Capturing the fastest spin dynamics in magnetic materials
Magnetism has been the subject of scientific inquiry for more than 2000 years. However, it is still an incompletely understood phenomenon. The fundamental length and time scales for magnetic phenomena range from Å (exchange lengths) and sub-femtoseconds (exchange splitting) on up. Furthermore, a detailed understanding of nanoscale magnetism is critical in the 21st century with dramatic increases in data usage and the the critical need for faster, energy-efficient nanodevices. However, a comprehensive microscopic model of how spins, electrons, photons, and phonons interact does not yet exist. This understanding is fundamentally constrained in large part by a limited ability to directly observe magnetism on all relevant time and length scales - and tools for addressing these questions have only recently become available.
Ultrafast X-ray pulses make it possible to probe element-specific spin dynamics in multi-component magnetic systems, providing rich new information not accessible using visible light. Recent research has shown that extreme ultraviolet (EUV) high harmonic beams are ideal for capturing the fastest spin dynamics in magnetic materials.[1-24] By combining HHG sources with new spectroscopic and imaging techniques, a series of new discoveries have been made. In exciting recent work, it was shown that light can manipulate spins in many materials on few-femtosecond to attosecond timescales. This manipulation could not be observed previously, because many spectroscopic probes average over all excitations and sample depths - and are simply not sensitive to the unique laser-induced spin states present in the material. Key to uncovering this new understanding was a suite of correlated high harmonic based spectroscopies [time- and angle-resolved photoemission spectroscopy (tr-ARPES)], combined with element-specific magneto-optic probes (e.g. EUV MOKE, XMCD), that make it possible to detect unique spin excitations present in the material, as illustrated in the Figure on the right. For example, direct (near-instantaneous) light-induced spin transfer can occur between two elements in magnetic materials, during the light pulse itself –– achieving the fastest manipulation of spins to date.
Looking to the future, it is now possible to extend these new spectroscopy and imaging measurements to the L absorption edges of magnetic media in the soft x-ray region of the spectrum. Recent advances in generating bright, coherent x-rays from femtosecond lasers in the keV region of the spectrum make this feasible for the first time. Imaging of buried magnetic structures, domain interactions, strongly coupled nano layers, and spin dynamics will all be accessible with femtosecond time and nanometer spatial resolution.
Direct light-induced spin transfer between elemental sublattices in a spintronic Heusler material via femtosecond laser excitation, P. Tengdin, C. Gentry, A. Blonsky, D. Zusin, M. Gerrity, L. Hellbruck, Justin Shaw, Y. Kvashnin, E. Delczeg-Czirjak, M. Arora, H. Nembach, T. Silva, S. Koumpouras, O. Eriksson, M. Murnane, Science Advances 6, eaaz1100, DOI: 10.1126/sciadv.aaz1100 (2020)
Coherent ultrafast spin transfer in ferromagnetic alloys, M. Hofherr, S. Huser, P. Tengdin, H. Nembach, S. Weber, J. Shaw, T. Silva, H. Kapteyn, M. Murnane, M. Cinchetti, B. Rethfeld, D. Steil, B. Stadtmuller, S. Sharma, M. Aeschlimann, S. Mathias, Science Advances 6, eaay8717 (2020). DOI: 10.1126/sciadv.aay8717
Attosecond light science and its application for probing quantum materials, X. Shi, C.T. Liao, Z. Tao, E. Cating, M. Murnane, C. Hernendez-Garcia, H. Kapteyn, Invited paper, JPhys Photonics/JPhys B Attosecond focus issue, 53, 184008 (2020). DOI: 10.1088/1361-6455/aba2fb
Recent advances in ultrafast X-ray sources, Robert Schoenlein, Thomas Elsaesser, Karsten Holldack, Zhirong Huang, Henry Kapteyn, Margaret Murnane and Michael Woerner, Phil. Trans. R. Soc. A 377: 20180384. (2019). https://doi.org/10.1098/rsta.2018.0384
Critical Behavior within 20fs Drives the Out-of-Equilibrium Laser-induced Magnetic Phase Transition in Nickel, P. Tengdin, W. You, C. Chen, X. Shi, D. Zusin, Y. Zhang, C. Gentry, A. Blonsky, M. Keller, P. Oppeneer, H. Kapteyn, Z. Tao, M. Murnane, Science Advances 4, 9744 (2018). DOI: 10.1126/sciadv.aap9744
Revealing the universal nature of the ultrafast magnetic phase transition in Ni by correlating extreme ultraviolet magneto-optic and photoemission spectroscopies, W. You, P. Tengdin, C. Chen, X. Shi, D. Zusin, Y. Zhang, C. Gentry, A. Blonsky, M. Keller, P. Oppeneer, H. Kapteyn, Z. Tao, M. Murnane, Phys. Rev. Lett. 121, 077204 (2018). doi/10.1103/PhysRevLett.121.077204. Also selected as an Editor’s Suggestion.
