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Special Issue "New Developments in Ferromagnetic Materials"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Physics".

Deadline for manuscript submissions: 31 August 2019.

Special Issue Editors

Guest Editor
Prof. Dr. Julián González Estévez

Department Materials Physics, Faculty of Chemistry, University of the Basque Country, 3, 20018 San Sebastian, Spain
Website | E-Mail
Interests: new amorphous; nanocrystalline and nanogranular ferromagnetic materials; new magnetic sensors; magnetoelastic effects; magnetotransport phenomena: Magnetoresistance, magnetoimpedance at high frequency and ferromagnetic resonance; metamaterials at the GHz range; spintronic: (dynamics of magnetic vortex); magnetocaloric and shape magnetic memory materials; magnonics; micromagnetic modelling and simulation
Guest Editor
Dr. Lourdes Dominguez

Department of Applied Physics I, Faculty of Engineering, University of the Basque Country, Plaza de Europa, 1, 20018 Donostia-San Sebastián, Spain
Website | E-Mail
Interests: new amorphous; nanocrystalline and nanogranular ferromagnetic materials; new magnetic sensors; magnetoelastic effects; magnetotransport phenomena: Magnetoresistance, magnetoimpedance at high frequency and ferromagnetic resonance; spintronic: (dynamics of magnetic vortex); micromagnetic modelling and simulation

Special Issue Information

Dear Colleagues,

Increasing economic and ecological demands, in particular energetic requirements, are compelling the development of novel multifunctional materials for applications in different fields of life and technology. In this context, new ferromagnetic materials are playing a crucial role in strategic industrial sectors, such as electronics, telecommunications, computation, health, etc. The goal of this Special Issue is to present the recent families of ferromagnetic materials: Soft magnetic materials, hard magnetic materials, materials exhibiting magnetotransport properties, low-dimensionality materials: Nanoparticles, nanodots, nanowires, nanotubes, thin films, multilayers, superlattices and materials with topological magnetic phases. It will be reviewed the conventional and modern magnetic properties, effects, responses, behaviors... that present these materials like hysteresis parameters (coercivity, remanence, energy losses, etc.), magnetoelastic parameters, magnetocaloric effect, magnetic memory shape, magnetoimpedance response, giant magnetoresistance, tunnel magnetic jumption, spin valves, magnetic vortex, skyrmions, etc.

Prof. Dr. Julián González
Dr. Lourdes Dominguez
Guest Editors

Manuscript Submission Information

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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. Materials 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 1800 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

  • Soft magnetic materials
  • hard magnetic materials
  • materials exhibiting magnetotransport properties
  • materials with topological magnetic phases

Published Papers (8 papers)

