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Matetskiy AV, Milotti V, Sheverdyaeva PM, Moras P, Carbone C, Mihalyuk AN. Interplay between magnetic order and electronic band structure in ultrathin GdGe 2 metalloxene films. NANOSCALE 2023; 15:16080-16088. [PMID: 37750836 DOI: 10.1039/d3nr03398h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Dimensionality can strongly influence the magnetic structure of solid systems. Here, we predict theoretically and confirm experimentally that the antiferromagnetic (AFM) ground state of bulk gadolinium germanide metalloxene, which has a quasi-layered defective GdGe2 structure, is preserved in the ultrathin film limit. Ab initio calculations demonstrate that ultrathin GdGe2 films present in-plane intra-layer ferromagnetic coupling and AFM inter-layer coupling in the ground state. Angle-resolved photoemission spectroscopy finds the AFM-induced band splitting expected for the 2 and 3 GdGe2 trilayer (TL) films, which disappear above the Néel temperature. The comparative analysis of isostructural ultrathin DyGe2 and GdSi2 films confirms the magnetic origin of the observed band splitting. These findings are in contrast with the recent report of ferromagnetism in ultrathin metalloxene films, which we ascribe to the presence of uncompensated magnetic moments.
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Affiliation(s)
- Andrey V Matetskiy
- Istituto di Struttura della Materia-CNR (ISM-CNR), Strada Statale 14 km 163.5, 34149, Trieste, Italy.
- Institute of Automation and Control Processes FEB RAS, 690041 Vladivostok, Russia.
| | - Valeria Milotti
- Istituto di Struttura della Materia-CNR (ISM-CNR), Strada Statale 14 km 163.5, 34149, Trieste, Italy.
| | - Polina M Sheverdyaeva
- Istituto di Struttura della Materia-CNR (ISM-CNR), Strada Statale 14 km 163.5, 34149, Trieste, Italy.
| | - Paolo Moras
- Istituto di Struttura della Materia-CNR (ISM-CNR), Strada Statale 14 km 163.5, 34149, Trieste, Italy.
| | - Carlo Carbone
- Istituto di Struttura della Materia-CNR (ISM-CNR), Strada Statale 14 km 163.5, 34149, Trieste, Italy.
| | - Alexey N Mihalyuk
- Institute of Automation and Control Processes FEB RAS, 690041 Vladivostok, Russia.
- Institute of High Technologies and Advanced Materials, Far Eastern Federal University, 690950 Vladivostok, Russia
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Kamber U, Bergman A, Eich A, Iuşan D, Steinbrecher M, Hauptmann N, Nordström L, Katsnelson MI, Wegner D, Eriksson O, Khajetoorians AA. Self-induced spin glass state in elemental and crystalline neodymium. Science 2020; 368:368/6494/eaay6757. [PMID: 32467362 DOI: 10.1126/science.aay6757] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 01/14/2020] [Accepted: 04/10/2020] [Indexed: 11/02/2022]
Abstract
Spin glasses are a highly complex magnetic state of matter intricately linked to spin frustration and structural disorder. They exhibit no long-range order and exude aging phenomena, distinguishing them from quantum spin liquids. We report a previously unknown type of spin glass state, the spin-Q glass, observable in bulk-like crystalline metallic neodymium thick films. Using spin-polarized scanning tunneling microscopy combined with ab initio calculations and atomistic spin-dynamics simulations, we visualized the variations in atomic-scale noncolinear order and its response to magnetic field and temperature. We quantified the aging phenomena relating the glassiness to crystalline symmetry and the energy landscape. This result not only resolves the long-standing debate of the magnetism of neodymium, but also suggests that glassiness may arise in other magnetic solids lacking extrinsic disorder.
