Journal articles: 'THz Spintronic'

1

Wang, Maorong, Yifan Zhang, Leilei Guo, Mengqi Lv, Peng Wang, and Xia Wang. "Spintronics Based Terahertz Sources." Crystals 12, no. 11 (November 18, 2022): 1661. http://dx.doi.org/10.3390/cryst12111661.

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Terahertz (THz) sources, covering a range from about 0.1 to 10 THz, are key devices for applying terahertz technology. Spintronics-based THz sources, with the advantages of low cost, ultra-broadband, high efficiency, and tunable polarization, have attracted a great deal of attention recently. This paper reviews the emission mechanism, experimental implementation, performance optimization, manipulation, and applications of spintronic THz sources. The recent advances and existing problems in spintronic THz sources are fully present and discussed. This review is expected to be an introduction of spintronic terahertz sources for novices in this field, as well as a comprehensive reference for experienced researchers.

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Kumar, Sandeep, and Sunil Kumar. "Ultrafast light-induced THz switching in exchange-biased Fe/Pt spintronic heterostructure." Applied Physics Letters 120, no. 20 (May 16, 2022): 202403. http://dx.doi.org/10.1063/5.0091934.

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The ultrafast optical control of magnetization in spintronic structures enables one to access to the high-speed information processing, approaching the realm of terahertz (THz). Femtosecond visible/near-infrared laser-driven ferromagnetic/nonmagnetic metallic spintronic heterostructures-based THz emitters combine the aspects from the ultrafast photo-induced dynamics and spin-charge inter-conversion mechanisms through the generation of THz electromagnetic pulses. In this Letter, we demonstrate photoexcitation density-dependent induced exchange-bias tunability and THz switching in an annealed Fe/Pt thin-film heterostructure, which otherwise is a widely used conventional spintronic THz emitter. By combining the exchange-bias effect along with THz emission, the photo-induced THz switching is observed without any applied magnetic field. These results pave the way for an all-optical ultrafast mechanism to exchange-bias tuning in spintronic devices for high-density storage, read/write magnetic memory applications.

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Wu, Weipeng, Charles Yaw Ameyaw, Matthew F. Doty, and M. Benjamin Jungfleisch. "Principles of spintronic THz emitters." Journal of Applied Physics 130, no. 9 (September 7, 2021): 091101. http://dx.doi.org/10.1063/5.0057536.

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Schneider, Robert, Mario Fix, Jannis Bensmann, Steffen Michaelis de Vasconcellos, Manfred Albrecht, and Rudolf Bratschitsch. "Spintronic GdFe/Pt THz emitters." Applied Physics Letters 115, no. 15 (October 7, 2019): 152401. http://dx.doi.org/10.1063/1.5120249.

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Agarwal, Piyush, Yingshu Yang, James Lourembam, Rohit Medwal, Marco Battiato, and Ranjan Singh. "Terahertz spintronic magnetometer (TSM)." Applied Physics Letters 120, no. 16 (April 18, 2022): 161104. http://dx.doi.org/10.1063/5.0079989.

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A ferromagnetic metal consists of localized electrons and conduction electrons coupled through strong exchange interaction. Together, these localized electrons contribute to the magnetization of the system, while conduction electrons lead to the formation of spin and charge current. Femtosecond out of equilibrium photoexcitation of ferromagnetic thin films generates a transient spin current at ultrafast timescales that have opened a route to probe magnetism offered by the conduction electrons. In the presence of a neighboring heavy metal layer, the non-equilibrium spin current is converted into a pulsed charge current and gives rise to terahertz (THz) emission. Here, we propose and demonstrate a tool known as the terahertz spintronic magnetometry. The hysteresis loop obtained by sweeping terahertz (THz) pulse amplitude as a function of the magnetic field is in excellent agreement with the vibrating-sample magnetometer measurements. Furthermore, a modified transfer-matrix method employed to model the THz propagation within the heterostructure theoretically elucidates a linear relationship between the THz pulse amplitude and sample magnetization. The strong correlation, thus, reveals spintronic terahertz emission as an ultrafast magnetometry tool with reliable in-plane magnetization detection, highlighting its technological importance in the characterization of ferromagnetic thin-films through terahertz spintronic emission spectroscopy.

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Liu, Shaojie, Chenhui Lu, Zhengquan Fan, Shixiang Wang, Peiyan Li, Xinhou Chen, Jun Pan, Yong Xu, Yi Liu, and Xiaojun Wu. "Modulated terahertz generation in femtosecond laser plasma filaments by high-field spintronic terahertz pulses." Applied Physics Letters 120, no. 17 (April 25, 2022): 172404. http://dx.doi.org/10.1063/5.0080234.

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Strong-field terahertz (THz) light-matter interaction provides various nonlinear control approaches in condensed matter physics, energy and material sciences, electron acceleration, and manipulation. Recently developed spintronic THz emission with minimum complexities has been demonstrated to have the capability for generating high field strengths. Up to now, nonlinear applications based on the spintronic THz transients have yet been realized. Here, we report THz emission from two-color femtosecond laser plasma filaments modulated by a 60-kV/cm THz pulse from W/CoFeB/Pt heterostructures. Enhanced THz radiation based on electron acceleration in plasma is recorded when the direction of the spintronic THz modulating field is in line with that of the electron movement. This behavior is quantitatively reproduced by a local current model of the plasma THz source. Our experimental and theoretical results may inspire further nonlinear THz investigation and accelerate ultrafast THz engineering in matter.

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Armelles, Gaspar, and Alfonso Cebollada. "Active photonic platforms for the mid-infrared to the THz regime using spintronic structures." Nanophotonics 9, no. 9 (July 13, 2020): 2709–29. http://dx.doi.org/10.1515/nanoph-2020-0250.

