Magnetoelectric Materials Research Articles

Recent Development of Flexible Magnetoelectric Material Systems and Related Additive Manufacturing Techniques

Recent Development of Flexible Magnetoelectric Material Systems and Related Additive Manufacturing Techniques

Ordered state of the intrinstic two-component magnetoelectric material Li2CuZrO4 according to 7Li NMR data

Ordered state of the intrinstic two-component magnetoelectric material Li2CuZrO4 according to 7Li NMR data

Моделирование магнитоэлектрического материала для антенн

The paper is devoted to the modeling of magnetoelectric material for antennas. The effect observed in magnetoelectric gradient structures is discussed. Gradient magnetoelectric structures are a new type of composite structures consisting of a magnetoelectric material and an artificial dielectric. A new principle of controlling the antenna wave properties based on the geometric displacement of the excitation point due to the application of an external electric field is being considered. The use of an artificial dielectric in a multiferroid structure will make it possible to more flexibly control the areas of conversion of a magnetostatic surface wave into an electromagnetic wave, which in practical terms will give new opportunities for controlling the characteristics of antennas. The conclusion about the possibility of controlled conversion of a magnetostatic surface wave into an electromagnetic wave was obtained as a result of calculations based on the developed model by selecting the values of stationary magnetic and electric fields, and the values of the permittivity of the artificial dielectric layer

Structural and Electronic Properties of Hexagonal Y1−xEuxMnO3

Magnetoelectric materials attract interest due to coupling between the magnetic and dipol moments, which provides additional degrees of freedom in magnetoelectric device design and nanotechnological applications. Despite intensive theoretical and experimental studies already carried out in magnetoelectric materials, some issues deserve more attention, specifically their structural and electronic properties. Here, density functional theory (DFT) was used to investigate the structural and electronic properties of hexagonal Y1-xEuxMnO3 (x = 0.0, 0.1 and 0.2) compounds. Our approach is based on the local spin density approximation (LSDA+U). The magnetic moment carried out by Mn atoms is very sensitive to the LSDA+U. We obtain the lattice parameters that compare well with experimental X-ray measurements, showing a difference between calculated values and experiment less than 2%. The calculated PDOS shows important contributions from the rare earth and the oxygen atoms in these systems, in which main contributions comes from the manganese atom. In addition, the electronic partial density of states (PDOS) shows a dominant contribution from the Mn and rare earth atoms near the Fermi level.

Magnetoelectric effect in three-layered gradient LiNbO3/Ni/Metglas composites

The effect of annealing in a permanent magnetic field on the magnitude of magnetoelectric coefficient in three-layered gradient magnetoelectric LiNbO3/Ni/Metglas composites has been studied. A method of electrochemical nickel deposition on bidomain lithium niobate crystals has been demonstrated. We show that the optimum annealing temperature in a permanent magnetic field for the generation of the highest remanence in the Ni layer is 350 °C. The specimens annealed at this temperature exhibit the greatest shift of the magnetoelectric coefficient dependence on external magnetic field magnitude relative to the value Hdc = 0. The quasi-static magnetoelectric coefficient in the absence of an external magnetic field proves to be 1.2 V/(cm ∙ Oe). The highest magnetoelectric coefficient that has been achieved at a bending structure resonance frequency of 278 Hz proves to be 199.3 V/(cm ∙ Oe) without application of an external magnetic field. The experimental magnetoelectric coefficient figures for three-layered gradient LiNbO3/Ni/Metglas composites are not inferior to those for most magnetoelectric composite materials reported earlier.

Piezoelectric and Magnetoelectric Effects of Flexible Magnetoelectric Heterostructure PVDF-TrFE/FeCoSiB.

Flexible polymer-based magnetoelectric (ME) materials have broad application prospects and are considered as a new research field. In this article, FeCoSiB thin films were deposited on poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) substrate by DC magnetron sputtering. The structure of PVDF-TrFE/FeCoSiB heterostructure thin films was similar to 2-2. Under a bias magnetic field of 70 Oe, the composites have a dramatically increased ME voltage coefficient as high as 111 V/cm⋅Oe at a frequency of about 85 kHz. The piezoelectric coefficient of PVDF-TrFE thin films is 34.87 pC/N. The surface morphology of PVDF-TrFE thin films were studied by FESEM, and the results of XRD and FTIR showed that the β-phase of PVDF-TrFE thin films was dominant. Meanwhile, the effects of different heating conditions on the crystallization and piezoelectric properties of PVDF-TrFE films were also studied. The flexible ME heterojunction composite has a significant ME voltage coefficient and excellent piezoelectric properties at room temperature, which allows it to be a candidate material for developing flexible magnetoelectric devices.

