The effect of magnetic domain boundaries displacement induced by electric field is observed in epitaxial ferrite garnet films (on substrates with the (210) crystallographic orientation). The effect is odd with respect to the electric field (the direction of wall displacement changes with the polarity of the voltage) and even with respect to the magnetization in domains. The inhomogeneous magnetoelectric interaction as a possible mechanism of the effect is proposed.
We have investigated the Faraday rotation of in-plane magnetized bismuth - substituted ferrite garnet films grown by liquid phase epitaxy on (100) oriented gadolinium gallium garnet substrates. The Faraday spectra were measured for photon energies between 1.7 - 2.6 eV. To interprete the spectra, we use a model based on two electric dipole transitions, one tetrahedral and one octahedral. Furthermore, the Faraday rotation sensitivity was measured at 2.3 eV, and found to be in good agreement with the theoretical predicitions. In particular, we find that the sensitivity increases linearly with the…
We report the use of high magnetomechanical coupling ferrites in magnetoelectric (ME) layered composites. Bilayer samples combining $(Ni_{0.973} Co_{0.027})_{1-x} Zn_x Fe_2 O_4$ ferrites ($x = 0-0.5$) synthesized by non conventional reactive Spark Plasma Sintering and commercial lead zirconate titanate (PZT) were characterized in term of ME voltage coefficients measured at sub-resonant frequency. Strong ME effects are obtained and we show that an annealing at 1000$^\circ$C and a quenching in air improve the piezomagnetic behavior of Zn-rich compositions. A theoretical model that predicts the M…
We have investigated the magnetoelectric (ME) effect in layered composite rings subjected to circumferential AC magnetic fields and DC magnetic fields in radial, axial or circumferential directions. Bilayer samples were obtained combining different grades of commercial Mn-Zn ferrites or Ni-Zn ferrites with commercial lead zirconate titanate (PZT). Mn-Zn ferrites with low magnetostriction saturation () and low magneto-crystalline anisotropy constants show high ME capabilities when associated with PZT in ring structures. In certain conditions, these ME effects are higher than those obtained with…
In this letter we show the presence of a spin-glass like phase in single crystals of magnetoelectric gallium ferrite (GaFeO3) below ~210 K via temperature dependent ac and dc magnetization studies. Analysis of frequency dispersion of the susceptibility peak at ~210 K using the critical slowing down model and Vogel-Fulcher law strongly suggests the existence of a classical spin-glass like phase. This classical spin glass behavior of GaFeO3 is understood in terms of an outcome of geometrical frustration arising from the inherent site disorder among the antiferromagnetically coupled Fe ions locat…
In this paper, we investigate the demagnetizing effect in ferrite/PZT/ferrite magnetoelectric (ME) trilayer composites consisting of commercial PZT discs bonded by epoxy layers to Ni-Co-Zn ferrite discs made by a reactive Spark Plasma Sintering (SPS) technique. ME voltage coefficients (transversal mode) were measured on ferrite/PZT/ferrite trilayer ME samples with different thicknesses or phase volume ratio in order to highlight the influence of the magnetic field penetration governed by these geometrical parameters. Experimental ME coefficients and voltages were compared to analytical calcula…
Magnetoelectric (ME) coupling at low frequencies and at x-band have been investigated in layered samples containing zinc substituted lithium ferrite and lead zirconate titanate (PZT). Multilayers of Li0.5-x/2ZnxFe2.5-x/2O4 (LZFO) (x=0-0.4) and PZT were prepared by lamination and sintering of thick films. At low frequencies (10-1000 Hz), the ME voltage coefficient for transverse fields is higher than for longitudinal fields. With Zn substitution in the ferrite, transverse coupling increases to a maximum for x=0.3 and then decreases for higher x. Analysis based on our model for a bilayer implies…
Thick film layered magnetoelectric composites consisting of ferromagnetic and ferroelectric phases have been synthesized with nickel ferrite (NFO), cobalt ferrite (CFO), La0.7Sr0.3MnO3 (LSMO), or La0.7Ca0.3MnO3 (LCMO) and lead zirconate titanate (PZT). Structural, magnetic and ferromagnetic resonance characterization shows evidence for defect free ferrites, but deterioration of manganite parameters. The resistivity and dielectric constants are smaller than expected values. The magnetoelectric effect (ME) is stronger in ferrite-PZT than in manganite-PZT. The ME voltage coefficient aE at room te…
Single crystalline films of bismuth-substituted ferrite garnets have been synthesized by the liquid phase epitaxy method where GGG substrates are dipped into the flux. The growth parameters are controlled to obtain films with in-plane magnetization and virtually no domain activity, which makes them excellently suited for magnetooptic imaging. The Faraday rotation spectra were measured across the visible range of wavelengths. To interprete the spectra we present a simple model based on the existence of two optical transitions of diamagnetic character, one tetrahedral and one octahedral. We find…