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Research

Open AccessArticle
Effect of Defects on Spontaneous Polarization in Pure and Doped LiNbO3: First-Principles Calculations
Materials 2019, 12(1), 100; https://doi.org/10.3390/ma12010100
Received: 7 December 2018 / Revised: 19 December 2018 / Accepted: 24 December 2018 / Published: 29 December 2018
Cited by 1 | PDF Full-text (2004 KB) | HTML Full-text | XML Full-text
Abstract
Numerous studies have indicated that intrinsic defects in lithium niobate (LN) dominate its physical properties. In an Nb-rich environment, the structure that consists of a niobium anti-site with four lithium vacancies is considered the most stable structure. Based on the density functional theory [...] Read more.
Numerous studies have indicated that intrinsic defects in lithium niobate (LN) dominate its physical properties. In an Nb-rich environment, the structure that consists of a niobium anti-site with four lithium vacancies is considered the most stable structure. Based on the density functional theory (DFT), the specific configuration of the four lithium vacancies of LN were explored. The results indicated the most stable structure consisted of two lithium vacancies as the first neighbors and the other two as the second nearest neighbors of Nb anti-site in pure LN, and a similar stable structure was found in the doped LN. We found that the defects dipole moment has no direct contribution to the crystal polarization. Spontaneous polarization is more likely due to the lattice distortion of the crystal. This was verified in the defects structure of Mg2+, Sc3+, and Zr4+ doped LN. The conclusion provides a new understanding about the relationship between defect clusters and crystal polarization. Full article
(This article belongs to the Special Issue New Developments in Ferromagnetic Materials)
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Open AccessArticle
Magneto-Dielectric Behaviour of M-Type Hexaferrite/Polymer Nanocomposites
Materials 2018, 11(12), 2551; https://doi.org/10.3390/ma11122551
Received: 19 October 2018 / Revised: 16 November 2018 / Accepted: 11 December 2018 / Published: 14 December 2018
Cited by 1 | PDF Full-text (6762 KB) | HTML Full-text | XML Full-text
Abstract
In the present study two sets of nanocomposites consisting of an epoxy resin and BaFe12O19 or SrFe12O19 nanoparticles were successfully developed and characterized morphologically and structurally via scanning electron microscopy and X-ray diffraction spectra. The dielectric response [...] Read more.
In the present study two sets of nanocomposites consisting of an epoxy resin and BaFe12O19 or SrFe12O19 nanoparticles were successfully developed and characterized morphologically and structurally via scanning electron microscopy and X-ray diffraction spectra. The dielectric response of the nanocomposites was investigated by means of broadband dielectric spectroscopy and their magnetic properties were derived from magnetization tests. Experimental data imply that the incorporation of the ceramic nanoparticles enhances significantly the dielectric properties of the examined systems and their ability to store electrical energy. Dielectric spectra of all systems revealed the presence of three distinct relaxation mechanisms, which are attributed both to the polymer matrix and the nanoinclusions: Interfacial polarization, glass to rubber transition of the polymer matrix and the re-orientation of small polar side groups of the polymer chain. The magnetic measurements confirmed the ferromagnetic nature of the nanocomposites. The induced magnetic properties increase with the inclusion of hexaferrite nanoparticles. The nanocomposites with SrFe12O19 nanoparticles exhibit higher values of coercive field, magnetization, magnetic saturation and remanence magnetization. A magnetic transition was detected in the ZFC/FC curves in the case of the BaFe12O19/epoxy nanocomposites. Full article
(This article belongs to the Special Issue New Developments in Ferromagnetic Materials)
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Open AccessArticle
Magnetic Characterization in the Rayleigh Region of Nanocrystalline Magnetic Cores
Materials 2018, 11(11), 2278; https://doi.org/10.3390/ma11112278
Received: 11 October 2018 / Revised: 9 November 2018 / Accepted: 12 November 2018 / Published: 14 November 2018
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Abstract
We report on the structural and magnetic characterization of two nanocrystalline Finemet-type magnetic cores. The nanocrystalline structure developed after annealing the amorphous precursor alloy at 550 °C for 30 and 60 min of annealing time. Structural analysis carried out by means of X-ray [...] Read more.
We report on the structural and magnetic characterization of two nanocrystalline Finemet-type magnetic cores. The nanocrystalline structure developed after annealing the amorphous precursor alloy at 550 °C for 30 and 60 min of annealing time. Structural analysis carried out by means of X-ray diffraction providing useful information on the grain size mean and partial volume of the nanocrystalline phase. The magnetic characterization was focused mainly in the Rayleigh region which, influenced by the intergranular coupling, was found to be more efficient in the sample treated for a longer time with a finer nanocrystalline structure. Full article
(This article belongs to the Special Issue New Developments in Ferromagnetic Materials)
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Open AccessArticle
Single Chiral Skyrmions in Ultrathin Magnetic Films
Materials 2018, 11(11), 2238; https://doi.org/10.3390/ma11112238
Received: 12 October 2018 / Revised: 30 October 2018 / Accepted: 7 November 2018 / Published: 11 November 2018
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Abstract
The stability and sizes of chiral skyrmions in ultrathin magnetic films are calculated accounting for the isotropic exchange, Dzyaloshinskii–Moriya exchange interaction (DMI), and out-of-plane magnetic anisotropy within micromagnetic approach. Bloch skyrmions in ultrathin magnetic films with B20 cubic crystal structure (MnSi, FeGe) and [...] Read more.
The stability and sizes of chiral skyrmions in ultrathin magnetic films are calculated accounting for the isotropic exchange, Dzyaloshinskii–Moriya exchange interaction (DMI), and out-of-plane magnetic anisotropy within micromagnetic approach. Bloch skyrmions in ultrathin magnetic films with B20 cubic crystal structure (MnSi, FeGe) and Neel skyrmions in ultrathin films and multilayers Co/X (X = Ir, Pd, Pt) are considered. The generalized DeBonte ansatz is used to describe the inhomogeneous skyrmion magnetization. The single skyrmion metastability/instability area, skyrmion radius, and skyrmion width are found analytically as a function of DMI strength d . It is shown that the single chiral skyrmions are metastable in infinite magnetic films below a critical value of DMI d c , and do not exist at d > d c . The calculated skyrmion radius increases as d increases and diverges at d d c 0 , whereas the skyrmion width increases monotonically as d increases up to d c without any singularities. The calculated skyrmion width is essentially smaller than the one calculated within the generalized domain wall model. Full article
(This article belongs to the Special Issue New Developments in Ferromagnetic Materials)
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Open AccessArticle
Structural and Magnetic Property of Cr3+ Substituted Cobalt Ferrite Nanomaterials Prepared by the Sol-Gel Method
Materials 2018, 11(11), 2095; https://doi.org/10.3390/ma11112095
Received: 18 August 2018 / Revised: 14 October 2018 / Accepted: 23 October 2018 / Published: 25 October 2018
Cited by 1 | PDF Full-text (3627 KB) | HTML Full-text | XML Full-text
Abstract
Cobalt-chromium ferrite, CoCrxFe2−xO4 (x = 01.2), has been synthesized by the sol-gel auto-combustion method. X-ray diffraction (XRD) indicates that samples calcined at 800 °C for 3 h were a single-cubic phase. The lattice parameter [...] Read more.
Cobalt-chromium ferrite, CoCrxFe2−xO4 (x = 01.2), has been synthesized by the sol-gel auto-combustion method. X-ray diffraction (XRD) indicates that samples calcined at 800 °C for 3 h were a single-cubic phase. The lattice parameter decreased with increasing Cr concentration. Scanning electron microscopy (SEM) confirmed that the sample powders were nanoparticles. It was confirmed from the room temperature Mössbauer spectra that transition from the ferrimagnetic state to the superparamagnetic state occurred with the doping of chromium. Both the saturation magnetization and the coercivity decreased with the chromium doping. With a higher annealing temperature, the saturation magnetization increased and the coercivity increased initially and then decreased for CoCr0.2Fe1.8O4. Full article
(This article belongs to the Special Issue New Developments in Ferromagnetic Materials)
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Open AccessArticle
Modeling the Hysteresis Loop of Ultra-High Permeability Amorphous Alloy for Space Applications
Materials 2018, 11(11), 2079; https://doi.org/10.3390/ma11112079
Received: 19 September 2018 / Revised: 13 October 2018 / Accepted: 22 October 2018 / Published: 24 October 2018
Cited by 1 | PDF Full-text (1977 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents investigation results regarding the Jiles-Atherton-based hysteresis loop modeling of ultra-high permeability amorphous alloy MELTA® MM-5Co. The measurement stand is capable of accurately measuring minor and major hysteresis loops for such a material together with exemplary measurement results. The main [...] Read more.
This paper presents investigation results regarding the Jiles-Atherton-based hysteresis loop modeling of ultra-high permeability amorphous alloy MELTA® MM-5Co. The measurement stand is capable of accurately measuring minor and major hysteresis loops for such a material together with exemplary measurement results. The main source of the measurement error is highlighted, which includes the Earth’s field influence. The results of hysteresis loop modeling with the original Jiles-Atherton model and with two of its modifications are given. In all cases, the parameters of the Jiles-Atherton model were identified in two-step identification on the basis of a differential evolution optimization algorithm. The results indicate that both the original and modified Jiles-Atherton models are suitable for modeling the ultra-soft amorphous alloy. However, the hysteresis model’s parameters vary significantly. Full article
(This article belongs to the Special Issue New Developments in Ferromagnetic Materials)
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Open AccessArticle
First Order Reversal Curve Study of SmFe2 Melt-Spun Ribbons
Materials 2018, 11(10), 1804; https://doi.org/10.3390/ma11101804
Received: 15 August 2018 / Revised: 12 September 2018 / Accepted: 20 September 2018 / Published: 22 September 2018
PDF Full-text (3461 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
First-order reversal curves (FORC) and the FORC distribution provide a detailed characterization of the relative proportions of reversible and irreversible components of the magnetization of a material, revealing the dominant interactions in the system. Alloys with the nominal composition SmFe2 were obtained [...] Read more.
First-order reversal curves (FORC) and the FORC distribution provide a detailed characterization of the relative proportions of reversible and irreversible components of the magnetization of a material, revealing the dominant interactions in the system. Alloys with the nominal composition SmFe2 were obtained by melt-spinning with a cooper wheel velocity of 30 m/s. X-ray powder diffraction analysis showed a greater part consisting of an amorphous phase and a very small amount of SmFe2 crystalline phase with an average crystallite size of 8 nm. A constant acceleration Mössbauer spectrum, measured at room temperature in transmission mode, was fitted to a continuous distribution of effective fields at the nucleus of the amorphous phase (about 84% of the total area), plus two sextets for the non-equivalent sites of Fe in the SmFe2 crystalline phase. 91 first-order reversal curves were collected in a Quantum Design PPMS-VSM with reversal fields from –800 mT to +800 mT and using a calibration field of 850 mT. The obtained FORC diagrams showed a combined effect of a local interaction field and a mean interaction field, and showed that the reversible magnetization is a function of both, the applied magnetic field and the irreversible magnetization. Full article
(This article belongs to the Special Issue New Developments in Ferromagnetic Materials)
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Graphical abstract

