22 results on '"Tom Seifert"'
Search Results
2. Ultrafast terahertz magnetometry
- Author
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Jacek Arabski, Dmitry Turchinovich, Tom Seifert, Eric Beaurepaire, Guy Schmerber, Peter M. Oppeneer, Wentao Zhang, Zuanming Jin, Mischa Bonn, Pablo Maldonado, Tobias Kampfrath, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), and Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS)
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Terahertz radiation ,Magnetism ,Physics::Optics ,General Physics and Astronomy ,02 engineering and technology ,01 natural sciences ,law.invention ,stress ,Ultrafast photonics ,law ,emission ,skin and connective tissue diseases ,lcsh:Science ,Multidisciplinary ,500 Naturwissenschaften und Mathematik::530 Physik::530 Physik ,food and beverages ,dynamics ,Physik (inkl. Astronomie) ,Condensed Matter Physics ,021001 nanoscience & nanotechnology ,Picosecond ,Optoelectronics ,0210 nano-technology ,Den kondenserade materiens fysik ,Materials science ,Magnetometer ,Science ,metals ,magnetization ,Article ,General Biochemistry, Genetics and Molecular Biology ,Magnetization ,Magnetic properties and materials ,0103 physical sciences ,010306 general physics ,Terahertz optics ,Magnetization dynamics ,[PHYS.PHYS]Physics [physics]/Physics [physics] ,Spintronics ,business.industry ,fungi ,General Chemistry ,transport ,lcsh:Q ,sense organs ,business ,Ultrashort pulse - Abstract
A material’s magnetic state and its dynamics are of great fundamental research interest and are also at the core of a wide plethora of modern technologies. However, reliable access to magnetization dynamics in materials and devices on the technologically relevant ultrafast timescale, and under realistic device-operation conditions, remains a challenge. Here, we demonstrate a method of ultrafast terahertz (THz) magnetometry, which gives direct access to the (sub-)picosecond magnetization dynamics even in encapsulated materials or devices in a contact-free fashion, in a fully calibrated manner, and under ambient conditions. As a showcase for this powerful method, we measure the ultrafast magnetization dynamics in a laser-excited encapsulated iron film. Our measurements reveal and disentangle distinct contributions originating from (i) incoherent hot-magnon-driven magnetization quenching and (ii) coherent acoustically-driven modulation of the exchange interaction in iron, paving the way to technologies utilizing ultrafast heat-free control of magnetism. High sensitivity and relative ease of experimental arrangement highlight the promise of ultrafast THz magnetometry for both fundamental studies and the technological applications of magnetism., Nature Communications, 11 (1), ISSN:2041-1723
- Published
- 2020
3. Exploiting ultrafast spintronics for terahertz photonics
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Tom Seifert
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Physics ,Spintronics ,Spins ,business.industry ,Terahertz radiation ,Broadband ,Physics::Optics ,Optoelectronics ,Photonics ,business ,Ultrashort pulse - Abstract
Terahertz (THz) time-domain spectroscopy is an emerging technique to probe and manipulate spins on ultrafast time scales. In this talk, I will highlight recent results of studying spintronic phenomena at terahertz rates, which holds great promise for next-generation THz photonic applications such as broadband THz generation and detection.
- Published
- 2021
4. Frequency-Independent Terahertz Anomalous Hall Effect in DyCo5, Co32Fe68, and Gd27Fe73 Thin Films from DC to 40 THz
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'Tom Seifert
- Subjects
terahertz spintronics - Abstract
Data for the publication "Frequency-Independent Terahertz Anomalous Hall Effect in DyCo5, Co32Fe68, and Gd27Fe73 Thin Films from DC to 40 THz" published in Advanced Materials (2021). The following datasets are provided: THz waveforms for different magnetizations for DyCo, optcial and visible hysteresis curves, diagonal and off-diagonal conductivities, calculated off-diagonal conductivities for different broadenings, and the anomalous Hall angles.
