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Magnetochemistry
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Recent Advances in Nanomagnetism
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Recent Advances in Nanomagnetism

A special issue of Magnetochemistry (ISSN 2312-7481). This special issue belongs to the section "Magnetic Nanospecies".

Deadline for manuscript submissions: closed (31 October 2021) | Viewed by 21845

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. David S. Schmool

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Guest Editor
UFR of Sciences Department of Physical Sciences, University Versailles St-Quentin-en-Yvelines, 78035 Versailles, France
Interests: nanotechnologies; nanomagnetism; magnetic nanoparticles and nanostructures; magnetic thin films and multilayers; magnetization dynamics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Nanomagnetism covers a broad range of research in magnetism and magnetic properties of low-dimensional systems, including both experimental methods in sample fabrication and characterization, as well as theoretical modeling and simulations. Size limitations in one, two, and three dimensions have led to a number of technologically important developments, having an extensive range of applications in sensors and activators, notably in the magnetic recording industry and spintronic devices and more recently in biomedical applications. Magnetic systems can have a variety of symmetries, from thin film geometries to wires and dots, as well as a number of nanoparticle structures, which can also have core–shell substructures. The magnetic state of nanometric magnetic structures results from the equilibrium between competing magnetic anisotropies, interactions, and the applied magnetic field. This can produce a number of phenomena, such as exchange bias effects, skyrmions, as well as magnetic instabilities, which can lead to superparamagnetic effects in magnetic nanoparticles and nanostructures. The physical dimensions and shape of a magnetic structure, as well as its intrinsic magnetic anisotropies, will determine whether it is a single domain or has a more complex magnetic domain structure. Traditionally patterned nanostructures have been planar arrays of nanomagnets, though recent trends have shown how this can be extended to three-dimensional structures where more complex magnetic configurations are possible and give rise to unprecedented magnetic properties.

Prof. David S. Schmool
Guest Editor

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. Magnetochemistry is an international peer-reviewed open access monthly 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 2700 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

  • Nanomagnetism
  • Thin-films and magnetic multilayers
  • Nanoparticles and core–shell structures
  • Magnetic nanostructures
  • Skyrmions
  • Superparamagnetism
  • Artificial spin–ice structures
  • Spintronics
  • Magnetization dynamics in nanostructures

Published Papers (7 papers)

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Editorial

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3 pages, 172 KiB  
Editorial
Recent Advances in Nanomagnetism
by David S. Schmool
Magnetochemistry 2022, 8(9), 110; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry8090110 - 19 Sep 2022
Viewed by 1340
Abstract
Nanomagnetism covers a broad range of research in magnetism and magnetic properties of low-dimensional systems, including both experimental methods in sample fabrication and characterization, as well as theoretical modeling and simulations [...] Full article
(This article belongs to the Special Issue Recent Advances in Nanomagnetism)