Open AccessArticle
Magnetic Properties and Spontaneous Polarization of La-, Mn- and N-Doped Tetragonal BiFeO3: A First-Principles Study
Materials 2018, 11(6), 985; https://doi.org/10.3390/ma11060985
Received: 18 May 2018 / Revised: 4 June 2018 / Accepted: 8 June 2018 / Published: 11 June 2018
Cited by 2 | PDF Full-text (4430 KB) | HTML Full-text | XML Full-text
Abstract
Multiferroic materials have been receiving attention for their potential applications in multifunctional devices. Chemical substitution is an effective method for improving the physical properties of BiFeO3 (BFO). However, different experimental results have been reported for Lanthanum- (La-) and Manganese (Mn) -doped BFO [...] Read more.
Multiferroic materials have been receiving attention for their potential applications in multifunctional devices. Chemical substitution is an effective method for improving the physical properties of BiFeO3 (BFO). However, different experimental results have been reported for Lanthanum- (La-) and Manganese (Mn) -doped BFO ceramics. Here, we systematically studied the magnetic properties and spontaneous polarization of La-, Mn-, and Nitrogen (N) -doped tetragonal BiFeO3 using density functional theory with the generalized gradient approximation and U-value method. The calculated results demonstrated that the systems show ferromagnetism with Mn and N doping, whereas no magnetization was found with La doping in G- and C-type antiferromagnetic orderings. Our research further revealed that the ferromagnetism is attributed to the p-d orbital hybridization. Berry-phase polarization calculations predicted a large polarization of 149.2 µC/cm2 along the [001] direction of pure tetragonal BFO. We found that La and N substitution had little influence on the spontaneous polarization, whereas Mn substitution reduced the spontaneous polarization. The reduced energy barrier heights of the doped systems indicate the reduced stability of the off-centering ferroelectricity against the thermal agitation. These findings provide greater understanding for controlling and tuning the multiferroic properties of BFO. Full article
(This article belongs to the Special Issue New Developments in Ferromagnetic Materials)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Magneto/dielectric behaviour of M-type hexaferrite/polymer nanocomposites
Author: A. Sanida1, S.G. Stavropoulos 1,Th. Speliotis 2, G.C. Psarras 1,*
Affiliation:
1 Smart Materials & Nanodielectrics Laboratory, Department of Materials Science, School of Natural Sciences, University of Patras, Patras 26504, Greece
2 Institute of Nanoscience and Nanotechnology, NCSR "Demokritos", Aghia Paraskevi, Athens 15310, Greece