The synthesis of layered ferrite-lead titanate zirconate (PZT) and lanthanum nanganite-PZT and the observation of giant magneto-electric interactions are discussed. The ferrites used in our studies included pure and Zn substituted cobalt-, nickel- and lithium ferrites. Ferromagnetic manganites used included both calcium and strontium substituted systems. The samples were prepared from 10-40 mm thick films obtained by tape-casting. Our studies showed strong ME coupling in manganite-PZT and cobalt zinc ferrite-PZT, and a giant ME effect in nickel zinc ferrite-PZT. We found evidence for Zn assist…
The room temperature magnetoelectric effect was observed in epitaxial iron garnet films that appeared as magnetic domain wall motion induced by electric field. The films grown on gadolinium-gallium garnet substrates with various crystallographic orientations were examined. The effect was observed in (210) and (110) films and was not observed in (111) films. Dynamic observation of the domain wall motion in 400 V voltage pulses gave the value of domain wall velocity in the range 30-50 m/s. The same velocity was achieved in magnetic field pulse about 50 Oe.
Magnetoelectric interactions in bilayers of magnetostrictive and piezoelectric phases are mediated by mechanical deformation. Here we discuss the theory and companion data for magnetoelectric (ME) coupling at electromechanical resonance (EMR) in a ferrite-lead zirconate titanate (PZT) bilayer. Estimated ME voltage coefficient versus frequency profiles for nickel, cobalt, or lithium ferrite and PZT reveal a giant ME effect at EMR with the highest coupling expected for cobalt ferrite-PZT. Measurements of resonance ME coupling have been carried out on layered and bulk composites of nickel ferrite…
Magnetoelectric (ME) materials are of fundamental interest and show broad potential for technological applications. Commonly the dominant contribution to the ME response is the lattice-mediated one, which is proportional to both the Born electric charge $Z^{\rm e}$ and its analogue, the dynamical magnetic charge $Z^{\rm m}$. Our previous study has shown that exchange striction acting on noncollinear spins induces much larger magnetic charges than those that depend on spin-orbit coupling. The hexagonal manganites $R$MnO$_3$ and ferrites $R$FeO$_3$ ($R$ = Sc, Y, In, Ho-Lu) exhibit strong couplin…
Low frequency magnetoelectric (ME) coupling has been investigated in bulk and multilayers of cobalt zinc ferrite, Co1-xZnxFe2O4 (x=0-0.6), and lead zirconate titanate. In bulk samples, the transverse and longitudinal couplings are weak and are of equal magnitude. A substantial strengthening of ME interactions is evident in layered structures, with the ME voltage coefficient a factor of 10-30 higher than in bulk samples. Important findings of the studies in layered composites are as follows. (i) The transverse coupling is stronger than the longitudinal coupling. (ii) The strength of ME interact…
The observation of strong magnetoelectric effects is reported in thick film bilayers and multilayers of ferrite-lead titanate zirconate (PZT) and lanthanum nanganite-PZT. The ferrites used in our studies included pure and zinc substituted cobalt-, nickel- and lithium ferrites. Samples were prepared by sintering 10-40 mm thick films obtained by tape-casting. Measurements of ME voltage coefficients at 10-1000 Hz indicated a giant ME effect in nickel ferrite-PZT, but a relatively weak coupling in other ferrite-PZT and manganite-PZT systems. Multilayers prepared by hot pressing was found to show a…
We present a combined experimental-theoretical study demonstrating the role of site disorder, off-stoichiometry and strain on the optical behavior of magnetoelectric gallium ferrite. Optical properties such as band-gap, refractive indices and dielectric constants were experimentally obtained by performing ellipsometric studies over the energy range 0.8 eV to 4.2 eV on pulsed laser deposited epitaxial thin films of stoichiometric gallium ferrite with b-axis orientation and the data was compared with theoretical results. Calculations on the ground state structure show that the optical activity i…
Magnetoelectric Coupling in Nickel-Cobalt Ferrite and Lanthanum Ferrite Heterostructure Composites: Experimental Evidence and Simulation-Driven Insights
In this paper we show that magnetic-dipolar-mode (MDM) oscillations of a quasi-2D ferrite disk are characterized by unique symmetry features with topological phases resulting in appearance of the magnetoelectric (ME) properties. The entire ferrite disk can be characterized as a pair of two, electric and magnetic, coupled eigen moments. However, there is no a "glued pair" of two dipoles. An external electromagnetic field in the near-field region "views" such a ME particle, as a system with a normally oriented eigen electric moment and an in-plane rotating eigen magnetic dipole moment.
