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Rodríguez-Sota A, Saxena V, Spethmann J, Wiesendanger R, Lo Conte R, Kubetzka A, von Bergmann K. Phase Coexistence of Mn Trimer Clusters and Antiferromagnetic Mn Islands on Ir(111). ACS NANO 2024; 18:3699-3706. [PMID: 38227829 PMCID: PMC10832046 DOI: 10.1021/acsnano.3c11459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 01/11/2024] [Accepted: 01/11/2024] [Indexed: 01/18/2024]
Abstract
Clusters supported by solid substrates are prime candidates for heterogeneous catalysis and can be prepared in various ways. While mass-selected soft-landing methods are often used for the generation of monodisperse particles, self-assembly typically leads to a range of different cluster sizes. Here we show by scanning tunneling microscopy measurements that in the initial stages of growth, Mn forms trimers on a close-packed hexagonal Ir surface, providing a route for self-organized monodisperse cluster formation on an isotropic metallic surface. For an increasing amount of Mn, first a phase with reconstructed monolayer islands is formed, until at full coverage a pseudomorphic Mn phase evolves, which is the most densely packed one of the three different observed Mn phases on Ir(111). The magnetic state of both the reconstructed islands and the pseudomorphic film is found to be the prototypical antiferromagnetic Néel state with a 120° spin rotation between all nearest neighbors in the hexagonal layer.
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Affiliation(s)
- Arturo Rodríguez-Sota
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
| | - Vishesh Saxena
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
| | - Jonas Spethmann
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
| | - Roland Wiesendanger
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
| | | | - André Kubetzka
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
| | - Kirsten von Bergmann
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
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2
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Van Raden JM, Alexandropoulos DI, Slota M, Sopp S, Matsuno T, Thompson AL, Isobe H, Anderson HL, Bogani L. Singly and Triply Linked Magnetic Porphyrin Lanthanide Arrays. J Am Chem Soc 2022; 144:8693-8706. [PMID: 35503091 PMCID: PMC9121389 DOI: 10.1021/jacs.2c02084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Indexed: 12/12/2022]
Abstract
The introduction of paramagnetic metal centers into a conjugated π-system is a promising approach toward engineering spintronic materials. Here, we report an investigation of two types of spin-bearing dysprosium(III) and gadolinium(III) porphyrin dimers: singly meso-meso-linked dimers with twisted conformations and planar edge-fused β,meso,β-linked tapes. The rare-earth spin centers sit out of the plane of the porphyrin, so that the singly linked dimers are chiral, and their enantiomers can be resolved, whereas the edge-fused tape complexes can be separated into syn and anti stereoisomers. We compare the crystal structures, UV-vis-NIR absorption spectra, electrochemistry, EPR spectroscopy, and magnetic behavior of these complexes. Low-temperature SQUID magnetometry measurements reveal intramolecular antiferromagnetic exchange coupling between the GdIII centers in the edge-fused dimers (syn isomer: J = -51 ± 2 MHz; anti isomer: J = -19 ± 3 MHz), whereas no exchange coupling is detected in the singly linked twisted complex. The phase-memory times, Tm, are in the range of 8-10 μs at 3 K, which is long enough to test quantum computational schemes using microwave pulses. Both the syn and anti Dy2 edge-fused tapes exhibit single-molecule magnetic hysteresis cycles at temperatures below 0.5 K with slow magnetization dynamics.
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Affiliation(s)
- Jeff M. Van Raden
- Department
of Chemistry, University of Oxford, Chemistry
Research Laboratory, Oxford OX1 3TA, U.K.
| | | | - Michael Slota
- Department
of Materials, University of Oxford, Oxford OX1 3PH, U.K.
| | - Simen Sopp
- Department
of Materials, University of Oxford, Oxford OX1 3PH, U.K.
| | - Taisuke Matsuno
- Department
of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
| | - Amber L. Thompson
- Department
of Chemistry, University of Oxford, Chemistry
Research Laboratory, Oxford OX1 3TA, U.K.
| | - Hiroyuki Isobe
- Department
of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
| | - Harry L. Anderson
- Department
of Chemistry, University of Oxford, Chemistry
Research Laboratory, Oxford OX1 3TA, U.K.
| | - Lapo Bogani
- Department
of Materials, University of Oxford, Oxford OX1 3PH, U.K.
