1
|
Lloyd-Hughes J, Oppeneer PM, Pereira Dos Santos T, Schleife A, Meng S, Sentef MA, Ruggenthaler M, Rubio A, Radu I, Murnane M, Shi X, Kapteyn H, Stadtmüller B, Dani KM, da Jornada FH, Prinz E, Aeschlimann M, Milot RL, Burdanova M, Boland J, Cocker T, Hegmann F. The 2021 ultrafast spectroscopic probes of condensed matter roadmap. J Phys Condens Matter 2021; 33:353001. [PMID: 33951618 DOI: 10.1088/1361-648x/abfe21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 05/05/2021] [Indexed: 06/12/2023]
Abstract
In the 60 years since the invention of the laser, the scientific community has developed numerous fields of research based on these bright, coherent light sources, including the areas of imaging, spectroscopy, materials processing and communications. Ultrafast spectroscopy and imaging techniques are at the forefront of research into the light-matter interaction at the shortest times accessible to experiments, ranging from a few attoseconds to nanoseconds. Light pulses provide a crucial probe of the dynamical motion of charges, spins, and atoms on picosecond, femtosecond, and down to attosecond timescales, none of which are accessible even with the fastest electronic devices. Furthermore, strong light pulses can drive materials into unusual phases, with exotic properties. In this roadmap we describe the current state-of-the-art in experimental and theoretical studies of condensed matter using ultrafast probes. In each contribution, the authors also use their extensive knowledge to highlight challenges and predict future trends.
Collapse
Affiliation(s)
- J Lloyd-Hughes
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, PO Box 516, S-75120 Uppsala, Sweden
| | - T Pereira Dos Santos
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - A Schleife
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
- Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
- National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - S Meng
- Institute of Physics, Chinese Academy of Sciences, Beijing, People's Republic of China
| | - M A Sentef
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
| | - M Ruggenthaler
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
| | - A Rubio
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
- Nano-Bio Spectroscopy Group and ETSF, Universidad del País Vasco UPV/EHU 20018 San Sebastián, Spain
- Center for Computational Quantum Physics (CCQ), The Flatiron Institute, 162 Fifth Avenue, New York, NY, 10010, United States of America
| | - I Radu
- Department of Physics, Freie Universität Berlin, Germany
- Max Born Institute, Berlin, Germany
| | - M Murnane
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - X Shi
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - H Kapteyn
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - B Stadtmüller
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - K M Dani
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Japan
| | - F H da Jornada
- Department of Materials Science and Engineering, Stanford University, Stanford, 94305, CA, United States of America
| | - E Prinz
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - M Aeschlimann
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - R L Milot
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - M Burdanova
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - J Boland
- Photon Science Institute, Department of Electrical and Electronic Engineering, University of Manchester, United Kingdom
| | - T Cocker
- Michigan State University, United States of America
| | | |
Collapse
|
2
|
Frietsch B, Donges A, Carley R, Teichmann M, Bowlan J, Döbrich K, Carva K, Legut D, Oppeneer PM, Nowak U, Weinelt M. The role of ultrafast magnon generation in the magnetization dynamics of rare-earth metals. Sci Adv 2020; 6:6/39/eabb1601. [PMID: 32967827 PMCID: PMC7531875 DOI: 10.1126/sciadv.abb1601] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 06/25/2020] [Indexed: 05/29/2023]
Abstract
Ultrafast demagnetization of rare-earth metals is distinct from that of 3d ferromagnets, as rare-earth magnetism is dominated by localized 4f electrons that cannot be directly excited by an optical laser pulse. Their demagnetization must involve excitation of magnons, driven either through exchange coupling between the 5d6s-itinerant and 4f-localized electrons or by coupling of 4f spins to lattice excitations. Here, we disentangle the ultrafast dynamics of 5d6s and 4f magnetic moments in terbium metal by time-resolved photoemission spectroscopy. We show that the demagnetization time of the Tb 4f magnetic moments of 400 fs is set by 4f spin-lattice coupling. This is experimentally evidenced by a comparison to ferromagnetic gadolinium and supported by orbital-resolved spin dynamics simulations. Our findings establish coupling of the 4f spins to the lattice via the orbital momentum as an essential mechanism driving magnetization dynamics via ultrafast magnon generation in technically relevant materials with strong magnetic anisotropy.
Collapse
Affiliation(s)
- B Frietsch
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - A Donges
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - R Carley
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - M Teichmann
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - J Bowlan
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - K Döbrich
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - K Carva
- Department of Physics and Astronomy, Uppsala University, P. O. Box 516, S-75120 Uppsala, Sweden
- Charles University, Faculty of Mathematics and Physics, DCMP, Ke Karlovu 5, CZ-12116 Prague 2, Czech Republic
| | - D Legut
- IT4Innovations-Czech National Supercomputing Centre, VSB-Technical University Ostrava, 17. listopadu 2172/15, CZ-708 00 Ostrava, Czech Republic
| | - P M Oppeneer
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
- Department of Physics and Astronomy, Uppsala University, P. O. Box 516, S-75120 Uppsala, Sweden
| | - U Nowak
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - M Weinelt
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
| |
Collapse
|
3
|
Mydosh JA, Oppeneer PM, Riseborough PS. Hidden order and beyond: an experimental-theoretical overview of the multifaceted behavior of URu 2Si 2. J Phys Condens Matter 2020; 32:143002. [PMID: 31801118 DOI: 10.1088/1361-648x/ab5eba] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
This topical review describes the multitude of unconventional behaviors in the hidden order, heavy fermion, antiferromagnetic and superconducting phases of the intermetallic compound URu2Si2 when tuned with pressure, magnetic field, and substitutions for all three elements. Such 'perturbations' result in a variety of new phases beyond the mysterious hidden order that are only now being slowly understood through a series of state-of-the-science experimentation, along with an array of novel theoretical approaches. Despite all these efforts spanning more than 30 years, hidden order (HO) remains puzzling and non-clarified, and the search continues in 2019 into a fourth decade for its final resolution. Here we attempt to update the present situation of URu2Si2 importing the latest experimental results and theoretical proposals. First, let us consider the pristine compound as a function of temperature and report the recent measurements and models relating to its heavy Fermi liquid crossover, its HO and superconductivity (SC). Recent experiments and theories are surmized that address four-fold symmetry breaking (or nematicity), Isingness and unconventional excitation modes. Second, we review the pressure dependence of URu2Si2 and its transformation to antiferromagnetic long-range order. Next we confront the dramatic high magnetic-field phases requiring fields above 40 T. And finally, we attempt to answer how does random substitutions of other 5f elements for U, and 3d, 4d, and 5d elements for Ru, and even P for Si affect and transform the HO. Commensurately, recent theoretical models are summarized and then related to the intriguing experimental behavior.
