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  • 1
    Publication Date: 2016-06-22
    Description: Author(s): L. Rettig, C. Dornes, N. Thielemann-Kühn, N. Pontius, H. Zabel, D. L. Schlagel, T. A. Lograsso, M. Chollet, A. Robert, M. Sikorski, S. Song, J. M. Glownia, C. Schüßler-Langeheine, S. L. Johnson, and U. Staub Using femtosecond time-resolved resonant magnetic x-ray diffraction at the Ho L 3 absorption edge, we investigate the demagnetization dynamics in antiferromagnetically ordered metallic Ho after femtosecond optical excitation. Tuning the x-ray energy to the electric dipole ( E 1 , 2 p → 5 d ) or quadrupole ( E … [Phys. Rev. Lett. 116, 257202] Published Tue Jun 21, 2016
    Keywords: Condensed Matter: Electronic Properties, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 2
    Publication Date: 2016-06-22
    Description: Author(s): T. Tsuyama, S. Chakraverty, S. Macke, N. Pontius, C. Schüßler-Langeheine, H. Y. Hwang, Y. Tokura, and H. Wadati We studied the electronic and magnetic dynamics of ferromagnetic insulating BaFeO 3 thin films by using pump-probe time-resolved resonant x-ray reflectivity at the Fe 2 p edge. By changing the excitation density, we found two distinctly different types of demagnetization with a clear threshold behavio… [Phys. Rev. Lett. 116, 256402] Published Tue Jun 21, 2016
    Keywords: Condensed Matter: Electronic Properties, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 3
    Publication Date: 2013-09-24
    Description: Nature Materials 12, 882 (2013). doi:10.1038/nmat3718 Authors: S. de Jong, R. Kukreja, C. Trabant, N. Pontius, C. F. Chang, T. Kachel, M. Beye, F. Sorgenfrei, C. H. Back, B. Bräuer, W. F. Schlotter, J. J. Turner, O. Krupin, M. Doehler, D. Zhu, M. A. Hossain, A. O. Scherz, D. Fausti, F. Novelli, M. Esposito, W. S. Lee, Y. D. Chuang, D. H. Lu, R. G. Moore, M. Yi, M. Trigo, P. Kirchmann, L. Pathey, M. S. Golden, M. Buchholz, P. Metcalf, F. Parmigiani, W. Wurth, A. Föhlisch, C. Schüßler-Langeheine & H. A. Dürr As the oldest known magnetic material, magnetite (Fe3O4) has fascinated mankind for millennia. As the first oxide in which a relationship between electrical conductivity and fluctuating/localized electronic order was shown, magnetite represents a model system for understanding correlated oxides in general. Nevertheless, the exact mechanism of the insulator–metal, or Verwey, transition has long remained inaccessible. Recently, three-Fe-site lattice distortions called trimerons were identified as the characteristic building blocks of the low-temperature insulating electronically ordered phase. Here we investigate the Verwey transition with pump–probe X-ray diffraction and optical reflectivity techniques, and show how trimerons become mobile across the insulator–metal transition. We find this to be a two-step process. After an initial 300 fs destruction of individual trimerons, phase separation occurs on a 1.5±0.2 ps timescale to yield residual insulating and metallic regions. This work establishes the speed limit for switching in future oxide electronics.
    Print ISSN: 1476-1122
    Electronic ISSN: 1476-4660
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 4
    Publication Date: 2013-06-12
    Description: Author(s): V. López-Flores, N. Bergeard, V. Halté, C. Stamm, N. Pontius, M. Hehn, E. Otero, E. Beaurepaire, and C. Boeglin Ultrafast magnetization dynamics induced by femtosecond laser pulses have been measured in ferrimagnetic Co 0.8 Gd 0.2 , Co 0.74 Tb 0.26 , and Co 0.86 Tb 0.14 alloys. Using element sensitivity of x-ray magnetic circular dichroism at the Co L 3 , Tb M 5 , and Gd M 5 edges, we see that the demagnetization dynamics is... [Phys. Rev. B 87, 214412] Published Tue Jun 11, 2013
    Keywords: Magnetism
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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  • 5
    Publication Date: 2014-01-24
    Description: Nature Materials 13, 102 (2014). doi:10.1038/nmat3851 Authors: A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Föhlisch, P. M. Oppeneer & C. Stamm
    Print ISSN: 1476-1122
    Electronic ISSN: 1476-4660
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 6
    Publication Date: 2014-03-13
    Description: Article Femtosecond laser pulses can induce ultrafast changes to the magnetization in magnetic materials. Here, the authors show that the ultrafast demagnetization in ferrimagnets is driven by the transfer of angular momenta between two coupled sublattices whilst the total angular momentum remains constant. Nature Communications doi: 10.1038/ncomms4466 Authors: N. Bergeard, V. López-Flores, V. Halté, M. Hehn, C. Stamm, N. Pontius, E. Beaurepaire, C. Boeglin
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 7
    Publication Date: 2010-05-28
    Description: For an isolated quantum particle, such as an electron, the orbital (L) and spin (S) magnetic moments can change provided that the total angular momentum of the particle is conserved. In condensed matter, an efficient transfer between L and S can occur owing to the spin-orbit interaction, which originates in the relativistic motion of electrons. Disentangling the absolute contributions of the orbital and spin angular momenta is challenging, however, as any transfer between the two occurs on femtosecond timescales. Here we investigate such phenomena by using ultrashort optical laser pulses to change the magnetization of a ferromagnetic film and then probe its dynamics with circularly polarized femtosecond X-ray pulses. Our measurements enable us to disentangle the spin and orbital components of the magnetic moment, revealing different dynamics for L and S. We highlight the important role played by the spin-orbit interaction in the ultrafast laser-induced demagnetization of ferromagnetic films, and show also that the magneto-crystalline anisotropy energy is an important quantity to consider in such processes. Our study provides insights into the dynamics in magnetic systems as well as perspectives for the ultrafast control of information in magnetic recording media.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Boeglin, C -- Beaurepaire, E -- Halte, V -- Lopez-Flores, V -- Stamm, C -- Pontius, N -- Durr, H A -- Bigot, J-Y -- England -- Nature. 2010 May 27;465(7297):458-61. doi: 10.1038/nature09070.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut de Physique et de Chimie des Materiaux de Strasbourg, UMR7504, CNRS et Universite de Strasbourg, 23, rue du Loess, 67034 Strasbourg, France. christine.boeglin@ipcms.u-strasbg.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20505724" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 8
