Article
Chemistry, Multidisciplinary
Shaojie Liu, Fengwei Guo, Peiyan Li, Gaoshuai Wei, Chun Wang, Xinhou Chen, Bo Wang, Weisheng Zhao, Jungang Miao, Li Wang, Yong Xu, Xiaojun Wu
Summary: The fashionable spintronic terahertz (THz) emission has opened up new pathways for contactless diagnosing femtosecond spin currents and presents a potential solution for improving THz efficiency through gold nanorods (GNRs) plasmonic resonances. Systematic investigations reveal the effectiveness of surface plasmon resonance in increasing THz emission from W/CoFeB/Pt heterostructures. Theoretical interpretations and numerical simulations semiquantitatively reproduce the experimental results, suggesting the potential for developing functional nano-THz optospintronic devices.
ADVANCED MATERIALS INTERFACES
(2022)
Article
Physics, Applied
Piyush Agarwal, Yingshu Yang, James Lourembam, Rohit Medwal, Marco Battiato, Ranjan Singh
Summary: A ferromagnetic metal is composed of localized electrons and conduction electrons that are coupled through strong exchange interaction. Non-equilibrium photoexcitation of the ferromagnetic thin films generates a transient spin current, which can be converted into a pulsed charge current and terahertz emission in the presence of a neighboring heavy metal layer. The proposed terahertz spintronic magnetometry tool allows reliable in-plane magnetization detection of ferromagnetic thin films and has technological importance in their characterization.
APPLIED PHYSICS LETTERS
(2022)
Article
Optics
Xiaoqiang Zhang, Yunqing Jiang, Yong Xu, Fengguang Liu, Guangghao Rui, Anting Wang, Weisheng Zhao
Summary: This Letter proposes a unidirectional spintronic terahertz emitter (USTE) that integrates a common STE with a metal grating to manipulate the THz emission process. Simulations show that the USTE has a unidirectional THz emission along the direction of the pump beam with a larger than 4-fold enhancement in intensity. The USTE also has the capability of tuning the central frequency and THz wave steering by adjusting the distance and angle between the STE and the metal grating.
Article
Physics, Applied
Zheng Feng, Hongsong Qiu, Dacheng Wang, Caihong Zhang, Song Sun, Biaobing Jin, Wei Tan
Summary: Despite the mature technology of microwave and infrared sources, there has been a lag in sources that can work well across the terahertz range, known as the THz gap. The emergence of a novel spintronic THz emitter (STE) has shown unique features and advantages, with the potential to develop new applications. Multidisciplinary efforts have been made to improve the performance of STE, which may inspire a variety of real-world applications in the near future.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Nanoscience & Nanotechnology
Hanbum Park, Kwangsik Jeong, InHee Maeng, Kyung Ik Sim, Sachin Pathak, Jonghoon Kim, Seok-Bo Hong, Taek Sun Jung, Chul Kang, Jae Hoon Kim, Jongill Hong, Mann-Ho Cho
Summary: Researchers induced dehybridization of ultrathin topological insulator films by breaking inversion symmetry between surfaces, leading to enhanced spin-charge conversion efficiency. By growing the film on an oxygen-deficient transition-metal oxide, they observed up to a 2.4 times increase in SCC efficiency through this method.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Optics
Yunqing Jiang, Hongqing LI, Xiaoqiang Zhang, Fan Zhang, Yong Xu, Yongguang Xiao, Fengguang Liu, Anting Wang, Qiwen Zhan, Weisheng Zhao
Summary: The Tamm plasmon coupling (TPC) between spin THz thin films and photonic crystal structures is achieved, resulting in enhanced THz radiation. Simulation results show that the absorptance of spin THz thin films with TPC can be increased from 36.8% to 94.3%. Experimental results demonstrate a 264% enhancement in THz radiation. This approach offers possibilities for ultrafast THz optospintronics and other similar devices.
