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Leenders RA, Afanasiev D, Kimel AV, Mikhaylovskiy RV. Canted spin order as a platform for ultrafast conversion of magnons. Nature 2024; 630:335-339. [PMID: 38811734 PMCID: PMC11168928 DOI: 10.1038/s41586-024-07448-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 04/19/2024] [Indexed: 05/31/2024]
Abstract
Traditionally, magnetic solids are divided into two main classes-ferromagnets and antiferromagnets with parallel and antiparallel spin orders, respectively. Although normally the antiferromagnets have zero magnetization, in some of them an additional antisymmetric spin-spin interaction arises owing to a strong spin-orbit coupling and results in canting of the spins, thereby producing net magnetization. The canted antiferromagnets combine antiferromagnetic order with phenomena typical of ferromagnets and hold great potential for spintronics and magnonics1-5. In this way, they can be identified as closely related to the recently proposed new class of magnetic materials called altermagnets6-9. Altermagnets are predicted to have strong magneto-optical effects, terahertz-frequency spin dynamics and degeneracy lifting for chiral spin waves10 (that is, all of the effects present in the canted antiferromagnets11,12). Here, by utilizing these unique phenomena, we demonstrate a new functionality of canted spin order for magnonics and show that it facilitates mechanisms converting a magnon at the centre of the Brillouin zone into propagating magnons using nonlinear magnon-magnon interactions activated by an ultrafast laser pulse. Our experimental findings supported by theoretical analysis show that the mechanism is enabled by the spin canting.
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Affiliation(s)
- R A Leenders
- Department of Physics, Lancaster University, Lancaster, UK
| | - D Afanasiev
- Radboud University, Institute for Molecules and Materials, Nijmegen, The Netherlands.
| | - A V Kimel
- Radboud University, Institute for Molecules and Materials, Nijmegen, The Netherlands
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Angulo G, Milkiewicz J, Kattnig D, Nejbauer M, Stepanenko Y, Szczepanek J, Radzewicz C, Wnuk P, Grampp G. Influence of the excitation light intensity on the rate of fluorescence quenching reactions: pulsed experiments. Phys Chem Chem Phys 2017; 19:6274-6285. [PMID: 28195278 DOI: 10.1039/c6cp08562h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effect of multiple light excitation events on bimolecular photo-induced electron transfer reactions in liquid solution is studied experimentally. It is found that the decay of fluorescence can be up to 25% faster if a second photon is absorbed after a first cycle of quenching and recombination. A theoretical model is presented which ascribes this effect to the enrichment of the concentration of quenchers in the immediate vicinity of fluorophores that have been previously excited. Despite its simplicity, the model delivers a qualitative agreement with the observed experimental trends. The original theory by Burshtein and Igoshin (J. Chem. Phys., 2000, 112, 10930-10940) was created for continuous light excitation though. A qualitative extrapolation from the here presented pulse experiments to the continuous excitation conditions lead us to conclude that in the latter the order of magnitude of the increase of the quenching efficiency upon increasing the light intensity of excitation, must also be on the order of tens of percent. These results mean that the rate constant for photo-induced bimolecular reactions depends not only on the usual known factors, such as temperature, viscosity and other properties of the medium, but also on the intensity of the excitation light.
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Affiliation(s)
- Gonzalo Angulo
- Institute of Physical Chemistry, Polish Academy of Sciences, 44/52 Kasprzaka, 01-224 Warsaw, Poland.
| | - Jadwiga Milkiewicz
- Institute of Physical Chemistry, Polish Academy of Sciences, 44/52 Kasprzaka, 01-224 Warsaw, Poland.
| | - Daniel Kattnig
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Michał Nejbauer
- Institute of Physical Chemistry, Polish Academy of Sciences, 44/52 Kasprzaka, 01-224 Warsaw, Poland.
| | - Yuriy Stepanenko
- Institute of Physical Chemistry, Polish Academy of Sciences, 44/52 Kasprzaka, 01-224 Warsaw, Poland.
| | - Jan Szczepanek
- Institute of Physical Chemistry, Polish Academy of Sciences, 44/52 Kasprzaka, 01-224 Warsaw, Poland. and Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - Czesław Radzewicz
- Institute of Physical Chemistry, Polish Academy of Sciences, 44/52 Kasprzaka, 01-224 Warsaw, Poland. and Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - Paweł Wnuk
- Institute of Physical Chemistry, Polish Academy of Sciences, 44/52 Kasprzaka, 01-224 Warsaw, Poland. and Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland and Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, D-85748 Garching, Germany and Fakultät für Physik, Ludwig-Maximilians-Universität München, Am Coulombwall 1, D-85748 Garching, Germany
| | - Günter Grampp
- Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria
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Peceli D, Hu H, Fishman DA, Webster S, Przhonska OV, Kurdyukov VV, Slominsky YL, Tolmachev AI, Kachkovski AD, Gerasov AO, Masunov AE, Hagan DJ, Van Stryland EW. Enhanced intersystem crossing rate in polymethine-like molecules: sulfur-containing squaraines versus oxygen-containing analogues. J Phys Chem A 2013; 117:2333-46. [PMID: 23427868 DOI: 10.1021/jp400276g] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two different approaches to increase intersystem crossing rates in polymethine-like molecules are presented: traditional heavy-atom substitution and molecular levels engineering. Linear and nonlinear optical properties of a series of polymethine dyes with Br- and Se-atom substitution, and a series of new squaraine molecules, where one or two oxygen atoms in a squaraine bridge are replaced with sulfur atoms, are investigated. A consequence of the oxygen-to-sulfur substitution in squaraines is the inversion of their lowest-lying ππ* and nπ* states leading to a significant reduction of singlet-triplet energy difference and opening of an additional intersystem channel of relaxation. Experimental studies show that triplet quantum yields for polymethine dyes with heavy-atom substitutions are small (not more than 10%), while for sulfur-containing squaraines these values reach almost unity. Linear spectroscopic characterization includes absorption, fluorescence, quantum yield, anisotropy, and singlet oxygen generation measurements. Nonlinear characterization, performed by picosecond and femtosecond laser systems (pump-probe and Z-scan measurements), includes measurements of the triplet quantum yields, excited state absorption, two-photon absorption, and singlet and triplet state lifetimes. Experimental results are in agreement with density functional theory calculations allowing determination of the energy positions, spin-orbital coupling, and electronic configurations of the lowest electronic transitions.
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Affiliation(s)
- Davorin Peceli
- CREOL: College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816, United States
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Riedle E, Bradler M, Wenninger M, Sailer CF, Pugliesi I. Electronic transient spectroscopy from the deep UV to the NIR: unambiguous disentanglement of complex processes. Faraday Discuss 2013; 163:139-58; discussion 243-75. [PMID: 24020200 DOI: 10.1039/c3fd00010a] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Eberhard Riedle
- Lehrstuhl für BioMolekulare Optik, Ludwig-Maximilians-Universität München, Oettingenstr. 67, 80538 Miünchen, Germany.
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