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Affiliation(s)
- Umut Kamber
- Institute for Molecules and Materials, Radboud University, Nijmegen, Netherlands
| | - Anders Bergman
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
| | - Andreas Eich
- Institute for Molecules and Materials, Radboud University, Nijmegen, Netherlands
| | - Diana Iuşan
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
| | - Manuel Steinbrecher
- Institute for Molecules and Materials, Radboud University, Nijmegen, Netherlands
| | - Nadine Hauptmann
- Institute for Molecules and Materials, Radboud University, Nijmegen, Netherlands
| | - Lars Nordström
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
| | - Mikhail I Katsnelson
- Institute for Molecules and Materials, Radboud University, Nijmegen, Netherlands
| | - Daniel Wegner
- Institute for Molecules and Materials, Radboud University, Nijmegen, Netherlands.
| | - Olle Eriksson
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.,School of Science and Technology, Örebro University, Örebro, Sweden
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Oroszlány L, Deák A, Simon E, Khmelevskyi S, Szunyogh L. Magnetism of Gadolinium: A First-Principles Perspective. PHYSICAL REVIEW LETTERS 2015; 115:096402. [PMID: 26371666 DOI: 10.1103/physrevlett.115.096402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Indexed: 06/05/2023]
Abstract
By calculating the spectral density of states in the ferromagnetic ground state and in the high temperature paramagnetic phase we provide the first concise study of finite temperature effects on the electronic structure of the bulk and the surface of gadolinium metal. The variation of calculated spectral properties of the Fermi surface and the density of states in the bulk and at the surface are in good agreement with recent photoemission experiments performed in both ferromagnetic and paramagnetic phases. In the paramagnetic state we find vanishing spin splitting of the conduction band, but finite local spin moments both in bulk and at the surface. We clearly demonstrate that the formation of these local spin moments in the conduction band is due to the asymmetry of the density of states in the two spin channels, suggesting a complex, non-Stoner behavior. We, therefore, suggest that the vanishing or nearly vanishing spin splitting of spectral features cannot be used as an indicator for Stoner-like magnetism.
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Affiliation(s)
- L Oroszlány
- Department of Theoretical Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
- Department of Physics of Complex Systems, Eötvös University, Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary
| | - A Deák
- Department of Theoretical Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
| | - E Simon
- Department of Theoretical Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
| | - S Khmelevskyi
- Department of Theoretical Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
- Faculty of Physics, Computational Materials Physics, University of Vienna, Vienna A-1090, Austria
| | - L Szunyogh
- Department of Theoretical Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
- MTA-BME Condensed Matter Research Group, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
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Gu Y, Halász GB, Robinson JWA, Blamire MG. Large Superconducting Spin Valve Effect and Ultrasmall Exchange Splitting in Epitaxial Rare-Earth-Niobium Trilayers. PHYSICAL REVIEW LETTERS 2015; 115:067201. [PMID: 26296128 DOI: 10.1103/physrevlett.115.067201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Indexed: 06/04/2023]
Abstract
Epitaxial Ho/Nb/Ho and Dy/Nb/Dy superconducting spin valves show a reversible change in the zero-field critical temperature (ΔT(c0)) of ∼400 mK and an infinite magnetoresistance on changing the relative magnetization of the Ho or Dy layers. Unlike transition-metal superconducting spin valves, which show much smaller ΔT(c0) values, our results can be quantitatively modeled. However, the fits require an extraordinarily low induced exchange splitting which is dramatically lower than known values for rare-earth Fermi-level electrons, implying that new models for the magnetic proximity effect may be required.
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Affiliation(s)
- Yuanzhou Gu
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Gábor B Halász
- Theoretical Physics, Oxford University, 1 Keble Road, Oxford OX1 3NP, United Kingdom
| | - J W A Robinson
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - M G Blamire
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
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Adachi H, Kawata H, Ito M. Resonance effect in white X-ray magnetic diffraction of GdAl 2. J Appl Crystallogr 2015. [DOI: 10.1107/s1600576715010699] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Using elliptically polarized white synchrotron radiation and an energy-sensitive detector, the 444 reflection from a single-crystal sample of the ferromagnetic compound GdAl2magnetized along the scattering vector has been measured, and the asymmetry of the diffraction intensity upon the magnetization reversal has been studied in the X-ray energy range across the GdLIIedge. The dependence of the magnetic asymmetry on the scattering angle or on the X-ray energy is understood as the superposition of the sharp near-edge structure and the much broader component arising from the interference between the electric scattering and the resonant and nonresonant magnetic scattering, respectively. To interpret the experimental results, an analytical treatment of the magnetic asymmetry is developed, and in the course of the analysis it is pointed out that in general the pseudo-extinction of the Bragg reflection due to the dispersion effects can be utilized as a technique to raise the magnetic sensitivity in the X-ray scattering from ferromagnetic materials. The potential of an unconventional approach to the resonant X-ray scattering using a white beam, as is clearly demonstrated by the present experiment, is also discussed.