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AbstractSpintronics and Photonics constitute separately two disciplines of huge scientific and technological impact. Exploring their conceptual and practical overlap offers vast possibilities of research and a clear scope for the corresponding communities to merge and consider innovative ideas taking advantage of each other’s potentials. As an example, here we review the magnetic field modification of the optical response of photonic systems fabricated out of spintronic materials, or in which spintronic components are incorporated. This magnetic actuation is due to the Magneto Refractive Effect (MRE), which accounts for the change in the optical constants of a spintronic system due to the magnetic field induced modification of the electrical resistivity. Due to the direct implication of conduction electrons in this phenomenon, this change in the optical constants covers from the mid-infrared to the THz regime. After introducing the non-expert reader into the spintronic concepts relevant to this work, we then present the MRE exhibited by a variety of spintronic systems, and finally show the different applications of this property in the generation of active spintronic-photonic platforms.

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Li, Peiyan, Shaojie Liu, Zheng Liu, Min Li, Hao Xu, Yong Xu, Heping Zeng, and Xiaojun Wu. "Laser terahertz emission microscopy of nanostructured spintronic emitters." Applied Physics Letters 120, no. 20 (May 16, 2022): 201102. http://dx.doi.org/10.1063/5.0080397.

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Laser terahertz (THz) emission spectroscopy has broken the diffraction limit of THz frequencies and offers multifaceted spectroscopic and imaging capabilities for understanding the light–matter interaction in various quantum and energy materials. However, this advanced technique has not yet been applied in the recently extensively studied spintronic THz emission process, in which the material surface morphology may play an important role. Here, we conduct THz emission microscopy on 5.4-nm thick Pt/CoFeB/W heterostructures and obtain twice enhanced THz by tightly focusing the pumping laser, delicately choosing the radiation location on nanofilms and coating gold nanorods. Through THz emission mapping, the material surface morphology and its modification have a strong correlation with THz emission performance from spintronic emitters. Our proposed femtosecond fiber laser driven spintronic THz emission microscopy can provide exciting possibilities for studying surface morphology sensitive THz emission materials and microdomain ultrafast dynamics for low-dimensional small samples via further coupling optical microscopy.

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9

Buryakov A.M., Gorbatova A. V., Avdeev P. Yu., Bezvikonny N. V., Ovcharenko S. V., Klimov A. A., Stankevich K. L., and Mishina E. D. "Spintronic emitter of terahertz radiation based on two-dimensional semiconductor tungsten diselenide." Technical Physics Letters 48, no. 9 (2022): 53. http://dx.doi.org/10.21883/tpl.2022.09.55084.19246.

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We propose a new spintronic emitter based on the Co/WSe2 heterostructure. The time of ultrafast demagnetization is estimated. It is shown that the two-dimensional ferromagnet/semiconductor interface exhibits strong spin-orbit coupling. Approaches to the description of the mechanism of generation of THz radiation are implemented. It is shown that the polarization orientation of THz radiation depends on the direction of magnetization Keywords: Spintronic emitter, THz radiation, two-dimensional semiconductors, Co/WSe2, THz polarization.

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10

Hewett, S. M., C. Bull, A. M. Shorrock, C. H. Lin, R. Ji, M. T. Hibberd, T. Thomson, P. W. Nutter, and D. M. Graham. "Spintronic terahertz emitters exploiting uniaxial magnetic anisotropy for field-free emission and polarization control." Applied Physics Letters 120, no. 12 (March 21, 2022): 122401. http://dx.doi.org/10.1063/5.0087282.

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We explore the terahertz (THz) emission from CoFeB/Pt spintronic structures in the below-magnetic-saturation regime and reveal an orientation dependence in the emission, arising from in-plane uniaxial magnetic anisotropy (UMA) in the ferromagnetic layer. Maximizing the UMA during the film deposition process and aligning the applied magnetic field with the easy axis of the structure allow the THz emission to reach saturation under weaker applied fields. In addition, the THz emission amplitude remains at saturation levels when the applied field is removed. The development of CoFeB/Pt spintronic structures that can emit broadband THz pulses without the need for an applied magnetic field is beneficial to THz magneto-optical spectroscopy and facilitates the production of large-area spintronic emitters. Furthermore, by aligning the applied field along the hard axis of the structure, the linear polarization plane of the emitted THz radiation can be manipulated by changing the magnitude of the applied field. We, therefore, demonstrate THz polarization control without the need for mechanical rotation of external magnets.

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Ciccarelli, Chiara, Hannah Joyce, Jason Robinson, Farhan Nur Kholid, Dominik Hamara, Srabani Kar, and Kun-Rok Jeon. "Terahertz Time-Domain Spectroscopy." Scientific Video Protocols 1, no. 1 (February 1, 2020): 1–4. http://dx.doi.org/10.32386/scivpro.000006.

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Time-Domain terahertz spectroscopy (THz TDS) has attracted attention from many scientific disciplines as it enables accessing the gap between electronic and optical techniques. One application is to probe spintronic dynamics in sub-picosecond time scale. Here, we discuss principles and technical aspects of a typical THz TDS setup. We also show an example of terahertz time-domain data obtained from a Co/Pt thin film calibrant, which is a well-studied spintronic structure emitting strong THz radiation. See video at https://youtu.be/X7vrvQcmy8c.

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Buryakov, Arseniy, Pavel Avdeev, Dinar Khusyainov, Nikita Bezvikonnyy, Andreas Coclet, Alexey Klimov, Nicolas Tiercelin, Sergey Lavrov, and Vladimir Preobrazhensky. "The Role of Ferromagnetic Layer Thickness and Substrate Material in Spintronic Emitters." Nanomaterials 13, no. 11 (May 23, 2023): 1710. http://dx.doi.org/10.3390/nano13111710.

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In this article, we investigate optically induced terahertz radiation in ferromagnetic FeCo layers of varying thickness on Si and SiO2 substrates. Efforts have been made to account for the influence of the substrate on the parameters of the THz radiation generated by the ferromagnetic FeCo film. The study reveals that the thickness of the ferromagnetic layer and the material of the substrate significantly affect the generation efficiency and spectral characteristics of the THz radiation. Our results also emphasize the importance of accounting for the reflection and transmission coefficients of the THz radiation when analyzing the generation process. The observed radiation features correlate with the magneto-dipole mechanism, triggered by the ultrafast demagnetization of the ferromagnetic material. This research contributes to a better understanding of THz radiation generation mechanisms in ferromagnetic films and may be useful for the further development of THz technology applications in the field of spintronics and other related areas. A key discovery of our study is the identification of a nonmonotonic relationship between the radiation amplitude and pump intensity for thin films on semiconductor substrates. This finding is particularly significant considering that thin films are predominantly used in spintronic emitters due to the characteristic absorption of THz radiation in metals.

