freedom and thin-film strain engineering in creating new physical properties that do not exist in bulk materials.
Article
Engineering, Electrical & Electronic
Derek A. Bas, Piyush J. Shah, Alexei Matyushov, Maksym Popov, Viktor Schell, Ramesh C. Budhani, Gopalan Srinivasan, Eckhard Quandt, Nian Sun, Michael R. Page
Summary: This study reports the first investigation of diverse ferromagnetic thin films using acoustically driven ferromagnetic resonance (ADFMR). Each magnetic material exhibits a unique ADFMR signature, showcasing different signal patterns and characteristics. The results demonstrate that strain-driven magnetization dynamics is a dynamic field with unexpected behavior in a variety of materials, highlighting the need for further research in this area.
IEEE TRANSACTIONS ON MAGNETICS
(2021)
Article
Chemistry, Multidisciplinary
Liguo Zhang, Toni Helm, Haicheng Lin, Fengren Fan, Congcong Le, Yan Sun, Anastasios Markou, Claudia Felser
Summary: The study demonstrates that doping with vanadium can effectively modify the band structure in magnetic topological insulators, leading to the enhancement of SdH oscillations and the induction of long-range ferromagnetic order. The angle-dependent SdH oscillations reveal their 2D nature and their connection to topological surface states. This tunability by doping and the coexistence of surface states with ferromagnetism highlight the potential of Sb2-xVxTe3 thin films in energy band engineering for quantum electronics and spintronics design.
ADVANCED MATERIALS
(2021)
Article
Computer Science, Hardware & Architecture
Advait Madhavan, Matthew W. Daniels, Mark D. Stiles
Summary: The research proposes to associate race logic with tropical algebra to build temporal circuits systematically, guiding the design of temporally coded tropical circuits. This allows for the expression of high-level timing-based algorithms and systematic exploration of race logic-based temporal architectures by leveraging temporal memory. A state machine operating purely on time-coded wavefronts is designed using analog memristor-based temporal memories for the implementation of a version of Dijkstra's algorithm, demonstrating the potential of temporal computing for significant energy and throughput advantages.
ACM JOURNAL ON EMERGING TECHNOLOGIES IN COMPUTING SYSTEMS
(2021)
Article
Physics, Applied
Yi Li, Chenbo Zhao, Vivek P. Amin, Zhizhi Zhang, Michael Vogel, Yuzan Xiong, Joseph Sklenar, Ralu Divan, John Pearson, Mark D. Stiles, Wei Zhang, Axel Hoffmann, Valentyn Novosad
Summary: This study demonstrates the electrical detection of magnon-magnon hybrid dynamics in YIG/Py thin film bilayer devices, where direct microwave current injection through the conductive Py layer excites the coupled hybrid modes. The phase resolution of the coupled dynamics is achieved by detecting spin rectification signals from the Py layer. Furthermore, the additional phase shift due to the perpendicular Oersted field on a nonlocally excited Py device is also revealed.
APPLIED PHYSICS LETTERS
(2021)
Article
Engineering, Electrical & Electronic
Qiming Shao, Peng Li, Luqiao Liu, Hyunsoo Yang, Shunsuke Fukami, Armin Razavi, Hao Wu, Kang Wang, Frank Freimuth, Yuriy Mokrousov, Mark D. Stiles, Satoru Emori, Axel Hoffmann, Johan Akerman, Kaushik Roy, Jian-Ping Wang, See-Hun Yang, Kevin Garello, Wei Zhang
Summary: Spin-orbit torque (SOT) is an emerging technology that allows efficient manipulation of spintronic devices, with interest expanding to various processes beyond electric field manipulation. In the past decade, research has focused on exploring materials for larger SOT efficiency. Recent developments have extended material research to include processes involving phonons, magnons, and heat.
IEEE TRANSACTIONS ON MAGNETICS
(2021)
Article
Physics, Applied
Jonathan M. Goodwill, Nitin Prasad, Brian D. Hoskins, Matthew W. Daniels, Advait Madhavan, Lei Wan, Tiffany S. Santos, Michael Tran, Jordan A. Katine, Patrick M. Braganca, Mark D. Stiles, Jabez J. McClelland
Summary: The increasing scale of neural networks and their expanding applications have led to a demand for more energy-efficient and memory-efficient artificial intelligence-specific hardware. To address the main issue of the von Neumann bottleneck, in-memory and near-memory architectures, as well as algorithmic methods, can be utilized. The low-power and binary operation of magnetic tunnel junctions (MTJs) have been leveraged for neural network hardware inference, showing the potential for efficient performance even with device imperfections.
PHYSICAL REVIEW APPLIED
(2022)
Article
Nanoscience & Nanotechnology
Axel Hoffmann, Shriram Ramanathan, Julie Grollier, Andrew D. Kent, Marcelo J. Rozenberg, Ivan K. Schuller, Oleg G. Shpyrko, Robert C. Dynes, Yeshaiahu Fainman, Alex Frano, Eric E. Fullerton, Giulia Galli, Vitaliy Lomakin, Shyue Ping Ong, Amanda K. Petford-Long, Jonathan A. Schuller, Mark D. Stiles, Yayoi Takamura, Yimei Zhu
Summary: Neuromorphic computing approaches are becoming increasingly important for efficiently processing large amounts of data. Quantum materials offer unique attributes that can enable new energy-efficient device concepts at the hardware level. This Perspective discusses select examples of these approaches and provides an outlook on the current opportunities and challenges for assembling quantum-material-based devices into larger complex network systems.
