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Determination of sub-ps lattice dynamics in FeRh thin films. Sci Rep 2022; 12:8584. [PMID: 35595862 PMCID: PMC9122986 DOI: 10.1038/s41598-022-12602-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 05/12/2022] [Indexed: 11/08/2022] Open
Abstract
Understanding the ultrashort time scale structural dynamics of the FeRh metamagnetic phase transition is a key element in developing a complete explanation of the mechanism driving the evolution from an antiferromagnetic to ferromagnetic state. Using an X-ray free electron laser we determine, with sub-ps time resolution, the time evolution of the (-101) lattice diffraction peak following excitation using a 35 fs laser pulse. The dynamics at higher laser fluence indicates the existence of a transient lattice state distinct from the high temperature ferromagnetic phase. By extracting the lattice temperature and comparing it with values obtained in a quasi-static diffraction measurement, we estimate the electron-phonon coupling in FeRh thin films as a function of laser excitation fluence. A model is presented which demonstrates that the transient state is paramagnetic and can be reached by a subset of the phonon bands. A complete description of the FeRh structural dynamics requires consideration of coupling strength variation across the phonon frequencies.
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Ahn Y, Cherukara MJ, Cai Z, Bartlein M, Zhou T, DiChiara A, Walko DA, Holt M, Fullerton EE, Evans PG, Wen H. X-ray nanodiffraction imaging reveals distinct nanoscopic dynamics of an ultrafast phase transition. Proc Natl Acad Sci U S A 2022; 119:e2118597119. [PMID: 35522708 PMCID: PMC9171639 DOI: 10.1073/pnas.2118597119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 04/11/2022] [Indexed: 12/04/2022] Open
Abstract
SignificancePhase transitions, the changes between states of matter with distinct electronic, magnetic, or structural properties, are at the center of condensed matter physics and underlie valuable technologies. First-order phase transitions are intrinsically heterogeneous. When driven by ultrashort excitation, nanoscale phase regions evolve rapidly, which has posed a significant experimental challenge to characterize. The newly developed laser-pumped X-ray nanodiffraction imaging technique reported here has simultaneous 100-ps temporal and 25-nm spatial resolutions. This approach reveals pathways of the nanoscale structural rearrangement upon ultrafast optical excitation, different from those transitions under slowly varying parameters. The spatiotemporally resolved structural characterization provides crucial nanoscopic insights into ultrafast phase transitions and opens opportunities for controlling nanoscale phases on ultrafast time scales.
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Affiliation(s)
- Youngjun Ahn
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439
- Department of Materials Science and Engineering, University of Wisconsin–Madison, Madison, WI 53706
| | - Mathew J. Cherukara
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, IL 60439
| | - Zhonghou Cai
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439
| | - Michael Bartlein
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, IL 60439
| | - Tao Zhou
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, IL 60439
| | - Anthony DiChiara
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439
| | - Donald A. Walko
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439
| | - Martin Holt
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, IL 60439
| | - Eric E. Fullerton
- Center for Magnetic Recording Research, University of California San Diego, La Jolla, CA 92903
| | - Paul G. Evans
- Department of Materials Science and Engineering, University of Wisconsin–Madison, Madison, WI 53706
| | - Haidan Wen
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439
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Current-induced Néel order switching facilitated by magnetic phase transition. Nat Commun 2022; 13:1629. [PMID: 35347132 PMCID: PMC8960908 DOI: 10.1038/s41467-022-29170-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Accepted: 02/11/2022] [Indexed: 11/24/2022] Open
Abstract
Terahertz (THz) spin dynamics and vanishing stray field make antiferromagnetic (AFM) materials the most promising candidate for the next-generation magnetic memory technology with revolutionary storage density and writing speed. However, owing to the extremely large exchange energy barriers, energy-efficient manipulation has been a fundamental challenge in AFM systems. Here, we report an electrical writing of antiferromagnetic orders through a record-low current density on the order of 106 A cm−2 facilitated by the unique AFM-ferromagnetic (FM) phase transition in FeRh. By introducing a transient FM state via current-induced Joule heating, the spin-orbit torque can switch the AFM order parameter by 90° with a reduced writing current density similar to ordinary FM materials. This mechanism is further verified by measuring the temperature and magnetic bias field dependences, where the X-ray magnetic linear dichroism (XMLD) results confirm the AFM switching besides the electrical transport measurement. Our findings demonstrate the exciting possibility of writing operations in AFM-based devices with a lower current density, opening a new pathway towards pure AFM memory applications. Electrical manipulation of antiferromagnetic order is crucial for future memory devices, but existing switching schemes require a large current density. Here, the authors achieve record low current density switching in FeRh by taking advantage of its antiferromagnetic to ferromagnetic phase transition.