Magnetic and ionic liquid inclusions in soft materials and engineering enhanced electro-magneto-mechanical response

Magnetoelectric soft materials that polarize in the existence of external magnetic field and magnetize in response to an applied electric voltage have several promising technological applications. However, finding the suitable candidate for device fabrication has been a challenging task. Previous experiments and numerical modeling suggested an enhanced electrostrictive properties for soft materials composites made by depositing high permittivity liquid inclusions. Similarly, it has been reported that small magnetic inclusions significantly improve the magnetostrictive response of a soft composite. In this work, we highlight a simple yet effective mechanism to design soft materials composites with unusually large magnetoelectric coupling, merely by adding minute spherical liquid inclusions. Using a simple homogenization model, we explore the interplay of electrostatics, magnetostatics, soft solids and liquid inclusions on the effective coupling behavior of the soft composite while properly accounting for the capillary effects. This soft composite, which naturally allows large deformations, is also capable of generating electric voltage when subject to an external magnetic field. Meticulous selection of the size of liquid or solid inclusions, volume fraction and matrix materials properties significantly impacts the magnetoelectric coupling coefficient of the soft composite. In particular, choosing ferrofluids improves magnetoelectric response by 134% or higher. Moreover, in the absence of an electric field, a stronger magnetostrictive effect is revealed by ionic liquid inclusions compared to stiff ones, even in the presence of an applied mechanical strain.

Electric field control of electromagnon frequency in multiferroics

Electromagnons, which are coupled polar and magnetic excitations in magnetoelectric materials, are of large interest for electronic and computing technological devices. Using molecular dynamics simulations based on an ab initio effective Hamiltonian, we predict that the frequency of several electromagnons can be tuned by the application of electric fields in the model multiferroic ${\mathrm{BiFeO}}_{3}$, with this frequency either increasing or decreasing depending on the selected electromagnon. In particular, we show that the frequency of electromagnons localized at ferroelectric domain walls can be tuned over a 200 GHz range by realistic dc electric fields. We interpret the realized frequency increase (decrease) by local hardening (softening) of the associated polar phonons which couples to the applied electric field. The increase versus decrease in the electromagnon frequency is further found to be correlated with the real-space localization of such phonons.

Phase Transitions in Magneto-Electric Hexaferrites.

Hexaferrites have long been the object of extensive studies because of their great possibility for applications-permanent magnets, high-density recording media, microwave devices, in biomedicine, to name but a few. Lately, many researchers' efforts have been focused on the existence of the magneto-electric effect in some hexaferrite systems and the appealing possibility of them being used as single-phase multiferroic and magneto-electric materials. As indicated by theoretical analyses, the origin of the large magneto-electric effect can be sought in the strong interaction between the magnetization and the electric polarization that coexist in insulators with noncollinear magnetic structures. The hexaferrites' magnetic structure and, particularly, the specific magnetic spin ordering are the key factors in observing magneto-electric phases in hexaferrites. Some of these phases are metastable, which hampers their direct practical use. However, as the hexaferrites' phase diagrams reveal, chemical doping can be used to prepare a number of noncollinear stable magnetic phases. Since the magneto-electric effect has to do with the magnetic moments ordering, it seems only logical that one should study the cation substitutions' influence on the magnetic phase transition temperature. In this paper, we summarize recent examples of advances in the exploration of magnetic phase transitions in Y-type hexaferrites. In particular, the effect is emphasized by substituting in Y-type hexaferrites the nonmagnetic Me2+ cations with magnetic ones and of the magnetic Fe3+ cations with nonmagnetic ones on their magnetic properties and magnetic phase transitions. The work deals with the structural properties of and the magnetic phase transitions in a specific Y-type hexaferrite, namely, Ba(Sr)2Me2Fe12O22.

Magnetodielectric and TMR effects in P(VDF-HFP)/SrFe12O19 composite films for magnetic field – Tuned photodetector application