PHOTONICS RESEARCH
(2023)
Article
Chemistry, Multidisciplinary
Mingyu Tong, Yuze Hu, Weibao He, Siyang Hu, Xiang'ai Cheng, Tian Jiang
Summary: This study proposes and experimentally validates coded terahertz emission, which achieves efficient generation and control of terahertz waves in the terahertz frequency band. By utilizing stripe-patterned ferromagnetic heterostructures as coding units, the states of the coding units can be switched by manipulating the optical field distribution, enabling terahertz coding and emission.
Article
Materials Science, Multidisciplinary
Yongshan Liu, Houyi Cheng, Yong Xu, Pierre Vallobra, Sylvain Eimer, Xiaoqiang Zhang, Xiaojun Wu, Tianxiao Nie, Weisheng Zhao
Summary: Spintronic thin films have been found to be high-performance broadband terahertz emitters, with emission mechanisms depending on the thickness of the ferromagnetic layer. The suppression of spin-charge conversion was observed when an ultrathin Al2O3 layer was inserted between the ferromagnetic and heavy metal layers, in agreement with theoretical predictions based on a simple spin-diffusion model.
Article
Nanoscience & Nanotechnology
Charlotte Bull, Simmone M. Hewett, Ruidong Ji, Cheng-Han Lin, Thomas Thomson, Darren M. Graham, Paul W. Nutter
Summary: Spintronic terahertz emitters, made of FM/NM thin films, show potential for use in THz time-domain spectroscopy and various applications. Researchers have been exploring optimal material combinations to enhance the amplitude and bandwidth of emitted THz pulses.
Editorial Material
Physics, Applied
Tom S. Seifert, Liang Cheng, Zhengxing Wei, Tobias Kampfrath, Jingbo Qi
Summary: This editorial reviews the recent developments and applications, current understanding of the physical processes, and future challenges and perspectives of broadband spintronic terahertz emitters.
APPLIED PHYSICS LETTERS
(2022)
Article
Optics
Zuanming Jin, Yan Peng, Yangyang Ni, Guanjie Wu, Bingyu Ji, Xu Wu, Zongzhi Zhang, Guohong Ma, Chao Zhang, Lin Chen, Alexey Balakin, Alexander P. Shkurinov, Yiming Zhu, Songlin Zhuang
Summary: This study demonstrates an efficient and practical approach to enhance and manipulate THz generation based on a cascaded Pt/CoFe/Ta trilayer fabricated on a flexible PET substrate. The cascaded design enables all THz emission from each PET/STE propagating almost in-phase and yields a 1.55 times amplification compared to a single PET/STE. Two proof-of-concept demonstrations highlight the potential of flexible PET/STE for building blocks of advanced functionalities.
LASER & PHOTONICS REVIEWS
(2022)
Article
Nanoscience & Nanotechnology
Tong Sun, Zhongyang Bai, Zhaoying Li, Yongshan Liu, Yaxuan Chen, Fan Xiong, Linliang Chen, Yong Xu, Fan Zhang, Dong Li, Junze Li, Weisheng Zhao, Tianxiao Nie, Lianggong Wen
Summary: Broadband spintronic terahertz radiation is efficiently generated by spin-to-charge current conversion in a ferromagnetic/nonmagnetic heterostructure. This study proposes a set of femtosecond laser-driven versatile spintronic terahertz devices by integrating meta-antenna structures with W/CoFeB/Pt nanolayer stacks. These monolithic integrated devices exhibit spintronic terahertz wave emission, spectral modulation, and polarization manipulation simultaneously.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Multidisciplinary Sciences
Valynn Katrine Mag-usara, Mary Clare Escano, Christopher E. Petoukhoff, Garik Torosyan, Laura Scheuer, Julien Madeo, Jessica Afalla, Miezel L. Talara, Joselito E. Muldera, Hideaki Kitahara, David R. Bacon, Makoto Nakajima, Keshav Dani, Evangelos Th. Papaioannou, Rene Beigang, Masahiko Tani
Summary: This study investigates the pump wavelength dependence of terahertz emission from an optimized Fe/Pt spintronic bilayer on MgO substrate. The results show the sensitivity of spintronic terahertz emission to both the optical absorptance of the heterostructure and the energy-dependent spin transport.
