Special Issue "Advances in Multiferroics"

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

Deadline for manuscript submissions: 1 October 2020.

Special Issue Editor

Prof. John Heron
Website
Guest Editor
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, United States
Interests: Magnetoelectrics, multiferroics, interfaces, devices

Special Issue Information

Dear Colleagues,

Multiferroics, materials with more than one ferroic order (magnetic, ferroelectric, or ferroelastic), are of significant interest due to the fascinating interplay between ferroic properties. Recent advances in theory, synthesis, and characterization has led to new insight into the complex interactions that occur in these materials and enabled the control of their properties. The discovery of new and engineered coupling between ferroelectric and magnetic orders in particular has opened doors to unprecedented functionalities for exploratory devices. Correlations at domain walls and heterointerfaces have been shown to lead to new emergent phenomena and functional behavior. Equilibrium ferroelectric and magnetoelectric switching has seen significant experimental and theoretical work, however, recent consideration of switching kinetics and dynamics is shedding new light on charge, spin, and lattice coupling. This issue of Materials aims to highlight and summarize recent advances in multiferroics research. Contributions in the areas of synthesis, new or improved experimental and theoretical techniques for determining magnetic or ferroelectric order and their coupling, linear magnetoelectric coupling and beyond, ferroelectric and magnetoelectric switching, switching dynamics, domain walls, flexible systems, and applications of magnetoelectric multiferroics are welcomed.

Prof. John Heron
Guest Editor

Manuscript Submission Information

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Keywords

  • Magnetoelectrics
  • Multiferroics
  • Ferroelectric/Ferromagnetic Composites
  • Domains and Topological Structures
  • Domain Walls and Heterointerfaces
  • Magnetization, Ferroelectric, and Magnetoelectric Switching and Dynamics

Published Papers (9 papers)

