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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.
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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.
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Legut D, Diviš M, Doležal P, Zhang SH, Javorský P. Ab initio calculations of the crystal field and phonon dispersions in CePd 2Al 2 and LaPd 2Al 2. J Phys Condens Matter 2020; 32:235402. [PMID: 31986499 DOI: 10.1088/1361-648x/ab7031] [Citation(s) in RCA: 1] [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] [Indexed: 06/10/2023]
Abstract
CePd2Al2 crystallizes in the CaBe2Ge2-type tetragonal structure (P4/nmm, 129) and undergoes a phase transition to the orthorhombic Cmme structure at around 13 K. Its inelastic neutron spectra reveal an additional magnetic excitation that was ascribed to electron-phonon interaction leading to a formation of a new quantum quasi-bound vibron state. We present the first-principles calculations of the crystal field excitations and lattice dynamics calculations of the phonon dispersions to compare with the experimental data. The calculated crystal field energy splitting in CePd2Al2 agrees well with the model used to describe the experimental neutron scattering spectra. The first excited crystal field level moves to higher energies when undergoing the transformation from tetragonal to orthorhombic structure, in agreement with the experiment. The analysis based on calculated elastic constants and lattice dynamics calculations show that in both tetragonal and orthorhombic structures there are no imaginary modes for any q-wave vector within the Brillouin zone, and therefore the lattice structures are stable. The phonon dispersions and density of states are calculated for both crystal structures of CePd2Al2 and its nonmagnetic counterpart LaPd2Al2. The results generally agree well with the experimental data including the high phonon density of states around 12 meV. The phonon density of states is also used to calculate the mean squared displacement, Debye temperature, lattice heat capacity and compared with similar properties of the available experiment.
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Affiliation(s)
- D Legut
- IT4Innovations, VSB-Technical University of Ostrava, 17. listopadu 2172/15, 708 00 Ostrava, Czech Republic. Nanotechnology Centre, VSB-Technical University of Ostrava, 17. listopadu 2172/15, 708 00 Ostrava, Czech Republic
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Zhang RF, Kong XF, Wang HT, Zhang SH, Legut D, Sheng SH, Srinivasan S, Rajan K, Germann TC. An informatics guided classification of miscible and immiscible binary alloy systems. Sci Rep 2017; 7:9577. [PMID: 28851941 PMCID: PMC5575349 DOI: 10.1038/s41598-017-09704-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [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: 05/04/2017] [Accepted: 07/28/2017] [Indexed: 11/22/2022] Open
Abstract
The classification of miscible and immiscible systems of binary alloys plays a critical role in the design of multicomponent alloys. By mining data from hundreds of experimental phase diagrams, and thousands of thermodynamic data sets from experiments and high-throughput first-principles (HTFP) calculations, we have obtained a comprehensive classification of alloying behavior for 813 binary alloy systems consisting of transition and lanthanide metals. Among several physics-based descriptors, the slightly modified Pettifor chemical scale provides a unique two-dimensional map that divides the miscible and immiscible systems into distinctly clustered regions. Based on an artificial neural network algorithm and elemental similarity, the miscibility of the unknown systems is further predicted and a complete miscibility map is thus obtained. Impressively, the classification by the miscibility map yields a robust validation on the capability of the well-known Miedema’s theory (95% agreement) and shows good agreement with the HTFP method (90% agreement). Our results demonstrate that a state-of-the-art physics-guided data mining can provide an efficient pathway for knowledge discovery in the next generation of materials design.
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Affiliation(s)
- R F Zhang
- School of Materials Science and Engineering, and International Research Institute for Multidisciplinary Science, Beihang University, Beijing, 100191, P. R. China.
