Special Issue "Atomic-Scale Properties of Magnetic Surfaces, Interfaces, and Nanostructures"

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Synthesis, Interfaces and Nanostructures".

Deadline for manuscript submissions: closed (31 August 2021) | Viewed by 9393

Special Issue Editors

Dr. Krisztián Palotás
E-Mail Website
Guest Editor
1. Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Budapest, Hungary
2. MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Szeged, Hungary
Interests: theoretical and computational magnetism; magnetic surfaces, interfaces, and nanostructures; topological magnetism and skyrmions; magnetic interactions; atomistic spin dynamics; electron charge and spin transport; scanning tunneling microscopy and spectroscopy; 2D materials; new materials for various applications; supported molecular nanostructures; surface chemistry; density functional theory; developments of theoretical and computational methods
Dr. Balázs Újfalussy
E-Mail Website
Guest Editor
Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Budapest, Hungary
Interests: magnetism; magnetic interactions; magnetic surfaces and nanostructures; magnetic alloys; magnetic phase transitions; computational materials science; theoretical and computational magnetism; density functional theory; topology and magnetism; magnetic superconductors; Majorana zero modes
Prof. Dr. László Szunyogh
E-Mail Website
Guest Editor
Department of Theoretical Physics and MTA-BME Condensed Matter Research Group, Budapest University of Technology and Economics, Budapest, Hungary
Interests: theoretical and computational magnetism; density functional theory; developments of theoretical and computational methods; magnetic interactions; magnetic anisotropy; atomistic spin dynamics; bulk magnets; magnetic surfaces and nanostructures; superparamagnetism; skyrmionics; magnetism of 2D materials; electron charge and spin transport

Special Issue Information

Dear Colleagues,

Magnetic surfaces, interfaces, and nanostructures are key elements for a wide spectrum of technological applications. Consequently, extensive research activities have been performed to explore the physical properties of these systems, including both fundamental and practical aspects.  A deep understanding of the physical mechanisms at the atomic scale, both from theoretical and experimental points of view, is a crucial step towards utilizing magnetic nanomaterials in devices with improved functionality and efficiency in order to realize commercially available products for future everyday life.

This Special Issue has the goal of collecting the latest original research contributions in the forms of short communications, articles, or comprehensive reviews on the atomic scale properties of magnetic surfaces, interfaces, and nanostructures. Our vision is to compile a high-impact Special Issue that will serve as an important reference for future research and development activities in this field. All considered papers should demonstrate clear links to atomic scale magnetic properties.

We kindly invite the reader to contribute to this Special Issue.

Dr. Krisztián Palotás
Dr. Balázs Újfalussy
Prof. Dr. László Szunyogh
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Nanomaterials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Atomic scale magnetic properties
  • Magnetic surfaces, interfaces, thin films, multilayers, and heterostructures
  • Magnetic nanostructures
  • Nanomagnetism
  • Topology and magnetism, topological spin textures
  • Magnetic interactions
  • Spin dynamics
  • Spin-polarized scanning tunneling microscopy/spectroscopy
  • Spintronics, orbitronics, and skyrmionics
  • Magnetic materials for industrial applications

Published Papers (9 papers)

