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159 results on '"Urazhdin, Sergei"'

52. Nanoscale Transient Magnetization Gratings Created and Probed by Femtosecond Extreme Ultraviolet Pulses

Author

Ksenzov, Dmitriy, primary, Maznev, Alexei A., additional, Unikandanunni, Vivek, additional, Bencivenga, Filippo, additional, Capotondi, Flavio, additional, Caretta, Antonio, additional, Foglia, Laura, additional, Malvestuto, Marco, additional, Masciovecchio, Claudio, additional, Mincigrucci, Riccardo, additional, Nelson, Keith A., additional, Pancaldi, Matteo, additional, Pedersoli, Emanuele, additional, Randolph, Lisa, additional, Rahmann, Hendrik, additional, Urazhdin, Sergei, additional, Bonetti, Stefano, additional, and Gutt, Christian, additional

Published
2021
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61. Spiral metamaterials for terahertz magnetic field enhancement

Author

Pancaldi, Matteo, Polley, Debanjan, Zhou Hagström, Nanna, Hudl, Matthias, Vavassori, Paolo, Urazhdin, Sergei, von Korff Schmising, Clemens, Eisebitt, Stefan, Bonetti, Stefano, Pancaldi, Matteo, Polley, Debanjan, Zhou Hagström, Nanna, Hudl, Matthias, Vavassori, Paolo, Urazhdin, Sergei, von Korff Schmising, Clemens, Eisebitt, Stefan, and Bonetti, Stefano

Abstract

We designed a class of spiral thin-film antennas for enhancing, in the near field, the incident terahertz (THz) magnetic field. Indeed, using existing laser-based THz sources, our metamaterial geometry allows generating magnetic fields of the order of 2 T over a time scale of few picoseconds, enabling the investigation of nonlinear ultrafast spin dynamics in table-top experiments.

Published
2019

63. Ultrathin Wetting Layer-Free Plasmonic Gold Films

Author

Lemasters, Robert, primary, Zhang, Cheng, additional, Manjare, Manoj, additional, Zhu, Wenqi, additional, Song, Junyeob, additional, Urazhdin, Sergei, additional, Lezec, Henri J., additional, Agrawal, Amit, additional, and Harutyunyan, Hayk, additional

Published
2019
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65. Anti-reflection coating design for metallic terahertz meta-materials

Author

Pancaldi, Matteo, Freeman, Ryan, Hudl, Matthias, Hoffmann, Matthias C., Urazhdin, Sergei, Vavassori, Paolo, Bonetti, Stefano, Pancaldi, Matteo, Freeman, Ryan, Hudl, Matthias, Hoffmann, Matthias C., Urazhdin, Sergei, Vavassori, Paolo, and Bonetti, Stefano

Abstract

We demonstrate a silicon-based, single-layer anti-reflection coating that suppresses the reflectivity of metals at near-infrared frequencies, enabling optical probing of nano-scale structures embedded in highly reflective surroundings. Our design does not affect the interaction of terahertz radiation with metallic structures that can be used to achieve terahertz near-field enhancement. We have verified the functionality of the design by calculating and measuring the reflectivity of both infrared and terahertz radiation from a silicon/gold double layer as a function of the silicon thickness. We have also fabricated the unit cell of a terahertz meta-material, a dipole antenna comprising two 20-nm thick extended gold plates separated by a 2 mu m gap, where the terahertz field is locally enhanced. We used the time-domain finite element method to demonstrate that such near-field enhancement is preserved in the presence of the anti-reflection coating. Finally, we performed magneto-optical Kerr effect measurements on a single 3-nm thick, 1-mu m wide magnetic wire placed in the gap of such a dipole antenna. The wire only occupies 2% of the area probed by the laser beam, but its magneto-optical response can be clearly detected. Our design paves the way for ultrafast time-resolved studies, using table-top femtosecond near-infrared lasers, of dynamics in nano-structures driven by strong terahertz radiation.

Published
2018
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66. THz-driven demagnetization with perpendicular magnetic anisotropy : towards ultrafast ballistic switching

Author

Polley, Debanjan, Pancaldi, Matteo, Hudl, Matthias, Vavassori, Paolo, Urazhdin, Sergei, Bonetti, Stefano, Polley, Debanjan, Pancaldi, Matteo, Hudl, Matthias, Vavassori, Paolo, Urazhdin, Sergei, and Bonetti, Stefano

Abstract

We study THz-driven spin dynamics in thin CoPt films with perpendicular magnetic anisotropy. Femtosecond magneto-optical Kerr effect measurements show that demagnetization amplitude of about 1% can be achieved with a peak THz electric field of 300 kV cm(-1), and a corresponding peak magnetic field of 0.1 T. The effect is more than an order of magnitude larger than observed in samples with easy-plane anisotropy irradiated with the same field strength. We also utilize finite-element simulations to design a meta-material structure that can enhance the THz magnetic field by more than an order of magnitude, over an area of several tens of square micrometers. Magnetic fields exceeding 1 Tesla, generated in such meta-materials with the available laser-based THz sources, are expected to produce full magnetization reversal via ultrafast ballistic precession driven by the THz radiation. Our results demonstrate the possibility of table-top ultrafast magnetization reversal induced by THz radiation.