Collapse
Affiliation(s)
- J A Mydosh
- Institute Lorentz and Kamerlingh Onnes Laboratory, Leiden University, NL-2300 RA Leiden, The Netherlands
| | | | | |
Collapse
|
4
|
Bekaert J, Petrov M, Aperis A, Oppeneer PM, Milošević MV. Hydrogen-Induced High-Temperature Superconductivity in Two-Dimensional Materials: The Example of Hydrogenated Monolayer MgB_{2}. Phys Rev Lett 2019; 123:077001. [PMID: 31491112 DOI: 10.1103/physrevlett.123.077001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Revised: 04/23/2019] [Indexed: 06/10/2023]
Abstract
Hydrogen-based compounds under ultrahigh pressure, such as the polyhydrides H_{3}S and LaH_{10}, superconduct through the conventional electron-phonon coupling mechanism to attain the record critical temperatures known to date. Here we exploit the intrinsic advantages of hydrogen to strongly enhance phonon-mediated superconductivity in a completely different system, namely, a two-dimensional material with hydrogen adatoms. We find that van Hove singularities in the electronic structure, originating from atomiclike hydrogen states, lead to a strong increase of the electronic density of states at the Fermi level, and thus of the electron-phonon coupling. Additionally, the emergence of high-frequency hydrogen-related phonon modes in this system boosts the electron-phonon coupling further. As a concrete example, we demonstrate the effect of hydrogen adatoms on the superconducting properties of monolayer MgB_{2}, by solving the fully anisotropic Eliashberg equations, in conjunction with a first-principles description of the electronic and vibrational states, and their coupling. We show that hydrogenation leads to a high critical temperature of 67 K, which can be boosted to over 100 K by biaxial tensile strain.
Collapse
Affiliation(s)
- J Bekaert
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - M Petrov
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - A Aperis
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
| | - M V Milošević
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| |
Collapse
|
5
|
Alekhin A, Razdolski I, Berritta M, Bürstel D, Temnov V, Diesing D, Bovensiepen U, Woltersdorf G, Oppeneer PM, Melnikov A. Magneto-optical properties of Au upon the injection of hot spin-polarized electrons across Fe/Au(0 0 1) interfaces. J Phys Condens Matter 2019; 31:124002. [PMID: 30625433 DOI: 10.1088/1361-648x/aafd06] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We demonstrate a novel method for the excitation of sizable magneto-optical effects in Au by means of the laser-induced injection of hot spin-polarized electrons in Au/Fe/MgO(0 0 1) heterostructures. It is based on the energy- and spin-dependent electron transmittance of Fe/Au interface which acts as a spin filter for non-thermalized electrons optically excited in Fe. We show that after crossing the interface, majority electrons propagate through the Au layer with the velocity on the order of 1 nm fs-1 (close to the Fermi velocity) and the decay length on the order of 100 nm. Featuring ultrafast functionality and requiring no strong external magnetic fields, spin injection results in a distinct magneto-optical response of Au. We develop a formalism based on the phase of the transient complex MOKE response and demonstrate its robustness in a plethora of experimental and theoretical MOKE studies on Au, including our ab initio calculations. Our work introduces a flexible tool to manipulate magneto-optical properties of metals on the femtosecond timescale that holds high potential for active magneto-photonics, plasmonics, and spintronics.
Collapse
Affiliation(s)
- A Alekhin
- Institute of Molecules and Materials of Le Mans, CNRS UMR 6283, 72085 Le Mans, France
| | | | | | | | | | | | | | | | | | | |
Collapse
|
6
|
Reid AH, Shen X, Maldonado P, Chase T, Jal E, Granitzka PW, Carva K, Li RK, Li J, Wu L, Vecchione T, Liu T, Chen Z, Higley DJ, Hartmann N, Coffee R, Wu J, Dakovski GL, Schlotter WF, Ohldag H, Takahashi YK, Mehta V, Hellwig O, Fry A, Zhu Y, Cao J, Fullerton EE, Stöhr J, Oppeneer PM, Wang XJ, Dürr HA. Beyond a phenomenological description of magnetostriction. Nat Commun 2018; 9:388. [PMID: 29374151 PMCID: PMC5786062 DOI: 10.1038/s41467-017-02730-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 12/19/2017] [Indexed: 11/10/2022] Open
Abstract
Magnetostriction, the strain induced by a change in magnetization, is a universal effect in magnetic materials. Owing to the difficulty in unraveling its microscopic origin, it has been largely treated phenomenologically. Here, we show how the source of magnetostriction-the underlying magnetoelastic stress-can be separated in the time domain, opening the door for an atomistic understanding. X-ray and electron diffraction are used to separate the sub-picosecond spin and lattice responses of FePt nanoparticles. Following excitation with a 50-fs laser pulse, time-resolved X-ray diffraction demonstrates that magnetic order is lost within the nanoparticles with a time constant of 146 fs. Ultrafast electron diffraction reveals that this demagnetization is followed by an anisotropic, three-dimensional lattice motion. Analysis of the size, speed, and symmetry of the lattice motion, together with ab initio calculations accounting for the stresses due to electrons and phonons, allow us to reveal the magnetoelastic stress generated by demagnetization.