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Strong ferromagnetism at the surface of an antiferromagnet caused by buried magnetic moments. Nat Commun 2015; 5:3171. [PMID: 24445395 DOI: 10.1038/ncomms4171] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Accepted: 12/20/2013] [Indexed: 11/08/2022] Open
Abstract
Carrying a large, pure spin magnetic moment of 7 μB per atom in the half-filled 4f shell, divalent europium is an outstanding element for assembling novel magnetic devices in which a two-dimensional electron gas may be polarized due to exchange interaction with an underlying magnetically-active Eu layer. Here we show that the Si-Rh-Si surface trilayer of the antiferromagnet EuRh2Si2 bears a surface state, which exhibits an unexpected and large spin splitting controllable by temperature. The splitting sets in below ~32.5 K, well above the ordering temperature of the Eu 4f moments (~24.5 K) in the bulk, indicating a larger ordering temperature in the topmost Eu layers. The driving force for the itinerant ferromagnetism at the surface is the aforementioned exchange interaction. Such a splitting may also be induced into states of functional surface layers deposited onto the surface of EuRh2Si2 or similarly ordered magnetic materials with metallic or semiconducting properties.
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Döbrich KM, Bostwick A, McChesney JL, Rossnagel K, Rotenberg E, Kaindl G. Fermi-surface topology and helical antiferromagnetism in heavy lanthanide metals. PHYSICAL REVIEW LETTERS 2010; 104:246401. [PMID: 20867317 DOI: 10.1103/physrevlett.104.246401] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Indexed: 05/29/2023]
Abstract
Detailed angle-resolved photoemission studies of Tb and Dy metal in the paramagnetic phase provide direct experimental proof of the presence of nesting features in the Fermi surfaces (FS) of these heavy lanthanide (Ln) metals. The observations clearly support the hypothesis that nesting of the FS in the paramagnetic phase is responsible for the development of helical antiferromagnetic ordering in heavy Ln metals. They also show that magnetic exchange splitting of the electronic states is responsible for the disappearance of FS nesting in the ferromagnetic phases.
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Affiliation(s)
- K M Döbrich
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin-Dahlem, Germany
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Chapter 241 The Dual, Localized or Band‐Like, Character of the 4f‐States. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/s0168-1273(08)00001-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Maiti K, Malagoli MC, Dallmeyer A, Carbone C. Finite temperature magnetism in Gd: evidence against a Stoner behavior. PHYSICAL REVIEW LETTERS 2002; 88:167205. [PMID: 11955260 DOI: 10.1103/physrevlett.88.167205] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2001] [Indexed: 05/23/2023]
Abstract
The temperature dependence of the rare-earth valence bands has been regarded as a realization of the Stoner behavior. The exchange splitting of the electronic states appears to scale as the magnetic order parameter for T<T(C) and to vanish at T = T(C). We report here a spin-resolved photoemission study on the evolution of Gd bulk bands for 0.5< or =T/T(C)< or=1. The spin-polarized spectral line shapes display a complex temperature dependence, which clearly contrasts with the interpretation of previous experimental results. The spin-resolved photoemission data demonstrate the inadequacy of the Stoner model to the description of magnetism in rare earths.
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Affiliation(s)
- K Maiti
- Institut für Festkörperforschung, Forschungszentrum Jülich, D-52428 Jülich, Germany
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