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10 pages, 2049 KiB

Open AccessArticle

Skyrmion Formation in Nanodisks Using Magnetic Force Microscopy Tip

by Mateusz Zelent, Iuliia V. Vetrova, Jan Šoltýs, Xiaoguang Li, Yan Zhou, Vladislav A. Gubanov, Alexandr V. Sadovnikov, Tomas Šcepka, Jan Dérer, Roman Stoklas, Vladimír Cambel and Michal Mruczkiewicz

Nanomaterials 2021, 11(10), 2627; https://doi.org/10.3390/nano11102627 - 6 Oct 2021

Cited by 3 | Viewed by 2778

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

(This article belongs to the Special Issue Atomic-Scale Properties of Magnetic Surfaces, Interfaces, and Nanostructures)

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9 pages, 2971 KiB

Open AccessArticle

Magnetism in Au-Supported Planar Silicene

by Mariusz Krawiec, Agnieszka Stępniak-Dybala, Andrzej Bobyk and Ryszard Zdyb

Nanomaterials 2021, 11(10), 2568; https://doi.org/10.3390/nano11102568 - 29 Sep 2021

Cited by 3 | Viewed by 1648

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

(This article belongs to the Special Issue Atomic-Scale Properties of Magnetic Surfaces, Interfaces, and Nanostructures)

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9 pages, 1183 KiB

Open AccessArticle

Topological Phase and Quantum Anomalous Hall Effect in Ferromagnetic Transition-Metal Dichalcogenides Monolayer

1 T - V {Se}_{2}

by Angus Huang, Chin-Hsuan Chen, Ching-Hao Chang and Horng-Tay Jeng

Nanomaterials 2021, 11(8), 1998; https://doi.org/10.3390/nano11081998 - 4 Aug 2021

Cited by 6 | Viewed by 4322

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

1 T - V {Se}_{2}

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

1 T - V {Se}_{2}

monolayer serves as a stoichiometric quantum anomalous Hall material. Full article

(This article belongs to the Special Issue Atomic-Scale Properties of Magnetic Surfaces, Interfaces, and Nanostructures)

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19 pages, 665 KiB

Open AccessArticle

Electronic and Magnetic Properties of Building Blocks of Mn and Fe Atomic Chains on Nb(110)

by András Lászlóffy, Krisztián Palotás, Levente Rózsa and László Szunyogh

Nanomaterials 2021, 11(8), 1933; https://doi.org/10.3390/nano11081933 - 27 Jul 2021

Cited by 8 | Viewed by 2151

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 [

1 \bar{1} 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

(This article belongs to the Special Issue Atomic-Scale Properties of Magnetic Surfaces, Interfaces, and Nanostructures)

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18 pages, 5963 KiB

Open AccessArticle

Interplay between Single-Ion and Two-Ion Anisotropies in Frustrated 2D Semiconductors and Tuning of Magnetic Structures Topology

by Danila Amoroso, Paolo Barone and Silvia Picozzi

Nanomaterials 2021, 11(8), 1873; https://doi.org/10.3390/nano11081873 - 21 Jul 2021

Cited by 26 | Viewed by 2492

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

(This article belongs to the Special Issue Atomic-Scale Properties of Magnetic Surfaces, Interfaces, and Nanostructures)

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24 pages, 3511 KiB

Open AccessArticle

Emergence of Nontrivial Spin Textures in Frustrated Van Der Waals Ferromagnets

by Aniekan Magnus Ukpong

Nanomaterials 2021, 11(7), 1770; https://doi.org/10.3390/nano11071770 - 7 Jul 2021

Cited by 10 | Viewed by 3300

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

(This article belongs to the Special Issue Atomic-Scale Properties of Magnetic Surfaces, Interfaces, and Nanostructures)

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11 pages, 3069 KiB

Open AccessArticle

Microstructures and Interface Magnetic Moments in Mn₂VAl/Fe Layered Films Showing Exchange Bias

by Takahide Kubota, Yusuke Shimada, Tomoki Tsuchiya, Tomoki Yoshikawa, Keita Ito, Yukiharu Takeda, Yuji Saitoh, Toyohiko J. Konno, Akio Kimura and Koki Takanashi

Nanomaterials 2021, 11(7), 1723; https://doi.org/10.3390/nano11071723 - 30 Jun 2021

Cited by 2 | Viewed by 1877

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, Mn

_{2}

VAl and a ferromagnet, Fe, is selected as a material system exhibiting exchange bias. Although the fully ordered Mn

_{2}

VAl is known as a ferrimagnet, with an optimum fabrication condition for the Mn

_{2}

VAl layer, the Mn

_{2}

VAl/Fe layered structure exhibits exchange bias. The appearance of the antiferromagnetic property in the Mn

_{2}

VAl is remarkable; however, the details have been unclear. To clarify the microscopic aspects on the crystal structures and magnetic moments around the Mn

_{2}

VAl/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 Mn

_{2}

VAl with the L2

_{1}

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 L2

_{1}

phase and antiferromagnetic Mn-moments in the Mn

_{2}

VAl were suggested as important factors for the exchange bias. Full article

(This article belongs to the Special Issue Atomic-Scale Properties of Magnetic Surfaces, Interfaces, and Nanostructures)

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12 pages, 2255 KiB

Open AccessArticle

Friedel Oscillations Induced by Magnetic Skyrmions: From Scattering Properties to All-Electrical Detection

by Mohammed Bouhassoune and Samir Lounis

Nanomaterials 2021, 11(1), 194; https://doi.org/10.3390/nano11010194 - 14 Jan 2021

Cited by 5 | Viewed by 2352

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

(This article belongs to the Special Issue Atomic-Scale Properties of Magnetic Surfaces, Interfaces, and Nanostructures)

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Review

Jump to: Research

18 pages, 8166 KiB

Open AccessReview

Manipulation of Molecular Spin State on Surfaces Studied by Scanning Tunneling Microscopy

by Zhen Xu, Jing Liu, Shimin Hou and Yongfeng Wang

Nanomaterials 2020, 10(12), 2393; https://doi.org/10.3390/nano10122393 - 30 Nov 2020

Cited by 12 | Viewed by 4300

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

(This article belongs to the Special Issue Atomic-Scale Properties of Magnetic Surfaces, Interfaces, and Nanostructures)

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