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42 results on '"Wawro, Andrzej"'

1. Huge Dzyaloshinskii-Moriya interactions in Re_Co_Pt thin films

Author

Fakhredine, Amar, Wawro, Andrzej, and Autieri, Carmine

Subjects
Condensed Matter - Materials Science
Abstract

We investigate the magnetization and the Dzyaloshinskii-Moriya interactions (DMI) in Pt/Co/Re thin films in the case of perfect interfaces and upon the introduction of intermixing on both Co interfaces. Calculations were implemented on a series of systems with a varied number of cobalt atomic layers (ALs). Remarkably, the Re is able to introduce a DMI at the interface with cobalt and also, increase the DMI at the Pt/Co interface. We demonstrate that the chiral magnetic multilayer Pt/Co/Re with chiral spin structure can achieve a huge DMI value which is almost double of that attained in the prototype system W/Co/Pt. We study also the DMI as a function of the Re thickness finding the optimal thickness to maximize the DMI. When we include a disorder that cancels a contribution from all first-neighbor Co atoms in the intermixed region, we found out that intermixing at the two interfaces affects the strength of the DMI solely when introduced at the Pt/Co interface where the DMI loses almost half of its value. On the contrary, the mixing at the Co/Re interface has very little or no effect as compared to the case with perfect interfaces. The value of the DMI would be somewhere between the perfect interface case and the totally intermixed case. The realization of such a device should focus on the reduction of the Pt/Co intermixing to realize this huge DMI interaction.

Published
2023
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2. Interfacial Dzyaloshinskii-Moriya interaction in epitaxial W/Co/Pt multilayers

Author

Jena, Sukanta Kumar, Islam, Rajibul, Milińska, Ewelina, Jakubowski, Marcin M., Minikayev, Roman, Lewińska, Sabina, Lynnyk, Artem, Pietruczik, Aleksiej, Aleszkiewicz, Paweł, Autieri, Carmine, and Wawro, Andrzej

Subjects
Condensed Matter - Materials Science
Abstract

Dzyaloshinskii-Moriya interaction (DMI) manifesting in asymmetric layered ferromagnetic films gives rise to non-colinear spin structures stabilizing magnetization configurations with nontrivial topology. In this work magnetization reversal, domain structure, and strength of DMI are related with the structure of W/Co/Pt multilayers grown by molecular beam epitaxy. Applied growth method enables fabrication of layered systems with higher crystalline quality than commonly applied sputtering techniques. As a result, a high value of D coefficient was determined from the aligned magnetic domain stripe structure, substantially exceeding 2 mJ/m2. The highest value of DMI value D$_{eff}$ = 2.64mj/m2 and strength of surface DMI parameter DS = 1.83pJ/m for N=10 has been observed. Experimental results coincide precisely with those obtained from structure based micromagnetic modelling and density functional theory calculations performed for well-defined layered stacks. This high value of DMI strength originates from dominating contributions of the interfacial atomic Co layers and additive character from both interface types.

Published
2023
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4. Structural, magnetostatic and magnetodynamic studies of Co/Mo-based uncompensated synthetic antiferromagnets

Author

Ogrodnik, Piotr, Kanak, Jarosław, Czapkiewicz, Maciej, Ziętek, Sławomir, Pietruczik, Aleksiej, Morawiec, Krzysztof, Dłużewski, Piotr, Dybko, Krzysztof, Wawro, Andrzej, and Stobiecki, Tomasz

Subjects
Condensed Matter - Materials Science, Physics - Applied Physics
Abstract

In this work, we comprehensively investigate and discuss the structural, magnetostatic, dynamic, and magnetoresistive properties of epitaxial Co/Mo superlattices. The magnetization of the Co sublayers is coupled antiferromagnetically with a strength that depends on the thickness of the nonmagnetic Mo spacer. The magnetization and magnetoresistance hysteresis loops clearly reflect interlayer exchange coupling and the occurrence of uniaxial magnetic anisotropy induced by the strained Co sublayers. Upon accounting for a deviation of the sublayer thicknesses from the nominal value, theoretical modeling, including both micromagnetic and macrospin approaches, precisely reproduces experimental magnetic hysteresis loops, magnetoresistance curves, and ferromagnetic resonance dispersion relations. The Mo spacer thickness as a function of the interlayer magnetic coupling is determined as a fitting parameter by modeling the experimental results.

Published
2019
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5. Huge Dzyaloshinskii–Moriya interactions in Pt/Co/Re thin films.