| | - X F Kong
- School of Materials Science and Engineering, and International Research Institute for Multidisciplinary Science, Beihang University, Beijing, 100191, P. R. China
| | - H T Wang
- CAS Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, P.R. China
| | - S H Zhang
- School of Materials Science and Engineering, and International Research Institute for Multidisciplinary Science, Beihang University, Beijing, 100191, P. R. China
| | - D Legut
- IT4Innovations Center & Nanotechnology Centre, VSB-Technical University of Ostrava, CZ-70833, Ostrava, Czech Republic
| | - S H Sheng
- School of Materials Science and Engineering, and International Research Institute for Multidisciplinary Science, Beihang University, Beijing, 100191, P. R. China
| | - S Srinivasan
- Plant Sciences Institute, Iowa State University, 2031 Roy J. Carver Co-Lab, Ames, IA, 50011, USA
| | - K Rajan
- Department of Materials Design and Innovation, University at Buffalo-State University of New York, 311 Bell Hall, Buffalo, NY, 14260, USA
| | - T C Germann
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
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Rogl G, Legut D, Sýkora R, Müller P, Müller H, Bauer E, Puchegger S, Zehetbauer M, Rogl P. Mechanical properties of non-centrosymmetric CePt 3Si and CePt 3B. J Phys Condens Matter 2017; 29:185402. [PMID: 28272023 DOI: 10.1088/1361-648x/aa655b] [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] [Indexed: 06/06/2023]
Abstract
Elastic moduli, hardness (both at room temperature) and thermal expansion (4.2-670 K) have been experimentally determined for polycrystalline CePt3Si and its prototype compound CePt3B as well as for single-crystalline CePt3Si. Resonant ultrasound spectroscopy was used to determine elastic properties (Young's modulus E and Poisson's ratio ν) via the eigenfrequencies of the sample and the knowledge of sample mass and dimensions. Bulk and shear moduli were calculated from E and ν, and the respective Debye temperatures were derived. In addition, ab initio DFT calculations were carried out for both compounds. A comparison of parameters evaluated from DFT with those of experiments revealed, in general, satisfactory agreement. Positive and negative thermal expansion values obtained from CePt3Si single crystal data are fairly well explained in terms of the crystalline electric field model, using CEF parameters derived recently from inelastic neutron scattering. DFT calculations, in addition, demonstrate that the atomic vibrations keep almost unaffected by the antisymmetric spin-orbit coupling present in systems with crystal structures having no inversion symmetry. This is opposite to electronic properties, where the antisymmetric spin-orbit interaction has shown to distinctly influence features like the superconducting condensate of CePt3Si.
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Affiliation(s)
- G Rogl
- Institute of Materials Chemistry and Research, University of Vienna, Waehringerstr. 42, A-1090 Wien, Austria. Solid State Physics, Vienna University of Technology, Wiedner Hauptstr. 8-10, A-1040 Wien, Austria
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Zhang H, Fu ZH, Legut D, Germann TC, Zhang RF. Stacking stability and sliding mechanism in weakly bonded 2D transition metal carbides by van der Waals force. RSC Adv 2017. [DOI: 10.1039/c7ra11139h] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The stability of the stacked two-dimensional (2D) transition metal carbides and their interlayered friction in different configurations are comparatively studied by means of density functional theory (DFT).
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Affiliation(s)
- H. Zhang
- School of Materials Science and Engineering
- Beihang University
- Beijing 100191
- P. R. China
- Center for Integrated Computational Materials Engineering
| | - Z. H. Fu
- School of Materials Science and Engineering
- Beihang University
- Beijing 100191
- P. R. China
- Center for Integrated Computational Materials Engineering
| | - D. Legut
- IT4Innovations Center
- VSB-Technical University of Ostrava
- CZ-70833 Ostrava
- Czech Republic
| | - T. C. Germann
- Theoretical Division
- Los Alamos National Laboratory
- Los Alamos
- USA
| | - R. F. Zhang
- School of Materials Science and Engineering
- Beihang University
- Beijing 100191
- P. R. China
- Center for Integrated Computational Materials Engineering
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Zhang Z, Zhang RF, Legut D, Li DQ, Zhang SH, Fu ZH, Guo HB. Pinning effect of reactive elements on adhesion energy and adhesive strength of incoherent Al2O3/NiAl interface. Phys Chem Chem Phys 2016; 18:22864-73. [PMID: 27480916 DOI: 10.1039/c6cp03609k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The profound effects of reactive elements (REs) on the adhesion energy and adhesive strength of the α-Al2O3/β-NiAl interface in thermal barrier coating (TBC) systems have attracted increasing attention because RE-doping has played a significant role in improving the thermal cycling lifetime of TBCs. However, the fundamental mechanism is, so far, not well understood due to the experimental difficulty and theoretical complexity in interface modelling. For this purpose, in the present study we have performed comprehensive density functional theory calculations and information targeted experiments to underline the origin of the surprising enhancement of interface adhesion, stability and mechanical strength of the α-Al2O3/β-NiAl interface by different RE doping levels. Our results suggest that the interface failure firstly appears within the NiAl layer adjacent to the Al-terminated oxide under mechanical loading, while the formation of O-RE-Ni bond pairs at the interface can effectively hinder the interface de-cohesion, providing a higher mechanical strength. By comparing several typical REs, it is observed that Hf can emerge not only with the highest interface adhesion energy, but also the highest mechanical strength; in agreement with our experimental results. By continuously increasing the dopant concentration, the strengthening effect may increase correspondingly, but is limited by the solute solubility. These results shed light into the effect of REs on the stability and strength of the α-Al2O3/β-NiAl interface, providing theoretical guidance for interface design via a combinational analysis of bond topology and electronic structure.