Authors: Pietro Galizia, Renato Pero, Frediano De Marco, Gheorghe Virgil Aldica, Marin Cernea, Giovanni Maizza, Carmen Galassi
Affiliation: CNR-ISTEC National Research Council of Italy - Institute of Science and Technology for Ceramics, Faenza (RA), 48018 Italy

Title: Self-guidingunidirectional electromagnetic edge states in two-dimensional ferromagnetic photonic crystal bymodified boundary condition
Author: Li Qing-bo
Affiliation: School of Physics and Electronic Electrical Engineering, Huaiyin normal university, Huaian Jiangsu 223300ˈChina
Email: [email protected]
A short manuscript summary see below:
we propose a way to realize a self-guiding unidirectional surface mode by modifying the size of the boundary cylinder in a magnetic photonic crystal. This manipulating design can support for the unidirectional transport of electromagnetic energy without requiring an ancillary cladding layer. In particular, this edge mode is insensitive to scattering from imperfections, such as defect and metal obstacle. As an example of its applications, we present a unidirectional topological insulator resonator.

Author: Lourdes Domínguez
Affiliation: Department of Applied Physics I, Faculty of Engineering, University of the Basque Country, Plaza de Europa, 1, 20018 Donostia-San Sebastián, Spain
Email: [email protected]

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