In this study we have compared magnetic, magnetostrictive and piezomagnetic properties of isotropic and anisotropic cobalt ferrite pellets. The isotropic sample was prepared by the ceramic method while the sample exhibiting uniaxial anisotropy was made by reactive sintering using Spark Plasma Sintering (SPS). This technique permits to induce a magnetic anisotropy in cobalt ferrite in the direction of the applied pressure during SPS process. Sample with uniaxial anisotropy revealed a higher longitudinal magnetostriction and piezomagnetism compared to the isotropic sample, but the transversal ma…
Temperature dependent X-ray diffraction and Raman spectroscopic studies were carried out on the flux grown single crystals of gallium ferrite with Ga:Fe ratio of 0.9:1.1. Site occupancy calculations from the Rietveld refinement of the X-ray data led to the estimated magnetic moment of ~0.60 \muB /f.u. which was in good agreement with the experimental data. Combination of these two measurements indicates that there is no structural phase transition in the material between 18 K to 700 K. A detailed line shape analysis of the Raman mode at ~375 cm^-1 revealed a discontinuity in the peak position …
Poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) based pyroelectric as well as magnetoelectric materials offer great promises for energy harvesting for flexible and wearable applications. Hence, this work focus on solar energy harvesting as well as magnetoelectric phenomenon in two phase nanocomposite film where the constituting phases are manganese ferrite (MnFe2O4) nanoparticles and P(VDF-TrFE) polymer. Composite films have been prepared using solution casting technique. X-ray diffraction result shows higher crystallinity of these films. The ferroelectric, magnetic and magnetoelec…
The possibility to control the magnetic properties of a material with an electric field at room temperature is highly desirable for modern applications. Moreover, a coupling between magnetic and electric orders within a single material presenting a wide range of exceptional physical properties, such as bismuth iron garnet (BIG), may lead to great advances in the field of spintronic applications. In particular, the combination of the magnetoelectric (ME) coupling with the low damping of spin waves in BIG can allow the control and manipulation of spin waves by an electric field in magnonic devic…
Hexagonal ferrites (h-RFeO$_3$, R=Y, Dy-Lu) have recently been identified as a new family of multiferroic complex oxides. The coexisting spontaneous electric and magnetic polarizations make h-RFeO$_3$ rare-case ferroelectric ferromagnets at low temperature. Plus the room-temperature multiferroicity and predicted magnetoelectric effect, h-RFeO$_3$ are promising materials for multiferroic applications. Here we review the structural, ferroelectric, magnetic, and magnetoelectric properties of h-RFeO$_3$. The thin film growth is also discussed because it is critical in making high quality single cr…
We have studied the structural stability of Sc-substituted rare earth (R) ferrites R1-xScxFeO3, and constructed a structural phase diagram for different R and x. While RFeO3 and ScFeO3 adopt the orthorhombic and the bixbyite structure respectively, the substituted compound R1-xScxFeO3 may be stable in a different structure. Specifically, for R0.5Sc0.5FeO3, the hexagonal structure can be stable for small R, such as Lu and Yb, while the garnet structure is stable for larger R, such as Er and Ho. The formation of garnet structure of the R0.5Sc0.5FeO3 compounds which requires that Sc occupies both…
Improper ferroelectricity (trimerization) in the hexagonal manganites RMnO$_3$ leads to a network of coupled structural and magnetic vortices that induce domain wall magnetoelectricity and magnetization neither of which, however, occurs in the bulk. Here we combined first-principles calculations, group-theoretic techniques, and microscopic spin models to show how the trimerization not only induces a polarization but also a bulk magnetization and bulk magnetoelectric (ME) effect. This results in the existence of a bulk linear ME vortex structure or a bulk ME coupling such that if direction of p…