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Research

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Open AccessArticle
Enhanced Multiferroic Properties of YFeO3 by Doping with Bi3+
Materials 2019, 12(13), 2054; https://doi.org/10.3390/ma12132054 - 26 Jun 2019
Cited by 1
Abstract
Tthe present work studied the cationic substitution of Y3+ by Bi3+ on the crystal structure of orthorhombic YFeO3 and its effect over magnetic, dielectric and electric properties of multiferroic yttrium orthoferrite. Stoichiometric mixtures of Y2O3, Fe [...] Read more.
Tthe present work studied the cationic substitution of Y3+ by Bi3+ on the crystal structure of orthorhombic YFeO3 and its effect over magnetic, dielectric and electric properties of multiferroic yttrium orthoferrite. Stoichiometric mixtures of Y2O3, Fe2O3 and Bi2O3 were mixed and milled for 5 h using a ball to powder weight ratio of 10:1 by high-energy ball milling. The obtained powders were pressed at 1500 MPa and sintered at 700 °C for 2 h. The test samples were characterized at room temperature by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and impedance spectroscopy (IS). The X-ray diffraction patterns disclosed a maximum solubility of 30 % mol. of Bi3+ into the orthorhombic YFeO3. For higher concentrations, a transformation from orthorhombic to garnet structure was produced, obtaining partially Y3Fe5O12 phase. The substitution of Bi3+ in Y3+ sites promoted a distortion into the orthorhombic structure and modified Fe-O-Fe angles and octahedral tilt. In addition, it promoted a ferromagnetic (FM) order, which was attributed to both the crystal distortion and Dzyaloshinskii-Moriya interaction. For doped samples, an increase in real permittivity values was observed, and reduced with the increase of frequency. This in good agreement with the Maxwell-Wagner effect. Full article
(This article belongs to the Special Issue Advances in Multiferroics)
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Open AccessArticle
Powder Metallurgy Synthesis of Heusler Alloys: Effects of Process Parameters
Materials 2019, 12(10), 1596; https://doi.org/10.3390/ma12101596 - 15 May 2019
Abstract
Ni45Co5Mn40Sn10 Heusler alloy was fabricated with elemental powders, using a powder processing route of press and sinter, in place of vacuum induction melting or arc melting route. The effects of process parameters, such as compaction load, [...] Read more.
Ni45Co5Mn40Sn10 Heusler alloy was fabricated with elemental powders, using a powder processing route of press and sinter, in place of vacuum induction melting or arc melting route. The effects of process parameters, such as compaction load, sintering time, and temperature, on the transformation characteristics and microstructures of the alloy were investigated. While the effect of compaction pressure was not significant, those of sintering time and temperature are important in causing or annulling martensitic transformation, which is characteristic of Heusler alloys. The processing condition of 1050 °C/24 h was identified to be favorable in producing ferromagnetic Heusler alloy. Longer durations of sintering resulted in an increased γ-phase fraction, which acts as an impediment to the structural transformation. Full article
(This article belongs to the Special Issue Advances in Multiferroics)
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Open AccessArticle
Mechanosynthesis of the Whole Y1−xBixMn1−xFexO3 Perovskite System: Structural Characterization and Study of Phase Transitions
Materials 2019, 12(9), 1515; https://doi.org/10.3390/ma12091515 - 09 May 2019
Abstract
Perovskite BiFeO3 and YMnO3 are both multiferroic materials with distinctive magnetoelectric coupling phenomena. Owing to this, the Y1−xBix Mn1−xFexO3 solid solution seems to be a promising system, though poorly studied. This is due [...] Read more.
Perovskite BiFeO3 and YMnO3 are both multiferroic materials with distinctive magnetoelectric coupling phenomena. Owing to this, the Y1−xBix Mn1−xFexO3 solid solution seems to be a promising system, though poorly studied. This is due to the metastable nature of the orthorhombic perovskite phase of YMnO3 at ambient pressure, and to the complexity of obtaining pure rhombohedral phases for BiFeO3-rich compositions. In this work, nanocrystalline powders across the whole perovskite system were prepared for the first time by mechanosynthesis in a high-energy planetary mill, avoiding high pressure and temperature routes. Thermal decomposition temperatures were determined, and structural characterization was carried out by X-ray powder diffraction and Raman spectroscopy on thermally treated samples of enhanced crystallinity. Two polymorphic phases with orthorhombic Pnma and rhombohedral R3c h symmetries, and their coexistence over a wide compositional range were found. A gradual evolution of the lattice parameters with the composition was revealed for both phases, which suggests the existence of two continuous solid solutions. Following bibliographic data for BiFeO3, first order ferroic phase transitions were located by differential thermal analysis in compositions with x ≥ 0.9. Furthermore, an orthorhombic-rhombohedral structural evolution across the ferroelectric transition was characterized with temperature-dependent X-ray diffraction. Full article
(This article belongs to the Special Issue Advances in Multiferroics)
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Open AccessArticle
The Microstructure, Electric, Optical and Photovoltaic Properties of BiFeO3 Thin Films Prepared by Low Temperature Sol–Gel Method
Materials 2019, 12(9), 1444; https://doi.org/10.3390/ma12091444 - 03 May 2019
Cited by 1
Abstract
Ferroelectrics have recently attracted attention as a candidate class of materials for use in photovoltaic devices due to their abnormal photovoltaic effect. However, the current reported efficiency is still low. Hence, it is urgent to develop narrow-band gap ferroelectric materials with strong ferroelectricity [...] Read more.
Ferroelectrics have recently attracted attention as a candidate class of materials for use in photovoltaic devices due to their abnormal photovoltaic effect. However, the current reported efficiency is still low. Hence, it is urgent to develop narrow-band gap ferroelectric materials with strong ferroelectricity by low-temperature synthesis. In this paper, the perovskite bismuth ferrite BiFeO3 (BFO) thin films were fabricated on SnO2: F (FTO) substrates by the sol–gel method and they were rapidly annealed at 450, 500 and 550 °C, respectively. The microstructure and the chemical state’s evolution with annealing temperature were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), and the relationship between the microstructure and electric, optical and photovoltaic properties were studied. The XRD, SEM and Raman results show that a pure phase BFO film with good crystallinity is obtained at a low annealing temperature of 450 °C. As the annealing temperature increases, the film becomes more uniform and has an improved crystallinity. The XPS results show that the Fe3+/Fe2+ ratio increases and the ratio of oxygen vacancies/lattice oxygen decreases with increasing annealing temperature, which results in the leakage current gradually being reduced. The band gap is reduced from 2.68 to 2.51 eV due to better crystallinity. An enhanced photovoltaic effect is observed in a 550 °C annealed BFO film with a short circuit current of 4.58 mA/cm2 and an open circuit voltage of 0.15 V, respectively. Full article
(This article belongs to the Special Issue Advances in Multiferroics)
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Review