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Affiliation(s)
- Z Zhang
- School of Materials Science and Engineering, Beihang University, Beijing 100191, P. R. China. and Center for Integrated Computational Engineering, International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191, P. R. China
| | - R F Zhang
- School of Materials Science and Engineering, Beihang University, Beijing 100191, P. R. China. and Center for Integrated Computational Engineering, International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191, P. R. China
| | - D Legut
- IT4 Innovations Center, VSB-Technical University of Ostrava, CZ-70833 Ostrava, Czech Republic
| | - D Q Li
- School of Materials Science and Engineering, Beihang University, Beijing 100191, P. R. China.
| | - S H Zhang
- School of Materials Science and Engineering, Beihang University, Beijing 100191, P. R. China. and Center for Integrated Computational Engineering, International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191, P. R. China
| | - Z H Fu
- School of Materials Science and Engineering, Beihang University, Beijing 100191, P. R. China. and Center for Integrated Computational Engineering, International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191, P. R. China
| | - H B Guo
- School of Materials Science and Engineering, Beihang University, Beijing 100191, P. R. China.
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Zhang Z, Fu ZH, Zhang RF, Legut D, Guo HB. Anomalous mechanical strengths and shear deformation paths of Al2O3 polymorphs with high ionicity. RSC Adv 2016. [DOI: 10.1039/c5ra25796d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Alumina (Al2O3) formed by selective oxidization provides an effective way to protect aluminide alloys against corrosion for sustainable applications.
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Affiliation(s)
- Z. Zhang
- School of Materials Science and Engineering
- Beihang University
- Beijing 100191
- P. R. China
- Center for Integrated Computational Engineering
| | - Z. H. Fu
- School of Materials Science and Engineering
- Beihang University
- Beijing 100191
- P. R. China
- Center for Integrated Computational Engineering
| | - R. F. Zhang
- School of Materials Science and Engineering
- Beihang University
- Beijing 100191
- P. R. China
- Center for Integrated Computational Engineering
| | - D. Legut
- IT4 Innovations Center
- VSB-Technical University of Ostrava
- CZ-70833 Ostrava
- Czech Republic
- Charles University
| | - H. B. Guo
- School of Materials Science and Engineering
- Beihang University
- Beijing 100191
- P. R. China
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Zhang RF, Legut D, Lin ZJ, Zhao YS, Mao HK, Veprek S. Stability and strength of transition-metal tetraborides and triborides. Phys Rev Lett 2012; 108:255502. [PMID: 23004618 DOI: 10.1103/physrevlett.108.255502] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Indexed: 06/01/2023]
Abstract
Using density functional theory, we show that the long-believed transition-metal tetraborides (TB(4)) of tungsten and molybdenum are in fact triborides (TB(3)). This finding is supported by thermodynamic, mechanical, and phonon instabilities of TB(4), and it challenges the previously proposed origin of superhardness of these compounds and the predictability of the generally used hardness model. Theoretical calculations for the newly identified stable TB(3) structure correctly reproduce their structural and mechanical properties, as well as the experimental x-ray diffraction pattern. However, the relatively low shear moduli and strengths suggest that TB(3) cannot be intrinsically stronger than c-BN. The origin of the lattice instability of TB(3) under large shear strain that occurs at the atomic level during plastic deformation can be attributed to valence charge depletion between boron and metal atoms, which enables easy sliding of boron layers between the metal ones.
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Affiliation(s)
- R F Zhang
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Wdowik UD, Legut D, Ruebenbauer K. Calibration of the Isomer Shift for Iodine Resonant Transitions by Ab Initio Calculations. J Phys Chem A 2010; 114:7146-52. [DOI: 10.1021/jp1019747] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- U. D. Wdowik
- Applied Computer Science Division, Institute of Technology, Pedagogical University, PL-30-084 Cracow, ul. Podchora̧żych 2, Poland, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, CZ-616 62 Brno, Žižkova 22, Czech Republic, Chair of Atomistic Modelling and Design of Materials, University of Leoben, A-8700 Leoben, Franz-Josef-Strasse 18, Austria, and Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, PL-30-084 Cracow, ul. Podchora̧żych 2, Poland
| | - D. Legut
- Applied Computer Science Division, Institute of Technology, Pedagogical University, PL-30-084 Cracow, ul. Podchora̧żych 2, Poland, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, CZ-616 62 Brno, Žižkova 22, Czech Republic, Chair of Atomistic Modelling and Design of Materials, University of Leoben, A-8700 Leoben, Franz-Josef-Strasse 18, Austria, and Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, PL-30-084 Cracow, ul. Podchora̧żych 2, Poland
| | - K. Ruebenbauer
- Applied Computer Science Division, Institute of Technology, Pedagogical University, PL-30-084 Cracow, ul. Podchora̧żych 2, Poland, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, CZ-616 62 Brno, Žižkova 22, Czech Republic, Chair of Atomistic Modelling and Design of Materials, University of Leoben, A-8700 Leoben, Franz-Josef-Strasse 18, Austria, and Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, PL-30-084 Cracow, ul. Podchora̧żych 2, Poland
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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.
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Affiliation(s)
- S Valencia
- Helmholtz-Zentrum-Berlin, BESSY, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany.
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