We present a theoretical study of the structure-property correlation in gallium ferrite, based on the first principles calculations followed by a subsequent comparison with the experiments. Local spin density approximation (LSDA+U) of the density functional theory has been used to calculate the ground state structure, electronic band structure, density of states and Born effective charges. Calculations reveal that the ground state structure is orthorhombic Pc21n having A-type antiferromagnetic spin configuration, with lattice parameters matching well with those obtained experimentally. Plots o…
In a normally magnetized thin-film ferrite disk with magnetic-dipolar modes, one can observe magnetoelectric oscillations. Such magnetoelectric properties of an electrically small sample can be considered as very attractive phenomena in microwaves. In this paper we discuss the question on novel microwave device applications based on ferrite magnetoelectric particles.
Bismuth ferrite (BiFeO3) is one of the most promising multiferroics with a sufficiently high ferroelectric (FE) and antiferromagnetic transition temperatures, and magnetoelectric (ME) coupling coefficient at room temperature, and thus it is highly sensitive to the impact of cross-influence of applied electric and magnetic fields. According to the urgent demands of nanotechnology miniaturization for ultra-high density data storage in advanced nonvolatile memory cells, it is very important to reduce the sizes of multiferroic nanoparticles in the self-assembled arrays without serious deterioratio…
We analyze the coupling between the ferroelectric and magnetic order parameters in the magnetoelectric multiferroic BiFeO_3 using density functional theory within the local spin density approximation and the LSDA+U method. We show that weak ferromagnetism of the Dzyaloshinskii-Moriya type occurs in this material, and we analyze the coupling between the resulting magnetization and the structural distortions. We explore the possibility of electric-field-induced magnetization reversal and show that, although it is unlikely to be realized in BiFeO_3, it is not in general impossible. Finally we out…
The dependencies on strain and oxygen vacancies of the ferroelectric polarization and the weak ferromagnetic magnetization in the multiferroic material bismuth ferrite, BiFeO_3, are investigated using first principles density functional theory calculations. The electric polarization is found to be rather independent of strain, in striking contrast to most conventional perovskite ferroelectrics. It is also not significantly affected by oxygen vacancies, or by the combined presence of strain and oxygen vacancies. The magnetization is also unaffected by strain, however the incorporation of oxygen…
The first observation of microwave magnetoelectric (ME) interactions through ferromagnetic resonance (FMR) in bilayers of single crystal ferromagnetic-piezoelectric oxides and a theoretical model for the effect are presented. An electric field E produces a mechanical deformation in the piezoelectric phase, resulting in a shift dHE in the resonance field for the ferromagnet. The strength of ME coupling is obtained from data on dHE vs E. Studies were performed at 9.3 GHz on bilayers of (111) yttrium iron garnet (YIG) films and (001) lead magnesium niobate-lead titanate (PMN-PT). The samples were…
There is a profound analogy between inhomogeneous magnetoelectric effect in multiferroics and flexoelectric effect in liquid crystals. This similarity gives rise to the flexomagnetoelectric polarization induced by spin modulation. The theoretical estimations of flexomagnetoelectric polarization agree with the value of jumps of polarization in magnetoelectric dependences (~20muC/m^2) observed at spin cycloid suppression at critical magnetic field 200kOe.