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Lezier, G., P. Koleják, J. F. Lampin, K. Postava, M. Vanwolleghem, and N. Tiercelin. "Fully reversible magnetoelectric voltage controlled THz polarization rotation in magnetostrictive spintronic emitters on PMN-PT." Applied Physics Letters 120, no. 15 (April 11, 2022): 152404. http://dx.doi.org/10.1063/5.0080372.

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THz polarization control upon generation is a crucially missing functionality. THz spintronic emitters based on the inverse spin Hall effect (ISHE) allow for this by the strict implicit orthogonality between their magnetization state and the emitted polarization. This control was until now only demonstrated using cumbersome external magnetic field biasing to impose a polarization direction. We present here an efficient voltage control of the polarization state of terahertz spintronic emitters. Using a ferromagnetic spin pumping multilayer exhibiting simultaneously strong uniaxial magnetic anisotropy and magnetostriction in a crossed configuration, an emitter is achieved where, in principle, the stable magnetization direction can be fully and reversibly controlled over a 90° angle span only by an electric voltage. To achieve this, an engineered rare-earth based ferromagnetic multilayer is deposited on a piezoelectric [Formula: see text] (PMN-PT) substrate. We demonstrate experimentally a reversible 70° THz polarization rotation by sweeping the substrate voltage over 400 V. This demonstration allows for a fully THz polarization controlled ISHE spintronic terahertz emitter not needing any control of the magnetic bias.

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Tsybrii, Z. F., S. N. Danilov, J. V. Gumenjuk-Sichevska, N. N. Mikhailov, S. A. Dvoretskii, E. O. Melezhik, and F. F. Sizov. "Spintronics phenomena induced by THz radiation in narrow-gap HgCdTe thin films in an external constant electric field." Semiconductor Physics, Quantum Electronics and Optoelectronics 24, no. 02 (June 16, 2021): 185–91. http://dx.doi.org/10.15407/spqeo24.02.185.

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The responses of uncooled (T = 300 K) and cooled to T = 78 K antenna-coupled Hg1–xCdxTe-based narrow-gap thin-film photoconductors having large spin-orbit coupling and irradiated by the terahertz (THz) radiation (linearly or circularly polarized) have been investigated. Powerful THz radiation excitation causes photocurrents, which signs and magnitudes are controlled by orientation of antenna axes, an external constant electric field direction and orientation of the polarized (circular or linear) radiation electric field falling onto photoconductors. The observed effects seem to be caused by the spin currents observed in devices where spintronic effects are revealed. spintronic phenomena, photoconductors, THz radiation, HgCdTe.

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Beermann, Nicolas S., Savio Fabretti, Karsten Rott, Hassan A. Hafez, Günter Reiss, and Dmitry Turchinovich. "Disentangling complex current pathways in a metallic Ru/Co bilayer nanostructure using THz spectroscopy." Applied Physics Letters 121, no. 20 (November 14, 2022): 203101. http://dx.doi.org/10.1063/5.0125464.

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Many modern spintronic technologies, such as spin valves, spin Hall applications, and spintronic THz emitters, are based on electrons crossing buried internal interfaces within metallic nanostructures. However, the complex current pathways within such nanostructures are difficult to disentangle using conventional experimental methods. Here, we measure the conductivity of a technologically relevant Ru/Co bilayer nanostructure in a contact-free fashion using THz time-domain spectroscopy. By applying an effective resistor network to the data, we resolve the complex current pathways within the nanostructure and determine the degree of electronic transparency of the internal interface between the Ru and Co nanolayers.

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Fix, Mario, Robert Schneider, Steffen Michaelis de Vasconcellos, Rudolf Bratschitsch, and Manfred Albrecht. "Spin valves as magnetically switchable spintronic THz emitters." Applied Physics Letters 117, no. 13 (September 28, 2020): 132407. http://dx.doi.org/10.1063/5.0025746.

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Hawecker, J., E. Rongione, A. Markou, S. Krishnia, F. Godel, S. Collin, R. Lebrun, et al. "Spintronic THz emitters based on transition metals and semi-metals/Pt multilayers." Applied Physics Letters 120, no. 12 (March 21, 2022): 122406. http://dx.doi.org/10.1063/5.0079955.

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Spintronic terahertz (THz) emitters based on the inverse spin Hall effect in ferromagnetic/heavy metal (FM/HM) heterostructures have become important sources for THz pulse generation. The design, materials, and control of these interfaces at the nanometer level have become vital to engineer their THz emission properties. In this work, we present studies of the optimization of such structures through a multi-pronged approach, taking advantage of material and interface engineering to enhance THz spintronic emission. This includes the application of multi-stacks of HM/FM junctions and their application to trilayer structures, the use of spin-sinks to simultaneously enhance the THz emitted fields and reduce the use of thick Pt layers to reduce optical absorption, and the use of semi-metals to increase the spin polarization and, thus, THz emission. Through these approaches, significant enhancements of the THz field can be achieved. Importantly, taking into account the optical absorption permits to elucidate novel phenomena such as the relation between the spin diffusion length and the spin-sink using THz spectroscopy, as well as possibly distinguishing between self- and interface-spin-to-charge conversion in semi-metals.

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Stiewe, Finn-Frederik, Tristan Winkel, Yuta Sasaki, Tobias Tubandt, Tobias Kleinke, Christian Denker, Ulrike Martens, et al. "Spintronic emitters for super-resolution in THz-spectral imaging." Applied Physics Letters 120, no. 3 (January 17, 2022): 032406. http://dx.doi.org/10.1063/5.0076880.

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Preobrazhensky, V. L., and L. M. Krutyansky. "Acoustic Control of Polarization in a Spintronic THz Emitter." Physics of Wave Phenomena 30, no. 4 (August 2022): 265–69. http://dx.doi.org/10.3103/s1541308x22040069.