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Open AccessReview
Why Do Ferroelectrics Exhibit Negative Capacitance?
Materials 2019, 12(22), 3743; https://doi.org/10.3390/ma12223743 - 13 Nov 2019
Abstract
The Landau theory of phase transitions predicts the presence of a negative capacitance in ferroelectric materials based on a mean-field approach. While recent experimental results confirm this prediction, the microscopic origin of negative capacitance in ferroelectrics is often debated. This study provides a [...] Read more.
The Landau theory of phase transitions predicts the presence of a negative capacitance in ferroelectric materials based on a mean-field approach. While recent experimental results confirm this prediction, the microscopic origin of negative capacitance in ferroelectrics is often debated. This study provides a simple, physical explanation of the negative capacitance phenomenon—i.e., ‘S’-shaped polarization vs. electric field curve—without having to invoke the Landau phenomenology. The discussion is inspired by pedagogical models of ferroelectricity as often presented in classic text-books such as the Feynman lectures on Physics and the Introduction of Solid State Physics by Charles Kittel, which are routinely used to describe the quintessential ferroelectric phenomena such as the Curie-Weiss law and the emergence of spontaneous polarization below the Curie temperature. The model presented herein is overly simplified and ignores many of the complex interactions in real ferroelectrics; however, this model reveals an important insight: The polarization catastrophe phenomenon that is required to describe the onset of ferroelectricity naturally leads to the thermodynamic instability that is negative capacitance. Considering the interaction of electric dipoles and saturation of the dipole moments at large local electric fields we derive the full ‘S’-curve relating the ferroelectric polarization and the electric field, in qualitative agreement with Landau theory. Full article
(This article belongs to the Special Issue Advances in Multiferroics)
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Open AccessReview
Dielectric and Energy Storage Properties of Ba(1−x)CaxZryTi(1−y)O3 (BCZT): A Review
Materials 2019, 12(21), 3641; https://doi.org/10.3390/ma12213641 - 05 Nov 2019
Abstract
The Ba(1−x)CaxZryTi(1−y)O3 (BCZT), a lead-free ceramic material, has attracted the scientific community since 2009 due to its large piezoelectric coefficient and resulting high dielectric permittivity. This perovskite material is a characteristic dielectric material for [...] Read more.
The Ba(1−x)CaxZryTi(1−y)O3 (BCZT), a lead-free ceramic material, has attracted the scientific community since 2009 due to its large piezoelectric coefficient and resulting high dielectric permittivity. This perovskite material is a characteristic dielectric material for the pulsed power capacitors industry currently, which in turn leads to devices for effective storage and supply of electric energy. After this remarkable achievement in the area of lead-free piezoelectric ceramics, the researchers are exploring both the bulk as well as thin films of this perovskite material. It is observed that the thin film of this materials have outstandingly high power densities and high energy densities which is suitable for electrochemical supercapacitor applications. From a functional materials point of view this material has also gained attention in multiferroic composite material as the ferroelectric constituent of these composites and has provided extraordinary electric properties. This article presents a review on the relevant scientific advancements that have been made by using the BCZT materials for electric energy storage applications by optimizing its dielectric properties. The article starts with a BCZT introduction and discussion of the need of this material for high energy density capacitors, followed by different synthesis techniques and the effect on dielectric properties of doping different materials in BCZT. The advantages of thin film BCZT material over bulk counterparts are also discussed and its use as one of the constituents of mutiferroic composites is also presented. Finally, it summarizes the future prospects of this material followed by the conclusions. Full article
(This article belongs to the Special Issue Advances in Multiferroics)
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Open AccessFeature PaperReview
Design and Manipulation of Ferroic Domains in Complex Oxide Heterostructures
Materials 2019, 12(19), 3108; https://doi.org/10.3390/ma12193108 - 24 Sep 2019
Cited by 1
Abstract
The current burst of device concepts based on nanoscale domain-control in magnetically and electrically ordered systems motivates us to review the recent development in the design of domain engineered oxide heterostructures. The improved ability to design and control advanced ferroic domain architectures came [...] Read more.