Collapse
Affiliation(s)
- A H Reid
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA. .,Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.
| | - X Shen
- Accelerator Division, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - P Maldonado
- Department of Physics and Astronomy, Uppsala University, P. O. Box 516, S-75120, Uppsala, Sweden
| | - T Chase
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.,Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
| | - E Jal
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.,CNRS, Laboratoire de Chimie Physique - Matière et Rayonnement, Sorbonne Universités, UPMC Univ. Paris 06, 75005, Paris, France
| | - P W Granitzka
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.,Van der Waals-Zeeman Institute, University of Amsterdam, 1018XE, Amsterdam, The Netherlands
| | - K Carva
- Faculty of Mathematics and Physics, Department of Condensed Matter Physics, Charles University, Ke Karlovu 5, CZ-12116, Prague 2, Czech Republic
| | - R K Li
- Accelerator Division, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - J Li
- Brookhaven National Laboratory, Upton, NY, 1193, USA
| | - L Wu
- Brookhaven National Laboratory, Upton, NY, 1193, USA
| | - T Vecchione
- Accelerator Division, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - T Liu
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.,Department of Physics, Stanford University, Stanford, CA, 94305, USA
| | - Z Chen
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.,Department of Physics, Stanford University, Stanford, CA, 94305, USA
| | - D J Higley
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.,Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
| | - N Hartmann
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - R Coffee
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - J Wu
- Accelerator Division, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - G L Dakovski
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - W F Schlotter
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - H Ohldag
- Stanford Synchrotron Radiation Laboratory, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - Y K Takahashi
- Magnetic Materials Unit, National Institute for Materials Science, Tsukuba, 305-0047, Japan
| | - V Mehta
- San Jose Research Center, HGST a Western Digital Company, 3403 Yerba Buena Road, San Jose, CA, 95135, USA.,Thomas J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY, 10598, USA
| | - O Hellwig
- San Jose Research Center, HGST a Western Digital Company, 3403 Yerba Buena Road, San Jose, CA, 95135, USA.,Institute of Physics, Technische Universität Chemnitz, Reichenhainer Straße 70, D-09107, Chemnitz, Germany.,Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328, Dresden, Germany
| | - A Fry
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - Y Zhu
- Brookhaven National Laboratory, Upton, NY, 1193, USA
| | - J Cao
- Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, 32310, USA
| | - E E Fullerton
- Center for Memory and Recording Research, UC San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0401, USA
| | - J Stöhr
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, P. O. Box 516, S-75120, Uppsala, Sweden
| | - X J Wang
- Accelerator Division, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - H A Dürr
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA. .,Department of Physics and Astronomy, Uppsala University, P. O. Box 516, S-75120, Uppsala, Sweden.
| |
Collapse
|
7
|
Bekaert J, Bignardi L, Aperis A, van Abswoude P, Mattevi C, Gorovikov S, Petaccia L, Goldoni A, Partoens B, Oppeneer PM, Peeters FM, Milošević MV, Rudolf P, Cepek C. Free surfaces recast superconductivity in few-monolayer MgB 2: Combined first-principles and ARPES demonstration. Sci Rep 2017; 7:14458. [PMID: 29089566 PMCID: PMC5663715 DOI: 10.1038/s41598-017-13913-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 10/02/2017] [Indexed: 11/08/2022] Open
Abstract
Two-dimensional materials are known to harbour properties very different from those of their bulk counterparts. Recent years have seen the rise of atomically thin superconductors, with a caveat that superconductivity is strongly depleted unless enhanced by specific substrates, intercalants or adatoms. Surprisingly, the role in superconductivity of electronic states originating from simple free surfaces of two-dimensional materials has remained elusive to date. Here, based on first-principles calculations, anisotropic Eliashberg theory, and angle-resolved photoemission spectroscopy (ARPES), we show that surface states in few-monolayer MgB2 make a major contribution to the superconducting gap spectrum and density of states, clearly distinct from the widely known, bulk-like σ- and π-gaps. As a proof of principle, we predict and measure the gap opening on the magnesium-based surface band up to a critical temperature as high as ~30 K for merely six monolayers thick MgB2. These findings establish free surfaces as an unavoidable ingredient in understanding and further tailoring of superconductivity in atomically thin materials.
Collapse
Affiliation(s)
- J Bekaert
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerp, Belgium.
| | - L Bignardi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands
- Elettra Sincrotrone Trieste, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
| | - A Aperis
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20, Uppsala, Sweden
| | - P van Abswoude
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands
| | - C Mattevi
- IOM-CNR, Laboratorio TASC, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
- Department of Materials, Imperial College London, Exhibition road, SW7 2AZ, London, United Kingdom
| | - S Gorovikov
- Elettra Sincrotrone Trieste, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
- Canadian Light Source Inc., 44 Innovation Blvd, Saskatoon, SK S7N 2V3, Canada
| | - L Petaccia
- Elettra Sincrotrone Trieste, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
| | - A Goldoni
- Elettra Sincrotrone Trieste, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
| | - B Partoens
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerp, Belgium
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20, Uppsala, Sweden
| | - F M Peeters
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerp, Belgium
| | - M V Milošević
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerp, Belgium.
| | - P Rudolf
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands.
| | - C Cepek
- IOM-CNR, Laboratorio TASC, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
| |
Collapse
|
8
|
Stamm C, Murer C, Berritta M, Feng J, Gabureac M, Oppeneer PM, Gambardella P. Magneto-Optical Detection of the Spin Hall Effect in Pt and W Thin Films. Phys Rev Lett 2017; 119:087203. [PMID: 28952751 DOI: 10.1103/physrevlett.119.087203] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Indexed: 06/07/2023]
Abstract
The conversion of charge currents into spin currents in nonmagnetic conductors is a hallmark manifestation of spin-orbit coupling that has important implications for spintronic devices. Here we report the measurement of the interfacial spin accumulation induced by the spin Hall effect in Pt and W thin films using magneto-optical Kerr microscopy. We show that the Kerr rotation has opposite sign in Pt and W and scales linearly with current density. By comparing the experimental results with ab initio calculations of the spin Hall and magneto-optical Kerr effects, we quantitatively determine the current-induced spin accumulation at the Pt interface as 5×10^{-12} μ_{B} A^{-1} cm^{2} per atom. From thickness-dependent measurements, we determine the spin diffusion length in a single Pt film to be 11±3 nm, which is significantly larger compared to that of Pt adjacent to a magnetic layer.