Magnetoelectric (ME) multiferroic materials possess extensive research interest as a result of their use in a variety of sectors. In this work, the optical properties of plain P(VDF-HFP) film and P(VDF-HFP)/SrFe12O19 composite films are investigated through UV-Vis absorption spectroscopy. In addition, the ME coupling of SrFe12O19 nanofibers reinforced P(VDF-HFP) composite films is investigated though magnetodielectric (MD) measurements. The parameters such as dielectric constant, capacitance, dielectric loss and impedance of the composite films are found to change with the applied magnetic field which is attributed to the direct ME coupling of the composite films. The prepared ME films show a negative tunneling magnetoresistance (TMR) effect with maximum TMR% of 14 % for the film (PSNF20) with 20 wt% of SrFe12O19 nanofiber loading. Photodetectors are fabricated using the films as active elements and the performance of the photodetectors is studied under various intensities of visible light radiation. All the devices exhibit good photosensitivity, responsivity and specific detectivity at an illumination intensity of 20 mW/cm2. The photodetector (PD20) fabricated using PSNF20 as an active element has the maximum rise/decay time, photosensitivity, responsivity and specific detectivity values as 468 /553 ms, 2.7 × 103, 22 mA/W and 6.77 × 1013 Jones, respectively at 20 mW/cm2. In addition, the performance of the devices is analyzed by subjecting the active element to external magnetic field. The photosensitivity, responsivity and specific detectivity all improve, showing that the magnetic field has an effect on the photodetector. The above parameters are maximum for PD20 device and the values are 4.3 × 103, 26 mA/W and, 8.01 × 1013 Jones, respectively at 4000 Oe and 20 mW/cm2. Thus, the prepared flexible magnetoelectric films of P(VDF-HFP)/SrFe12O19 nanofiber composites have been shown to be good options for the magnetic field tuned photodetector applications such as environmental sensing monitor, safety and security, optical communication systems, magnetic sensors, piezoelectric sensors and spintronics devices.

Theory of hard magnetic soft materials to create magnetoelectricity

Materials that generate electrical signals upon exposure to a well-controlled stimuli are high desirable. In that context, magnetoelectrics are unusual in the sense that the stimulus may be applied remotely (and wirelessly) without recourse to any physical contact. Wireless energy harvesting, remotely triggered biomedical agents, soft robots among others are some of the applications of such materials. The magnetoelectric property however is somewhat elusive in natural materials and artificial composites designed to exhibit this effect are invariably hard materials, require a pre-existing magnetic field and only exhibit a non-trivial coupling at high frequencies. Our recent experiments (presented elsewhere) demonstrated a facile route to create highly deformable soft magnetoelectric materials predicated on the concept of programmable hard magnetic soft materials with embedded immobile electric charges (electrets). In this work, we offer a nonlinear theoretical framework to both understand the emergent magnetoelectric effect in this class of soft materials as well as to design novel structures and devices with tailored functionality. Specifically, we are able to show that mechanical strain convects residual electrical and magnetic field states to mediate an unprecedented strong magnetoelectric coupling that is independent of the applied external magnetic field and retains its potency at low frequencies. We analytically solve simple illustrative examples to establish insights and present a finite element approach to handle complexities that may be otherwise intractable. The predictions of our theory agree very well with published experiments.

Quasi-static modulation of multiferroic properties in flexible magnetoelectric Cr2O3/muscovite heteroepitaxy

Due to the strong coupling between electrical polarization and magnetization, magnetoelectric materials show promising features for low-power spintronics and ultra-sensitive magnetic sensors. Compared to the conventional tunning of magnetoelectricity, this work presents a modulation of magnetic and electric orders in magnetoelectric material through a quasi-static mechanical strain. To acquire this, linear magnetoelectric Cr2O3 film is fabricated epitaxially on muscovite substrates. Taking the natural flexibility of muscovite, applying a strain to the heterostructure is feasible via mechanical bending. In the bending experiment, the magnetization of Cr2O3 film can be enhanced significantly, and the techniques of X-ray absorption dichroism unveil insights with support from theoretical predictions. Besides, the electric polarization and magnetoelectric coupling of Cr2O3 can also be adjusted by mechanical bending. This work offers a comprehensive understanding of the relationship between quasi-static strain and magnetic and electrical behaviors and opens a new aspect of the combination between magnetoelectric materials and flexible substrates for future development.

Chromium doped NH2(CH3)2Ga(SO4)2 × 6H2O crystal – representative of a new family of magnetoelectric materials

The paper is devoted to the detailed study of electric and magnetic properties and magnetoelectric interactions in NH2(CH3)2Ga(SO4)2 × 6H2O crystals doped with chromium—DMAGaS:Cr. The temperature dependence of the specific heat revealed clear evidence of a series of phase transitions related to the electric dipoles ordering. The different types of the DMA cation ordering in the structure of DMAGaS:Cr were evidenced in the temperature evolution of the EPR spectra. In addition, a considerable magnetoelectric coupling was demonstrated within the paramagnetic and ferroelectric phase of DMAGaS:Cr crystal. In the narrow temperature range in the vicinity of the Curie point, this crystal was found to possess the largest values of the coefficient of ME interaction as well as the largest magnetodielectric effect within the family of ferroics with organic cation. The model describing the ME effect was proposed. The magnetic field through the magnetostriction effect changes the level of the local lattice deformations caused by metal ion substitution. The applied magnetic field changes Cr-Cr distances and modifies the hydrogen bonds and process of DMA group ordering, affecting spontaneous polarization.