- Published
- 2021
5. High-Throughput Techniques for Measuring the Spin Hall Effect
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Björn Gliniors, Sebastian Wimmer, Lukas Liensberger, Tom Seifert, Mathias Weiler, Oliver Gueckstock, Tobias Kampfrath, Hubert Ebert, and Markus Meinert
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Spin torque ,Terahertz radiation ,FOS: Physical sciences ,General Physics and Astronomy ,Inverse ,Spin Hall effect ,02 engineering and technology ,Metrology ,01 natural sciences ,7. Clean energy ,Ferromagnetic resonance ,Spin generation ,Magnetization ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Hall bar ,Spin-orbit coupling ,010306 general physics ,Spin-½ ,Physics ,Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Spintronics ,Materials Science (cond-mat.mtrl-sci) ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Ferromagnetism ,Terahertz spectroscopy ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology - Abstract
The spin Hall effect in heavy-metal thin films is routinely employed to convert charge currents into transverse spin currents and can be used to exert torque on adjacent ferromagnets. Conversely, the inverse spin Hall effect is frequently used to detect spin currents by charge currents in spintronic devices up to the terahertz frequency range. Numerous techniques to measure the spin Hall effect or its inverse were introduced, most of which require extensive sample preparation by multi-step lithography. To enable rapid screening of materials in terms of charge-to-spin conversion, suitable high-throughput methods for measuring the spin Hall angle are required. Here, we compare two lithography-free techniques, terahertz emission spectroscopy and broadband ferromagnetic resonance, to standard harmonic Hall measurements and theoretical predictions using the binary-alloy series Au$_x$Pt$_{1-x}$ as benchmark system. Despite being highly complementary, we find that all three techniques yield a spin Hall angle with approximately the same $x$~dependence, which is also consistent with first-principles calculations. Quantitative discrepancies are discussed in terms of magnetization orientation and interfacial spin-memory loss., Comment: 9 pages, 3 figures
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- 2020
6. Study of ultrafast magnetism by THz emission spectroscopy (Conference Presentation)
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Mischa Bonn, Tom Seifert, Wentao Zhang, Tobias Kampfrath, Guy Schmerber, Dmitry Turchinovich, Pablo Maldonado, Peter M. Oppeneer, Eric Beaurepaire, Zuanming Jin, and Jacek Arabski
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Magnetization dynamics ,Materials science ,Magnetism ,business.industry ,Terahertz radiation ,Physics::Optics ,Magnetization ,Ferromagnetism ,Magnet ,Optoelectronics ,Emission spectrum ,business ,Ultrashort pulse ,Computer Science::Databases - Abstract
In laser-excited ferromagnetic heterostructures, both ultrafast local magnetization dynamics and spin-transport processes can lead to a THz emission. Here, we demonstrate that the THz emission spectroscopy is a powerful tool to investigate ultrafast magnetization dynamics in laser-excited magnetic systems. The polarity of emitted THz can be used to distinguish which process, local or non-local, dominates the emission of THz in a ferromagnetic heterostructure. The measured THz radiation can be used for rigorous reconstruction of ultrafast magnetization process in the laser-excited magnetic material.
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- 2020
7. Ultrafast Magnetization Dynamics Revealed by Terahertz Magnetometry
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Eric Beaurepaire, Guy Schmerber, Tom Seifert, Jacek Arabski, Mischa Bonn, Zuanming Jin, Dmitry Turchinovich, Wentao Zhang, Pablo Maldonado, Peter M. Oppeneer, and Tobias Kampfrath
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Magnetization dynamics ,Materials science ,Kerr effect ,Condensed matter physics ,Magnetometer ,Terahertz radiation ,Astrophysics::High Energy Astrophysical Phenomena ,Physics::Optics ,Electromagnetic radiation ,law.invention ,Magnetic field ,law ,Electric field ,Ultrashort pulse - Abstract
We investigate ultrafast magnetization dynamics in encapsulated iron films, benefitting from their laser-induced terahertz emission. Combined with first-principles theoretical modeling, the experimental results provide quantitative insights into the observed magnetization dynamics.