Research

Jump to: Editorial

18 pages, 2674 KiB  
Article
Ferromagnetic Resonance Studies in Magnetic Nanosystems
by David S. Schmool, Daniel Markó, Ko-Wei Lin, Aurelio Hierro-Rodríguez, Carlos Quirós, Javier Díaz, Luis Manuel Álvarez-Prado and Jong-Ching Wu
Magnetochemistry 2021, 7(9), 126; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7090126 - 12 Sep 2021
Cited by 3 | Viewed by 4944
Abstract
Ferromagnetic resonance is a powerful method for the study of all classes of magnetic materials. The experimental technique has been used for many decades and is based on the excitation of a magnetic spin system via a microwave (or rf) field. While earlier [...] Read more.
Ferromagnetic resonance is a powerful method for the study of all classes of magnetic materials. The experimental technique has been used for many decades and is based on the excitation of a magnetic spin system via a microwave (or rf) field. While earlier methods were based on the use of a microwave spectrometer, more recent developments have seen the widespread use of the vector network analyzer (VNA), which provides a more versatile measurement system at almost comparable sensitivity. While the former is based on a fixed frequency of excitation, the VNA enables frequency-dependent measurements, allowing more in-depth analysis. We have applied this technique to the study of nanostructured thin films or nanodots and coupled magnetic layer systems comprised of exchange-coupled ferromagnetic layers with in-plane and perpendicular magnetic anisotropies. In the first system, we have investigated the magnetization dynamics in Co/Ag bilayers and nanodots. In the second system, we have studied Permalloy (Ni80Fe20, hereafter Py) thin films coupled via an intervening Al layer of varying thickness to a NdCo film which has perpendicular magnetic anisotropy. Full article
(This article belongs to the Special Issue Recent Advances in Nanomagnetism)
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14 pages, 4873 KiB  
Article
Control of Dynamics in Weak PMA Magnets
by Luis M. Álvarez-Prado
Magnetochemistry 2021, 7(3), 43; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7030043 - 17 Mar 2021
Cited by 4 | Viewed by 2190
Abstract
We have recently shown that a hybrid magnetic thin film with orthogonal anisotropies presenting weak stripe domains can achieve a high degree of controllability of its ferromagnetic resonance. This work explores the origin of the reconfigurability through micromagnetic simulations. The static domain structures [...] Read more.
We have recently shown that a hybrid magnetic thin film with orthogonal anisotropies presenting weak stripe domains can achieve a high degree of controllability of its ferromagnetic resonance. This work explores the origin of the reconfigurability through micromagnetic simulations. The static domain structures which control the thin film resonance can be found under a deterministic applied field protocol. In contrast to similar systems reported, our effect can be obtained under low magnetic fields. We have also found through simulations that the spin wave propagation in the hybrid is nonreciprocal: two adjacent regions emit antiparallel spin waves along the stripe domains. Both properties convert the hybrid in a candidate for future magnonic devices at the nanoscale. Full article
(This article belongs to the Special Issue Recent Advances in Nanomagnetism)
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10 pages, 3353 KiB  
Article
Effects of Perpendicular Magnetic Field Annealing on the Structural and Magnetic Properties of [Co/Ni]2/PtMn Thin Films
by Roshni Yadav, Chun-Hsien Wu, I-Fen Huang, Xu Li, Te-Ho Wu and Ko-Wei Lin
Magnetochemistry 2021, 7(3), 38; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7030038 - 12 Mar 2021
Cited by 2 | Viewed by 2407
Abstract
In this study, [Co/Ni]2/PtMn thin films with different PtMn thicknesses (2.7 to 32.4 nm) were prepared on Si/SiO2 substrates. The post-deposition perpendicular magnetic field annealing (MFA) processes were carried out to modify the structures and magnetic properties. The MFA process [...] Read more.
In this study, [Co/Ni]2/PtMn thin films with different PtMn thicknesses (2.7 to 32.4 nm) were prepared on Si/SiO2 substrates. The post-deposition perpendicular magnetic field annealing (MFA) processes were carried out to modify the structures and magnetic properties. The MFA process also induced strong interlayer diffusion, rendering a less sharp interface between Co and Ni and PtMn layers. The transmission electron microscopy (TEM) lattice image analysis has shown that the films consisted of face-centered tetragonal (fct) PtMn (ordered by MFA), body-centered cubic (bcc) NiMn (due to intermixing), in addition to face-centered cubic (fcc) Co, Ni, and PtMn phases. The peak shift (2-theta from 39.9° to 40.3°) in X-ray diffraction spectra also confirmed the structural transition from fcc PtMn to fct PtMn after MFA, in agreement with those obtained by lattice images in TEM. The interdiffusion induced by MFA was also evidenced by the depth profile of X-ray photoelectron spectroscopy (XPS). Further, the magnetic properties measured by vibrating sample magnetometry (VSM) have shown an increased coercivity in MFA-treated samples. This is attributed to the presence of ordered fct PtMn, and NiMn phases exchange coupled to the ferromagnetic [Co/Ni]2 layers. The vertical shift (Mshift = −0.03 memu) of the hysteresis loops is ascribed to the pinned spins resulting from perpendicular MFA processes. Full article
(This article belongs to the Special Issue Recent Advances in Nanomagnetism)
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11 pages, 2245 KiB  
Article
Microresonators and Microantennas—Tools to Explore Magnetization Dynamics in Single Nanostructures
by Hamza Cansever and Jürgen Lindner
Magnetochemistry 2021, 7(2), 28; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7020028 - 19 Feb 2021
Cited by 5 | Viewed by 2418
Abstract
The phenomenon of magnetic resonance and its detection via microwave spectroscopy provide insight into the magnetization dynamics of bulk or thin film materials. This allows for direct access to fundamental properties, such as the effective magnetization, g-factor, magnetic anisotropy, and the various damping [...] Read more.