Numerical simulation investigation of direct and converse magnetoelectric effects in laminated composites with longitudinally magnetization and polarization

Numerical simulation is often used for piezoelectric materials or magnetostrictive materials, but it is rarely used for magnetoelectric materials due to the coupling complexity. COMSOL multiphysics is a powerful and effective numerical simulation software package. It can not only study the influence of parameter and frequency changes, but also extract stress distribution, electric potential, vibration mode, etc. In this paper, based on the existing equivalent circuit theory of L-L mode magnetoelectric laminates, COMSOL software is used to analyze the changes of DME and CME coefficients with frequency, the frequency curves of different proportions of magnetostrictive materials, and the vibration modes at the frequency peaks. It is obvious that the L-L mode laminated composite vibrates along the length direction regardless of DME and CME effects. The numerical simulation results are in good agreement with the existing theoretical analysis and experimental research. The results show that this simulation method is desirable and lays a foundation for further nonlinear theoretical analysis.

Electrical Manipulation of Oxygen Ion Migrations for the Voltage‐Controlled Adjustment of Magnetic Anisotropy and Optimized Skyrmion Generations

AbstractWith the prospect of energy‐efficient spintronics by voltage‐controlled magnetic anisotropy (VCMA), various mechanisms are investigated involving electron orbital state modulations for enhanced spin–orbit interactions, couplings with piezoelectric strain, and electrochemical effect at the interface within diverse magnetoelectric coupled material systems. In the present work, chemistry and spatial distributions of atoms are fine‐tuned at the interface between ferromagnetic Co and partially oxidized Gd layers via voltage‐controlled ion migrations, achieving highly sensitive and stable VCMA operations. With combined actions of chemical diffusion and electrical driving of oxygen through amorphous Gd layer, asymmetric electrical adjustments of magnetic anisotropy could be established. Accompanied changes in the domain morphologies in the magnetic thin film layers could also be confirmed at room temperature. As the fine‐adjustments of domain morphology are essential for the skyrmions generation, voltage‐controlled interfacial chemistry and magnetic anisotropy provide an effective route to stable skyrmion generations and manipulations in the low‐power spintronics technology.

Intrinsic bitunable magnetism/polarity behavior in 2D Janus Cr2I3Y3 (Y = F, Cl, or Br) systems

Two-dimensional (2D) magnetoelectric (ME) materials with spontaneous magnetism and polarity have drawn a lot of research interest due to their potentially valuable physics and spintronic applications. One of the obstacles in the current study of 2D ME materials is to achieve flexible magnetism/polarity switches because of a fundamental contradiction between magnetism and polarity. In this work, we propose an intrinsic magnetism/polarity switchable 2D Janus structure Cr2I3Y3 (Y = F, Cl, or Br) with mechanical and thermodynamic stability. Janus Cr2I3Y3 monolayers show indirect-gap semiconductors with ferromagnetic ordering. Intrinsic vertical electric polarity (EP) in Janus Cr2I3Y3 structures is investigated by surface potential difference analysis and dipole calculations. We discover that there is an obvious ME coupling between magnetic anisotropy energy (MAE) and EP. MAE can be obviously tuned by rotating the orientations of spins within yz and zx vertical planes, and the easily distinguishable MAE on vertical planes has strong inherent relevance with vertical EP. Simultaneously, magnetic phase transition and magnetic moments can be manipulated by introducing vertical strain, which directly corresponds to the linear response of the EP strength. Our work provides a promising candidate for realizing the spintronic devices with multiple functionalities.

Microstructure and physical properties of ε-Fe2O3 thin films fabricated by pulsed laser deposition

ε-Fe2O3 has attracted intense interest in the field of magnetoelectric materials due to its promising physical properties. The epitaxial growth of ε-Fe2O3 thin films is challenging since it is a metastable phase of iron oxide. In this study, ε-Fe2O3 (001) thin films are epitaxially grown on SrTiO3 (111) substrates by pulsed laser deposition (PLD). The crystal structure, valence state, and microstructure of the ε-Fe2O3 thin films are investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. It is revealed that the oxygen pressure, deposition and annealing temperatures, and laser beam energy affect significantly the epitaxial growth of ε-Fe2O3 thin films. The orientation relationship between films and substrates is ε-Fe2O3 (001)[010] // SrTiO3 (111)[1¯10]. The magnetic hysteresis loops tested by a superconducting quantum interference device and UV–Vis reflection spectra suggest that the ε-Fe2O3 thin film with thickness of ∼ 20 nm has a strong magnetic anisotropy, a coercivity of 600 Oe, and an indirect band gap of 3.26 eV.