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- 2020
8. Modulating the polarization of broadband terahertz pulses from a spintronic emitter at rates up to 10 kHz
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Lukas Nadvornik, Tom Seifert, Martin Borchert, Georg Woltersdorf, Oliver Gueckstock, Mathias Kläui, Georg Schmidt, Martin Wolf, Gerhard Jakob, and Tobias Kampfrath
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Materials science ,530 Physics ,Spatial light modulators ,Terahertz radiation ,Physics::Optics ,Low-noise modulation spectroscopy ,02 engineering and technology ,Nonlinear optical crystals ,01 natural sciences ,spintronic terahertz emitters ,Electric field ,0103 physical sciences ,Electromagnetic pulse ,010302 applied physics ,500 Naturwissenschaften und Mathematik::530 Physik::539 Moderne Physik ,Condensed Matter::Other ,business.industry ,Linear polarization ,Nonlinear spectroscopy ,Broadband terahertz pulses ,530 Physik ,021001 nanoscience & nanotechnology ,Polarization (waves) ,Magnetostatics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Modulation ,Optoelectronics ,0210 nano-technology ,business ,Modulation spectroscopy - Abstract
Reliable modulation of terahertz electromagnetic waveforms is important for many applications. Here, we rapidly modulate the direction of the electric field of linearly polarized terahertz electromagnetic pulses with 1–30 THz bandwidth by applying time-dependent magnetic fields to a spintronic terahertz emitter. Polarity modulation of the terahertz field with more than 99% contrast at a rate of 10 kHz is achieved using a harmonic magnetic field. By adding a static magnetic field, we modulate the direction of the terahertz field between angles of, for instance, −53° and 53° at kilohertz rates. We believe our approach makes spintronic terahertz emitters a promising source for low-noise modulation spectroscopy and polarization-sensitive techniques such as ellipsometry at 1–30 THz.
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- 2021
9. Effect of DC Electric Field on the Emitted THz Signal of Antenna-Coupled Spintronic Emitters
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M. R. S Rouzegar, Oliver Gueckstock, M. S. Abdelaziz, Tom Seifert, Samridh Jaiswal, Sascha Preu, Gerhard Jakob, M. Kläui, Tobias Kampfrath, and U. Nandi
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Materials science ,Spintronics ,business.industry ,Terahertz radiation ,Biasing ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Magnetic field ,Magnetization ,Electric field ,0103 physical sciences ,Optoelectronics ,Antenna (radio) ,010306 general physics ,0210 nano-technology ,Joule heating ,business - Abstract
We study the impact of an external electric DC field on antenna-coupled spintronic THz emitters driven by a 90 fs, 1550 nm laser oscillator. Simultaneous application of external electric and magnetic field shows a quadratic decrease in peak-peak THz pulse with increase in the bias voltage. We ascribe this decrease to Joule heating caused by the DC current flowing through the spintronic material.
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- 2019
10. Antenna-coupled spintronic terahertz emitters driven by a 1550 nm femtosecond laser oscillator
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U. Nandi, Samridh Jaiswal, Tom Seifert, Seyed Mohammedreza Rouzegar, Oliver Gueckstock, Tobias Kampfrath, M. S. Abdelaziz, Gerhard Jakob, Sascha Preu, and Mathias Kläui
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Materials science ,Physics and Astronomy (miscellaneous) ,Terahertz radiation ,02 engineering and technology ,01 natural sciences ,law.invention ,law ,antenna-coupled spintronic terahertz emitters ,laser oscillator ,0103 physical sciences ,Laser power scaling ,010302 applied physics ,Spintronics ,business.industry ,Dynamic range ,Photoconductivity ,Bandwidth (signal processing) ,500 Naturwissenschaften und Mathematik::530 Physik::530 Physik ,021001 nanoscience & nanotechnology ,Laser ,Femtosecond ,Optoelectronics ,terahertz emitters ,0210 nano-technology ,business - Abstract
We demonstrate antenna-coupled spintronic terahertz (THz) emitters excited by 1550 nm, 90 fs laser pulses. Antennas are employed to optimize THz outcoupling and frequency coverage of ferromagnetic/nonmagnetic metallic spintronic structures. We directly compare the antenna-coupled devices to those without antennas. Using a 200 μm H-dipole antenna and an ErAs:InGaAs photoconductive receiver, we obtain a 2.42-fold larger THz peak-peak signal, a bandwidth of 4.5 THz, and an increase in the peak dynamic range (DNR) from 53 dB to 65 dB. A 25 μm slotline antenna offered 5 dB larger peak DNR and a bandwidth of 5 THz. For all measurements, we use a comparatively low laser power of 45 mW from a commercial fiber-coupled system that is frequently employed in table-top THz time-domain systems.We demonstrate antenna-coupled spintronic terahertz (THz) emitters excited by 1550 nm, 90 fs laser pulses. Antennas are employed to optimize THz outcoupling and frequency coverage of ferromagnetic/nonmagnetic metallic spintronic structures. We directly compare the antenna-coupled devices to those without antennas. Using a 200 μm H-dipole antenna and an ErAs:InGaAs photoconductive receiver, we obtain a 2.42-fold larger THz peak-peak signal, a bandwidth of 4.5 THz, and an increase in the peak dynamic range (DNR) from 53 dB to 65 dB. A 25 μm slotline antenna offered 5 dB larger peak DNR and a bandwidth of 5 THz. For all measurements, we use a comparatively low laser power of 45 mW from a commercial fiber-coupled system that is frequently employed in table-top THz time-domain systems.