Collapse
Affiliation(s)
- C Stamm
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - C Murer
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - M Berritta
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-75120 Uppsala, Sweden
| | - J Feng
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - M Gabureac
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-75120 Uppsala, Sweden
| | - P Gambardella
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| |
Collapse
|
9
|
Frietsch B, Bowlan J, Carley R, Teichmann M, Wienholdt S, Hinzke D, Nowak U, Carva K, Oppeneer PM, Weinelt M. Disparate ultrafast dynamics of itinerant and localized magnetic moments in gadolinium metal. Nat Commun 2015; 6:8262. [PMID: 26355196 PMCID: PMC4579838 DOI: 10.1038/ncomms9262] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 08/04/2015] [Indexed: 01/26/2023] Open
Abstract
The Heisenberg–Dirac intra-atomic exchange coupling is responsible for the formation of the atomic spin moment and thus the strongest interaction in magnetism. Therefore, it is generally assumed that intra-atomic exchange leads to a quasi-instantaneous aligning process in the magnetic moment dynamics of spins in separate, on-site atomic orbitals. Following ultrashort optical excitation of gadolinium metal, we concurrently record in photoemission the 4f magnetic linear dichroism and 5d exchange splitting. Their dynamics differ by one order of magnitude, with decay constants of 14 versus 0.8 ps, respectively. Spin dynamics simulations based on an orbital-resolved Heisenberg Hamiltonian combined with first-principles calculations explain the particular dynamics of 5d and 4f spin moments well, and corroborate that the 5d exchange splitting traces closely the 5d spin-moment dynamics. Thus gadolinium shows disparate dynamics of the localized 4f and the itinerant 5d spin moments, demonstrating a breakdown of their intra-atomic exchange alignment on a picosecond timescale. Due the strength of the intra-atomic exchange interaction, it is generally assumed that alignment of spin moments in intra-atomic orbitals is quasi-instantaneous. Here, the authors demonstrate the breakdown of this relation between the 4f and 5d electrons in gadolinium following ultrashort optical excitation.
Collapse
Affiliation(s)
- B Frietsch
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.,Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin, Germany
| | - J Bowlan
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.,Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin, Germany
| | - R Carley
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.,Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin, Germany
| | - M Teichmann
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.,Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin, Germany
| | - S Wienholdt
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - D Hinzke
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - U Nowak
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - K Carva
- Department of Physics and Astronomy, Uppsala University, PO Box 516, 75120 Uppsala, Sweden.,Charles University, Faculty of Mathematics and Physics, DCMP, Ke Karlovu 5, CZ-12116 Prague 2, Czech Republic
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, PO Box 516, 75120 Uppsala, Sweden
| | - M Weinelt
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| |
Collapse
|
10
|
Magnani N, Caciuffo R, Wilhelm F, Colineau E, Eloirdi R, Griveau JC, Rusz J, Oppeneer PM, Rogalev A, Lander GH. Magnetic polarization of the americium J=0 ground state in AmFe(2). Phys Rev Lett 2015; 114:097203. [PMID: 25793847 DOI: 10.1103/physrevlett.114.097203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Indexed: 06/04/2023]
Abstract
Trivalent americium has a nonmagnetic (J=0) ground state arising from the cancellation of the orbital and spin moments. However, magnetism can be induced by a large molecular field if Am^{3+} is embedded in a ferromagnetic matrix. Using the technique of x-ray magnetic circular dichroism, we show that this is the case in AmFe_{2}. Since ⟨J_{z}⟩=0, the spin component is exactly twice as large as the orbital one, the total Am moment is opposite to that of Fe, and the magnetic dipole operator ⟨T_{z}⟩ can be determined directly; we discuss the progression of the latter across the actinide series.