Multiple polarization phases and strong magnetoelectric coupling in the layered transition metal phosphorus chalcogenides TMP2X6(T=Cu,Ag;M=Cr,V;X=S,Se) by controlling the interlayer interaction and dimension

Magnetoelectric multiferroic materials are the potential candidates for the high-density nonvolatile data storage devices. However, up to now, multiferroic materials with strong magnetoelectric coupling are still rare. Here, based on the first-principles calculations and theoretical model, we predict a different class of single phase multiferroic materials, transition metal phosphorus chalcogenides $TM{\mathrm{P}}_{2}{X}_{6}(T=\mathrm{Cu},\phantom{\rule{0.16em}{0ex}}\mathrm{Ag};\phantom{\rule{0.16em}{0ex}}M=\mathrm{Cr},\phantom{\rule{0.16em}{0ex}}\mathrm{V};\phantom{\rule{0.16em}{0ex}}X=\mathrm{S},\phantom{\rule{0.16em}{0ex}}\mathrm{Se})$ with multiple polarization phases and strong magnetoelectric coupling. The ferroelectric polarization originates from the movement of Cu/Ag atoms breaking the symmetry of spatial inversion and the magnetism arises from partially filled $d$ orbitals of the V/Cr atoms. It is predicted that the different ferroelectric phases of $TM{\mathrm{P}}_{2}{X}_{6}$ bulk have different band gaps, providing a way to control electronic and transport properties by the external electric field. Most prominently, for $\mathrm{CuV}{\mathrm{P}}_{2}{\mathrm{S}}_{6}$ bilayer and few layers, one of the ferroelectric phases has ferromagnetic ground state and the other has antiferromagnetic states, realizing the electric-field control of magnetism. We reveal that the physical mechanism of the strong magnetoelectric coupling is from the reduced dimension and symmetry by constructing a theoretical model including the crystal field splitting, electric polarization effect, and exchange interaction. This work not only predicts a different class of magnetoelectric multiferroic materials, but also proposes a strategy to design them by controlling the interlayer interaction in van der Waals layered materials.

Role of carbonaceous fillers in electromagnetic interference shielding behavior of polymeric composites: A review

AbstractIn this review, the EMI shielding properties of the various carbonaceous fillers are thoroughly reviewed. Electromagnetic interference (EMI) had been a cause of major concern in the live broadcasting, entertainment, aviation and defense industries since vital radio signals could create more interference, which could lead to poor performance. To reduce the effect of EMI, the organic polymeric composites along with the carbonaceous fillers are mostly used since they are flexible, low denser, high mechanical strength, high thermo‐stability, high electrical and thermal conductivity, excellent fracture toughness, and high friction/wear resistance. There are lot of carbon based materials are being used as EMI shielding material in mono and compound form. This review gives a broad understanding of the utilization of carbonaceous fillers in polymer matrixes. Thus, the overall coverage on this carbon based materials and their effectiveness could help the researchers to find right carbon material for suitable application. According to this review, the absorption mechanism is vital to achieve high EMI shielding effect. The fillers such as graphene and CNTs are most preferable EMI shielding filler, according to the vast coverage of previous articles. However, there are more magnetoelectric materials also evolved recently, having combined properties of both conductive and magnetic, yielding high SE at elevated frequencies.

Researching progress on bio-reactive electrogenic materials with electrophysiological activity for enhanced bone regeneration.

Bone tissues are dynamically reconstructed during the entire life cycle phase, which is an exquisitely regulated process controlled by intracellular and intercellular signals transmitted through physicochemical and biochemical stimulation. Recently, the role of electrical activity in promoting bone regeneration has attracted great attention, making the design, fabrication, and selection of bioelectric bio-reactive materials a focus. Under specific conditions, piezoelectric, photoelectric, magnetoelectric, acoustoelectric, and thermoelectric materials can generate bioelectric signals similar to those of natural tissues and stimulate osteogenesis-related signaling pathways to enhance the regeneration of bone defects, which can be used for designing novel smart biological materials for engineering tissue regeneration. However, literature summarizing studies relevant to bioelectric materials for bone regeneration is rare to our knowledge. Consequently, this review is mainly focused on the biological mechanism of electrical stimulation in the regeneration of bone defects, the current state and future prospects of piezoelectric materials, and other bioelectric active materials suitable for bone tissue engineering in recent studies, aiming to provide a theoretical basis for novel clinical treatment strategies for bone defects.