Value Of Magnetoelectric Coupling Coefficient Research Articles

Enhanced magnetoelectric coupling in novel rare earth metal substituted Sr based Z-hexaferrites/P(VDF-HFP) composites

This research is driven by a desire to create composite films that combine the ferrimagnetic capabilities of pure and La/Nd substituted Sr3Co2Fe24O41 Z-hexaferrites with the multifunctional features of ferroelectric polymers. A flexible magnetoelectric (ME) polymer composite films, with Sr3Co2Fe24O41 (SF), Sr2.85La0.15Co2Fe24O41(SF–La) and Sr2.85Nd0.15Co2Fe24O41 (SF-Nd) as the ferrimagnetic material and poly vinylidene fluoride-hexafluoropropylene (PH) as a ferroelectric component, were synthesized using solution casting method. In the current case, two steps have been used to synthesize ferroelectric and ferrimagnetic composites films: first, SF, SF-La and SF-Nd hexaferrite samples were synthesized using solid state reaction method and then 20% weight percentage of these hexaferrites were incorporated into the PH matrix using solution casting method to form composite film. In order to find the traces of collaborative interactions between the two phases, the structural, magnetic, and ferroelectric properties of these composite samples have been studied. The XRD data confirm the formation of SF, SF-La and SF-Nd hexaferrite dispersed in a piezoelectric copolymer PH matrix. The changes in the ferroelectric properties in different magnetic fields demonstrated the existence of ME coupling in the composite films. The inclusion of PH enhanced the magnetoelectric coupling of composite films. The maximal value of magnetoelectric coupling coefficient (αME) observed is 0.213, 1.227, 3.403 and 9.797 mV cm−1 Oe−1 for SF, PHSF, PHSF-La and PHSF-Nd, respectively. There is approximately 46-time increase in the maximum value of magnetoelectric coupling coefficient (αME) in PHSF-Nd (9.797 mV/cm.Oe) composites as compare to pure SF (0.213 mV/cm.Oe).

Magnetocapacitance based magnetoelectric coupling behavior of multiferroic BiFeO3 nanocrystals: An empirical investigation

BiFeO3 is an attractive multiferroic ceramic for device application. The magnetoelectric coupling coefficient (αE ~ 2.2 mV/cm-Oe) of single-phase BiFeO3 ceramic is denominated here, which is calculated by theoretical method (by using the numerical value of capacitance) in place of direct measurement of voltage. An applied magnetic field raises the capacitance of the pellet of BiFeO3; analogous change in voltage gives the values of magnetoelectric coupling coefficient. Moreover, using the Ginzburg-Landau theory, the magnetoelectric interaction constant (γ) was calculated around ~ 9.3 × 10−1, which is numerically two times lower than the magnetoelectric coupling coefficient. This theoretical cum experimental study is very important in the view point of science and devices.

Structural, magnetic, magneto-dielectric and magneto-electric properties of (1-x) Ba0.85Ca0.15Ti0.90Zr0.10O3 – (x) CoFe2O4 lead-free multiferroic composites sintered at higher temperature

Here in this article synthesis of lead-free magnetoelectric composites (1-x) Ba0.85Ca0.15 Ti0.9Zr0.1)O3 - xCoFe2O3 (BCTZ-CFO, x = 0.4, 0.5, and 0.6) is reported. Structural, magnetic, dielectric, magnetodielectric and magnetoelectric properties of lead-free BCTZ-CFO composites sintered at higher sintering temperature have been systematically investigated. The piezoelectric (ferroelectric) phase has been synthesized using the sol–gel route, while Metallo-organic decomposition (MOD) route was employed to prepare piezomagnetic (ferrite) phase. The structural and microstructural properties were studied using X-Ray diffraction and Scanning electron Microscope respectively acknowledged the presence of two distinct phases as ferrite and ferroelectric in composite samples. The dense microstructure and larger average grain size were observed for samples with higher ferrite phase content. Long-range magnetic order was observed under magnetic study for all-composites. The magnetic properties enhanced for composites prepared with higher ferrite phase content. Dielectric properties were studied at room temperature and enhanced dielectric constant has been observed for samples with higher ferroelectric phase content, while minimum dielectric loss was observed for sample with 50/50 ferrite/ferroelectric phase composition. The magnetodielectric response has been also investigated for all ME composites. Leakage current characterization has been also discussed at and above the room temperature. The magneto-electric coupling response was measured of all composites. The higher value of magneto-electric coupling coefficient has been observed for 0.5BCTZ-0.5CFO composite due to maximum possible ferrite-ferroelectric hetero-structure phase contact area.

Mn0.7Zn0.3Fe2O4 + BaTiO3 composites: structural, morphological, magnetic, M–E effect and dielectric properties

Here in the present investigation, constituent phases of (1 − x)Mn0.7Zn0.3Fe2O4(MZFO) + (x)BaTiO3(BTO) (where x = 0.0, 0.25, 0.50, 0.75 and 1.0) composites have been synthesized by sol–gel auto-ignition route and the composite structure by ceramic route. The XRD analysis ensures that the composite structure consists of both cubic spinel piezomagnetic and perovskite piezoelectric phases. The average crystallite size estimated from Scherrer equation increases from 15.36 to 21.94 nm. The strain induced in individual phases has been investigated by W–H analysis and it is observed that the MZFO phase shows comprehensive type strain while BTO phase shows tensile type strain. Scanning electron micrographs confirm the microstructure of the sample with grain size ranges from 36.006 to 54 nm. Energy dispersive X-ray spectra and elemental color mappings of typical samples (x = 0.0 and 0.75) clearly indicates the phase purity and stoichiometric proportion of the composites. Fourier transform infrared spectra showed five major absorption bands related to stretching vibrations of different kinds of metal ions and oxygen ions. Increasing percentage of BTO phase in the composite reduces the saturation magnetization, remnant magnetization and coercivity. Real and imaginary parts of permittivity show maximum values at lower frequency region and decrease with increase in applied frequency. For the composition (0.25)MZFO–(0.75)BTO, composite shows maximum value of magnetoelectric coupling coefficient (αME = 20.45 mVcm−1 Oe−1). The improved magnetoelectric properties make MZFO–BTO composite applicable for electronic devices.