- Published
- 2019
11. Impact of pump wavelength on terahertz emission of a cavity-enhanced spintronic trilayer
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Samuel M. Hornett, Gerhard Jakob, Tom Seifert, Euan Hendry, Jacopo Bertolotti, Rosamund I. Herapath, Mathias Kläui, and Tobias Kampfrath
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Materials science ,Terahertz radiation ,FOS: Physical sciences ,Physics::Optics ,terahertz emission ,02 engineering and technology ,Dielectric ,pump wavelength ,01 natural sciences ,Condensed Matter::Materials Science ,0103 physical sciences ,Stimulated emission ,Common emitter ,010302 applied physics ,Spintronics ,business.industry ,021001 nanoscience & nanotechnology ,spintronic trilayer ,Wavelength ,Transmission (telecommunications) ,Physics::Accelerator Physics ,Optoelectronics ,0210 nano-technology ,business ,Intensity (heat transfer) ,Optics (physics.optics) ,Physics - Optics - Abstract
We systematically study the pump-wavelength dependence of terahertz pulse generation in thin-film spintronic THz emitters composed of a ferromagnetic Fe layer between adjacent nonmagnetic W and Pt layers. We find that the efficiency of THz generation is essentially at for excitation by 150 fs pulses with center wavelengths ranging from 900 to 1500 nm, demonstrating that the spin current does not depend strongly on the pump photon energy. We show that the inclusion of dielectric overlayers of TiO2 and SiO2, designed for a particular excitation wavelength, can enhance the terahertz emission by a factor of of up to two in field., 7 pages including 2 supplementary
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- 2019
12. Frequency‐Independent Terahertz Anomalous Hall Effect in DyCo 5 , Co 32 Fe 68 , and Gd 27 Fe 73 Thin Films from DC to 40 THz
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Martin Wolf, Tom Seifert, Mirkow Ribow, Marco Berritta, Peter M. Oppeneer, R. Starke, Georg Woltersdorf, Ilie Radu, Florin Radu, Markus Münzenberg, Tomas Jungwirth, Ulrike Martens, L. Nadvornik, and Tobias Kampfrath
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Materials science ,Spintronics ,Condensed matter physics ,Terahertz radiation ,Mechanical Engineering ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Condensed Matter::Materials Science ,Mechanics of Materials ,Hall effect ,Spin Hall effect ,Condensed Matter::Strongly Correlated Electrons ,General Materials Science ,Thin film ,0210 nano-technology ,Terahertz time-domain spectroscopy - Abstract
The anomalous Hall effect (AHE) is a fundamental spintronic charge-to-charge-current conversion phenomenon and closely related to spin-to-charge-current conversion by the spin Hall effect. Future h ...