Article
Physics, Applied
Jonathan Gibbons, Takaaki Dohi, Vivek P. Amin, Fei Xue, Haowen Ren, Jun -Wen Xu, Hanu Arava, Soho Shim, Hilal Saglam, Yuzi Liu, John E. Pearson, Nadya Mason, Amanda K. Petford-Long, Paul M. Haney, Mark D. Stiles, Eric E. Fullerton, Andrew D. Kent, Shunsuke Fukami, Axel Hoffmann
Summary: Spin torque is a promising tool for driving magnetization dynamics for computing technologies. However, crystal symmetry limits the geometry of spin torques for most conventional spin source materials. Magnetic ordering reduces material symmetry and allows for the production of exotic torques, with antiferromagnets being particularly robust against external fields.
PHYSICAL REVIEW APPLIED
(2022)
Article
Materials Science, Multidisciplinary
Patrick Quarterman, Yabin Fan, Zhijie Chen, Christopher J. Jensen, Rajesh V. Chopdekar, Dustin A. Gilbert, Megan E. Holtz, Mark D. Stiles, Julie A. Borchers, Kai Liu, Luqiao Liu, Alexander J. Grutter
Summary: Using depth- and element-resolved characterization, this study investigates the antiferromagnetic coupling in Y3Fe5O12/permalloy and Y3Fe5O12/Co thin-film heterostructures. The results reveal that the choice of ferromagnet, seed layer, and substrate influences the sample structure and magnetic properties, leading to notable changes in interface coupling sign, magnetic reversal mechanisms, magnetic depth profiles, and domain structure.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Computer Science, Hardware & Architecture
Siyuan Huang, Brian D. Hoskins, Matthew W. Daniels, Mark D. Stiles, Gina C. Adam
Summary: The movement of large quantities of data during deep neural network training poses challenges for machine learning. Strategies such as functional memories based on flash, resistive switches, and magnetic tunnel junctions can store ultra-large models. However, new approaches are needed to minimize hardware overhead, especially for gradient information that cannot be efficiently stored in these memories.
ACM JOURNAL ON EMERGING TECHNOLOGIES IN COMPUTING SYSTEMS
(2023)
Article
Engineering, Electrical & Electronic
Prashansa Mukim, Pragya R. Shrestha, Advait Madhavan, Nitin Prasad, Jason Campbell, Forrest D. Brewer, Mark D. Stiles, Jabez J. McClelland
Summary: Allan deviation is a useful tool for characterizing the time-dependent noise in oscillators and determining its source characteristics. In this study, measurements on a 130 nm, 7-stage ring oscillator revealed that the Allan deviation exhibited expected behavior from 300 K to 150 K but unexpectedly increased from 150 K to 11 K. Further analysis showed that the measured Allan deviation at low temperatures could be well explained by a few random telegraph noise (RTN) sources, which play a significant role in low-frequency noise at lower temperatures.
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Fei Xue, Mark D. Stiles, Paul M. Haney
Summary: This paper investigates the mechanism of controlling magnetism through spin-orbit torque in ferromagnets, focusing on the two-dimensional monolayer ferromagnet Fe3GeTe2. The study finds that higher order terms play an important role in the magnetic dynamics in this material, enabling magnetic field-free electrical switching.
Article
Engineering, Electrical & Electronic
Nitin Prasad, Prashansa Mukim, Advait Madhavan, Mark D. Stiles
Summary: Simulations of complex-valued Hopfield networks based on spin-torque oscillators can recover phase-encoded images. Tunable delay elements implemented by phase shifting the oscillatory output of the oscillators provide complex weights in a set of memristor-augmented inverters. Pseudo-inverse training is used for storing multiple images, and the energy required for image recovery depends on the desired error level. The simulations show the network performs well when the resonant frequency of the oscillators can be finely tuned and have a small fractional spread, depending on the strength of feedback.
NEUROMORPHIC COMPUTING AND ENGINEERING
(2022)
Article
Materials Science, Multidisciplinary
Danijela Markovic, Matthew W. Daniels, Pankaj Sethi, Andrew D. Kent, Mark D. Stiles, Julie Grollier
Summary: Analytically showing that easy-plane spin Hall nano-oscillators excited by a spin current polarized perpendicularly to the easy plane have phase dynamics similar to Josephson junctions, suitable for neuromorphic computing. Utilizing a specific nanoconstriction geometry, the easy-plane spiking dynamics are maintained in an experimentally feasible architecture. Two elementary neural network blocks essential for neuromorphic computing are simulated, demonstrating the summing and injection of output spikes energies and the multiplication of outputs by synaptic weights.
Article
Materials Science, Multidisciplinary
Philippe Talatchian, Matthew W. Daniels, Advait Madhavan, Matthew R. Pufall, Emilie Jue, William H. Rippard, Jabez J. McClelland, Mark D. Stiles
Summary: Coupling SMTJs can lead to collective behavior beneficial for cognitive computing. By using a simple linear electrical circuit to mutually couple two SMTJs, the transitions of one SMTJ can affect the states of the other, resulting in significant correlation between the two devices.
Article
Materials Science, Multidisciplinary
H. Arava, F. Barrows, M. D. Stiles, A. K. Petford-Long
Summary: The study explores the role of using topology to stabilize different magnetic textures in a magnetic heterostructure, such as a vortex or an antivortex state. By controlling the magnetization configuration of nanomagnetic bars, a topological boundary condition can be set to match the topological state in the disk. The study also identifies conditions under which the boundary may fail, such as a critical angle between nanomagnets or certain separations and diameters.
Review
Engineering, Electrical & Electronic
J. Grollier, D. Querlioz, K. Y. Camsari, K. Everschor-Sitte, S. Fukami, M. D. Stiles
NATURE ELECTRONICS
(2020)