The near fields originated from a small quasi-two-dimensional ferrite disk with magnetic-dipolar-mode (MDM) oscillations are the fields with broken dual (electric-magnetic) symmetry. Numerical studies show that such fields, called the magnetoelectric (ME) fields, are distinguished by the power-flow vortices and helicity parameters [E. O. Kamenetskii, R. Joffe, and R. Shavit, Phys. Rev. E 87, 023201 (2013)]. These numerical studies can well explain recent experimental results with MDM ferrite disks. In the present paper, we obtain analytically topological characteristics of the ME-field modes. …
Here, we report the catalytic degradation of organic compounds by exploiting the magnetoelectric (ME) nature of cobalt ferrite-bismuth ferrite (CFO-BFO) core-shell nanoparticles. The combination of magnetostrictive CFO with the multiferroic BFO gives rise to a magnetoelectric engine that purifies water under wireless magnetic fields via advanced oxidation processes, without involvement of any sacrificial molecules or co-catalysts. Magnetostrictive CoFe2O4 nanoparticles are fabricated using hydrothermal synthesis, followed by sol-gel synthesis to create the multiferroic BiFeO3 shell. We perform…
Structural, magnetic and ferromagnetic resonance characterization studies have been performed on lay-ered ferromagnetic-ferroelectric oxides that show strong magnetoelectric coupling. The samples contained thick films of ferrites or substituted lanthanum manganites for the ferromagnetic phase and lead zirconate titanate for the ferroelectric phase, and were sintered high temperatures. Results indicate defect free ferrites, but deterioration of manganite parameters due to diffusion at the interface and accounts for poor magnetoelectric coupling in manganite-PZT samples.
There have been a large number of papers on bismuth ferrite (BiFeO3) over the past few years, trying to exploit its room-temperature magnetoelectric multiferroic properties. Although these are attractive, BiFeO3 is not the ideal multiferroic, due to weak magnetization and the difficulty in limiting leakage currents. Thus there is an ongoing search for alternatives, including such materials as gallium ferrite (GaFeO3). In the present work we report a comprehensive study of the perovskite PbTi1-xPdxO3 with 0 < x < 0.3. Our study includes dielectric, impedance and magnetization measurements, cond…
A theoretical model is presented for low-frequency magnetoelectric (ME) effects in bilayers of magnetostrictive and piezoelectric phases. A novel approach, the introduction of an interface coupling parameter k, is proposed for the consideration of actual boundary conditions at the interface. An averaging method is used to estimate effective material parameters. Expressions for ME voltage coefficients are obtained by solving elastostatic and electrostatic equations. We consider both unclamped and rigidly clamped bilayers and three different field orientations of importance: (i) longitudinal fie…
University of Duisburg-Essen（杜伊斯堡-埃森大学）；European Organization for Nuclear Research (CERN)（欧洲核子研究组织（CERN））；Universidade de Aveiro（阿威罗大学）；Institute for Research in Fundamental Sciences (IPM)（基础科学研究所（IPM））
We demonstrate room temperature ferroelectricity in the epitaxial thin films of magnetoelectric GaFeO3. Piezo-force measurements show a 180o phase shift of piezoresponse upon switching the electric field indicating nanoscale ferroelectricity in epitaxial thin films of gallium ferrite. Further, temperature dependent impedance analysis with and without the presence of an external magnetic field clearly reveals a pronounced magneto-dielectric effect across the magnetic transition temperature. In addition, our first principles calculations show that Fe ions are not only responsible for ferrimagnet…
To tune the magnetic properties of hexagonal ferrites, a family of magnetoelectric multiferroic materials, by atomic-scale structural engineering, we studied the effect of structural distortion on the magnetic ordering temperature (TN). Using the symmetry analysis, we show that unlike most antiferromagnetic rare-earth transition-metal perovskites, a larger structural distortion leads to a higher TN in hexagonal ferrites and manganites, because the K3 structural distortion induces the three-dimensional magnetic ordering, which is forbidden in the undistorted structure by symmetry. We also revea…
Laterally Differentiated Polymorphs: a route to multifunctional nanostructures
Massachusetts Institute of Technology（麻省理工学院）；Nagoya University（名古屋大学）；National Institute for Materials Science (NIMS)（国立材料研究所）；Fujikura Limited（藤仓株式会社）；Brno University of Technology（布尔诺理工大学）