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- 2021
13. Terahertz spectroscopy for all-optical spintronic characterization of the spin-Hall-effect metals Pt, W and Cu80Ir20
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Markus Münzenberg, Oliver Gueckstock, Vasily V. Temnov, Samridh Jaiswal, Lukas Nadvornik, Tom Seifert, Mathias Kläui, S.M. Rouzegar, Gerhard Jakob, Tobias Kampfrath, Martin Wolf, N.M. Tran, Institut des Molécules et Matériaux du Mans (IMMM), Le Mans Université (UM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Fritz-Haber-Institut der Max-Planck-Gesellschaft (FHI), Max Planck Society, Institut für Physik [Mainz], Johannes Gutenberg - Universität Mainz (JGU), Fachbereich Physik [Berlin], and Freie Universität Berlin
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Materials science ,Acoustics and Ultrasonics ,530 Physics ,terahertz emission spectroscopy ,FOS: Physical sciences ,02 engineering and technology ,01 natural sciences ,Transition metal ,Hall effect ,0103 physical sciences ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,ultrafast spincaloritronics ,010306 general physics ,Spectroscopy ,ComputingMilieux_MISCELLANEOUS ,terahertz transmission spectroscopy ,ultrafast spintronics ,Condensed Matter - Materials Science ,Spintronics ,Condensed Matter - Mesoscale and Nanoscale Physics ,business.industry ,Relaxation (NMR) ,Refractory metals ,Materials Science (cond-mat.mtrl-sci) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,530 Physik ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,3. Good health ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Terahertz spectroscopy and technology ,Spin Hall effect ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Optoelectronics ,0210 nano-technology ,business - Abstract
Identifying materials with an efficient spin-to-charge conversion is crucial for future spintronic applications. In this respect, the spin Hall effect is a central mechanism as it allows for the interconversion of spin and charge currents. Spintronic material research aims at maximizing its efficiency, quantified by the spin Hall angle and the spin-current relaxation length . We develop an all-optical contact-free method with large sample throughput that allows us to extract and . Employing terahertz spectroscopy and an analytical model, magnetic metallic heterostructures involving Pt, W and Cu80Ir20 are characterized in terms of their optical and spintronic properties. The validity of our analytical model is confirmed by the good agreement with literature DC values. For the samples considered here, we find indications that the interface plays a minor role for the spin-current transmission. Our findings establish terahertz emission spectroscopy as a reliable tool complementing the spintronics workbench., Journal of Physics D: Applied Physics, 51 (36), ISSN:0022-3727, ISSN:1361-6463
- Published
- 2018
14. Femtosecond formation dynamics of the spin Seebeck effect revealed by terahertz spectroscopy
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Gerhard Jakob, Samridh Jaiswal, Baerbel Rethfeld, Sebastian T. Weber, Piet W. Brouwer, Martin Wolf, Alexey Melnikov, Sebastian F. Maehrlein, Georg Woltersdorf, Joel Cramer, Mathias Kläui, Ilya Razdolski, Markus Münzenberg, Shun Watanabe, Joseph Barker, Chiara Ciccarelli, Tobias Kampfrath, Sebastian T. B. Goennenwein, Lukas Nadvornik, Tom Seifert, Oliver Gueckstock, Barker, Joseph [0000-0003-4843-5516], Ciccarelli, Chiara [0000-0003-2299-3704], Goennenwein, Sebastian TB [0000-0002-5388-700X], Kläui, Mathias [0000-0002-4848-2569], and Apollo - University of Cambridge Repository
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Magnetism ,Terahertz radiation ,0299 Other Physical Sciences ,Science ,General Physics and Astronomy ,FOS: Physical sciences ,Physics::Optics ,02 engineering and technology ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,Condensed Matter::Materials Science ,Ferrimagnetism ,0103 physical sciences ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,ddc:530 ,010306 general physics ,Spin (physics) ,lcsh:Science ,Terahertz optics ,Physics ,Spin pumping ,Condensed Matter - Materials Science ,Multidisciplinary ,Condensed matter physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Magnon ,Far-infrared laser ,Materials Science (cond-mat.mtrl-sci) ,General Chemistry ,Spintronics ,021001 nanoscience & nanotechnology ,3. Good health ,Terahertz spectroscopy and technology ,lcsh:Q ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology - Abstract
Understanding the transfer of spin angular momentum is essential in modern magnetism research. A model case is the generation of magnons in magnetic insulators by heating an adjacent metal film. Here, we reveal the initial steps of this spin Seebeck effect with, 14 pages, 5 figures
- Published
- 2018
15. Complex Terahertz and Direct Current Inverse Spin Hall Effect in YIG/Cu1-xIrx Bilayers Across a Wide Concentration Range
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Martin Jourdan, Tom Seifert, Gerhard Jakob, Alexander Kronenberg, Felix Fuhrmann, Tobias Kampfrath, Joel Cramer, and Mathias Kläui
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Physics ,Spintronics ,Condensed matter physics ,Terahertz radiation ,Mechanical Engineering ,Direct current ,Yttrium iron garnet ,Bioengineering ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Thermoelectric effect ,Spin Hall effect ,General Materials Science ,Thin film ,010306 general physics ,0210 nano-technology ,Spin-½ - Abstract
We measure the inverse spin Hall effect of Cu1-xIrx thin films on yttrium iron garnet over a wide range of Ir concentrations (0.05 ⩽ x ⩽ 0.7). Spin currents are triggered through the spin Seebeck effect, either by a continuous (dc) temperature gradient or by ultrafast optical heating of the metal layer. The spin Hall current is detected by electrical contacts or measurement of the emitted terahertz radiation. With both approaches, we reveal the same Ir concentration dependence that follows a novel complex, nonmonotonous behavior as compared to previous studies. For small Ir concentrations a signal minimum is observed, whereas a pronounced maximum appears near the equiatomic composition. We identify this behavior as originating from the interplay of different spin Hall mechanisms as well as a concentration-dependent variation of the integrated spin current density in Cu1-xIrx. The coinciding results obtained for dc and ultrafast stimuli provide further support that the spin Seebeck effect extends to terahertz frequencies, thus enabling a transfer of established spintronic measurement schemes into the terahertz regime. Our findings also show that the studied material allows for efficient spin-to-charge conversion even on ultrafast time scales.
