Special Issue "Novel Magnetic Properties in Curved Geometries"

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Inorganic Materials and Metal-Organic Frameworks".

Deadline for manuscript submissions: 31 July 2021.

Special Issue Editor

Dr. Cristina Bran
E-Mail Website
Guest Editor
CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM), Cantoblanco, Spain
Interests: nanomagnetism; spintronics; cylindrical nanostructures; synthesis of nanoporous materials; domain walls

Special Issue Information

Dear Colleagues,

Cylindrical nano and micro-wires are attracting a great deal of attention due to their novel geometry-dependent physical properties. They are investigated for applications in advanced technology areas such as new-generation spintronic-based magnetic recording, bio-magnetics, robotics, sensors, and actuators devices. The circular symmetry determines novel spin phenomena and magnetization dynamics related to topology as compared to planar geometries. Multiple topologically non-trivial magnetization structures such as Bloch-point domain walls, helical magnetic configurations, vortices, or skyrmion tubes are the consequences of cylindrical curvature and geometrical confinement. Their responses to electric/magnetic fields, electric current, mechanical stress, or thermal gradients are relevant for the applications in advanced technologies.

This Special Issue of Nanomaterials will attempt to cover the recent advancements in the fabrication, characterization, and potential technological applications of cylindrical magnetic wires, as single magnetic structures or as part of 3D ordered architectures, in magnetic sensors and data storage, microwave devices, thermomagneto-electric devices, or bio-applications.

Dr. Cristina Bran
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 papers will be 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 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 2200 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

  • cylindrical wires
  • domain walls
  • magnetization processes
  • template-based nanowires
  • template-free cylindrical wires
  • microwires
  • data storage and sensing applications

Published Papers (6 papers)

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Research

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Open AccessArticle
High-Frequency Magnetoimpedance (MI) and Stress-MI in Amorphous Microwires with Different Anisotropies
Nanomaterials 2021, 11(5), 1208; https://doi.org/10.3390/nano11051208 - 02 May 2021
Viewed by 607
Abstract
Magnetoimpedance (MI) in Co-based microwires with an amorphous and partially crystalline state was investigated at elevated frequencies (up to several GHz), with particular attention paid to the influence of tensile stress on the MI behavior, which is called stress-MI. Two mechanisms of MI [...] Read more.
Magnetoimpedance (MI) in Co-based microwires with an amorphous and partially crystalline state was investigated at elevated frequencies (up to several GHz), with particular attention paid to the influence of tensile stress on the MI behavior, which is called stress-MI. Two mechanisms of MI sensitivity related to the DC magnetization re-orientation and AC permeability dispersion were discussed. Remarkable sensitivity of impedance changes with respect to applied tensile stress at GHz frequencies was obtained in partially crystalline wires subjected to current annealing. Increasing the annealing current enhanced the axial easy anisotropy of a magnetoelastic origin, which made it possible to increase the frequency of large stress-MI: for 90mA-annealed wire, the impedance at 2 GHz increased by about 300% when a stress of 450 MPa was applied. Potential applications included sensing elements in stretchable substrates for flexible electronics, wireless sensors, and tunable smart materials. For reliable microwave measurements, an improved SOLT (short-open-load-thru) calibration technique was developed that required specially designed strip cells as wire holders. The method made it possible to precisely measure the impedance characteristics of individual wires, which can be further employed to characterize the microwave scattering at wire inclusions used as composites fillers. Full article
(This article belongs to the Special Issue Novel Magnetic Properties in Curved Geometries)
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Open AccessArticle
An Indirect Method of Micromagnetic Structure Estimation in Microwires
Nanomaterials 2021, 11(2), 274; https://doi.org/10.3390/nano11020274 - 21 Jan 2021
Viewed by 386
Abstract
The tunable magnetic properties of amorphous ferromagnetic glass-coated microwires make them suitable for a wide range of applications. Accurate knowledge of the micromagnetic structure is highly desirable since it affects almost all magnetic properties. To select an appropriate wire-sample for a specific application, [...] Read more.
The tunable magnetic properties of amorphous ferromagnetic glass-coated microwires make them suitable for a wide range of applications. Accurate knowledge of the micromagnetic structure is highly desirable since it affects almost all magnetic properties. To select an appropriate wire-sample for a specific application, a deeper understanding of the magnetization reversal process is required, because it determines the measurable response (such as induced voltage waveform and its spectrum). However, the experimental observation of micromagnetic structure of micro-scale amorphous objects has strict size limitations. In this work we proposed a novel experimental technique for evaluating the microstructural characteristics of glass-coated microwires. The cross-sectional permeability distribution in the sample was obtained from impedance measurements at different frequencies. This distribution enables estimation of the prevailing anisotropy in the local region of the wire cross-section. The results obtained were compared with the findings of magnetostatic measurements and remanent state analysis. The advantages and limitations of the methods were discussed. Full article
(This article belongs to the Special Issue Novel Magnetic Properties in Curved Geometries)
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Open AccessArticle
Spin Caloritronics in 3D Interconnected Nanowire Networks
Nanomaterials 2020, 10(11), 2092; https://doi.org/10.3390/nano10112092 - 22 Oct 2020
Cited by 3 | Viewed by 471
Abstract
Recently, interconnected nanowire networks have been found suitable as flexible macroscopic spin caloritronic devices. The 3D nanowire networks are fabricated by direct electrodeposition in track-etched polymer templates with crossed nano-channels. This technique allows the fabrication of crossed nanowires consisting of both homogeneous ferromagnetic [...] Read more.
Recently, interconnected nanowire networks have been found suitable as flexible macroscopic spin caloritronic devices. The 3D nanowire networks are fabricated by direct electrodeposition in track-etched polymer templates with crossed nano-channels. This technique allows the fabrication of crossed nanowires consisting of both homogeneous ferromagnetic metals and multilayer stack with successive layers of ferromagnetic and non-magnetic metals, with controlled morphology and material composition. The networks exhibit extremely high, magnetically modulated thermoelectric power factors. Moreover, large spin-dependent Seebeck coefficients were directly extracted from experimental measurements on multilayer nanowire networks. This work provides a simple and cost-effective way to fabricate large-scale flexible and shapeable thermoelectric devices exploiting the spin degree of freedom. Full article
(This article belongs to the Special Issue Novel Magnetic Properties in Curved Geometries)
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Review