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Fix, Mario, Robert Schneider, Jannis Bensmann, Steffen Michaelis de Vasconcellos, Rudolf Bratschitsch, and Manfred Albrecht. "Thermomagnetic control of spintronic THz emission enabled by ferrimagnets." Applied Physics Letters 116, no. 1 (January 6, 2020): 012402. http://dx.doi.org/10.1063/1.5132624.

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Wu, Weipeng, Sergi Lendinez, Mojtaba Taghipour Kaffash, Richard D. Schaller, Haidan Wen, and M. Benjamin Jungfleisch. "Controlling polarization of spintronic THz emitter by remanent magnetization texture." Applied Physics Letters 121, no. 5 (August 1, 2022): 052401. http://dx.doi.org/10.1063/5.0096252.

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Terahertz (THz) sciences and technologies have contributed to a rapid development of a wide range of applications and expanded the frontiers in fundamental science. Spintronic terahertz emitters offer conceptual advantages since the spin orientation in the magnetic layer can be easily controlled either by the externally applied magnetic field or by the internal magnetic field distribution determined by the specific shape of the magnetic elements. Here, we report a switchable terahertz source based on micropatterned magnetic heterostructures driven by femtosecond laser pulses. We show that the precise tunability of the polarization state is facilitated by the underlying magnetization texture of the magnetic layer that is dictated by the shape of the microstructure. These results also reveal the underlying physical mechanisms of a nonuniform magnetization state on the generation of ultrafast spin currents in the magnetic heterostructures. Our findings indicate that the emission of the linearly polarized THz waves can be switched on and off by saturating the sample using a biasing magnetic field, opening fascinating perspectives for integrated on-chip THz devices with wide-ranging potential applications.

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Khusyainov, Dinar, Andrey Guskov, Sergei Ovcharenko, Nicolas Tiercelin, Vladimir Preobrazhensky, Arseniy Buryakov, Alexander Sigov, and Elena Mishina. "Increasing the Efficiency of a Spintronic THz Emitter Based on WSe2/FeCo." Materials 14, no. 21 (October 28, 2021): 6479. http://dx.doi.org/10.3390/ma14216479.

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We report an increase in terahertz (THz) radiation efficiency due to FeCo/WSe2 structures in the reflection geometry. This can be attributed to an absorption increase in the alloy FeCo layer at the input FeCo/WSe2 interface due to constructive interference, as well as to the backward transport of hot carriers from FeCo to WSe2. In contrast to the transmission geometry, the THz generation efficiency in the reflection is much less dependent on the magnetic layer thickness. Our results suggest a cheap and efficient way to improve the characteristics of THz spintronic emitters with the conservation of a full set of their important properties.

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Gorchon, Jon, Stéphane Mangin, Michel Hehn, and Gregory Malinowski. "Is terahertz emission a good probe of the spin current attenuation length?" Applied Physics Letters 121, no. 1 (July 4, 2022): 012402. http://dx.doi.org/10.1063/5.0097448.

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Terahertz (THz) emission from magnetic films has recently become an important characterization tool of spintronic properties, particularly since no patterning is required. One such property of interest is the spin-current attenuation length. When separating a magnetic film from a spin-to-charge converter with a light metal, the emitted intensity reduces almost exponentially with the thickness of the spacer. However, the extracted characteristic length is more than an order of magnitude smaller than the spin diffusion length measured in equilibrium. In this work, we experimentally and theoretically demonstrate that most of the observed decay in the THz emission is of optical (THz) origin. We are able to estimate a spin current attenuation length for Cu of ∼50 nm in much closer agreement with spin diffusion length measurements. We conclude that THz emission remains a powerful characterization technique, but due to the high number of intricate conversion mechanisms, and most importantly, due to the high sensitivity to changes in the optical properties, extracting absolute numbers for spintronic phenomena remains extremely challenging.

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Zhu, Zhao-Zhao, Zheng Feng, and Jian-Wang Cai. "Field-free spintronic terahertz emitters based on IrMn/Fe/Pt exchage bias heterostructures." Acta Physica Sinica 71, no. 4 (2022): 048703. http://dx.doi.org/10.7498/aps.71.20211831.

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Spintronic terahertz (THz) emitter has more advantages such as lower cost, broader spectrum and easier operation than the commercial THz emitters, and thus has become a focus of research towards the next-generation THz source. However, in such a spintronic THz emitter, an external magnetic field is technologically required to align the orientation of the magnetization, which is detrimental for practical applications. Here, a spintronic terahertz emitter based on IrMn/Fe/Pt exchange bias structure is presented. By means of ultrafast spin injection on Fe/Pt interface followed by the spin-to-charge conversion in Pt, plus the effective magnetic field originating from the IrMn/Fe interface, the THz pulse with considerable intensity can be generated in such a structure without the assistance of external field. Besides, the remanent magnetization for thin Fe layer is enhanced by inserting an ultrathin Cu layer between the IrMn surface and the Fe surface, which is beneficial to the field-free THz emission. The range of obtained dynamic THz spectrum exceeds 60 dB and the positive saturation field can reach up to ~ –10 mT by optimizing the multilayer thickness, meeting the standard for commercial application. By rotating the sample, it is found that the polarization direction of the generated THz wave circulates simultaneously and keeps perpendicular to the direction of exchange bias field in the film plane. Moreover, we design a spin valve THz emitter based on the structure of IrMn/Fe/Pt/Fe by adding a free ferromagnetic Fe layer into the exchange bias multilayers. The emitted THz pulse amplitude is larger for the antiparallel alignment of the Fe layers at zero field than for the parallel alignment or exchange bias structure. The present work shows that the spin terahertz emitter based on IrMn/Fe/Pt exchange bias structure can produce the considerable terahertz signals without external field. Furthermore, the polarization direction of the emitted THz signal can be easily manipulated by rotating the sample. Because of this series of advantages, such exchange bias heterostructures are expected to play an important role in designing the next-generation THz source.

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Schneider, Robert, Mario Fix, Richard Heming, Steffen Michaelis de Vasconcellos, Manfred Albrecht, and Rudolf Bratschitsch. "Magnetic-Field-Dependent THz Emission of Spintronic TbFe/Pt Layers." ACS Photonics 5, no. 10 (September 9, 2018): 3936–42. http://dx.doi.org/10.1021/acsphotonics.8b00839.