Author

Fakhredine, Amar, Wawro, Andrzej, and Autieri, Carmine

Subjects
*THIN films, *ATOMIC number, *NUMBER systems, *CHIRALITY of nuclear particles, *MAGNETIZATION, *COBALT
Abstract

We investigate the magnetization and the Dzyaloshinskii–Moriya interactions (DMI) in Pt/Co/Re thin films in the case of perfect interfaces and upon the introduction of intermixing on both Co interfaces. Calculations were implemented on a series of systems with a countable number of cobalt atomic layers. Remarkably, Re can introduce a DMI at the interface with cobalt and also increase the DMI at the Pt/Co interface. We demonstrate that the chiral magnetic multilayer Pt/Co/Re with a chiral spin structure can achieve a substantial DMI value, which is almost double that attained in the prototype system Pt/Co/W. We also study the DMI as a function of the Re thickness, finding the optimal thickness to maximize the DMI. When we include a disorder that cancels a contribution from all first-neighbor Co atoms in the intermixed region, we find out that intermixing at the two interfaces affects the strength of the DMI solely when introduced at the Pt/Co interface, where the DMI loses almost half of its value. On the contrary, the mixing at the Co/Re interface has very little or no effect where the calculated values were not significantly decreased as compared to the case with perfect interfaces. [ABSTRACT FROM AUTHOR]

Published
2024
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6. Mitigating space charge in time-resolved photoelectron spectroscopy to study laser-heated copper dynamics in the high fluence regime

Author

Lévy, Anna, primary, Villa, Manuel De Anda, additional, Hatifi, Mohamed, additional, Lamour, Emily, additional, Macé, Stéphane, additional, Prigent, Christophe, additional, Steydli, Sébastien, additional, Trassinelli, Martino, additional, Vernhet, Dominique, additional, Grisenti, Robert E., additional, Sobierajski, Ryszard, additional, Wawro, Andrzej, additional, Lecherbourg, Ludovic, additional, Jouin, Hervé, additional, Bouillaud, Rodrigue, additional, Descamps, Dominique, additional, Dorchies, Fabien, additional, Fedorov, Nikita, additional, Petit, Stéphane, additional, and Gaudin, Jérôme, additional

Published
2024
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13. Effects of the deposition rate on growth modes of Ag islands on the hydrogen-terminated Si(111)-(1×1) surface: The role of surface energy and quantum size effect.

Author

Jungmin Kang, Toyoaki Eguchi, Erina Kawamoto, Stephane Yu Matsushita, Kenya Haga, Shino Kanagawa, Wawro, Andrzej, Czajka, Ryszard, Hiroki Kato, and Shozo Suto

Subjects
GOLD, CRYSTAL growth, LOW energy electron diffraction, SCANNING tunneling microscopy, EPITAXY
Abstract

We have investigated the early stage of Ag island growth at 2 monolayer (ML) coverage on the hydrogen-terminated Si(111)-(1×1) surface using low-energy electron-diffraction (LEED) and scanning tunneling microscopy (STM) at room temperature. First, it is found that the Ag(10) LEED pattern varies from arc-like spots to three spots by changing the Ag deposition rate from 1:0 × 10-1 (a fast deposition rate) to 1:1 × 10-4 (a slow deposition rate) ML/s. Second, STM observation reveals that adsorbed Ag atoms grow into dome-like three dimensional (3D) clusters at the fast deposition rate and flat-top two dimensional (2D) islands at the slow deposition rate. Third, most abundant 2D islands show the 8 atomic layer height, which coincides with that obtained from the quantum size effect. The side structures of 2D islands agree well with those calculated from Wulff theory. We will discuss the exact nature of 3D clusters and 2D islands of Ag grown on the hydrogen-terminated Si(111)-(1×1) surface and these results indicate the possibility of using kinetic controlled growth to investigate the physics of crystal growth. [ABSTRACT FROM AUTHOR]

Published
2017
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21. HREELS, STM, and STS study of CH3-terminated Si(111)-(1×1) surface.