The properties of antiferromagnetic materials with violated space-time parity are considered. Particular attention is given to the bismuth ferrite BiFeO3 ferroelectric magnet. This material is distinguished from other antiferromagnets in that the inversion center is absent in its crystal and magnetic structures. This circumstance gives rise to the diversified and unusual properties, namely, to the appearance of a spatially modulated spin structure and to the unique possibility of the linear magnetoelectric effect coexisting with a weak ferromagnetic moment. The magnetic-induced phase transitio…
The linear magnetoelectric (ME) effect provides a special route for linking magnetic and electric properties. In microwaves, a local ME effect appears due to the dynamical symmetry breakings of magnetic-dipolar modes (MDMs) in a ferrite disk particle. The fact that for MDMs in a ferrite disk one has evident both classical and quantum-like attributes, puts special demands on the methods used for study of interacting ME particles. A proper model for coupled particles should be based on the spectral characteristics of MDM oscillations and an analysis of the overlap integrals for interacting eigen…
The structural, dielectric, magnetic, and magnetoelectric (ME) properties of particulate composites containing lead-iron niobate and lead titanate piezoelectric 0.94[PbFe$_{0.5}$Nb$_{0.5}$O$_3$]-0.06[PbTi$_{0.5}$O$_3$] (PFN-PT) and Zn-substituted cobalt ferrite magnetostrictive CoFe$_{2-x}$Zn$_{x}$O$_4$ (CF$_{2-x}$Z$_{x}$O); 0.6(PFN-PT)/0.4(CF$_{2-x}$Z$_{x}$O), x=0, 0.025, 0.1, 0.2, 0.3 (with ratio of 60 Wt\% ferroelectric and 40 Wt\% ferrite); have been investigated. We investigated the ME voltage coefficient as a complex quantity for all composite samples using the dynamic piezomagnetic coef…
Discovering materials that display a linear magnetoelectric effect at room temperature is challenge. Such materials could facilitate novel devices based on the electric-field control of magnetism. Here we present simple, chemically intuitive design rules to identify a new class of bulk magnetoelectric materials based on the 'bicolor' layering of $Pnma$ ferrite perovskites, e.g., LaFeO$_3$/ LnFeO$_3$ superlattices for which Ln = lanthanide cation. We use first-principles density-functional theory calculations to confirm these ideas. Additionally, we elucidate the origin of this effect and show …
In this article, we perform the symmetry analysis of perovskite-based multiferroics: bismuth ferrite (BiFeO3)-like, orthochromites (RCrO3), and Ruddlesden-Popper perovskites (Ca3Mn2O7-like), being the typical representatives of multiferroics of the trigonal, rhombic, and tetragonal crystal families and explore the effect of crystallographic distortions on magnetoelectric properties. We determine the principal order parameters for each of the considered structures and obtain their invariant combinations consistent with the particular symmetry. This approach allowed us to analyze the features of…
The dynamic observation of domain wall motion induced by electric field in magnetoelectric iron garnet film is reported. Measurements in 800 kV/cm electric field pulses gave the domain wall velocity ~45 m/s. Similar velocity was achieved in magnetic field pulse about 50 Oe. Reversible and irreversible micromagnetic structure transformation is demonstrated. These effects are promising for applications in spintronics and magnetic memory.
We investigate a magnetization-dependent voltage that appears at the interface between garnets and various metals. The voltage is even in the applied magnetic field and is dependent on the surface roughness and the pressure holding the surfaces together. Large variations in the size, sign and magnetic dependence are observed between different metal surfaces. Some patterns have been identified in the measured voltages and a simple model is described that can accommodate the gross features. The bulk magnetoelectric response of one of our polycrystalline YIG samples is measured and is found to be…
We study the magnetic properties of Gadolinium-Yttrium Iron Garnet ($\text{Gd}_{x}\text{Y}_{3-x}\text{Fe}_5\text{0}_{12}$, $x=3,1.8$) ferrite ceramics. The complex initial permeability is measured in the temperature range 2 K to 295 K at frequency of 1 kHz, and in the frequency range 100 Hz to 200 MHz at temperatures 4 K, 77 K, and 295 K. The magnetic viscosity-induced imaginary part of the permeability is observed at low frequencies. Measurements of the magnetization noise are made at 4 K. Using the fluctuation-dissipation theorem, we find that the observed magnetization fluctuations are cons…
Magnetic phase transitions in multiferroic bismuth ferrite (BiFeO3) induced by magnetic field, epitaxial strain, and composition modification are considered. These transitions from a spatially modulated spin spiral state to a homogenous antiferromagnetic one are accompanied by the release of latent magnetization and a linear magnetoelectric effect that makes BiFeO3-based materials efficient room-temperature single phase multiferroics.