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Буряков, А. М., А. В. Горбатова, П. Ю. Авдеев, Н. В. Безвиконный, С. В. Овчаренко, А. А. Климов, К. Л. Станкевич, and Е. Д. Мишина. "Спинтронный терагерцевый эмиттер на основе двумерного полупроводникового диселенида вольфрама." Письма в журнал технической физики 48, no. 18 (2022): 19. http://dx.doi.org/10.21883/pjtf.2022.18.53393.19246.

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We propose a new spintronic emitter based on the Co/WSe2 heterostructure. The time of ultrafast demagnetization is estimated. It is shown that the two-dimensional ferromagnet/semiconductor interface exhibits strong spin-orbit coupling. Approaches to the description of the mechanism of generation of THz radiation are implemented. It is shown that the polarization orientation of THz radiation depends on the direction of magnetization.

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Kueny, Elias, Anne-Laure Calendron, Sven Velten, Lars Bocklage, Franz X. Kärtner, and Ralf Röhlsberger. "Spin-structured multilayer THz emitters by oblique incidence deposition." Journal of Applied Physics 133, no. 3 (January 21, 2023): 033903. http://dx.doi.org/10.1063/5.0128437.

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State-of-the-art THz spintronic emitters require a constant magnetic field to saturate their magnetization. We demonstrate that depositing the ferromagnetic layers at oblique incidence confines the magnetization to a chosen in-plane easy axis and maintains the saturation in the absence of an external magnetic field. We use this method to build THz emitters structured as spin valves, for which we use an external magnetic field to turn on and off the emission of THz radiation as well as to change its polarization. We are able to reproduce the THz waveforms by modeling the spin current and the THz propagation through the multilayer system.

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Stiewe, Finn-Frederik, Tristan Winkel, Tobias Kleinke, Tobias Tubandt, Hauke Heyen, Lucas Vollroth, Ulrike Martens, et al. "Magnetic domain scanning imaging using phase-sensitive THz-pulse detection." AIP Advances 12, no. 9 (September 1, 2022): 095010. http://dx.doi.org/10.1063/5.0106651.

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In our study, we determine the alignment of magnetic domains in a CoFeB layer using THz radiation. We generate THz pulses by fs laser pulses in magnetized CoFeB/Pt heterostructures based on spin currents. An LT-GaAs Auston switch detects the radiation phase sensitively and allows us to determine the magnetization alignment. Our scanning technique with motorized stages, with step sizes in the sub-micrometer range, allows us to image two dimensional magnetic structures. Theoretically, the resolution is restricted to half of the wavelength if focusing optics in the far-field limit are used. By applying near-field imaging, the spatial resolution is enhanced to the single digit micrometer range. For this purpose, spintronic emitters in diverse geometric shapes, e.g., circles, triangles, squares, and sizes are prepared to observe the formation of magnetization patterns. The alignment of the emitted THz radiation can be influenced by applying unidirectional external magnetic fields. We demonstrate how magnetic domains with opposite alignment and different shapes divided by domain walls are created by demagnetizing the patterns using minor loops and imaged using phase sensitive THz radiation detection. For analysis, the data are compared to Kerr microscope images. The possibility of combining this method with THz range spectroscopic information of magnetic texture or antiferromagnets in direct vicinity to the spintronic emitter makes this detection method interesting for a much wider range of applications probing THz excitation in spin systems with high resolution beyond the Abbe diffraction limit, limited solely by the laser excitation area.

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Schneider, Robert, Mario Fix, Jannis Bensmann, Steffen Michaelis de Vasconcellos, Manfred Albrecht, and Rudolf Bratschitsch. "Composition-dependent ultrafast THz emission of spintronic CoFe/Pt thin films." Applied Physics Letters 120, no. 4 (January 24, 2022): 042404. http://dx.doi.org/10.1063/5.0076699.

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Zhang, Xiaoqiang, Yunqing Jiang, Fengguang Liu, Yong Xu, Anting Wang, and Weisheng Zhao. "Focused THz wave from a spintronic terahertz Fresnel Zone Plate emitter." Optics & Laser Technology 171 (April 2024): 110418. http://dx.doi.org/10.1016/j.optlastec.2023.110418.

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Schneider, Robert, Mario Fix, Richard Heming, Steffen Michaelis de Vasconcellos, Manfred Albrecht, and Rudolf Bratschitsch. "Correction to “Magnetic-Field-Dependent THz Emission of Spintronic TbFe/Pt Layers”." ACS Photonics 6, no. 9 (September 5, 2019): 2366–67. http://dx.doi.org/10.1021/acsphotonics.9b01191.

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32

Zhang, Xiaoqiang, Yong Xu, Bin Hong, Fan Zhang, Anting Wang, and Weisheng Zhao. "Generation of a Focused THz Vortex Beam from a Spintronic THz Emitter with a Helical Fresnel Zone Plate." Nanomaterials 13, no. 14 (July 10, 2023): 2037. http://dx.doi.org/10.3390/nano13142037.

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Similar to optical vortex beams, terahertz (THz) vortex beams (TVBs) also carry orbital angular momentum (OAM). However, little research has been reported on the generation of TVBs. In this paper, based on the detour phase technique, we design a series of spintronic terahertz emitters with a helical Fresnel zone plate (STE-HFZP) to directly generate focused TVBs with topological charges (TCs) of l = ±1, ±2 and ±3, respectively. The STE-HFZP is a hybrid THz device composed of a terahertz emitter and a THz lens, and it has a high numerical aperture (NA), achieving subwavelength focal spots. Its focus properties are surveyed systemically through accurate simulations. This STE-HFZP can also generate focused TVBs with higher order TCs. More importantly, the components of the focused electric field with OAM make up the majority of the intensity and have potential applications in the field of THz communications, THz imaging and atom trapping.

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Gorbatova, Anastasiya V., and Arseny M. Buryakov. "Optimization of optical absorption in spintronic terahertz emitters using Bragg reflectors." Radioelectronics. Nanosystems. Information Technologies. 16, no. 1 (March 14, 2024): 101–10. http://dx.doi.org/10.17725/j.rensit.2023.16.101.