Collapse
Affiliation(s)
- N Magnani
- European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, D-76125 Karlsruhe, Germany
| | - R Caciuffo
- European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, D-76125 Karlsruhe, Germany
| | - F Wilhelm
- European Synchrotron Radiation Facility (ESRF), Boîte Postale 220, F-38043 Grenoble, France
| | - E Colineau
- European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, D-76125 Karlsruhe, Germany
| | - R Eloirdi
- European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, D-76125 Karlsruhe, Germany
| | - J-C Griveau
- European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, D-76125 Karlsruhe, Germany
| | - J Rusz
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, S-75120 Uppsala, Sweden
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, S-75120 Uppsala, Sweden
| | - A Rogalev
- European Synchrotron Radiation Facility (ESRF), Boîte Postale 220, F-38043 Grenoble, France
| | - G H Lander
- European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, D-76125 Karlsruhe, Germany
| |
Collapse
|
11
|
Eschenlohr A, Battiato M, Maldonado P, Pontius N, Kachel T, Holldack K, Mitzner R, Föhlisch A, Oppeneer PM, Stamm C. Reply to 'Optical excitation of thin magnetic layers in multilayer structures'. Nat Mater 2014; 13:102-3. [PMID: 24452341 DOI: 10.1038/nmat3851] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Affiliation(s)
- A Eschenlohr
- 1] Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany [2] Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany [3] Fakultät für Physik, Universität Duisburg-Essen, Lotharstr. 1, 47048 Duisburg, Germany(A. E.); Department of Materials, ETH Zurich, CH-8093 Zurich, Switzerland
| | - M Battiato
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
| | - P Maldonado
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
| | - N Pontius
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - T Kachel
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - K Holldack
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - R Mitzner
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - A Föhlisch
- 1] Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany [2] Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
| | - C Stamm
- 1] Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany [2] Fakultät für Physik, Universität Duisburg-Essen, Lotharstr. 1, 47048 Duisburg, Germany(A. E.); Department of Materials, ETH Zurich, CH-8093 Zurich, Switzerland
| |
Collapse
|
12
|
Eschenlohr A, Battiato M, Maldonado P, Pontius N, Kachel T, Holldack K, Mitzner R, Föhlisch A, Oppeneer PM, Stamm C. Ultrafast spin transport as key to femtosecond demagnetization. Nat Mater 2013; 12:332-6. [PMID: 23353629 DOI: 10.1038/nmat3546] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 12/12/2012] [Indexed: 05/15/2023]
Abstract
Irradiating a ferromagnet with a femtosecond laser pulse is known to induce an ultrafast demagnetization within a few hundred femtoseconds. Here we demonstrate that direct laser irradiation is in fact not essential for ultrafast demagnetization, and that electron cascades caused by hot electron currents accomplish it very efficiently. We optically excite a Au/Ni layered structure in which the 30 nm Au capping layer absorbs the incident laser pump pulse and subsequently use the X-ray magnetic circular dichroism technique to probe the femtosecond demagnetization of the adjacent 15 nm Ni layer. A demagnetization effect corresponding to the scenario in which the laser directly excites the Ni film is observed, but with a slight temporal delay. We explain this unexpected observation by means of the demagnetizing effect of a superdiffusive current of non-equilibrium, non-spin-polarized electrons generated in the Au layer.
Collapse
Affiliation(s)
- A Eschenlohr
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Kampfrath T, Battiato M, Maldonado P, Eilers G, Nötzold J, Mährlein S, Zbarsky V, Freimuth F, Mokrousov Y, Blügel S, Wolf M, Radu I, Oppeneer PM, Münzenberg M. Terahertz spin current pulses controlled by magnetic heterostructures. Nat Nanotechnol 2013; 8:256-60. [PMID: 23542903 DOI: 10.1038/nnano.2013.43] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 02/25/2013] [Indexed: 05/23/2023]
Abstract
In spin-based electronics, information is encoded by the spin state of electron bunches. Processing this information requires the controlled transport of spin angular momentum through a solid, preferably at frequencies reaching the so far unexplored terahertz regime. Here, we demonstrate, by experiment and theory, that the temporal shape of femtosecond spin current bursts can be manipulated by using specifically designed magnetic heterostructures. A laser pulse is used to drive spins from a ferromagnetic iron thin film into a non-magnetic cap layer that has either low (ruthenium) or high (gold) electron mobility. The resulting transient spin current is detected by means of an ultrafast, contactless amperemeter based on the inverse spin Hall effect, which converts the spin flow into a terahertz electromagnetic pulse. We find that the ruthenium cap layer yields a considerably longer spin current pulse because electrons are injected into ruthenium d states, which have a much lower mobility than gold sp states. Thus, spin current pulses and the resulting terahertz transients can be shaped by tailoring magnetic heterostructures, which opens the door to engineering high-speed spintronic devices and, potentially, broadband terahertz emitters.
Collapse
Affiliation(s)
- T Kampfrath
- Department of Physical Chemistry, Fritz Haber Institute, Faradayweg 4-6, 14195 Berlin, Germany.
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Tarafder K, Kanungo S, Oppeneer PM, Saha-Dasgupta T. Pressure and temperature control of spin-switchable metal-organic coordination polymers from ab initio calculations. Phys Rev Lett 2012; 109:077203. [PMID: 23006399 DOI: 10.1103/physrevlett.109.077203] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Indexed: 06/01/2023]
Abstract
We explore a combination of density-functional theory with supplemented Coulomb U (DFT+U) and ab initio molecular dynamics simulations to investigate the spin-crossover (SCO) phenomenon in coordination polymers. We demonstrate the applicability of the method for the case of bimetallic metal-organic framework Fe(2)[Nb(CN)(8)]·(4-pyridinealdoxime)(8)·2H(2)O [see S. Ohkoshi et al. Nat. Chem. 3, 564 (2011)]. Our study shows that this approach is capable of capturing the SCO transitions driven by pressure as well as temperature. In addition to discovering novel spin-state transitions, magnetic states involving changes in the long-range magnetic ordering pattern are achieved, thereby offering the tunability of spin states as well as the long-range order of the spins. We compare the SCO transition in the Fe-based framework with a computer designed Mn-based variant.
Collapse
Affiliation(s)
- K Tarafder
- Department of Physics and Astronomy, Uppsala University, Sweden
| | | | | | | |
Collapse
|
15
|
Feng Q, Oppeneer PM. An advanced multi-orbital impurity solver for dynamical mean field theory based on the equation of motion approach. J Phys Condens Matter 2012; 24:055603. [PMID: 22248628 DOI: 10.1088/0953-8984/24/5/055603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We propose an improved fast multi-orbital impurity solver for the dynamical mean field theory based on equations of motion (EOM) for Green's functions and a decoupling scheme. In this scheme the inter-orbital Coulomb interactions are treated fully self-consistently, and involve the inter-orbital fluctuations. As an example of the use of the derived multi-orbital impurity solver, the two-orbital Hubbard model is studied for various cases. Comparisons are made between numerical results obtained with our EOM scheme and those obtained with quantum Monte Carlo and numerical renormalization group methods. The comparison shows a good agreement, but also reveals a dissimilarity of the behaviors of the densities of states which is caused by inter-site inter-orbital hopping effects and on-site inter-orbital fluctuation effects, thus corroborating the assertion of the value of the EOM method for the study of multi-orbital strongly correlated systems.