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Brinker S, Küster F, Parkin SSP, Sessi P, Lounis S. Anomalous excitations of atomically crafted quantum magnets. SCIENCE ADVANCES 2022; 8:eabi7291. [PMID: 35080983 PMCID: PMC8791613 DOI: 10.1126/sciadv.abi7291] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 12/06/2021] [Indexed: 06/14/2023]
Abstract
High-energy resolution spectroscopic studies of quantum magnets proved extremely valuable in accessing magnetodynamics quantities, such as energy barriers, magnetic interactions, and lifetime of excited states. Here, we investigate a previously unexplored flavor of low-energy spin excitations for quantum spins coupled to an electron bath. In sharp contrast to the usual tunneling signature of two steps symmetrically centered around the Fermi level, we find a single step in the conductance. Combining time-dependent and many-body perturbation theories, magnetic field-dependent tunneling spectra are explained as the result of an interplay between weak magnetic anisotropy energy, magnetic interactions, and Stoner-like electron-hole excitations that are strongly dependent on the magnetic states of the nanostructures. The results are rationalized in terms of a noncollinear magnetic ground state and the dominance of ferro- and antiferromagnetic interactions. The atomically crafted nanomagnets offer an appealing model for the exploration of electrically pumped spin systems.
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Affiliation(s)
- Sascha Brinker
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, Jülich D-52425, Germany
| | - Felix Küster
- Max Planck Institute of Microstructure Physics, Halle 06120, Germany
| | | | - Paolo Sessi
- Max Planck Institute of Microstructure Physics, Halle 06120, Germany
| | - Samir Lounis
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, Jülich D-52425, Germany
- Faculty of Physics, University of Duisburg-Essen and CENIDE, 47053 Duisburg, Germany
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4
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Indirect chiral magnetic exchange through Dzyaloshinskii-Moriya-enhanced RKKY interactions in manganese oxide chains on Ir(100). Nat Commun 2019; 10:2610. [PMID: 31197169 PMCID: PMC6565667 DOI: 10.1038/s41467-019-10515-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 05/16/2019] [Indexed: 11/08/2022] Open
Abstract
Localized electron spins can couple magnetically via the Ruderman-Kittel-Kasuya-Yosida interaction even if their wave functions lack direct overlap. Theory predicts that spin-orbit scattering leads to a Dzyaloshinskii-Moriya type enhancement of this indirect exchange interaction, giving rise to chiral exchange terms. Here we present a combined spin-polarized scanning tunneling microscopy, angle-resolved photoemission, and density functional theory study of MnO2 chains on Ir(100). Whereas we find antiferromagnetic Mn-Mn coupling along the chain, the inter-chain coupling across the non-magnetic Ir substrate turns out to be chiral with a 120° rotation between adjacent MnO2 chains. Calculations reveal that the Dzyaloshinskii-Moriya interaction results in spin spirals with a periodicity in agreement with experiment. Our findings confirm the existence of indirect chiral magnetic exchange, potentially giving rise to exotic phenomena, such as chiral spin-liquid states in spin ice systems or the emergence of new quasiparticles.
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Hermenau J, Brinker S, Marciani M, Steinbrecher M, Dos Santos Dias M, Wiesendanger R, Lounis S, Wiebe J. Stabilizing spin systems via symmetrically tailored RKKY interactions. Nat Commun 2019; 10:2565. [PMID: 31189872 PMCID: PMC6561942 DOI: 10.1038/s41467-019-10516-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 05/16/2019] [Indexed: 11/17/2022] Open
Abstract
Spins of single atoms adsorbed on substrates are promising building blocks for spintronics and quantum computation schemes. To process spin information and for increased magnetic stability, these spins have to be coupled to arrays. For a single atom, a high symmetry of the environment increases its spin stability. However, little is known about the role of the symmetry of the magnetic couplings in the arrays. Here, we study arrays of atomic spins coupled via Ruderman−Kittel−Kasuya−Yosida interaction, focusing on Dzyaloshinskii−Moriya and symmetric anisotropic exchange. We show that the high spin stability of a trimer can be remotely detected by a nearby atom, and how the Dzyaloshinskii−Moriya interaction leads to its destabilization. Adding more nearby atoms further destabilizes the trimer, due to a non-local effective transverse anisotropy originating in the symmetric anisotropic exchange. This transverse anisotropy can be quenched for highly symmetric structures, where the spin lifetime of the array increases drastically. Exploration of the atomic spin interactions promises next generation information technologies. Here the authors show the observation and understanding of the Dzyaloshinskii−Moriya and symmetric anisotropic exchange interactions controlled spin dynamics and stability in Fe cluster-adatom complexes on Pt surfaces.