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An optimized design of a spintronic terahertz emitter has been developed, based on a bilayer Co/Pt structure with an integrated distributed Bragg reflector. The incorporation of the Bragg mirror between the Co/Pt structure and the silicon substrate enhances optical absorption in the ferromagnetic layer, thereby amplifying spin current generation and, consequently, THz signal. A model was developed for calculating the optical absorption in the ferromagnetic layer of the spintronic emitter, taking into account the parameters of the Bragg mirror (layer thicknesses, period) based on the superlattice structure [TiO2/SiO2]N. This model is grounded on the solution of Maxwell's equations for electromagnetic waves using the COMSOL Multiphysics software. The effect of anti-reflective dielectric coatings on the level of optical absorption in the ferromagnetic layer was also analyzed. The study confirmed that using the optimized Bragg mirror is sufficient for achieving optimal absorption.

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Buryakov, Arseniy, Anastasia Gorbatova, Pavel Avdeev, Nikita Bezvikonnyi, Daniil Abdulaev, Alexey Klimov, Sergei Ovcharenko, and Elena Mishina. "Controlled Spintronic Emitter of THz Radiation on an Atomically Thin WS2/Silicon Substrate." Metals 12, no. 10 (October 6, 2022): 1676. http://dx.doi.org/10.3390/met12101676.

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The control and monitoring of the polarization of terahertz radiation are of interest for numerous applications. Here we present a simple controllable THz emitter with a small coercive magnetic field. It is based on a Co/WS2/silicon structure, in which the presence of uniaxial magnetic anisotropy caused by mechanical stress in a ferromagnetic film was found. Our results show that a ferromagnet/semiconductor emitter can become a technologically simple device for terahertz spintronics.

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35

Zheng, Yueqian, Tao Xu, Xuan Wang, Zhi Sun, and Bai Han. "Study on Bulk-Surface Transport Separation and Dielectric Polarization of Topological Insulator Bi1.2Sb0.8Te0.4Se2.6." Molecules 29, no. 4 (February 15, 2024): 859. http://dx.doi.org/10.3390/molecules29040859.

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This study successfully fabricated the quaternary topological insulator thin films of Bi1.2Sb0.8Te0.4Se2.6 (BSTS) with a thickness of 25 nm, improving the intrinsic defects in binary topological materials through doping methods and achieving the separation of transport characteristics between the bulk and surface of topological insulator materials by utilizing a comprehensive Physical Properties Measurement System (PPMS) and Terahertz Time-Domain Spectroscopy (THz-TDS) to extract electronic transport information for both bulk and surface states. Additionally, the dielectric polarization behavior of BSTS in the low-frequency (10–107 Hz) and high-frequency (0.5–2.0 THz) ranges was investigated. These research findings provide crucial experimental groundwork and theoretical guidance for the development of novel low-energy electronic devices, spintronic devices, and quantum computing technology based on topological insulators.

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36

Choi, B. C., J. Rudge, K. Jordan, and T. Genet. "Terahertz excitation of spin dynamics in ferromagnetic thin films incorporated in metallic spintronic-THz-emitter." Applied Physics Letters 116, no. 13 (March 30, 2020): 132406. http://dx.doi.org/10.1063/1.5143133.

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37

Meer, H., O. Gomonay, A. Wittmann, and M. Kläui. "Antiferromagnetic insulatronics: Spintronics in insulating 3d metal oxides with antiferromagnetic coupling." Applied Physics Letters 122, no. 8 (February 20, 2023): 080502. http://dx.doi.org/10.1063/5.0135079.

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Antiferromagnetic transition metal oxides are an established and widely studied materials system in the context of spin-based electronics, commonly used as passive elements in exchange bias-based memory devices. Currently, major interest has resurged due to the recent observation of long-distance spin transport, current-induced switching, and THz emission. As a result, insulating transition metal oxides are now considered to be attractive candidates for active elements in future spintronic devices. Here, we discuss some of the most promising materials systems and highlight recent advances in reading and writing antiferromagnetic ordering. This article aims to provide an overview of the current research and potential future directions in the field of antiferromagnetic insulatronics.

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Safin, Ansar, Sergey Nikitov, Andrei Kirilyuk, Vasyl Tyberkevych, and Andrei Slavin. "Theory of Antiferromagnet-Based Detector of Terahertz Frequency Signals." Magnetochemistry 8, no. 2 (February 12, 2022): 26. http://dx.doi.org/10.3390/magnetochemistry8020026.

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We present a theory of a detector of terahertz-frequency signals based on an antiferromagnetic (AFM) crystal. The conversion of a THz-frequency electromagnetic signal into the DC voltage is realized using the inverse spin Hall effect in an antiferromagnet/heavy metal bilayer. An additional bias DC magnetic field can be used to tune the antiferromagnetic resonance frequency. We show that if a uniaxial AFM is used, the detection of linearly polarized signals is possible only for a non-zero DC magnetic field, while circularly polarized signals can be detected in a zero DC magnetic field. In contrast, a detector based on a biaxial AFM can be used without a bias DC magnetic field for the rectification of both linearly and circularly polarized signals. The sensitivity of a proposed AFM detector can be increased by increasing the magnitude of the bias magnetic field, or by by decreasing the thickness of the AFM layer. We believe that the presented results will be useful for the practical development of tunable, sensitive and portable spintronic detectors of THz-frequency signals based of the antiferromagnetic resonance (AFMR).

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Seifert, T., U. Martens, S. Günther, M. A. W. Schoen, F. Radu, X. Z. Chen, I. Lucas, et al. "Terahertz Spin Currents and Inverse Spin Hall Effect in Thin-Film Heterostructures Containing Complex Magnetic Compounds." SPIN 07, no. 03 (September 2017): 1740010. http://dx.doi.org/10.1142/s2010324717400100.