Collapse
Affiliation(s)
- Qingguo Feng
- Department of Physics and Astronomy, Uppsala University, Box 516, S-75120 Uppsala, Sweden.
| | | |
Collapse
|
16
|
Carva K, Battiato M, Oppeneer PM. Ab Initio investigation of the Elliott-Yafet electron-phonon mechanism in laser-induced ultrafast demagnetization. Phys Rev Lett 2011; 107:207201. [PMID: 22181762 DOI: 10.1103/physrevlett.107.207201] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Indexed: 05/23/2023]
Abstract
The spin-flip (SF) Eliashberg function is calculated from first principles for ferromagnetic Ni to accurately establish the contribution of Elliott-Yafet electron-phonon SF scattering to Ni's femtosecond laser-driven demagnetization. This is used to compute the SF probability and demagnetization rate for laser-created thermalized as well as nonequilibrium electron distributions. Increased SF probabilities are found for thermalized electrons, but the induced demagnetization rate is extremely small. A larger demagnetization rate is obtained for nonequilibrium electron distributions, but its contribution is too small to account for femtosecond demagnetization.
Collapse
Affiliation(s)
- K Carva
- Department of Physics and Astronomy, Uppsala University, Sweden.
| | | | | |
Collapse
|
17
|
Battiato M, Carva K, Oppeneer PM. Superdiffusive spin transport as a mechanism of ultrafast demagnetization. Phys Rev Lett 2010; 105:027203. [PMID: 20867735 DOI: 10.1103/physrevlett.105.027203] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Indexed: 05/23/2023]
Abstract
We propose a semiclassical model for femtosecond laser-induced demagnetization due to spin-polarized excited electron diffusion in the superdiffusive regime. Our approach treats the finite elapsed time and transport in space between multiple electronic collisions exactly, as well as the presence of several metal films in the sample. Solving the derived transport equation numerically we show that this mechanism accounts for the experimentally observed demagnetization within 200 fs in Ni, without the need to invoke any angular momentum dissipation channel.
Collapse
Affiliation(s)
- M Battiato
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
| | | | | |
Collapse
|
18
|
Valencia S, Kleibert A, Gaupp A, Rusz J, Legut D, Bansmann J, Gudat W, Oppeneer PM. Quadratic X-ray magneto-optical effect upon reflection in a near-normal-incidence configuration at the M edges of 3d-transition metals. Phys Rev Lett 2010; 104:187401. [PMID: 20482206 DOI: 10.1103/physrevlett.104.187401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Indexed: 05/22/2023]
Abstract
We have observed a quadratic x-ray magneto-optical effect in near-normal-incidence reflection at the M edges of iron. The effect appears as the magnetically induced rotation of approximately 0.1 degrees of the polarization plane of linearly polarized x-ray radiation upon reflection. A comparison of the measured rotation spectrum with results from x-ray magnetic linear dichroism data demonstrates that this is the first observation of the Schäfer-Hubert effect in the x-ray regime. Ab initio density-functional theory calculations reveal that hybridization effects of the 3p core states necessarily need to be considered when interpreting experimental data. The discovered magneto-x-ray effect holds promise for future ultrafast and element-selective studies of ferromagnetic as well as antiferromagnetic materials.
Collapse
Affiliation(s)
- S Valencia
- Helmholtz-Zentrum-Berlin, BESSY, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
19
|
Samsel-Czekała M, Elgazzar S, Oppeneer PM, Talik E, Walerczyk W, Troć R. The electronic structure of UCoGe by ab initio calculations and XPS experiment. J Phys Condens Matter 2010; 22:015503. [PMID: 21386229 DOI: 10.1088/0953-8984/22/1/015503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The crystal and electronic structures of the orthorhombic compound UCoGe are presented and discussed. It has been either refined by the x-ray diffraction on a single crystal or computed within the local spin density functional theory, employing the fully relativistic version of the full-potential local-orbital band structure code, respectively. We particularly give our attention to investigating the Fermi surface and de Haas-van Alphen quantities of UCoGe. The calculated electronic density is then examined by x-ray photoelectron spectroscopy (XPS). Fairly good agreement is achieved between theoretical and experimental XPS results in the paramagnetic state. A small difference in the position (in energy scale) of the U 5f bands is caused by the electron localization effect observed in the experimental XPS. There is also some discrepancy for the Co 3d electron contributions below E(F). The Fermi surface in the non-magnetic state is of a semimetallic type while that in the ferromagnetic state, with the ordered moment of -0.47 μ(B)/f.u. along the c axis, is more metallic, with nesting properties that may favour superconductivity.
Collapse
Affiliation(s)
- M Samsel-Czekała
- Leibniz-Institut für Festkörper- und Werkstoffforschung, IFW Dresden, Dresden, Germany.
| | | | | | | | | | | |
Collapse
|
20
|
Elgazzar S, Rusz J, Amft M, Oppeneer PM, Mydosh JA. Hidden order in URu2Si2 originates from Fermi surface gapping induced by dynamic symmetry breaking. Nat Mater 2009; 8:337-341. [PMID: 19234447 DOI: 10.1038/nmat2395] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Accepted: 01/20/2009] [Indexed: 05/27/2023]
Abstract
Spontaneous, collective ordering of electronic degrees of freedom leads to second-order phase transitions that are characterized by an order parameter driving the transition. The notion of a 'hidden order' has recently been used for a variety of materials where a clear phase transition occurs without a known order parameter. The prototype example is the heavy-fermion compound URu(2)Si(2), where a mysterious hidden-order transition occurs at 17.5 K. For more than twenty years this system has been studied theoretically and experimentally without a firm grasp of the underlying physics. Here, we provide a microscopic explanation of the hidden order using density-functional theory calculations. We identify the Fermi surface 'hot spots' where degeneracy induces a Fermi surface instability and quantify how symmetry breaking lifts the degeneracy, causing a surprisingly large Fermi surface gapping. As the mechanism for the hidden order, we deduce spontaneous symmetry breaking through a dynamic mode of antiferromagnetic moment excitations.