    Publication Date: 2011-04-01
    Description: Ferromagnetic or antiferromagnetic spin ordering is governed by the exchange interaction, the strongest force in magnetism. Understanding spin dynamics in magnetic materials is an issue of crucial importance for progress in information processing and recording technology. Usually the dynamics are studied by observing the collective response of exchange-coupled spins, that is, spin resonances, after an external perturbation by a pulse of magnetic field, current or light. The periods of the corresponding resonances range from one nanosecond for ferromagnets down to one picosecond for antiferromagnets. However, virtually nothing is known about the behaviour of spins in a magnetic material after being excited on a timescale faster than that corresponding to the exchange interaction (10-100 fs), that is, in a non-adiabatic way. Here we use the element-specific technique X-ray magnetic circular dichroism to study spin reversal in GdFeCo that is optically excited on a timescale pertinent to the characteristic time of the exchange interaction between Gd and Fe spins. We unexpectedly find that the ultrafast spin reversal in this material, where spins are coupled antiferromagnetically, occurs by way of a transient ferromagnetic-like state. Following the optical excitation, the net magnetizations of the Gd and Fe sublattices rapidly collapse, switch their direction and rebuild their net magnetic moments at substantially different timescales; the net magnetic moment of the Gd sublattice is found to reverse within 1.5 picoseconds, which is substantially slower than the Fe reversal time of 300 femtoseconds. Consequently, a transient state characterized by a temporary parallel alignment of the net Gd and Fe moments emerges, despite their ground-state antiferromagnetic coupling. These surprising observations, supported by atomistic simulations, provide a concept for the possibility of manipulating magnetic order on the timescale of the exchange interaction.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Radu, I -- Vahaplar, K -- Stamm, C -- Kachel, T -- Pontius, N -- Durr, H A -- Ostler, T A -- Barker, J -- Evans, R F L -- Chantrell, R W -- Tsukamoto, A -- Itoh, A -- Kirilyuk, A -- Rasing, Th -- Kimel, A V -- England -- Nature. 2011 Apr 14;472(7342):205-8. doi: 10.1038/nature09901. Epub 2011 Mar 30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands. i.radu@science.ru.nl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21451521" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 9
    Publication Date: 2013-08-24
    Description: Resonant inelastic X-ray scattering and X-ray emission spectroscopy can be used to probe the energy and dispersion of the elementary low-energy excitations that govern functionality in matter: vibronic, charge, spin and orbital excitations. A key drawback of resonant inelastic X-ray scattering has been the need for high photon densities to compensate for fluorescence yields of less than a per cent for soft X-rays. Sample damage from the dominant non-radiative decays thus limits the materials to which such techniques can be applied and the spectral resolution that can be obtained. A means of improving the yield is therefore highly desirable. Here we demonstrate stimulated X-ray emission for crystalline silicon at photon densities that are easily achievable with free-electron lasers. The stimulated radiative decay of core excited species at the expense of non-radiative processes reduces sample damage and permits narrow-bandwidth detection in the directed beam of stimulated radiation. We deduce how stimulated X-ray emission can be enhanced by several orders of magnitude to provide, with high yield and reduced sample damage, a superior probe for low-energy excitations and their dispersion in matter. This is the first step to bringing nonlinear X-ray physics in the condensed phase from theory to application.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Beye, M -- Schreck, S -- Sorgenfrei, F -- Trabant, C -- Pontius, N -- Schussler-Langeheine, C -- Wurth, W -- Fohlisch, A -- England -- Nature. 2013 Sep 12;501(7466):191-4. doi: 10.1038/nature12449. Epub 2013 Aug 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Methods and Instrumentation of Synchrotron Radiation Research G-ISRR, Helmholtz-Zentrum Berlin fur Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany. martin.beye@helmholtz-berlin.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23965622" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 10
    Publication Date: 2013-03-21
    Description: Nature Materials 12, 332 (2013). doi:10.1038/nmat3546 Authors: A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Föhlisch, P. M. Oppeneer & C. Stamm
    Print ISSN: 1476-1122
    Electronic ISSN: 1476-4660
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Natural Sciences in General , Physics
    Published by Springer Nature
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