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Terahertz emission spectroscopy (TES) of ultrathin multilayers of magnetic and heavy metals has recently attracted much interest. This method not only provides fundamental insights into photoinduced spin transport and spin–orbit interaction at highest frequencies, but has also paved the way for applications such as efficient and ultrabroadband emitters of terahertz (THz) electromagnetic radiation. So far, predominantly standard ferromagnetic materials have been exploited. Here, by introducing a suitable figure of merit, we systematically compare the strength of THz emission from [Formula: see text]/Pt bilayers with [Formula: see text] being a complex ferro-, ferri- and antiferromagnetic metal, that is, dysprosium cobalt (DyCo5), gadolinium iron (Gd[Formula: see text]Fe[Formula: see text]), magnetite (Fe3O4) and iron rhodium (FeRh). We find that the performance in terms of spin-current generation not only depends on the spin polarization of the magnet’s conduction electrons, but also on the specific interface conditions, thereby suggesting TES to be a highly interface-sensitive technique. In general, our results are relevant for all applications that rely on the optical generation of ultrafast spin currents in spintronic metallic multilayers.

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LV, XIAO-RONG, SHI-HENG LIANG, LING-LING TAO, and XIU-FENG HAN. "ORGANIC SPINTRONICS: PAST, PRESENT AND FUTURE." SPIN 04, no. 02 (June 2014): 1440013. http://dx.doi.org/10.1142/s201032471440013x.

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Organic spintronics, extended the conventional spintronics with metals, oxides and semiconductors, has opened new routes to explore the important process of spin-injection, transport, manipulation and detection, holding significant promise of revolutionizing future spintronic applications in high density information storage, multi-functional devices, seamless integration, and quantum computing. Here we survey this fascinating field from some new viewpoints on research hotspots and emerging trends. The main achievements and challenges arising from spin injection and transport, in organic materials are highlighted, as well as prospects of novel organic spintronic devices are also emphasized.

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41

KIM, Dong-Hyun. "Ultrafast Spin Dynamics." Physics and High Technology 29, no. 9 (September 30, 2020): 2–6. http://dx.doi.org/10.3938/phit.29.029.

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Ultrafast spin dynamics is one of the key aspects in the realization of ultrafast spintronic devices. Moreover, it has attracted much attention due to important fundamental spin phenomena existing on nano-, pico-, and femtosecond timescales. The most important interaction of magnetism is, of course, an exchange interaction. However, in practice, spin generally exists interacting with a lattice and an electron in the form of solid. Therefore, a fundamental understanding of ultrafast spin dynamics is involved in various physical phenomena, such as spin-orbit interactions and optomagnetism. In this article, recent trends in ultrafast spin dynamics research are discussed. Ultrafast spin dynamics, which started with the observation of ultrafast demagnetization/remagnetization triggered by femtosecond laser pulses, has been intensively investigated so far. The magnetooptical Kerr effect and X-ray magnetic circular dichroism techniques are introduced as two of the main experimental techniques for exploring ultrafast spin dynamics. THz emission and ultrafast magnetic cooling phenomena are briefly introduced as examples of recent topics in the field of ultrafast spin dynamics.

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Papaioannou, Evangelos Th, and René Beigang. "THz spintronic emitters: a review on achievements and future challenges." Nanophotonics, December 18, 2020. http://dx.doi.org/10.1515/nanoph-2020-0563.

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AbstractThe field of THz spintronics is a novel direction in the research field of nanomagnetism and spintronics that combines magnetism with optical physics and ultrafast photonics. The experimental scheme of the field involves the use of femtosecond laser pulses to trigger ultrafast spin and charge dynamics in thin films composed of ferromagnetic and nonmagnetic thin layers, where the nonmagnetic layer features a strong spin–orbit coupling. The technological and scientific key challenges of THz spintronic emitters are to increase their intensity and to shape the frequency bandwidth. To achieve the control of the source of the radiation, namely the transport of the ultrafast spin current is required. In this review, we address the generation, detection, efficiency and the future perspectives of THz emitters. We present the state-of-the-art of efficient emission in terms of materials, geometrical stack, interface quality and patterning. The impressive so far results hold the promise for new generation of THz physics based on spintronic emitters.

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Agarwal, Piyush, Lisen Huang, Sze Ter Lim, and Ranjan Singh. "Electric-field control of nonlinear THz spintronic emitters." Nature Communications 13, no. 1 (July 14, 2022). http://dx.doi.org/10.1038/s41467-022-31789-0.

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AbstractEnergy-efficient spintronic technology holds tremendous potential for the design of next-generation processors to operate at terahertz frequencies. Femtosecond photoexcitation of spintronic materials generates sub-picosecond spin currents and emission of terahertz radiation with broad bandwidth. However, terahertz spintronic emitters lack an active material platform for electric-field control. Here, we demonstrate a nonlinear electric-field control of terahertz spin current-based emitters using a single crystal piezoelectric Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) that endows artificial magnetoelectric coupling onto a spintronic terahertz emitter and provides 270% modulation of the terahertz field at remnant magnetization. The nonlinear electric-field control of the spins occurs due to the strain-induced change in magnetic energy of the ferromagnet thin-film. Results also reveal a robust and repeatable switching of the phase of the terahertz spin current. Electric-field control of terahertz spintronic emitters with multiferroics and strain engineering offers opportunities for the on-chip realization of tunable energy-efficient spintronic-photonic integrated platforms.

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Nenno, Dennis M., Laura Scheuer, Dominik Sokoluk, Sascha Keller, Garik Torosyan, Alexander Brodyanski, Jörg Lösch, et al. "Modification of spintronic terahertz emitter performance through defect engineering." Scientific Reports 9, no. 1 (September 16, 2019). http://dx.doi.org/10.1038/s41598-019-49963-8.

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Abstract Spintronic ferromagnetic/non-magnetic heterostructures are novel sources for the generation of THz radiation based on spin-to-charge conversion in the layers. The key technological and scientific challenge of THz spintronic emitters is to increase their intensity and frequency bandwidth. Our work reveals the factors to engineer spintronic Terahertz generation by introducing the scattering lifetime and the interface transmission for spin polarized, non-equilibrium electrons. We clarify the influence of the electron-defect scattering lifetime on the spectral shape and the interface transmission on the THz amplitude, and how this is linked to structural defects of bilayer emitters. The results of our study define a roadmap of the properties of emitted as well as detected THz-pulse shapes and spectra that is essential for future applications of metallic spintronic THz emitters.