Collapse
Affiliation(s)
- S Elgazzar
- Department of Physics and Materials Science, Uppsala University, Box 530, S-751 21 Uppsala, Sweden
| | | | | | | | | |
Collapse
|
21
|
Hild K, Maul J, Schönhense G, Elmers HJ, Amft M, Oppeneer PM. Magnetic circular dichroism in two-photon photoemission. Phys Rev Lett 2009; 102:057207. [PMID: 19257547 DOI: 10.1103/physrevlett.102.057207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Indexed: 05/27/2023]
Abstract
We report the observation of magnetic circular dichroism (MCD) in two-photon photoemission (2PPE). The Heusler alloys Ni2MnGa and Co2FeSi were investigated by excitation with femtosecond laser light, showing MCD asymmetries of A=(3.5+/-0.5)x10;{-3} for Ni2MnGa and of A=(2.1+/-1.0)x10;{-3} for Co2FeSi, respectively. A theoretical explanation is provided based on local spin-density calculations for the magnetic dichroic response; the computed 2PPE MCD agrees well with the experiment. The observed 2PPE magnetic contrast represents an interesting alternative for future time-resolved photoemission studies on surface magnetism practicable in the laboratory.
Collapse
Affiliation(s)
- K Hild
- Institut für Physik, Staudinger Weg 7, Universität Mainz, D-55128 Mainz, Germany
| | | | | | | | | | | |
Collapse
|
22
|
Bernien M, Miguel J, Weis C, Ali ME, Kurde J, Krumme B, Panchmatia PM, Sanyal B, Piantek M, Srivastava P, Baberschke K, Oppeneer PM, Eriksson O, Kuch W, Wende H. Tailoring the nature of magnetic coupling of Fe-porphyrin molecules to ferromagnetic substrates. Phys Rev Lett 2009; 102:047202. [PMID: 19257470 DOI: 10.1103/physrevlett.102.047202] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Indexed: 05/25/2023]
Abstract
We demonstrate that an antiferromagnetic coupling between paramagnetic Fe-porphyrin molecules and ultrathin Co and Ni magnetic films on Cu(100) substrates can be established by an intermediate layer of atomic oxygen. The coupling energies have been determined from the temperature dependence of x-ray magnetic circular dichroism measurements. By density functional theory+U calculations the coupling mechanism is shown to be superexchange between the Fe center of the molecules and Co surface-atoms, mediated by oxygen.
Collapse
Affiliation(s)
- M Bernien
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Amft M, Oppeneer PM. Calculated magneto-optical Kerr spectra of the half-Heusler compounds AuMnX (X = In, Sn, Sb). J Phys Condens Matter 2007; 19:315216. [PMID: 21694116 DOI: 10.1088/0953-8984/19/31/315216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The ferromagnetic ground states of the half-Heusler compounds AuMnX (X = In, Sn, Sb) have been calculated in the framework of the local spin-density approximation (LSDA) to density functional theory (DFT). AuMnSn is computed to be a half-metallic ferromagnet, whereas AuMnIn and AuMnSb are not half-metallic, due to their different band filling. The computed relativistic electronic structures served as inputs to calculate the magneto-optical Kerr rotations and ellipticities for all three materials. In the case of AuMnSn the largest, zero-temperature, polar Kerr rotation has been found to be -0.45° at about 1 eV photon energy. The computed MOKE spectra of AuMnSn are in qualitative agreement with recent experiments. The largest Kerr rotations of AuMnIn and AuMnSb have been calculated to be +0.64° at 4.3 eV and -0.85° at 0.9 eV, respectively.
Collapse
|
24
|
Wende H, Bernien M, Luo J, Sorg C, Ponpandian N, Kurde J, Miguel J, Piantek M, Xu X, Eckhold P, Kuch W, Baberschke K, Panchmatia PM, Sanyal B, Oppeneer PM, Eriksson O. Substrate-induced magnetic ordering and switching of iron porphyrin molecules. Nat Mater 2007; 6:516-20. [PMID: 17558431 DOI: 10.1038/nmat1932] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2006] [Accepted: 04/18/2007] [Indexed: 05/15/2023]
Abstract
To realize molecular spintronic devices, it is important to externally control the magnetization of a molecular magnet. One class of materials particularly promising as building blocks for molecular electronic devices is the paramagnetic porphyrin molecule in contact with a metallic substrate. Here, we study the structural orientation and the magnetic coupling of in-situ-sublimated Fe porphyrin molecules on ferromagnetic Ni and Co films on Cu(100). Our studies involve X-ray absorption spectroscopy and X-ray magnetic circular dichroism experiments. In a combined experimental and computational study we demonstrate that owing to an indirect, superexchange interaction between Fe atoms in the molecules and atoms in the substrate (Co or Ni) the paramagnetic molecules can be made to order ferromagnetically. The Fe magnetic moment can be rotated along directions in plane as well as out of plane by a magnetization reversal of the substrate, thereby opening up an avenue for spin-dependent molecular electronics.
Collapse
Affiliation(s)
- H Wende
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin-Dahlem, Germany.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Abstract
On the basis of electronic structure calculations we identify the superconductivity in the novel, high-temperature superconductor PuCoGa5 to be caused by the pairing of Pu 5f electrons. Assuming delocalized Pu 5f states, we compute theoretical crystallographic constants very near to the experimental ones, and the calculated specific heat coefficient compares reasonably to the measured coefficient. The theoretical Fermi surface is quasi-two-dimensional and the material appears to be close to a magnetic phase instability.