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Affiliation(s)
- Jan Hermenau
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - Sascha Brinker
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, 52425, Jülich, Germany.,Department of Physics, RWTH Aachen University, 52056, Aachen, Germany
| | - Marco Marciani
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA, Leiden, The Netherlands.,Univ Lyon, Ens de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, 69342, Lyon, France
| | | | - Manuel Dos Santos Dias
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, 52425, Jülich, Germany
| | | | - Samir Lounis
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, 52425, Jülich, Germany
| | - Jens Wiebe
- Department of Physics, Hamburg University, 20355, Hamburg, Germany.
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Ibañez-Azpiroz J, Dos Santos Dias M, Blügel S, Lounis S. Spin-fluctuation and spin-relaxation effects of single adatoms from first principles. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:343002. [PMID: 30020083 DOI: 10.1088/1361-648x/aad43d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Single adatoms offer an exceptional playground for studying magnetism and its associated dynamics at the atomic scale. Here we review recent results on single adatoms deposited on metallic substrates, based on time-dependent density functional theory. First we analyze quantum zero-point spin-fluctuations (ZPSF) as calculated from the fluctuation-dissipation theorem, and show how they affect the magnetic stability by modifying the magnetic anisotropy energy. We also assess the impact of ZPSF in the limit of small hybridization to the substrate characteristic of semi-insulating substrates, connecting to recent experimental investigations where magnetic stability of a single adatom was achieved for the first time. Secondly, we inspect further the dynamics of single adatoms by considering the longitudinal and transverse spin-relaxation processes, whose time-scales are analyzed and related to the underlying electronic structure of both the adatom and the substrate. Thirdly, we analyze spin-fluctuation modes of paramagnetic adatoms, i.e. adatoms where the Stoner criterion for magnetism is almost fulfilled. Interestingly, such modes can develop well-defined peaks in the meV range, their main characteristics being determined by two fundamental electronic properties, namely the Stoner parameter and the density of states at the Fermi level. Furthermore, simulated inelastic scanning tunneling spectroscopy curves reveal that these spin-fluctuation modes can be triggered by tunneling electrons, opening up potential applications also for paramagnetic adatoms. Lastly, an overview of the outstanding issues and future directions is given.
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Affiliation(s)
- Julen Ibañez-Azpiroz
- Centro de Física de Materiales, Universidad del País Vasco, 20018 San Sebastián, Spain
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7
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Non-collinear spin states in bottom-up fabricated atomic chains. Nat Commun 2018; 9:2853. [PMID: 30030446 PMCID: PMC6054618 DOI: 10.1038/s41467-018-05364-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 06/25/2018] [Indexed: 11/08/2022] Open
Abstract
Non-collinear spin states with unique rotational sense, such as chiral spin-spirals, are recently heavily investigated because of advantages for future applications in spintronics and information technology and as potential hosts for Majorana Fermions when coupled to a superconductor. Tuning the properties of such spin states, e.g., the rotational period and sense, is a highly desirable yet difficult task. Here, we experimentally demonstrate the bottom-up assembly of a spin-spiral derived from a chain of iron atoms on a platinum substrate using the magnetic tip of a scanning tunneling microscope as a tool. We show that the spin-spiral is induced by the interplay of the Heisenberg and Dzyaloshinskii-Moriya components of the Ruderman-Kittel-Kasuya-Yosida interaction between the iron atoms. The relative strengths and signs of these two components can be adjusted by the interatomic iron distance, which enables tailoring of the rotational period and sense of the spin-spiral.