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Flavell W. Spiers Memorial Lecture: Prospects for photoelectron spectroscopy. Faraday Discuss 2022; 236:9-57. [DOI: 10.1039/d2fd00071g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An overview is presented of recent advances in photoelectron spectroscopy, focussing on advances in in situ and time-resolved measurements, and in extending the sampling depth of the technique. The future...
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Subpicosecond metamagnetic phase transition in FeRh driven by non-equilibrium electron dynamics. Nat Commun 2021; 12:5088. [PMID: 34429414 PMCID: PMC8384879 DOI: 10.1038/s41467-021-25347-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 07/22/2021] [Indexed: 11/11/2022] Open
Abstract
Femtosecond light-induced phase transitions between different macroscopic orders provide the possibility to tune the functional properties of condensed matter on ultrafast timescales. In first-order phase transitions, transient non-equilibrium phases and inherent phase coexistence often preclude non-ambiguous detection of transition precursors and their temporal onset. Here, we present a study combining time-resolved photoelectron spectroscopy and ab-initio electron dynamics calculations elucidating the transient subpicosecond processes governing the photoinduced generation of ferromagnetic order in antiferromagnetic FeRh. The transient photoemission spectra are accounted for by assuming that not only the occupation of electronic states is modified during the photoexcitation process. Instead, the photo-generated non-thermal distribution of electrons modifies the electronic band structure. The ferromagnetic phase of FeRh, characterized by a minority band near the Fermi energy, is established 350 ± 30 fs after the laser excitation. Ab-initio calculations indicate that the phase transition is initiated by a photoinduced Rh-to-Fe charge transfer. In FeRh, it is possible to optically drive a phase transition between ferromagnetic (FM) and anti-ferromagnetic (AFM) ordering. Here, using a combination of photoelectron spectroscopy and ab-initio calculations, the authors demonstrate the existence of a transient intermediate phase, explaining the delayed appearance of the FM phase.
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Kalha C, Fernando NK, Bhatt P, Johansson FOL, Lindblad A, Rensmo H, Medina LZ, Lindblad R, Siol S, Jeurgens LPH, Cancellieri C, Rossnagel K, Medjanik K, Schönhense G, Simon M, Gray AX, Nemšák S, Lömker P, Schlueter C, Regoutz A. Hard x-ray photoelectron spectroscopy: a snapshot of the state-of-the-art in 2020. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:233001. [PMID: 33647896 DOI: 10.1088/1361-648x/abeacd] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 03/01/2021] [Indexed: 06/12/2023]
Abstract
Hard x-ray photoelectron spectroscopy (HAXPES) is establishing itself as an essential technique for the characterisation of materials. The number of specialised photoelectron spectroscopy techniques making use of hard x-rays is steadily increasing and ever more complex experimental designs enable truly transformative insights into the chemical, electronic, magnetic, and structural nature of materials. This paper begins with a short historic perspective of HAXPES and spans from developments in the early days of photoelectron spectroscopy to provide an understanding of the origin and initial development of the technique to state-of-the-art instrumentation and experimental capabilities. The main motivation for and focus of this paper is to provide a picture of the technique in 2020, including a detailed overview of available experimental systems worldwide and insights into a range of specific measurement modi and approaches. We also aim to provide a glimpse into the future of the technique including possible developments and opportunities.