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Research

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Article
Skyrmion Formation in Nanodisks Using Magnetic Force Microscopy Tip
Nanomaterials 2021, 11(10), 2627; https://doi.org/10.3390/nano11102627 - 06 Oct 2021
Viewed by 760
Abstract
We demonstrated numerically the skyrmion formation in ultrathin nanodisks using a magnetic force microscopy tip. We found that the local magnetic field generated by the magnetic tip significantly affects the magnetization state of the nanodisks and leads to the formation of skyrmions. Experimentally, [...] Read more.
We demonstrated numerically the skyrmion formation in ultrathin nanodisks using a magnetic force microscopy tip. We found that the local magnetic field generated by the magnetic tip significantly affects the magnetization state of the nanodisks and leads to the formation of skyrmions. Experimentally, we confirmed the influence of the local field on the magnetization states of the disks. Micromagnetic simulations explain the evolution of the magnetic state during magnetic force microscopy scanning and confirm the possibility of skyrmion formation. The formation of the horseshoe magnetic domain is a key transition from random labyrinth domain states into the skyrmion state. We showed that the formation of skyrmions by the magnetic probe is a reliable and repetitive procedure. Our findings provide a simple solution for skyrmion formation in nanodisks. Full article
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Article
Magnetism in Au-Supported Planar Silicene
Nanomaterials 2021, 11(10), 2568; https://doi.org/10.3390/nano11102568 - 29 Sep 2021
Cited by 1 | Viewed by 597
Abstract
The adsorption and substitution of transition metal atoms (Fe and Co) on Au-supported planar silicene have been studied by means of first-principles density functional theory calculations. The structural, energetic and magnetic properties have been analyzed. Both dopants favor the same atomic configurations with [...] Read more.
The adsorption and substitution of transition metal atoms (Fe and Co) on Au-supported planar silicene have been studied by means of first-principles density functional theory calculations. The structural, energetic and magnetic properties have been analyzed. Both dopants favor the same atomic configurations with rather strong binding energies and noticeable charge transfer. The adsorption of Fe and Co atoms do not alter the magnetic properties of Au-supported planar silicene, unless a full layer of adsorbate is completed. In the case of substituted system only Fe is able to produce magnetic ground state. The Fe-doped Au-supported planar silicene is a ferromagnetic structure with local antiferromagnetic ordering. The present study is the very first and promising attempt towards ferromagnetic epitaxial planar silicene and points to the importance of the substrate in structural and magnetic properties of silicene. Full article
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Article
Topological Phase and Quantum Anomalous Hall Effect in Ferromagnetic Transition-Metal Dichalcogenides Monolayer 1TVSe2
Nanomaterials 2021, 11(8), 1998; https://doi.org/10.3390/nano11081998 - 04 Aug 2021
Cited by 1 | Viewed by 1474
Abstract
Magnetic two-dimensional (2D) van der Waals materials have attracted tremendous attention because of their high potential in spintronics. In particular, the quantum anomalous Hall (QAH) effect in magnetic 2D layers shows a very promising prospect for hosting Majorana zero modes at the topologically [...] Read more.
Magnetic two-dimensional (2D) van der Waals materials have attracted tremendous attention because of their high potential in spintronics. In particular, the quantum anomalous Hall (QAH) effect in magnetic 2D layers shows a very promising prospect for hosting Majorana zero modes at the topologically protected edge states in proximity to superconductors. However, the QAH effect has not yet been experimentally realized in monolayer systems to date. In this work, we study the electronic structures and topological properties of the 2D ferromagnetic transition-metal dichalcogenides (TMD) monolayer 1TVSe2 by first-principles calculations with the Heyd–Scuseria–Ernzerhof (HSE) functional. We find that the spin-orbit coupling (SOC) opens a continuous band gap at the magnetic Weyl-like crossing point hosting the quantum anomalous Hall effect with Chern number C=2. Moreover, we demonstrate the topologically protected edge states and intrinsic (spin) Hall conductivity in this magnetic 2D TMD system. Our results indicate that 1TVSe2 monolayer serves as a stoichiometric quantum anomalous Hall material. Full article
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Article
Electronic and Magnetic Properties of Building Blocks of Mn and Fe Atomic Chains on Nb(110)
Nanomaterials 2021, 11(8), 1933; https://doi.org/10.3390/nano11081933 - 27 Jul 2021
Cited by 2 | Viewed by 759
Abstract
We present results for the electronic and magnetic structure of Mn and Fe clusters on Nb(110) surface, focusing on building blocks of atomic chains as possible realizations of topological superconductivity. The magnetic ground states of the atomic dimers and most of the monatomic [...] Read more.
We present results for the electronic and magnetic structure of Mn and Fe clusters on Nb(110) surface, focusing on building blocks of atomic chains as possible realizations of topological superconductivity. The magnetic ground states of the atomic dimers and most of the monatomic chains are determined by the nearest-neighbor isotropic interaction. To gain physical insight, the dependence on the crystallographic direction as well as on the atomic coordination number is analyzed via an orbital decomposition of this isotropic interaction based on the spin-cluster expansion and the difference in the local density of states between ferromagnetic and antiferromagnetic configurations. A spin-spiral ground state is obtained for Fe chains along the [11¯0] direction as a consequence of the frustration of the isotropic interactions. Here, a flat spin-spiral dispersion relation is identified, which can stabilize spin spirals with various wave vectors together with the magnetic anisotropy. This may lead to the observation of spin spirals of different wave vectors and chiralities in longer chains instead of a unique ground state. Full article
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Article
Interplay between Single-Ion and Two-Ion Anisotropies in Frustrated 2D Semiconductors and Tuning of Magnetic Structures Topology
Nanomaterials 2021, 11(8), 1873; https://doi.org/10.3390/nano11081873 - 21 Jul 2021
Cited by 4 | Viewed by 790
Abstract
The effects of competing magnetic interactions in stabilizing different spin configurations are drawing renewed attention in order to unveil emerging topological spin textures and to highlight microscopic mechanisms leading to their stabilization. The possible key role of the two-site exchange anisotropy in selecting [...] Read more.