- Published
- 2018
16. Complex Terahertz and Direct Current Inverse Spin Hall Effect in YIG/Cu
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Joel, Cramer, Tom, Seifert, Alexander, Kronenberg, Felix, Fuhrmann, Gerhard, Jakob, Martin, Jourdan, Tobias, Kampfrath, and Mathias, Kläui
- Abstract
We measure the inverse spin Hall effect of Cu
- Published
- 2018
17. Terahertz electrical writing speed in an antiferromagnetic memory
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Peter Wadley, Jairo Sinova, K. Olejník, Zdeněk Kašpar, R. P. Campion, Vít Novák, Tom Seifert, Tomas Jungwirth, Petr Kužel, Manuel Baumgartner, Melanie Müller, Tobias Kampfrath, Petr Němec, Joerg Wunderlich, and Pietro Gambardella
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Terahertz radiation ,Physics::Optics ,02 engineering and technology ,Hardware_PERFORMANCEANDRELIABILITY ,01 natural sciences ,Computer Science::Hardware Architecture ,Hertz ,0103 physical sciences ,Hardware_INTEGRATEDCIRCUITS ,Antiferromagnetism ,Atomic lattice ,010306 general physics ,Research Articles ,Spin-½ ,Physics ,Multidisciplinary ,business.industry ,SciAdv r-articles ,021001 nanoscience & nanotechnology ,electrical writing ,Ferromagnetism ,Applied Sciences and Engineering ,writing speed ,Computer Science ,Optoelectronics ,Condensed Matter::Strongly Correlated Electrons ,antiferromagnetic memory ,0210 nano-technology ,business ,Realization (systems) ,Research Article - Abstract
The speed of writing of state-of-the-art ferromagnetic memories is physically limited by an intrinsic gigahertz threshold. Recently, realization of memory devices based on antiferromagnets, in which spin directions periodically alternate from one atomic lattice site to the next has moved research in an alternative direction. We experimentally demonstrate at room temperature that the speed of reversible electrical writing in a memory device can be scaled up to terahertz using an antiferromagnet. A current-induced spin-torque mechanism is responsible for the switching in our memory devices throughout the 12-order-of-magnitude range of writing speeds from hertz to terahertz. Our work opens the path toward the development of memory-logic technology reaching the elusive terahertz band., Science Advances, 4 (3), ISSN:2375-2548
- Published
- 2018
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18. Ultrabroadband single-cycle terahertz pulses with peak fields of 300 kV cm-1 from a metallic spintronic emitter
- Author
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Gerhard Jakob, Mathias Kläui, Stephan Winnerl, Mohsen Sajadi, Tom Seifert, Tobias Kampfrath, Martin Wolf, and Samridh Jaiswal
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Electromagnetic field ,Materials science ,Physics and Astronomy (miscellaneous) ,Terahertz radiation ,FOS: Physical sciences ,02 engineering and technology ,01 natural sciences ,law.invention ,law ,0103 physical sciences ,Common emitter ,010302 applied physics ,Condensed Matter - Materials Science ,business.industry ,Materials Science (cond-mat.mtrl-sci) ,021001 nanoscience & nanotechnology ,Laser ,3. Good health ,Pulse (physics) ,Wavelength ,Amplitude ,Femtosecond ,Optoelectronics ,0210 nano-technology ,business ,Optics (physics.optics) ,Physics - Optics - Abstract
To explore the capabilities of metallic spintronic thin-film stacks as a source of intense and broadband terahertz electromagnetic fields, we excite a W/CoFeB/Pt trilayer on a large-area glass substrate (diameter of 7.5 cm) by a femtosecond laser pulse (energy 5.5 mJ, duration 40 fs, wavelength 800 nm). After focusing, the emitted terahertz pulse is measured to have a duration of 230 fs, a peak field of 300 kV cm$^{-1}$ and an energy of 5 nJ. In particular, the waveform exhibits a gapless spectrum extending from 1 to 10 THz at 10% of amplitude maximum, thereby facilitating nonlinear control over matter in this difficult-to-reach frequency range and on the sub-picosecond time scale., 7 pages, 4 figures
- Published
- 2017