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Affiliation(s)
- Curran Kalha
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, United Kingdom
| | - Nathalie K Fernando
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, United Kingdom
| | - Prajna Bhatt
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, United Kingdom
| | - Fredrik O L Johansson
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
| | - Andreas Lindblad
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
| | - Håkan Rensmo
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
| | - León Zendejas Medina
- Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, SE-75121, Uppsala, Sweden
| | - Rebecka Lindblad
- Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, SE-75121, Uppsala, Sweden
| | - Sebastian Siol
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Joining Technologies and Corrosion, Dübendorf, Switzerland
| | - Lars P H Jeurgens
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Joining Technologies and Corrosion, Dübendorf, Switzerland
| | - Claudia Cancellieri
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Joining Technologies and Corrosion, Dübendorf, Switzerland
| | - Kai Rossnagel
- Institute of Experimental and Applied Physics, Kiel University, 24098 Kiel, Germany
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - Katerina Medjanik
- Johannes Gutenberg Universität, Institut für Physik, 55128 Mainz, Germany
| | - Gerd Schönhense
- Johannes Gutenberg Universität, Institut für Physik, 55128 Mainz, Germany
| | - Marc Simon
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, LCPMR, F-75005 Paris, France
| | - Alexander X Gray
- Department of Physics, Temple University, Philadelphia, PA 19122, United States of America
| | - Slavomír Nemšák
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States of America
| | - Patrick Lömker
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | | | - Anna Regoutz
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, United Kingdom
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Cress CD, Wickramaratne D, Rosenberger MR, Hennighausen Z, Callahan PG, LaGasse SW, Bernstein N, van 't Erve OM, Jonker BT, Qadri SB, Prestigiacomo JC, Currie M, Mazin II, Bennett SP. Direct-Write of Nanoscale Domains with Tunable Metamagnetic Order in FeRh Thin Films. ACS APPLIED MATERIALS & INTERFACES 2021; 13:836-847. [PMID: 33216550 DOI: 10.1021/acsami.0c13565] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We have directly written nanoscale patterns of magnetic ordering in FeRh films using focused helium-ion beam irradiation. By varying the dose, we pattern arrays with metamagnetic transition temperatures that range from the as-grown film temperature to below room temperature. We employ transmission electron microscopy, X-ray diffraction, and temperature-dependent transport measurements to characterize the as-grown film, and magneto-optic Kerr effect imaging to quantify the He+ irradiation-induced changes to the magnetic order. Moreover, we demonstrate temperature-dependent optical microscopy and conductive atomic force microscopy as indirect probes of the metamagnetic transition that are sensitive to the differences in dielectric properties and electrical conductivity, respectively, of FeRh in the antiferromagnetic (AF) and ferromagnetic (FM) states. Using density functional theory, we quantify strain- and defect-induced changes in spin-flip energy to understand their influence on the metamagnetic transition temperature. This work holds promise for in-plane AF-FM spintronic devices, by reducing the need for multiple patterning steps or different materials, and potentially eliminating interfacial polarization losses due to cross material interfacial spin scattering.
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Affiliation(s)
- Cory D Cress
- Electronics Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Darshana Wickramaratne
- NRC Postdoc Residing at the Materials Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Matthew R Rosenberger
- Materials Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Zachariah Hennighausen
- NRC Postdoc Residing at the Materials Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Patrick G Callahan
- Materials Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Samuel W LaGasse
- NRC Postdoc Residing at the Electronics Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Noam Bernstein
- Materials Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Olaf M van 't Erve
- Materials Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Berend T Jonker
- Materials Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Syed B Qadri
- Materials Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Joseph C Prestigiacomo
- Materials Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Marc Currie
- Optical Sciences Division, United States Naval Research Laboratory, Washington, DC 20375, United States
| | - Igor I Mazin
- Department of Physics and Astronomy and the Quantum Materials Center, George Mason University, Fairfax, Virginia 22030, United States
| | - Steven P Bennett
- Materials Science and Technology Division, United States Naval Research Laboratory, Washington, DC 20375, United States
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