The phenomenon of magnetic resonance and its detection via microwave spectroscopy provide insight into the magnetization dynamics of bulk or thin film materials. This allows for direct access to fundamental properties, such as the effective magnetization, g-factor, magnetic anisotropy, and the various damping (relaxation) channels that govern the decay of magnetic excitations. Cavity-based and broadband ferromagnetic resonance techniques that detect the microwave absorption of spin systems require a minimum magnetic volume to obtain a sufficient signal-to-noise ratio (S/N). Therefore, conventional techniques typically do not offer the sensitivity to detect individual micro- or nanostructures. A solution to this sensitivity problem is the so-called planar microresonator, which is able to detect even the small absorption signals of magnetic nanostructures, including spin-wave or edge resonance modes. As an example, we describe the microresonator-based detection of spin-wave modes within microscopic strips of ferromagnetic A2 Fe60Al40 that are imprinted into a paramagnetic B2 Fe60Al40-matrix via focused ion-beam irradiation. While microresonators operate at a fixed microwave frequency, a reliable quantification of the key magnetic parameters like the g-factor or spin relaxation times requires investigations within a broad range of frequencies. Furthermore, we introduce and describe the step from microresonators towards a broadband microantenna approach. Broadband magnetic resonance experiments on single nanostructured magnetic objects in a frequency range of 2–18 GHz are demonstrated. The broadband approach has been employed to explore the influence of lateral structuring on the magnetization dynamics of a Permalloy (Ni80Fe20) microstrip. Full article
(This article belongs to the Special Issue Recent Advances in Nanomagnetism)
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12 pages, 3623 KiB  
Article
Geometrically Constrained Skyrmions
by Swapneel Amit Pathak and Riccardo Hertel
Magnetochemistry 2021, 7(2), 26; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7020026 - 12 Feb 2021
Cited by 11 | Viewed by 2694
Abstract
Skyrmions are chiral swirling magnetization structures with nanoscale size. These structures have attracted considerable attention due to their topological stability and promising applicability in nanodevices, since they can be displaced with spin-polarized currents. However, for the comprehensive implementation of skyrmions in devices, it [...] Read more.
Skyrmions are chiral swirling magnetization structures with nanoscale size. These structures have attracted considerable attention due to their topological stability and promising applicability in nanodevices, since they can be displaced with spin-polarized currents. However, for the comprehensive implementation of skyrmions in devices, it is imperative to also attain control over their geometrical position. Here we show that, through thickness modulations introduced in the host material, it is possible to constrain three-dimensional skyrmions to desired regions. We investigate skyrmion structures in rectangular FeGe platelets with micromagnetic finite element simulations. First, we establish a phase diagram of the minimum-energy magnetic state as a function of the external magnetic field strength and the film thickness. Using this understanding, we generate preferential sites for skyrmions in the material by introducing dot-like “pockets” of reduced film thickness. We show that these pockets can serve as pinning centers for the skyrmions, thus making it possible to obtain a geometric control of the skyrmion position. This control allows for stabilization of skyrmions at positions and in configurations that they would otherwise not attain. Our findings may have implications for technological applications in which skyrmions are used as units of information that are displaced along racetrack-type shift register devices. Full article
(This article belongs to the Special Issue Recent Advances in Nanomagnetism)
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22 pages, 5617 KiB  
Article
Novel Magnetic Nanohybrids: From Iron Oxide to Iron Carbide Nanoparticles Grown on Nanodiamonds
by Panagiotis Ziogas, Athanasios B. Bourlinos, Jiri Tucek, Ondrej Malina and Alexios P. Douvalis
Magnetochemistry 2020, 6(4), 73; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry6040073 - 21 Dec 2020
Cited by 6 | Viewed by 3468
Abstract
The synthesis and characterization of a new line of magnetic hybrid nanostructured materials composed of spinel-type iron oxide to iron carbide nanoparticles grown on nanodiamond nanotemplates is reported in this study. The realization of these nanohybrid structures is achieved through thermal processing under [...] Read more.
The synthesis and characterization of a new line of magnetic hybrid nanostructured materials composed of spinel-type iron oxide to iron carbide nanoparticles grown on nanodiamond nanotemplates is reported in this study. The realization of these nanohybrid structures is achieved through thermal processing under vacuum at different annealing temperatures of a chemical precursor, in which very fine maghemite (γ-Fe2O3) nanoparticles seeds were developed on the surface of the nanodiamond nanotemplates. It is seen that low annealing temperatures induce the growth of the maghemite nanoparticle seeds to fine dispersed spinel-type non-stoichiometric ~5 nm magnetite (Fe3−xO4) nanoparticles, while intermediate annealing temperatures lead to the formation of single phase ~10 nm cementite (Fe3C) iron carbide nanoparticles. Higher annealing temperatures produce a mixture of larger Fe3C and Fe5C2 iron carbides, triggering simultaneously the growth of large-sized carbon nanotubes partially filled with these carbides. The magnetic features of the synthesized hybrid nanomaterials reveal the properties of their bearing magnetic phases, which span from superparamagnetic to soft and hard ferromagnetic and reflect the intrinsic magnetic properties of the containing phases, as well as their size and interconnection, dictated by the morphology and nature of the nanodiamond nanotemplates. These nanohybrids are proposed as potential candidates for important technological applications in nano-biomedicine and catalysis, while their synthetic route could be further tuned for development of new magnetic nanohybrid materials. Full article
(This article belongs to the Special Issue Recent Advances in Nanomagnetism)
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