19. Efficient metallic spintronic emitters of ultrabroadband terahertz radiation
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Yuriy Mokrousov, Peter M. Oppeneer, Martin Wolf, Tom Seifert, Alexander Kronenberg, Eric Beaurepaire, Dmitry Turchinovich, Mathias Kläui, John Hannegan, Frank Freimuth, Martin Jourdan, Markus Münzenberg, Samridh Jaiswal, J. Henrizi, Tobias Kampfrath, Gerhard Jakob, L. M. Hayden, Ulrike Martens, Lukas Braun, Ilie Radu, and Pablo Maldonado
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Terahertz gap ,Materials science ,Terahertz radiation ,FOS: Physical sciences ,Physics::Optics ,02 engineering and technology ,7. Clean energy ,01 natural sciences ,Photomixing ,Optics ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,010306 general physics ,Terahertz time-domain spectroscopy ,Condensed Matter - Materials Science ,Spintronics ,Condensed Matter - Mesoscale and Nanoscale Physics ,business.industry ,Far-infrared laser ,Materials Science (cond-mat.mtrl-sci) ,Physik (inkl. Astronomie) ,021001 nanoscience & nanotechnology ,Atomic and Molecular Physics, and Optics ,3. Good health ,Electronic, Optical and Magnetic Materials ,Terahertz spectroscopy and technology ,Spin Hall effect ,Optoelectronics ,0210 nano-technology ,business - Abstract
Terahertz electromagnetic radiation is extremely useful for numerous applications such as imaging and spectroscopy. Therefore, it is highly desirable to have an efficient table-top emitter covering the 1-to-30-THz window whilst being driven by a low-cost, low-power femtosecond laser oscillator. So far, all solid-state emitters solely exploit physics related to the electron charge and deliver emission spectra with substantial gaps. Here, we take advantage of the electron spin to realize a conceptually new terahertz source which relies on tailored fundamental spintronic and photonic phenomena in magnetic metal multilayers: ultrafast photo-induced spin currents, the inverse spin-Hall effect and a broadband Fabry-P\'erot resonance. Guided by an analytical model, such spintronic route offers unique possibilities for systematic optimization. We find that a 5.8-nm-thick W/CoFeB/Pt trilayer generates ultrashort pulses fully covering the 1-to-30-THz range. Our novel source outperforms laser-oscillator-driven emitters such as ZnTe(110) crystals in terms of bandwidth, terahertz-field amplitude, flexibility, scalability and cost., Comment: 18 pages, 10 figures
- Published
- 2015
20. Origin of surface trap states in CdS quantum dots: relationship between size dependent photoluminescence and sulfur vacancy trap states
- Author
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Masayuki Kanehara, Aisea Veamatahau, Tom Seifert, Kay Latham, Satoshi Makuta, Toshiharu Teranishi, Yasuhiro Tachibana, and Bo Jiang
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education.field_of_study ,Photoluminescence ,Chemistry ,Population ,Analytical chemistry ,General Physics and Astronomy ,Penning trap ,X-ray photoelectron spectroscopy ,Quantum dot ,Vacancy defect ,Physical and Theoretical Chemistry ,education ,Spectroscopy ,Surface states - Abstract
Monodisperse cadmium sulphide (CdS) quantum dots (QDs) with a tunable size from 1.4 to 4.3 nm were synthesized by a non-injection method, and their surface states were characterized by photoluminescence spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The steady state photoluminescence study identified that the proportion of the trap state emission increased with the QD size decrease, while from the photoluminescence decay study, it appeared that the trap state emission results from the emission via a surface deep trap state. The XPS measurements revealed the existence of surface Cd with sulfur vacancy sites which act as electron trap sites, and the population of these sites increases with the QD size decrease. These results are consistent to conclude that the trap state emission mainly originates from the surface deep trapped electrons at the surface Cd with sulfur vacancy sites.