Published
2018
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73. Current-induced reversal in magnetic nanopillars passivated by silicon

Author

Urazhdin, Sergei and Tabor, Phillip

Subjects
Nanotechnology -- Research, Oxidation-reduction reaction -- Analysis, Silicon -- Magnetic properties, Silicon -- Electric properties, Silicon -- Thermal properties, Physics
Abstract

The magnetic multilayer nanopillars are efficiently protected from oxidation by coating with silicon and both the protected and the oxidized nanopillars have displayed an increase in reversal current at cryogenic temperatures. The studies have shown that oxidized nanopillars have displayed anomalous switching statistics at low temperatures, which has provided a simple test for the quality of magnetic nanodevices.

Published
2009

79. Magnetic nano-oscillator driven by pure spin current

Author

Demidov, Vladislav E., primary, Urazhdin, Sergei, additional, Ulrichs, Henning, additional, Tiberkevich, Vasyl, additional, Slavin, Andrei, additional, Baither, Dietmar, additional, Schmitz, Guido, additional, and Demokritov, Sergej O., additional

Published
2012
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98. Excitation and detection of coherent nanoscale spin waves via extreme ultraviolet transient gratings.

Author

Miedaner, Peter R., Berndt, Nadia, Deschamps, Jude, Urazhdin, Sergei, Khatu, Nupur, Fainozzi, Danny, Brioschi, Marta, Carrara, Pietro, Cucini, Riccardo, Rossi, Giorgio, Wittrock, Stefen, Ksenzov, Dmitriy, Mincigrucci, Riccardo, Bencivenga, Filippo, Foglia, Laura, Paltanin, Ettore, Bonetti, Stefano, Engel, Dieter, Schick, Daniel, and Gutt, Christian

Subjects
*SPIN waves, *FEMTOSECOND pulses, *FOUR-wave mixing, *MAGNONS, *INELASTIC scattering, *FREE electron lasers
Abstract

The advent of free electron lasers has opened the opportunity to explore interactions between extreme ultraviolet (EUV) photons and collective excitations in solids. While EUV transient grating spectroscopy, a noncollinear four-wave mixing technique, has already been applied to probe coherent phonons, the potential of EUV radiation for studying nanoscale spin waves has not been harnessed. Here we report EUV transient grating experiments with coherent magnons in Fe/Gd ferrimagnetic multilayers. Magnons with tens of nanometers wavelengths are excited by a pair of femtosecond EUV pulses and detected via diffraction of a probe pulse tuned to an absorption edge of Gd. The results unlock the potential of nonlinear EUV spectroscopy for studying magnons and provide a tool for exploring spin waves in a wave vector range not accessible by established inelastic scattering techniques. [ABSTRACT FROM AUTHOR]

Published
2024
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99. Ultrafast electron dynamics in platinum and gold thin films driven by optical and terahertz fields

Author

Unikandanunni, Vivek, Hoffmann, Matthias, Vavassori, Paolo, Urazhdin, Sergei, Bonetti, Stefano, Unikandanunni, Vivek, Hoffmann, Matthias, Vavassori, Paolo, Urazhdin, Sergei, and Bonetti, Stefano

Abstract

We investigate the ultrafast electron dynamics triggered by terahertz and optical pulses in thin platinum and gold films by probing their transient optical reflectivity. The response of the platinum film to an intense terahertz pulse is similar to the optically-induced dynamics of both films and can be described by a two-temperature model. Surprisingly, gold exhibits a much smaller terahertz pulse-induced reflectivity change and with opposite sign. For platinum, we estimate a 20% larger electron-phonon coupling for the terahertz-driven dynamics compared to the optically-induced one, which we ascribe to an additional nonthermal electron-phonon coupling contribution. We explain the remarkable response of gold to the terahertz field as the field emission of electrons due to Fowler-Nordheim tunneling. Our results provide fundamental insight into the ultrafast processes relevant to modern electro- and magneto-optical applications.

100. THz-driven demagnetization with perpendicular magnetic anisotropy: towards ultrafast ballistic switching

Author

Polley, Debanjan, Pancaldi, Matteo, Hudl, Matthias, Vavassori, Paolo, Urazhdin, Sergei, and Bonetti, Stefano

Subjects
metamaterials, perpendicular magnetic anisotropy, spin transport, terahertz, ultrafast demagnetization, Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Acoustics and Ultrasonics, Surfaces, Coatings and Films, Condensed Matter - Mesoscale and Nanoscale Physics, Settore FIS/01 - Fisica Sperimentale, Physics::Optics, FOS: Physical sciences, Settore FIS/03 - Fisica della Materia, Surfaces, Coatings and Films, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Electronic, Optical and Magnetic Materials
Abstract

We study THz-driven spin dynamics in thin CoPt films with perpendicular magnetic anisotropy. Femtosecond magneto-optical Kerr effect measurements show that demagnetization amplitude of about $1\%$ can be achieved with a peak THz electric field of $300$~kV/cm, and a corresponding peak magnetic field of $0.1$~T. The effect is more than an order of magnitude larger than observed in samples with easy-plane anisotropy irradiated with the same field strength. We also utilize finite-element simulations to design a meta-material structure that can enhance the THz magnetic field by more than an order of magnitude, over an area of several tens of square micrometers. Magnetic fields exceeding $1$~Tesla, generated in such meta-materials with the available laser-based THz sources, are expected to produce full magnetization reversal via ultrafast ballistic precession driven by the THz radiation. Our results demonstrate the possibility of table-top ultrafast magnetization reversal induced by THz radiation., Comment: 9 pages, 5 figures

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