Article
Physics, Multidisciplinary
Yangkai Wang, Weiwei Li, Hao Cheng, Zheng Liu, Zhangzhang Cui, Jun Huang, Bing Xiong, Jiwen Yang, Haoliang Huang, Jianlin Wang, Zhengping Fu, Qiuping Huang, Yalin Lu
Summary: This study presents a spintronic terahertz (THz) emitter based on Pt0.93(MgO)0.07/CoFeB nanofilm, which achieves a 200% intensity enhancement compared to Pt/CoFeB. The authors find that the thickness of a Pt layer has a significant impact on the THz emission intensity, which is attributed to the combined effect of bulk spin Hall angle and interfacial skew scattering.
COMMUNICATIONS PHYSICS
(2023)
Article
Nanoscience & Nanotechnology
Yiwen Song, Zhihao Ji, Yu Zhang, Yuna Song, Ziyang Li, Jingying Zhang, Jiali Zhang, Zhiyao Jiang, Yaowen Liu, Qingyuan Jin, Zongzhi Zhang
Summary: This study investigates the THz emission in Pt/CoFe/Ru/CoFe/Pt films induced by femtosecond laser and reveals the effects of compensated and uncompensated magnetic moments. The THz amplitude significantly decreases in symmetric SAF films, while the asymmetric SAF structure is more favorable for enhanced THz emission.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Materials Science, Multidisciplinary
Franziska Martin, Kyujoon Lee, Maurice Schmitt, Anna Liedtke, Aga Shahee, Haakon Thomt Simensen, Tanja Scholz, Tom G. Saunderson, Dongwook Go, Martin Gradhand, Yuriy Mokrousov, Thibaud Denneulin, Andras Kovacs, Bettina Lotsch, Arne Brataas, Mathias Klaeui
Summary: We investigate the current-induced magnetisation manipulation in two-dimensional Fe3GeTe2 material and find that its crystalline structure allows for the presence of both interfacial and bulk spin-orbit torques, enabling efficient magnetisation switching without the need for complex multilayer engineering.
MATERIALS RESEARCH LETTERS
(2023)
Article
Physics, Applied
Marie-Luise Braatz, Nils-Eike Weber, Barthi Singh, Klaus Muellen, Xinliang Feng, Mathias Klaeui, Martin Gradhand
Summary: In this study, the structural and electronic properties of co-doped graphene were analyzed using Raman spectroscopy, magneto-transport, and Hall measurements. The results demonstrate the challenges in understanding the microscopic properties of graphene beyond simple preparation methods, as the introduction of dopants can have complex effects. Additionally, the inhomogeneities across individual graphene sheets pose challenges in interpreting measurements.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
I. Boventer, H. T. Simensen, B. Brekke, M. Weides, A. Anane, M. Klaeui, A. Brataas, R. Lebrun
Summary: Cavity spintronics is explored by studying the interaction between spintronic and quantum phenomena. Previous studies focused on the hybridization between magnons in ferromagnets and cavity photons. This study demonstrates the realization of antiferromagnetic cavity magnon polaritons. The interaction arises from the collective spin motion in single hematite crystals and the microwave field of integrated cavities. These findings show the potential for harnessing antiferromagnetic cavity magnon polaritons for coherent information exchange.