The current burst of device concepts based on nanoscale domain-control in magnetically and electrically ordered systems motivates us to review the recent development in the design of domain engineered oxide heterostructures. The improved ability to design and control advanced ferroic domain architectures came hand in hand with major advances in investigation capacity of nanoscale ferroic states. The new avenues offered by prototypical multiferroic materials, in which electric and magnetic orders coexist, are expanding beyond the canonical low-energy-consuming electrical control of a net magnetization. Domain pattern inversion, for instance, holds promises of increased functionalities. In this review, we first describe the recent development in the creation of controlled ferroelectric and multiferroic domain architectures in thin films and multilayers. We then present techniques for probing the domain state with a particular focus on non-invasive tools allowing the determination of buried ferroic states. Finally, we discuss the switching events and their domain analysis, providing critical insight into the evolution of device concepts involving multiferroic thin films and heterostructures. Full article
(This article belongs to the Special Issue Advances in Multiferroics)
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Open AccessReview
Functional Ferroic Domain Walls for Nanoelectronics
Materials 2019, 12(18), 2927; https://doi.org/10.3390/ma12182927 - 10 Sep 2019
Cited by 1
Abstract
A prominent challenge towards novel nanoelectronic technologies is to understand and control materials functionalities down to the smallest scale. Topological defects in ordered solid-state (multi-)ferroic materials, e.g., domain walls, are a promising gateway towards alternative sustainable technologies. In this article, we review advances [...] Read more.
A prominent challenge towards novel nanoelectronic technologies is to understand and control materials functionalities down to the smallest scale. Topological defects in ordered solid-state (multi-)ferroic materials, e.g., domain walls, are a promising gateway towards alternative sustainable technologies. In this article, we review advances in the field of domain walls in ferroic materials with a focus on ferroelectric and multiferroic systems and recent developments in prototype nanoelectronic devices. Full article
(This article belongs to the Special Issue Advances in Multiferroics)
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Open AccessReview
Mechanical-Resonance-Enhanced Thin-Film Magnetoelectric Heterostructures for Magnetometers, Mechanical Antennas, Tunable RF Inductors, and Filters
Materials 2019, 12(14), 2259; https://doi.org/10.3390/ma12142259 - 13 Jul 2019
Cited by 5
Abstract
The strong strain-mediated magnetoelectric (ME) coupling found in thin-film ME heterostructures has attracted an ever-increasing interest and enables realization of a great number of integrated multiferroic devices, such as magnetometers, mechanical antennas, RF tunable inductors and filters. This paper first reviews the thin-film [...] Read more.
The strong strain-mediated magnetoelectric (ME) coupling found in thin-film ME heterostructures has attracted an ever-increasing interest and enables realization of a great number of integrated multiferroic devices, such as magnetometers, mechanical antennas, RF tunable inductors and filters. This paper first reviews the thin-film characterization techniques for both piezoelectric and magnetostrictive thin films, which are crucial in determining the strength of the ME coupling. After that, the most recent progress on various integrated multiferroic devices based on thin-film ME heterostructures are presented. In particular, rapid development of thin-film ME magnetometers has been seen over the past few years. These ultra-sensitive magnetometers exhibit extremely low limit of detection (sub-pT/Hz1/2) for low-frequency AC magnetic fields, making them potential candidates for applications of medical diagnostics. Other devices reviewed in this paper include acoustically actuated nanomechanical ME antennas with miniaturized size by 1–2 orders compared to the conventional antenna; integrated RF tunable inductors with a wide operation frequency range; integrated RF tunable bandpass filter with dual H- and E-field tunability. All these integrated multiferroic devices are compact, lightweight, power-efficient, and potentially integrable with current complementary metal oxide semiconductor (CMOS) technology, showing great promise for applications in future biomedical, wireless communication, and reconfigurable electronic systems. Full article
(This article belongs to the Special Issue Advances in Multiferroics)
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