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Hermenau J, Ternes M, Steinbrecher M, Wiesendanger R, Wiebe J. Long Spin-Relaxation Times in a Transition-Metal Atom in Direct Contact to a Metal Substrate. NANO LETTERS 2018; 18:1978-1983. [PMID: 29466854 DOI: 10.1021/acs.nanolett.7b05392] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Long spin-relaxation times are a prerequisite for the use of spins in data storage or nanospintronics technologies. An atomic-scale solid-state realization of such a system is the spin of a transition-metal atom adsorbed on a suitable substrate. For the case of a metallic substrate, which enables the direct addressing of the spin by conduction electrons, the experimentally measured lifetimes reported to date are on the order of only hundreds of femtoseconds. Here, we show that the spin states of iron atoms adsorbed directly on a conductive platinum substrate have a surprisingly long spin-relaxation time in the nanosecond regime, which is comparable to that of a transition metal atom decoupled from the substrate electrons by a thin decoupling layer. The combination of long spin-relaxation times and strong coupling to conduction electrons implies the possibility to use flexible coupling schemes to process the spin information.
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Affiliation(s)
- Jan Hermenau
- Department of Physics , Hamburg University , Jungiusstrasse 11 , D-20355 Hamburg , Germany
| | - Markus Ternes
- Max-Planck Institute for Solid State Research , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
| | - Manuel Steinbrecher
- Department of Physics , Hamburg University , Jungiusstrasse 11 , D-20355 Hamburg , Germany
| | - Roland Wiesendanger
- Department of Physics , Hamburg University , Jungiusstrasse 11 , D-20355 Hamburg , Germany
| | - Jens Wiebe
- Department of Physics , Hamburg University , Jungiusstrasse 11 , D-20355 Hamburg , Germany
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9
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Willke P, Paul W, Natterer FD, Yang K, Bae Y, Choi T, Fernández-Rossier J, Heinrich AJ, Lutz CP. Probing quantum coherence in single-atom electron spin resonance. SCIENCE ADVANCES 2018; 4:eaaq1543. [PMID: 29464211 PMCID: PMC5815865 DOI: 10.1126/sciadv.aaq1543] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Accepted: 01/16/2018] [Indexed: 05/24/2023]
Abstract
Spin resonance of individual spin centers allows applications ranging from quantum information technology to atomic-scale magnetometry. To protect the quantum properties of a spin, control over its local environment, including energy relaxation and decoherence processes, is crucial. However, in most existing architectures, the environment remains fixed by the crystal structure and electrical contacts. Recently, spin-polarized scanning tunneling microscopy (STM), in combination with electron spin resonance (ESR), allowed the study of single adatoms and inter-atomic coupling with an unprecedented combination of spatial and energy resolution. We elucidate and control the interplay of an Fe single spin with its atomic-scale environment by precisely tuning the phase coherence time T2 using the STM tip as a variable electrode. We find that the decoherence rate is the sum of two main contributions. The first scales linearly with tunnel current and shows that, on average, every tunneling electron causes one dephasing event. The second, effective even without current, arises from thermally activated spin-flip processes of tip spins. Understanding these interactions allows us to maximize T2 and improve the energy resolution. It also allows us to maximize the amplitude of the ESR signal, which supports measurements even at elevated temperatures as high as 4 K. Thus, ESR-STM allows control of quantum coherence in individual, electrically accessible spins.
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Affiliation(s)
- Philip Willke
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, Republic of Korea
- IBM Almaden Research Center, San Jose, CA 95120, USA
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
- IV. Physical Institute, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - William Paul
- IBM Almaden Research Center, San Jose, CA 95120, USA
| | - Fabian D. Natterer
- IBM Almaden Research Center, San Jose, CA 95120, USA
- Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Kai Yang
- IBM Almaden Research Center, San Jose, CA 95120, USA
| | - Yujeong Bae
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, Republic of Korea
- IBM Almaden Research Center, San Jose, CA 95120, USA
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Taeyoung Choi
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, Republic of Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Joaquin Fernández-Rossier
- QuantaLab, International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga, 4715-310 Braga, Portugal
| | - Andreas J. Heinrich
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, Republic of Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
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