Induced vs. intrinsic magnetic moments in ultrafast magnetization dynamics, M. Hofherr, S. Moretti, J. Shim, S. Heuser, N.Y. Safonova, M. Stiehl, A. Ali, S. Sakshath, J.W. Kim, D.H. Kim, H.J. Kim, J.I. Hong, H. C. Kapteyn, M. M. Murnane, M. Cinchetti, D. Steil, S. Mathias, B. Stadtmuller, M. Albrecht, D.E. Kim, U. Nowak, M. Aeschlimann, Physical Review B 98, 174419 (2018). DOI: 10.1103/PhysRevB.98.174419. Also selected as an Editor's Suggestion.
Direct measurement of the static and transient magneto-optical permittivity of cobalt across the entire M-edge in a reflection geometry by use of polarization scanning, D. Zusin, D. Legut, K. Carva, H. Nembach, S. Mathias, M. Aeschlimann, T. Silva, G. Zhang, P. Oppeneer, H. Kapteyn, M. Murnane, Physical Review B 97, 024433 (2018). https://doi.org/10.1103/PhysRevB.97.024433
Band-structure evolution during the ultrafast ferromagnetic-paramagnetic phase transition in Cobalt, S. Eich, M. Plötzing, M. Rollinger, S. Emmerich, R. Adam, C. Chen, H. Kapteyn, M. Murnane, L. Plucinski, D. Steil, B. Stadtmüller, M. Cinchetti, M. Aeschlimann, C. Schneider, S. Mathias, Science Advances 3, e1602094 (2017). DOI: 10.1126/sciadv.1602094
Distinguishing Attosecond Electron-Electron Scattering and Screening in Transition Metals, C. Chen, Z. Tao, A. Carr, P. Matyba, T. Szilvási, M. Piecuch, S. Emmerich, M. Keller, Dmitriy Zusin, M. Rollinger, W. You, S. Mathias, U. Thumm, M. Mavrikakis, M. Aeschlimann, P. Oppeneer, H. Kapteyn, M. Murnane, PNAS 114, E5300 (2017). doi:10.1073/pnas.1706466114
Observation of ionization enhancement in two-color circularly polarized laser fields, C. Mancuso, K. Dorney, D. Hickstein, J. Chaloupka, X-M. Tong, J. Ellis, H. Kapteyn, M. Murnane, Physical Review A 96, 023402 (2017). DOI: 10.1103/PhysRevA.96.023402
Heisenberg vs. Stoner: Magnon Generation and Exchange Renormalization during Ultrafast Demagnetization, E. Turgut, P. Grychtol, J. Shaw, R. Knut, D. Zusin, D. Legut, K. Carva, H. Nembach, S. Mathias, T. Silva, P. Oppeneer, M. Murnane, H. Kapteyn, Phys. Rev. B 94, 220408 (2016). Selected as Editor’s Suggestion. doi/ 10.1103/PhysRevB.94.220408
Self-amplified photo-induced gap quenching in a correlated electron material, S. Mathias, S. Eich, J. Urbancic, S. Michael, A. Carr, A. Stange, T. Popmintchev, T. Rohwer, M. Wiesenmayer, A. Ruffing, S. Jakobs, S. Hellmann, P. Matyba, C. Chen, L. Kipp, M. Bauer, H. Kapteyn, H. Schneider, K. Rossnagel, M. Murnane, M. Aeschlimann, Nature Commun. 7, 12902 (2016). doi:10.1038/ncomms12902
Helicity-selective phase-matching and quasi-phase matching in generation of circularly polarized high-order harmonics: Towards chiral attosecond pulses, O. Kfir, P. Grychtol, E. Turgut, R. Knut, D. Zusin, A. Fleischer, E. Bordo, T. Fan, D. Popmintchev, T. Popmintchev, H. Kapteyn, M. Murnane, O. Cohen, Invited Paper, Journal of Physics B: At. Mol. Opt. Phys. 49, 123501 (2016). doi.org/10.1088/0953-4075/49/12/123501
Nondestructive measurement of the evolution of layer-specific mechanical properties in sub-10nm bilayer films, K. Hoogeboom-Pot, E. Turgut, J. Hernandez-Charpak, J. Shaw, H. Kapteyn, M. Murnane, D. Nardi, Nano Letters 16, 4773 (2016). DOI: 10.1021/acs.nanolett.6b00606