Collapse
Affiliation(s)
- I Opahle
- Leibniz-Institute of Solid State and Materials Research, P.O. Box 270016, D-01171 Dresden, Germany
| | | |
Collapse
|
26
|
Mitra C, Raychaudhuri P, Dörr K, Müller KH, Schultz L, Oppeneer PM, Wirth S. Observation of minority spin character of the new electron doped manganite La0.7Ce0.3MnO3 from tunneling magnetoresistance. Phys Rev Lett 2003; 90:017202. [PMID: 12570643 DOI: 10.1103/physrevlett.90.017202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2002] [Indexed: 05/24/2023]
Abstract
We report the magnetotransport characteristics of a trilayer ferromagnetic tunnel junction built of an electron doped manganite (La0.7Ce0.3MnO3) and a hole doped manganite (La0.7Ca0.3MnO3). At low temperatures the junction exhibits a large positive tunneling magnetoresistance (TMR), irrespective of the bias voltage. At intermediate temperatures below T(C) the sign of the TMR is dependent on the bias voltage across the junction. The magnetoresistive characteristics of the junction strongly suggest that La0.7Ce0.3MnO3 is a minority spin carrier ferromagnet with a high degree of spin polarization, i.e., a transport half-metal.
Collapse
Affiliation(s)
- C Mitra
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany.
| | | | | | | | | | | | | |
Collapse
|
27
|
Mertins HC, Oppeneer PM, Kunes J, Gaupp A, Abramsohn D, Schäfers F. Observation of the x-ray magneto-optical Voigt effect. Phys Rev Lett 2001; 87:047401. [PMID: 11461644 DOI: 10.1103/physrevlett.87.047401] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2001] [Indexed: 05/22/2023]
Abstract
The existence of the x-ray magneto-optical Voigt effect is demonstrated. By means of polarization analysis the Voigt rotation and ellipticity of linearly polarized synchrotron radiation are measured at the Co L3 edge upon transmission through an amorphous Co film. The observed x-ray Voigt rotation is about 7.5 degrees /microm. On the basis of ab initio calculations it is shown that the x-ray Voigt effect follows sensitively the amount of spin polarization of the 2p core states. Therefore it provides a unique measure of the spin splitting of the core states.
Collapse
Affiliation(s)
- H C Mertins
- BESSY GmbH, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | | | | | | | | | | |
Collapse
|
28
|
Oppeneer PM, Lodder A. An application of interstitial Green functions: electron scattering in dilute Pd-based interstitial alloys. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0305-4608/17/9/015] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
29
|
|
30
|
Oppeneer PM, Lodder A. Influence of zero-point motion of hydrogen isotopes on the scattering of Bloch electrons in palladium. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0305-4608/18/5/008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
31
|
|
32
|
Antonov VN, Perlov AY, Oppeneer PM, Yaresko AN, Halilov SV. Mechanism of the Giant Magnetoresistance in UNiGa from First-Principles Calculations. Phys Rev Lett 1996; 77:5253-5256. [PMID: 10062754 DOI: 10.1103/physrevlett.77.5253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
|
33
|
Oppeneer PM, Yaresko AN, Perlov AY, Antonov VN, Eschrig H. Theory of the anomalous magnetic phase transition in UNiSn. Phys Rev B Condens Matter 1996; 54:R3706-R3709. [PMID: 9986352 DOI: 10.1103/physrevb.54.r3706] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
34
|
Oppeneer PM, Brooks MS, Antonov VN, Kraft T, Eschrig H. Band-theoretical description of the magneto-optical spectra of UAsSe. Phys Rev B Condens Matter 1996; 53:R10437-R10440. [PMID: 9982700 DOI: 10.1103/physrevb.53.r10437] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
35
|
Oppeneer PM, Kraft T, Eschrig H. Anisotropic magneto-optical Kerr effect of hcp and fcc Co from first principles. Phys Rev B Condens Matter 1995; 52:3577-3580. [PMID: 9981482 DOI: 10.1103/physrevb.52.3577] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
36
|
Kraft T, Oppeneer PM, Antonov VN, Eschrig H. Relativistic calculations of the magneto-optical Kerr spectra in (001) and (111) US, USe, and UTe. Phys Rev B Condens Matter 1995; 52:3561-3570. [PMID: 9981480 DOI: 10.1103/physrevb.52.3561] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
37
|
Oppeneer PM, Hierse W. Two-center overlap integrals over Slater-type orbitals constrained to a spherical integration volume: Analytical expressions. Phys Rev A 1994; 50:2232-2238. [PMID: 9911134 DOI: 10.1103/physreva.50.2232] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
|
38
|
|
39
|
Richter M, Oppeneer PM, Eschrig H, Johansson B. Calculated crystal-field parameters of SmCo5. Phys Rev B Condens Matter 1992; 46:13919-13927. [PMID: 10003457 DOI: 10.1103/physrevb.46.13919] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
40
|
Oppeneer PM, Sticht J, Maurer T, K�bler J. Ab initio investigation of microscopic enhancement factors in tuning the magneto-optical Kerr effect. ACTA ACUST UNITED AC 1992. [DOI: 10.1007/bf01470918] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
41
|
Oppeneer PM, Maurer T, Sticht J, Kübler J. Ab initio calculated magneto-optical Kerr effect of ferromagnetic metals: Fe and Ni. Phys Rev B Condens Matter 1992; 45:10924-10933. [PMID: 10001013 DOI: 10.1103/physrevb.45.10924] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
42
|
Abstract
A theoretical and experimental study on the detection of a square wave pattern of random dots is presented. Our theory applies to two-alternative forced choice experiments as well as to "seen"-"not seen" discrimination experiments. In our experiments we used the forced choice method. The theory provides a good description of the psychometric function of the percentage of correct decisions versus contrast. From these frequency of seeing (FOS) curves the apparent signal-to-noise ratio of the detection mechanism of human subjects can be derived. It is found that this ratio can have values of up to 100% and that it decreases with the number of dots in the stimulus and with the number of periods of the square wave. It is shown that a more precise description of the human performance can be obtained from the mid-points of the FOS-curves (i.e. the thresholds) rather than from the slopes.
Collapse
|