PHYSICAL REVIEW APPLIED
(2023)
Article
Physics, Applied
Hiroto Masuda, Yuta Yamane, Takeshi Seki, Klaus Raab, Takaaki Dohi, Rajkumar Modak, Ken-ichi Uchida, Jun'ichi Ieda, Mathias Klaui, Koki Takanashi
Summary: We report current-induced magnetization switching in Pt/Co/Ir/Co/Pt multilayers with different Ir layer thicknesses. The domain structures formed during switching vary depending on the magnetization alignment, either ferromagnetic or antiferromagnetic. Numerical calculations reveal the switching dynamics triggered by dual spin-orbit torques for both cases. Our findings deepen the understanding of the switching mechanism in magnetic multilayers and provide a pathway for designing spintronic devices with more efficient spin-orbit torque switching.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
H. Meer, O. Gomonay, A. Wittmann, M. Klaeui
Summary: Antiferromagnetic transition metal oxides are extensively studied in the field of spin-based electronics, commonly used as passive elements in exchange bias-based memory devices. Recent observations of long-distance spin transport, current-induced switching, and THz emission have renewed interest in these insulating materials, which are now considered attractive candidates for active elements in future spintronic devices. This article discusses promising materials systems and recent advances in reading and writing antiferromagnetic ordering, providing an overview of current research and potential future directions in the field of antiferromagnetic insulatronics.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Multidisciplinary
Eva Schmoranzerova, Jozef Kimak, Richard Schlitz, Sebastian T. B. Goennenwein, Dominik Kriegner, Helena Reichlova, Zbynek Soban, Gerhard Jakob, Er-Jia Guo, Mathias Klaeui, Markus Muenzenberg, Petr Nemec, Tomas Ostatnicky
Summary: All-optical ferromagnetic resonance (AO-FMR) is used to detect micromagnetic parameters in yttrium iron garnet (YIG) thin films with a metallic capping layer (Au, Pt) by triggering magnetization precession through heating of the metallic layer with femtosecond laser pulses. The laser-induced precession corresponds to a uniform (Kittel) magnon mode, allowing for the measurement of local magnetic properties with a resolution determined by the laser spot size.
NEW JOURNAL OF PHYSICS
(2023)
Article
Multidisciplinary Sciences
Zhizhong Zhang, Kelian Lin, Yue Zhang, Arnaud Bournel, Ke Xia, Mathias Klaeui, Weisheng Zhao
Summary: This study proposes a neural network based on magnon scattering modulated by an omnidirectional mobile hopfion in antiferromagnets. The states of neurons are encoded in the frequency distribution of magnons, and the connections between them are related to the frequency dependence of magnon scattering. By controlling the hopfion's state, hyperparameters in the network can be modulated, realizing the first verified well-functioning meta-learning device. This research not only breaks the connection density bottleneck but also provides a guideline for future designs of neuromorphic devices.
Article
Physics, Applied
G. Masciocchi, M. Fattouhi, E. Spetzler, M. -A Syskaki, R. Lehndorff, E. Martinez, J. McCord, L. Lopez-Diaz, A. Kehlberger, M. Klaeui
Summary: In this work, the authors propose a CMOS-compatible and inexpensive method for applying local strain on a Si/SiOx substrate. They demonstrate how the magnetoelastic energy landscape created by a pair of openings can be used to create pinning sites in a magnetic nanowire, leading to changes in the local magnetic anisotropy. The experimental results are supported by simulations and calculations, and the authors discuss the potential applications of this technology.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Oscar Lee, Robin Msiska, Maarten A. Brems, Mathias Klaeui, Hidekazu Kurebayashi, Karin Everschor-Sitte
Summary: Learning and pattern recognition require memory, which is simulated artificially in conventional CMOS hardware. Dynamical systems naturally provide the necessary memory, complexity, and nonlinearity for unconventional computing approaches. This article focuses on reservoir computing and provides an overview of key physical reservoir works, particularly in the promising platform of magnetic structures, such as skyrmions, for low-power applications. The article also discusses skyrmion-based implementations of Brownian computing, leveraging thermal fluctuations in skyrmion systems, and outlines the important challenges in this field.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Giovanni Masciocchi, Thomas J. Kools, Pingzhi Li, Adrien A. D. Petrillo, Bert Koopmans, Reinoud Lavrijsen, Andreas Kehlberger, Mathias Klaeui