The effects of competing magnetic interactions in stabilizing different spin configurations are drawing renewed attention in order to unveil emerging topological spin textures and to highlight microscopic mechanisms leading to their stabilization. The possible key role of the two-site exchange anisotropy in selecting specific helicity and vorticity of skyrmionic lattices has only recently been proposed. In this work, we explore the phase diagram of a frustrated localized magnet characterized by a two-dimensional centrosymmetric triangular lattice, focusing on the interplay between the two-ion anisotropy and the single-ion anisotropy. The effects of an external magnetic field applied perpendicularly to the magnetic layer, are also investigated. By means of Monte Carlo simulations, we find an abundance of different spin configurations, going from trivial to high-order Q skyrmionic and meronic lattices. In closer detail, we find that a dominant role is played by the two-ion over the single-ion anisotropy in determining the planar spin texture; the strength and the sign of single ion anisotropy, together with the magnitude of the magnetic field, tune the perpendicular spin components, mostly affecting the polarity (and, in turn, the topology) of the spin texture. Our analysis confirms the crucial role of the anisotropic symmetric exchange in systems with dominant short-range interactions; at the same time, we predict a rich variety of complex magnetic textures, which may arise from a fine tuning of competing anisotropic mechanisms. Full article
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Article
Emergence of Nontrivial Spin Textures in Frustrated Van Der Waals Ferromagnets
Nanomaterials 2021, 11(7), 1770; https://doi.org/10.3390/nano11071770 - 07 Jul 2021
Cited by 2 | Viewed by 1354
Abstract
In this work, first principles ground state calculations are combined with the dynamic evolution of a classical spin Hamiltonian to study the metamagnetic transitions associated with the field dependence of magnetic properties in frustrated van der Waals ferromagnets. Dynamically stabilized spin textures are [...] Read more.
In this work, first principles ground state calculations are combined with the dynamic evolution of a classical spin Hamiltonian to study the metamagnetic transitions associated with the field dependence of magnetic properties in frustrated van der Waals ferromagnets. Dynamically stabilized spin textures are obtained relative to the direction of spin quantization as stochastic solutions of the Landau–Lifshitz–Gilbert–Slonczewski equation under the flow of the spin current. By explicitly considering the spin signatures that arise from geometrical frustrations at interfaces, we may observe the emergence of a magnetic skyrmion spin texture and characterize the formation under competing internal fields. The analysis of coercivity and magnetic hysteresis reveals a dynamic switch from a soft to hard magnetic configuration when considering the spin Hall effect on the skyrmion. It is found that heavy metals in capped multilayer heterostructure stacks host field-tunable spiral skyrmions that could serve as unique channels for carrier transport. The results are discussed to show the possibility of using dynamically switchable magnetic bits to read and write data without the need for a spin transfer torque. These results offer insight to the spin transport signatures that dynamically arise from metamagnetic transitions in spintronic devices. Full article
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Article
Microstructures and Interface Magnetic Moments in Mn2VAl/Fe Layered Films Showing Exchange Bias
Nanomaterials 2021, 11(7), 1723; https://doi.org/10.3390/nano11071723 - 30 Jun 2021
Cited by 1 | Viewed by 663
Abstract
Heusler alloys are a material class exhibiting various magnetic properties, including antiferromagnetism. A typical application of antiferromagnets is exchange bias that is a shift of the magnetization curve observed in a layered structure consisting of antiferromagnetic and ferromagnetic films. In this study, a [...] Read more.
Heusler alloys are a material class exhibiting various magnetic properties, including antiferromagnetism. A typical application of antiferromagnets is exchange bias that is a shift of the magnetization curve observed in a layered structure consisting of antiferromagnetic and ferromagnetic films. In this study, a layered sample consisting of a Heusler alloy, Mn2VAl and a ferromagnet, Fe, is selected as a material system exhibiting exchange bias. Although the fully ordered Mn2VAl is known as a ferrimagnet, with an optimum fabrication condition for the Mn2VAl layer, the Mn2VAl/Fe layered structure exhibits exchange bias. The appearance of the antiferromagnetic property in the Mn2VAl is remarkable; however, the details have been unclear. To clarify the microscopic aspects on the crystal structures and magnetic moments around the Mn2VAl/Fe interface, cross-sectional scanning transmission electron microscope (STEM) observation, and synchrotron soft X-ray magnetic circular dichroism (XMCD) measurements were employed. The high-angle annular dark-field STEM images demonstrated clusters of Mn2VAl with the L21 phase distributed only around the interface to the Fe layer in the sample showing the exchange bias. Furthermore, antiferromagnetic coupling between the Mn- and Fe-moments were observed in element-specific hysteresis loops measured using the XMCD. The locally ordered L21 phase and antiferromagnetic Mn-moments in the Mn2VAl were suggested as important factors for the exchange bias. Full article
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Article
Friedel Oscillations Induced by Magnetic Skyrmions: From Scattering Properties to All-Electrical Detection
Nanomaterials 2021, 11(1), 194; https://doi.org/10.3390/nano11010194 - 14 Jan 2021
Cited by 1 | Viewed by 822
Abstract
Magnetic skyrmions are spin swirling solitonic defects that can play a major role in information technology. Their future in applications and devices hinges on their efficient manipulation and detection. Here, we explore from ab-initio their nature as magnetic inhomongeities in an otherwise unperturbed [...] Read more.
Magnetic skyrmions are spin swirling solitonic defects that can play a major role in information technology. Their future in applications and devices hinges on their efficient manipulation and detection. Here, we explore from ab-initio their nature as magnetic inhomongeities in an otherwise unperturbed magnetic material, Fe layer covered by a thin Pd film and deposited on top of Ir(111) surface. The presence of skyrmions triggers scattering processes, from which Friedel oscillations emerge. The latter mediate interactions among skyrmions or between skyrmions and other potential surrounding defects. In contrast to their wavelengths, the amplitude of the oscillations depends strongly on the size of the skyrmion. The analogy with the scattering-off atomic defects enables the assignment of an effective scattering potential and a phase shift to the skyrmionic particles, which can be useful to predict their behavior on the basis of simple scattering frameworks. The induced charge ripples can be utilized for a noninvasive all-electrical detection of skyrmions located on a surface or even if buried a few nanometers away from the detecting electrode. Full article
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Review