Generation of bright circularly-polarized extreme ultraviolet high harmonics for magnetic circular dichroism spectroscopy, O. Kfir, P. Grychtol, E. Turgut, R. Knut D. Zusin, D. Popmintchev, T. Popmintchev, H. Nembach, J. Shaw, A. Fleicher, H. Kapteyn, M. Murnane, O. Cohen, Nature Photonics 9, 99 (2015). Featured on the cover of Science (special issue, 2015 Year of Light). doi.org/10.1038/nphoton.2014.293
Femtosecond-laser–induced modifications in Co/Pt multilayers studied with tabletop resonant magnetic scattering, C Weier, R Adam, D Rudolf, R Frömter, P Grychtol, G Winkler, A Kobs, H Oepen, H Kapteyn, M Murnane, C Schneider, Europhys. Lett. 109, 17001 (2015). doi.org/10.1209/0295-5075/109/17001
Bright Circularly Polarized Soft X-Ray High Harmonics for X-Ray Magnetic Circular Dichroism, T. Fan, P. Gychtol, R. Knut, C. Hernández-García, D. Hickstein, C. Gentry, C. Hogle, D. Zusin, K. Dorney, O. Shpyrko, O. Cohen, O. Kfir, L. Plaja, A. Becker, A. Jaron-Becker, T. Popmintchev, M. Murnane, H. Kapteyn, PNAS 112, 14206 (2015). 10.1073/pnas.1519666112
 S. Mathias, C. La-O-Vorakiat, J. Shaw, E. Turgut, P. Grychtol, R. Adam, D. Rudolf, H. Nembach, T. Silva, M. Aeschlimann, C. Schneider, H. Kapteyn, M. Murnane , "Ultrafast element-specific magnetization dynamics of complex magnetic materials on a table-top", Journal of Electron Spectroscopy and Related Phenomena 189 , 164 (2013).
E.Turgut, C. La-O-Vorakiat, J. Shaw, P. Grychtol, H. Nembach, D. Rudolf, R. Adam, M. Aeschlimann, C. Schneider, T. Silva, H. Kapteyn, M. Murnane, S. Mathias , "Controlling the Competition between Spin Transport and Optically Induced Demagnetization in Magnetic Multilayers,", Physical Review Letters 110 , 197201 (2013).
D. Rudolf, C. La-O-Vorakiat, M. Battiato, R. Adam, J. Shaw, E. Turgut, P. Maldonado, S. Mathias, P. Grychtol, T. Nembach, T. Silva, M. Aeschlimann, H. Kapteyn, M. Murnane, C. Schneider, P. Oppeneer , "Ultrafast magnetization enhancement in metallic multilayers driven by superdiffusive spin current", Nature Communications 3, 1037 (2012).
S. Mathias, C. La-O-Vorakiat, P. Grychtol, P. Granitzka, E. Turgut, J. Shaw, R. Adam, H. Nembach, M. Siemens, S. Eich, C. Schneider, T. Silva, M. Aeschlimann, M. Murnane, H. Kapteyn , "Probing the timescale of the exchange interaction in a ferromagnetic alloy", PNAS 109 , 4792 (2012).
C. La-O-Vorakiat, E. Turgut, C. Teale, H. Kapteyn, M. Murnane, S. Mathias, M. Aeschlimann, C. Schneider, J. Shaw, Hans T. Nembach, T. Silva , "Ultrafast Demagnetization Measurements using Extreme Ultraviolet Light: Comparison of Electronic and Magnetic Contributions", Physical Review X 2 , 011005 (2012).
C. La-O-Vorakiat, M. Siemens, M. Murnane, H. Kapteyn, S. Mathias, M. Aeschlimann, P. Grychtol, R. Adam, C. Schneider, J. Shaw, H. Nembach, T. Silva , "Ultrafast Demagnetization Dynamics at the M Edges of Magnetic Elements Observed Using a Tabletop High-Harmonic Soft X-Ray Source", Physical Review Letters 103 , 257402 (2009).