Summary: In this work, the effects of strain on the perpendicular magnetic anisotropy and magnetization compensation of Co/Gd and Co/Gd/Co/Gd synthetic ferrimagnets are systematically studied. It is found that the presence of in-plane strain increases the perpendicular magnetic anisotropy in the bilayer system. The magnetization compensation of the quadlayer system is not altered by external strain, indicating the resilience of the Co/Gd ferrimagnets against strain. These findings make them suitable candidates for spintronics applications.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Physical
Yael Kapon, Fabian Kammerbauer, Shira Yochelis, Mathias Klaeui, Yossi Paltiel
Summary: Chiral molecules have the potential to create new magnetic devices by locally manipulating the magnetic properties of metallic surfaces. By chemisorbing onto ferromagnets, chiral polypeptides can induce magnetization locally through spin exchange interactions. In this study, magneto-optical Kerr microscopy was used to directly image surface magnetization changes induced by chiral molecules, demonstrating their ability to control and manipulate magnetization.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Physics, Multidisciplinary
Fabian Kammerbauer, Frank Freimuth, Robert Froemter, Yuriy Mokrousov, Mathias Klaeui
Summary: The Dzyaloshinskii-Moriya interaction (DMI) is crucial in the design of advanced spintronic devices, enabling the stabilization of domain walls and topologically non-trivial magnetic textures. This review focuses on the potential to manipulate DMI through electrical fields and currents, offering post-growth control over the sign and strength of DMI. The effects of currents and fields are discussed from both a theoretical and experimental perspective.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2023)
Article
Chemistry, Multidisciplinary
Fabian Kammerbauer, Won-Young Choi, Frank Freimuth, Kyujoon Lee, Robert Froemter, Dong-Soo Han, Reinoud Lavrijsen, Henk J. M. Swagten, Yuriy Mokrousov, Mathias Klaeui
Summary: The recently discovered interlayer Dzyaloshinskii-Moriya interaction (IL-DMI) in multilayers with perpendicular magnetic anisotropy can stabilize intriguing spin textures such as Hopfions. To control the IL-DMI, the influence of an electric current on a synthetic antiferromagnet with growth-induced IL-DMI was investigated. The study revealed that the azimuthal dependence of IL-DMI shifts with increasing current, suggesting the presence of an additional current-induced term that linearly increases the IL-DMI in the direction of current flow, opening the possibility of easily manipulating 3D spin textures by currents.
Article
Physics, Applied
Leo Schnitzspan, Mathias Klaeui, Gerhard Jakob
Summary: This study investigates nanosecond superparamagnetic switching in 50-nm-diameter in-plane magnetized magnetic tunnel junctions (MTJs). The circular superparamagnetic tunnel junctions (SMTJs) exhibit probabilistic switching of the magnetic free layer, which can be utilized for random number generation. A low-footprint CMOS circuit is proposed for fast and energy-efficient random-number generation, and the device design can be optimized based on the effects of spin-transfer torque and Joule heating.
PHYSICAL REVIEW APPLIED
(2023)
Article
Materials Science, Multidisciplinary
Arnab Bose, Fabian Kammerbauer, Rahul Gupta, Dongwook Go, Yuriy Mokrousov, Gerhard Jakob, Mathias Klaeui
Summary: We report and quantify a large orbital-Hall torque generated by Nb and Ru in this study, identified by the strong dependence of the torques on the ferromagnets. We observed a strong enhancement in the dampinglike torques measured in Nb (or Ru)/Ni bilayers compared to Nb (or Ru)/FeCoB bilayers, including a sign reversal in the case of Nb/(Ni or FeCoB) samples. Furthermore, we discovered a significant increase in the measured torques with the increase of ferromagnetic Ni thickness, which may indicate the unique signature of long-range action of the orbital-Hall torques.