Author

Yamada, Taro, Kawai, Maki, Wawro, Andrzej, Suto, Shozo, and Kasuya, Atsuo

Subjects
CHEMICAL reagents, SILICON, SPECTRUM analysis, GRIGNARD reagents, MICROSCOPY, ELECTRON spectroscopy
Abstract

An ideally (1×1)-CH3(methyl)-terminated Si(111) surface was composed by Grignard reaction of photochlorinated Si(111) and the surface structure was for the first time confirmed by Auger electron spectroscopy, low energy electron diffraction, high-resolution electron energy loss spectroscopy (HREELS), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS). HREELS revealed the vibration modes associated to the CH3-group as well as the C-Si bond. STM discerned an adlattice with (1×1) periodicity on Si(111) composed of protrusions with internal features, covering all surface terraces. The surface structure was confirmed to be stable at temperatures below 600 K. STS showed that an occupied-state band exists at gap voltage of -1.57 eV, generated by the surface CH3 adlattice. This CH3:Si(111)-(1×1) adlayer with high stability and unique electronic property is prospective for applications such as nanoscale lithography and advanced electrochemistry.© 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2004
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24. Effects of the deposition rate on growth modes of Ag islands on the hydrogen-terminated Si(111)-(1 × 1) surface: The role of surface energy and quantum size effect

Author

Kang, Jungmin, primary, Eguchi, Toyoaki, additional, Kawamoto, Erina, additional, Matsushita, Stephane Yu, additional, Haga, Kenya, additional, Kanagawa, Shino, additional, Wawro, Andrzej, additional, Czajka, Ryszard, additional, Kato, Hiroki, additional, and Suto, Shozo, additional

Published
2017
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26. Polarized neutron reflectivity and X-ray scattering measurements as tools to study properties of Pt/Co/Pt ultrathin layers irradiated by femtosecond laser pulses

Author

Szuszkiewicz, Wojciech, primary, Ott, Frédéric, additional, Kisielewski, Jan, additional, Sveklo, Iosif, additional, Dynowska, Elżbieta, additional, Minikayev, Roman, additional, Kurant, Zbigniew, additional, Kuna, Rafał, additional, Jakubowski, Marcin, additional, Wawro, Andrzej, additional, Sobierajski, Ryszard, additional, and Maziewski, Andrzej, additional

Published
2016
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27. Vibrational Modes of C_<60> Fullerene Adsorbed on Si(100)2×1 Surface Studied by High-Resolution Electron-Energy-Loss Spectroscopy

Author

SUTO, Shozo, KASUYA, Atsuo, IKENO, Osamu, HORIGUCHI, Nobuhiro, WAWRO, Andrzej, GOTO, Takenari, and NISHINA, Yuichiro

Subjects
HREELS, fullerene, %22">C_<60>, Vibrational mode, Si(100)2x1 surface
Abstract

We have measured the inelastic electron-energy-loss spectra of C_ on the Si(100)2x1 surface in the infra-red energy range. If C_ is evaporated 5Å (approximately half a monolayer) on Si(100), a strong energy loss peak appears at 65 meV, and weak peaks and shoulders at 72, 144, and 175 meV. In the 12Å thick film, additional weak peaks at 96, 160, and 189 meV become more apparent. Intensities of these peaks are comparable to those of thick films measured by infra-red absorption and by Raman scattering spectroscopies. Moreover, we have measured the angle dependence of the inelastic electron intensity. These results suggest appreciable interactions between C_ and the dangling bonds of Si surface.

Published
1994

29. Magnetization states and magnetization processes in nanostructures: From a single layer to multilayers (Phys. Status Solidi A 5∕2014)

Author

Maziewski, Andrzej, primary, Fassbender, Jürgen, additional, Kisielewski, Jan, additional, Kisielewski, Marek, additional, Kurant, Zbigniew, additional, Mazalski, Piotr, additional, Stobiecki, Feliks, additional, Stupakiewicz, Andrzej, additional, Sveklo, Iosif, additional, Tekielak, Maria, additional, Wawro, Andrzej, additional, and Zablotskii, Vitalii, additional

Published
2014
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33. Preparation of an Ultraclean and Atomically Controlled Hydrogen-Terminated Si(111)-(1× 1) Surface Revealed by High Resolution Electron Energy Loss Spectroscopy, Atomic Force Microscopy, and Scanning Tunneling Microscopy: Aqueous NH4F Etching Process of Si(111)

Author

Kato, Hiroki, primary, Taoka, Takumi, additional, Nishikata, Susumu, additional, Sazaki, Gen, additional, Yamada, Taro, additional, Czajka, Ryszard, additional, Wawro, Andrzej, additional, Nakajima, Kazuo, additional, Kasuya, Atsuo, additional, and Suto, Shozo, additional

Published
2007
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34. XAS and XMCD studies of magnetic properties modifications of Pt/Co/Au and Pt/Co/Pt trilayers induced by Ga+ ions irradiation.