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Open AccessReview
Magnetic Configurations in Modulated Cylindrical Nanowires
Nanomaterials 2021, 11(3), 600; https://doi.org/10.3390/nano11030600 - 28 Feb 2021
Viewed by 462
Abstract
Cylindrical magnetic nanowires show great potential for 3D applications such as magnetic recording, shift registers, and logic gates, as well as in sensing architectures or biomedicine. Their cylindrical geometry leads to interesting properties of the local domain structure, leading to multifunctional responses to [...] Read more.
Cylindrical magnetic nanowires show great potential for 3D applications such as magnetic recording, shift registers, and logic gates, as well as in sensing architectures or biomedicine. Their cylindrical geometry leads to interesting properties of the local domain structure, leading to multifunctional responses to magnetic fields and electric currents, mechanical stresses, or thermal gradients. This review article is summarizing the work carried out in our group on the fabrication and magnetic characterization of cylindrical magnetic nanowires with modulated geometry and anisotropy. The nanowires are prepared by electrochemical methods allowing the fabrication of magnetic nanowires with precise control over geometry, morphology, and composition. Different routes to control the magnetization configuration and its dynamics through the geometry and magnetocrystalline anisotropy are presented. The diameter modulations change the typical single domain state present in cubic nanowires, providing the possibility to confine or pin circular domains or domain walls in each segment. The control and stabilization of domains and domain walls in cylindrical wires have been achieved in multisegmented structures by alternating magnetic segments of different magnetic properties (producing alternative anisotropy) or with non-magnetic layers. The results point out the relevance of the geometry and magnetocrystalline anisotropy to promote the occurrence of stable magnetochiral structures and provide further information for the design of cylindrical nanowires for multiple applications. Full article
(This article belongs to the Special Issue Novel Magnetic Properties in Curved Geometries)
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Open AccessFeature PaperReview
Focused-Electron-Beam Engineering of 3D Magnetic Nanowires
Nanomaterials 2021, 11(2), 402; https://doi.org/10.3390/nano11020402 - 04 Feb 2021
Viewed by 565
Abstract
Focused-electron-beam-induced deposition (FEBID) is the ultimate additive nanofabrication technique for the growth of 3D nanostructures. In the field of nanomagnetism and its technological applications, FEBID could be a viable solution to produce future high-density, low-power, fast nanoelectronic devices based on the domain wall [...] Read more.
Focused-electron-beam-induced deposition (FEBID) is the ultimate additive nanofabrication technique for the growth of 3D nanostructures. In the field of nanomagnetism and its technological applications, FEBID could be a viable solution to produce future high-density, low-power, fast nanoelectronic devices based on the domain wall conduit in 3D nanomagnets. While FEBID has demonstrated the flexibility to produce 3D nanostructures with almost any shape and geometry, the basic physical properties of these out-of-plane deposits are often seriously degraded from their bulk counterparts due to the presence of contaminants. This work reviews the experimental efforts to understand and control the physical processes involved in 3D FEBID growth of nanomagnets. Co and Fe FEBID straight vertical nanowires have been used as benchmark geometry to tailor their dimensions, microstructure, composition and magnetism by smartly tuning the growth parameters, post-growth purification treatments and heterostructuring. Full article
(This article belongs to the Special Issue Novel Magnetic Properties in Curved Geometries)
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Open AccessReview
Reversible and Non-Reversible Transformation of Magnetic Structure in Amorphous Microwires
Nanomaterials 2020, 10(8), 1450; https://doi.org/10.3390/nano10081450 - 24 Jul 2020
Viewed by 637
Abstract
We provide an overview of the tools directed to reversible and irreversible transformations of the magnetic structure of glass-covered microwires. The irreversible tools are the selection of the chemical composition, geometric ratio, and the stress-annealing. For reversible tuning we use the combination of [...] Read more.
We provide an overview of the tools directed to reversible and irreversible transformations of the magnetic structure of glass-covered microwires. The irreversible tools are the selection of the chemical composition, geometric ratio, and the stress-annealing. For reversible tuning we use the combination of magnetic fields and mechanical stresses. The studies were focused on the giant magnetoimpedance effect and the velocity of the domain walls propagation important for the technological applications. The essential increase of the giant magnetoimpedance effect and the control of the domain wall velocity were achieved as a result of the use of two types of control tools. The performed simulations reflect the real transformation of the helical domain structures experimentally found. Full article
(This article belongs to the Special Issue Novel Magnetic Properties in Curved Geometries)
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