One-dimensional magnonic crystals have been implemented as gratings of shallow grooves chemically etched into the surface of yttrium-iron garnet films. Scattering of backward volume magnetostatic spin waves from such structures is investigated experimentally and theoretically. Well-defined rejection frequency bands are observed in transmission characteristics of the magnonic crystals. The loss inserted by the gratings and the rejections bands bandwidths are studied as a function of the film thickness, the groove depth, the number of grooves, and the groove width. The experimental data are well…
We show that in a source-free subwavelength region of microwave fields there can exist the field structures with local coupling between the time-varying electric and magnetic fields differing from the electric-magnetic coupling in regular-propagating free-space electromagnetic waves. To distinguish such field structures from regular electromagnetic (EM) field structures, we term them as magnetoelectric (ME) fields. We study a structure and conservation laws of microwave ME near fields. We show that there exist sources of microwave ME near fields - the ME particles. These particles are represen…
Antisymmetric Dzyaloshinskii-Moriya (DM) interactions generating from the spin-orbit coupling induce various fascinating properties, like magnetoelectric (ME) effect, weak ferromagnetism and non-trivial topological spin textures like skyrmions, in real materials. Compared to their symmetric isotropic exchange counterpart, these interactions are generally of a weaker order of strength, creating modest twisting in the spin structure which results in weak ferromagntism or weak linear ME effect. Our proposed two-sublattice model, in contrast, predicts a hitherto unobserved, charge ordered non-coll…
Chirality discrimination is of a fundamental interest in biology, chemistry, and metamaterial studies. In optics, near-field plasmon-resonance spectroscopy with superchiral probing fields is effectively applicable for analyses of large biomolecules with chiral properties. We show possibility for microwave near-field chirality discrimination analysis based on magnon-resonance spectroscopy. Newly developed capabilities in microwave sensing using magnetoelectric (ME) probing fields originated from multiresonance magnetic-dipolar-mode (MDM) oscillations in quasi-2D yttrium-iron-garnet (YIG) disks,…
The chirality-dependent magnetoelectric properties of Neel-type domain walls in iron garnet films is observed. The electrically driven magnetic domain wall motion changes the direction to the opposite with the reversal of electric polarity of the probe and with the chirality switching of the domain wall from clockwise to counterclockwise. This proves that the origin of the electric field induced micromagnetic structure transformation is inhomogeneous magnetoelectric interaction.
Ferromagnetic-ferroelectric nanocomposites are of interest for realizing strong strain mediated coupling between electric and magnetic subsystems due to high surface area-to-volume ratio. This report is on the synthesis of nickel ferrite (NFO) -barium titanate (BTO) core-shell nano-fibers, magnetic field assisted assembly into superstructures, and studies on magneto-electric (ME) interactions. Electrospinning techniques were used to prepare coaxial fibers of 0.5-1.5 micron in diameter. The core-shell structure of annealed fibers was confirmed by electron microscopy and scanning probe microscop…
Recent microwave experiments demonstrate the anapole-moment and magnetoelectric properties in quasi-2D ferrite particles with magnetic-dipolar-wave oscillating spectra. The theory developed in this paper shows that there are the macroscopically quantum topological effects. Quantum coherence for macroscopic systems refers to circumstances when large numbers of particles can collectively cooperate in a single quantum state. These effects are rarely observed through macroscopic measurements because statistical averaging over many states usually masks all evidence of quantum discreteness. Magnetic…