- Published
- 2014
21. Tuning whispering gallery modes using internal aerostatic pressure
- Author
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Jonathan M. Ward, Tom Seifert, Oliver Benson, and Rico Henze
- Subjects
Materials science ,Atmospheric pressure ,Bar (music) ,business.industry ,Physics::Optics ,Atomic and Molecular Physics, and Optics ,law.invention ,Physics::Fluid Dynamics ,Resonator ,Pressure measurement ,Optics ,law ,Q factor ,Microbubbles ,Whispering-gallery wave ,business ,Refractive index - Abstract
Aerostatic tuning of whispering gallery modes (WGMs) in a microbubble resonator is demonstrated. The optical modes are redshifted over hundreds of gigahertz (GHz) simply by increasing the air pressure (up to 6 bars) inside the microbubble. A description of the pressure tuning properties of the WGMs in microbubbles is given in terms of the corresponding elasto-optical equations of spherical shells and the results are compared to experimental data. Microbubbles as small as 74 μm are tested and the experimental results show excellent agreement with the theory. An estimation method is developed for calculating the wall thicknesses of the microbubbles from the diameters, which are measured via direct microscopy. A geometrical factor χ is defined and a linear relationship between the shift rate (GHz/bar) of the bubbles modes and χ is observed.
- Published
- 2011
22. Terahertz Spin‐to‐Charge Conversion by Interfacial Skew Scattering in Metallic Bilayers
- Author
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Lukas Nadvornik, Tom Seifert, Mehran Vafaee, Mathias Kläui, Genaro Bierhance, Joel Cramer, Maria Andromachi Syskaki, Oliver Gueckstock, Tobias Kampfrath, Gerhard Jakob, Georg Woltersdorf, Martin Gradhand, Reza Rouzegar, Ingrid Mertig, and Martin Wolf
- Subjects
spectroscopy ,Materials science ,spin-to-charge conversion ,530 Physics ,Terahertz radiation ,terahertz emission spectroscopy ,terahertz emission ,02 engineering and technology ,Electron ,010402 general chemistry ,7. Clean energy ,01 natural sciences ,General Materials Science ,Spectroscopy ,Spin-½ ,Condensed matter physics ,Scattering ,Mechanical Engineering ,Charge (physics) ,Heterojunction ,530 Physik ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,skew scattering ,Ferromagnetism ,Mechanics of Materials ,interface ,0210 nano-technology - Abstract
The efficient conversion of spin to charge transport and vice versa is of major relevance for the detection and generation of spin currents in spin‐based electronics. Interfaces of heterostructures are known to have a marked impact on this process. Here, terahertz (THz) emission spectroscopy is used to study ultrafast spin‐to‐charge‐current conversion (S2C) in about 50 prototypical F|N bilayers consisting of a ferromagnetic layer F (e.g., Ni81Fe19, Co, or Fe) and a nonmagnetic layer N with strong (Pt) or weak (Cu and Al) spin‐orbit coupling. Varying the structure of the F/N interface leads to a drastic change in the amplitude and even inversion of the polarity of the THz charge current. Remarkably, when N is a material with small spin Hall angle, a dominant interface contribution to the ultrafast charge current is found. Its magnitude amounts to as much as about 20% of that found in the F|Pt reference sample. Symmetry arguments and first‐principles calculations strongly suggest that the interfacial S2C arises from skew scattering of spin‐polarized electrons at interface imperfections. The results highlight the potential of skew scattering for interfacial S2C and propose a promising route to enhanced S2C by tailored interfaces at all frequencies from DC to terahertz. ISSN:0935-9648 ISSN:1521-4095
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