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Dai, Mingcong, Jiahua Cai, Zejun Ren, Mingxuan Zhang, Jiaqi Wang, Hongting Xiong, Yihang Ma, et al. "Spintronic terahertz metasurface emission characterized by scanning near-field nanoscopy." Nanophotonics, March 13, 2024. http://dx.doi.org/10.1515/nanoph-2023-0858.

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Abstract Understanding the ultrafast excitation, detection, transportation, and manipulation of nanoscale spin dynamics in the terahertz (THz) frequency range is critical to developing spintronic THz optoelectronic nanodevices. However, the diffraction limitation of the sub-millimeter waves – THz wavelengths – has impaired experimental investigation of spintronic THz nano-emission. Here, we present an approach to studying laser THz emission nanoscopy from W|CoFeB|Pt metasurfaces with ∼60-nm lateral spatial resolution. When comparing with statistic near-field THz time-domain spectroscopy with and without the heterostructures on fused silica substrates, we find that polarization- and phase-sensitive THz emission nanoscopy is more sensitive than the statistic THz scattering intensity nanoscopy. Our approach opens explorations of nanoscale ultrafast THz spintronic dynamics in optically excited metasurfaces.

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Liu, Sheng, Iftikhar Ahmed Malik, Vanessa Li Zhang, and Ting Yu. "Lightning the Spin: Harnessing the Potential of 2D Magnets in Opto‐Spintronics." Advanced Materials, October 31, 2023. http://dx.doi.org/10.1002/adma.202306920.

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AbstractSince the emergence of two‐dimensional (2D) magnets in 2017, the diversity of these materials has greatly expanded. Their 2D nature (atomic‐scale thickness) endows these magnets with strong magnetic anisotropy, layer‐dependent and switchable magnetic order, and quantum‐confined quasiparticles, which distinguish them from conventional three‐dimensional (3D) magnetic materials. Moreover, the 2D geometry facilitates light incidence for opto‐spintronic applications and potential on‐chip integration. In analogy to optoelectronics based on optical‐electronic interactions, opto‐spintronics use light‐spin interactions to process spin information stored in the solid state. In this review, we divide opto‐spintronics into three types with respect to the wavelengths of radiation interacting with 2D magnets: (1) GHz (microwave) to THz (mid‐infrared), (2) visible, and (3) UV to X‐rays. We focus on the recent research advancements on the newly discovered mechanisms of light‐spin interactions in 2D magnets and introduce the potential design of novel opto‐spintronic applications based on these interactions.This article is protected by copyright. All rights reserved

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DeCamp, M. F., S. Bhatt, M. T. Hossain, W. Wu, and M. B. Jungfleisch. "Demonstration of high-throughput magnetic hysteresis measurements based on spintronic THz emission." Journal of Applied Physics 134, no. 23 (December 15, 2023). http://dx.doi.org/10.1063/5.0165081.

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Spintronic terahertz (THz) emitters have been shown to be a cost-efficient source for use in time-domain THz spectroscopy. The use of external magnetic fields to control the polarity of the THz emission provides an opportunity to measure the magnetization of spintronic materials as well as shaping THz emission. Here, we demonstrate an efficient method of measuring magnetic hysteresis with material sensitivity and speed several orders of magnitude greater than typical magnetometry methods. In addition, we utilize the rapid control of material magnetization for lock-in detection in time-domain THz spectroscopy of spintronic emitters. The ability to rapidly control and measure the material magnetization on very small volumes provides an opportunity to study magnetic hetero-structures with sub-micron spatial resolution.

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Chen, Si-Chao, Zheng Feng, Jiang Li, Wei Tan, Liang-Hui Du, Jianwang Cai, Yuncan Ma, et al. "Ghost spintronic THz-emitter-array microscope." Light: Science & Applications 9, no. 1 (June 8, 2020). http://dx.doi.org/10.1038/s41377-020-0338-4.

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Li, Peiyan, Shaojie Liu, Xinhou Chen, Chunyan Geng, and Xiaojun Wu. "Spintronic terahertz emission with manipulated polarization (STEMP)." Frontiers of Optoelectronics 15, no. 1 (April 21, 2022). http://dx.doi.org/10.1007/s12200-022-00011-w.

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AbstractHighly efficient generation and arbitrary manipulation of spin-polarized terahertz (THz) radiation will enable chiral lightwave driven quantum nonequilibrium state regulation, induce new electronic structures, consequently provide a powerful experimental tool for investigation of nonlinear THz optics and extreme THz science and applications. THz circular dichromic spectroscopy, ultrafast electron bunch manipulation, as well as THz imaging, sensing, and telecommunication, also need chiral THz waves. Here we review optical generation of circularly-polarized THz radiation but focus on recently emerged polarization tunable spintronic THz emission techniques, which possess many advantages of ultra-broadband, high efficiency, low cost, easy for integration and so on. We believe that chiral THz sources based on the combination of electron spin, ultrafast optical techniques and material structure engineering will accelerate the development of THz science and applications. Graphical Abstract

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50

Cai, Jiahua, Mingcong Dai, Sai Chen, Peng Chen, Jiaqi Wang, Hongting Xiong, Zejun Ren, et al. "Terahertz spin currents resolved with nanometer spatial resolution." Applied Physics Reviews 10, no. 4 (December 1, 2023). http://dx.doi.org/10.1063/5.0170207.

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The development of coherent terahertz (THz) spin currents with femtosecond temporal resolution has been extensively studied due to its significant implications for advancing high-speed information processing devices. However, the precise spatial resolution of THz spin currents, which is crucial for increasing storage density, is still unknown. In this study, we employ spintronic THz emission nanoscopy (STEN) to achieve efficient injection and accurate detection of femtosecond THz spin currents with nanoscale lateral spatial resolution (∼60 nm). The occurrence of emission signals at the fifth harmonic order indicates a substantial signal-to-noise ratio. Additionally, STEN proves to be an effective method for characterizing and etching nanoscale spintronic heterostructures. The integration of nanophotonics, nanospintronics, and THz-nanotechnology into a unified platform is poised to enable the characterization of spin states at micro-to-nanoscale densities, accelerate the development of high-frequency spintronic optoelectronic nanodevices, and catalyze other revolutionary technical applications.

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Journal articles on the topic 'THz Spintronic'

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