Author

Mazalski, Piotr, Sveklo, Iosif, Kurant, Zbigniew, Ollefs, Katharina, Rogalev, Andrei, Wilhelm, Fabrice, Fassbender, Juergen, Baczewski, Lech Tomasz, Wawro, Andrzej, and Maziewski, Andrzej

Subjects
MAGNETIC films, PERPENDICULAR magnetic anisotropy, X-ray absorption, COMPUTER simulation, ELECTRONIC structure
Abstract

Magnetic and magneto-optical properties of Pt/Co/Au and Pt/Co/Pt trilayers subjected to 30 keV Ga+ ion irradiation are compared. In two-dimensional maps of these properties as a function of cobalt thickness and ion fluence, two branches with perpendicular magnetic anisotropy (PMA) for Pt/Co/Pt trilayers are well distinguished. The replacement of the Pt capping layer with Au results in the two branches still being visible but the in-plane anisotropy for the low-fluence branch is suppressed whereas the high-fluence branch displays PMA. The X-ray absorption spectra and X-ray magnetic circular dichroism (XMCD) spectra are discussed and compared with non-irradiated reference samples. The changes of their shapes and peak amplitude, particularly for the high-fluence branch, are related to the modifications of the local environment of Co(Pt) atoms and the etching effects induced by ion irradiation. Additionally, in irradiated trilayers the XMCD measurements at the Pt L2,3-edge reveal an increase of the magnetic moment induced in Pt atoms. [ABSTRACT FROM AUTHOR]

Published
2015
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39. (100) GaAs surface treatment prior to contact metal deposition in AlGaAs/GaAs quantum cascade laser processing.

Author

PAPIS, EWA, BARAŃSKA, ANNA, KARBOWNIK, PIOTR, SZERLING, ANNA, WÓJCIK-JEDLIŃSKA, ANNA, BUGAJSKI, MACIEJ, RZODKIEWICZ, WITOLD, SZADE, JACEK, and WAWRO, ANDRZEJ

Subjects
GALLIUM arsenide, ARGON, SEMICONDUCTOR lasers, SPUTTERING (Physics), ELLIPSOMETRY
Abstract

The effects of HCl-based chemical and Ar+ sputter etching treatment on (100) GaAs surface properties with the aim to develop the procedure of surface preparation before metal deposition have been investigated. Variable angle spectroscopic ellipsometry, X-ray photoelectron spectroscopy, atomic force microscopy and photoluminescence have been used to study the surface characterization. We show that combining chemical etching in 5% HCl with Ar+ sputter etching gives the best results for surface cleaning prior to metal deposition. The application of this two-step treatment allows to obtain Ni/AuGe/Ni/Au ohmic contact with rc = 2x10-6 Ωcm² with excellent adhesion and long-term thermal stability. [ABSTRACT FROM AUTHOR]

Published
2009

40. VIBRATIONAL PROPERTIES AND STRUCTURE OF 60 THIN FILMS ON (111)-(7×7) AND GRAPHITE SURFACES.

Author

SUTO, SHOZO, KASUYA, ATSUO, HU, CHANG-WU, WAWRO, ANDRZEJ, GOTO, TAKENARI, and NISHINA, YUICHIRO

Abstract

We have investigated the vibrational modes of 60 thin films adsorbed on the (111)-(7×7) and graphite surfaces using high-resolution electron energy-loss spectroscopy in combination with scanning tunneling microscopy (STM). The energy-loss spectra are different in energies and in oscillator strengths for the two surfaces. The differences are attributed to the surface morphology observed with STM. The relation between macroscopic dielectric theory manifested by electron energy loss and microscopic structure measured with STM is discussed in terms of dielectric function theory. [ABSTRACT FROM AUTHOR]

Published
1996
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42. Vibrational Modes of C60Fullerene on Si(111)7×7 Surface: Estimation of Charge Transfer from Silicon Dangling Bonds to C60Molecules

Author

Suto, Shozo, Kasuya, Atsuo, Ikeno, Osamu, Hu, Chang-Wu, Wawro, Andrzej, Nishitani, Ryusuke, and Nishina, Takenari Goto

Abstract

We have investigated vibrational modes of C60monolayer film adsorbed on the Si(111)7×7 surface using high-resolution electron-energy-loss spectroscopy in combination with scanning tunneling microscopy. The differences in energies and in oscillator strengths from a thick C60film (i.e., bulk C60) are discussed in terms of the charge transfer from silicon dangling bonds to C60molecules. The amount of charge transfer is estimated to be 1±1 electron(s) compared with the infrared absorption spectra of alkaline-doped C60fullerides and with the weak electron-molecular-vibration coupling calculation.

Published
1994
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