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Review
Manipulation of Molecular Spin State on Surfaces Studied by Scanning Tunneling Microscopy
Nanomaterials 2020, 10(12), 2393; https://doi.org/10.3390/nano10122393 - 30 Nov 2020
Cited by 4 | Viewed by 1161
Abstract
The adsorbed magnetic molecules with tunable spin states have drawn wide attention for their immense potential in the emerging fields of molecular spintronics and quantum computing. One of the key issues toward their application is the efficient controlling of their spin state. This [...] Read more.
The adsorbed magnetic molecules with tunable spin states have drawn wide attention for their immense potential in the emerging fields of molecular spintronics and quantum computing. One of the key issues toward their application is the efficient controlling of their spin state. This review briefly summarizes the recent progress in the field of molecular spin state manipulation on surfaces. We focus on the molecular spins originated from the unpaired electrons of which the Kondo effect and spin excitation can be detected by scanning tunneling microscopy and spectroscopy (STM and STS). Studies of the molecular spin-carriers in three categories are overviewed, i.e., the ones solely composed of main group elements, the ones comprising 3d-metals, and the ones comprising 4f-metals. Several frequently used strategies for tuning molecular spin state are exemplified, including chemical reactions, reversible atomic/molecular chemisorption, and STM-tip manipulations. The summary of the successful case studies of molecular spin state manipulation may not only facilitate the fundamental understanding of molecular magnetism and spintronics but also inspire the design of the molecule-based spintronic devices and materials. Full article
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