Influence of Pr3+ and Lu3+ co-doping on the magnetoelectric coupling response in BiFeO3 mutiferroic ceramics

Perovskite-type bismuth ferrite (BiFeO3) multiferroic material is being considered as a potential candidate for magnetoelectric coupling and field-controlled multi-state memory applications. We report the Pr3+ and Lu3+ co-doping effect on the magnetoelectric coupling in BiFeO3 ceramics. In this study, Bi0.94Pr0.06FeO3 (BPO), Bi0.94Lu0.06FeO3 (BLO), and Bi0.94Pr0.03Lu0.03FeO3 (BPLO) ceramics were synthesized by conventional solid-state ceramic synthesis technique. The BPO sample displayed higher saturation magnetization as compared to BLO and BPLO samples which may be due to canting of spin cycloid of BFO and also due to the discrepancy between the antiparallel sublattice of Fe3+/Fe2+, the value of ferroelectric polarization of the BPO sample was found to be better than BLO and BPLO samples. However, the magnetocapacitance (MC) of the BPLO sample is found to be MC ~ 2.3% which is higher than that of BLO (MC ~ 1.4%) and BPO (MC ~ 1.7%) samples. In addition, the enhanced value of magnetoelectric coupling coefficient (αE) has been obtained for the BPLO sample. Overall, our results indicate that BPLO sample displays interesting magnetoelectric response for device applications.

Magnetoelectric properties of multiferroic aurivillius type Bi7Fe3Ti3O21 ceramics

Multiferroic Bi7Fe3Ti3O21 ceramic materials having six perovskite-like layers were prepared by solid state reaction from simple oxides and sintered at 1263K. The microstructure and magnetoelectric properties were investigated. Based on dielectric measurements, the value of magnetoelectric coupling coefficient was figured. The magnetization as a function of temperature and magnetic field at selected temperatures was examined. Additionally, the hysteresis loop at 2 K was measured. The molar concentration of magnetic ions Fe3+ in the multiferroic Bi7Fe3Ti3O21 compound was also determined.

Influence of Cr3+ doping on multiferroic properties in the morphotropic phase boundary compositions of BiFeO3–PbTiO3 system

In this paper, we have investigated the effect of Cr3+ substitution on the crystal structure, microstructure, dielectric and magnetic behavior of the morphotropic phase boundary (MPB) composition of the multiferroic ceramic 0.675BiFe(1−x)CrxO3–0.325PbTiO3 (x = 0, 0.02 and 0.05). The average grain size of the specimens increased from ~ 150 nm for x = 0 to 470 nm for x = 0.05. Rietveld refinement analysis of the X-Ray powder diffraction patterns confirmed the coexistence of multiphase i.e. monoclinic Cc and tetragonal P4 mm polymorphs for all the compositions. The system exhibits weak ferromagnetism for x = 0.05. We estimated the magnetoelectric interaction constant (γ ~ 0.31) for x = 0.05 by Ginzburg–Landau theory. The value of magnetoelectric coupling coefficient ( $$\alpha_{ME}$$ ) is found to be 0.054 mV/cm-Oe, 0.073 mV/cm-Oe, 0.133 mV/cm-Oe for x = 0, 00.02 and 0.05, respectively. High temperature dielectric data also reveals that Curie temperature decreases with increasing Cr3+ concentration.

Investigation of magnetoelectric coupling effect in strongly ferroic oxide composites

The composites of (1 − x)Ba0.6Sr0.4TiO3 + (x)Ni0.5Zn0.5Fe2O4, i.e. (1 − x)BST + (x)NZF (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were synthesized using double sintering solid-state reaction method. Temperature-dependent resistivity showed systematic metal to semiconducting transition behavior for all the samples except for the pure BST. From magnetic hysteresis characterization, values of saturation magnetization, coercivity, and remanence have been obtained and found to increase with doping of NZF into BST. In our earlier reported work, x = 0.4 sample came out with excellent dielectric properties. Here, for the same sample, i.e. x = 0.4, reasonable magnetic properties were observed. Lower values of magnetoelectric coupling coefficient may be ascribed to the leakage of charges through the comparatively lower resistant ferrite grains.

Structural, Energy Storage Analysis and Enhanced Magnetoelectric Coupling in Mn Modified Multiferroic BiFeO3

The present work is focused on the structural, microstructural, dielectric, multiferroic properties, including magnetoelectric coupling and energy storage density analysis of Mn modified multiferroic BiFeO3 (BFO) samples. The samples were prepared via solid state reaction method. The structural and microstructural properties were investigated using powder x-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The single phase of Mn modified multiferroic BFO was confirmed from XRD patterns which exhibited predominantly a majority phase of BFO. SEM micrographs indicated decrease in grain size and more homogeneous grain structure with the increase of Mn content into the BFO. A nonzero value of coercivity was obtained in the 5% Mn BFO (BFMO5) sample, which confirmed the antiferromagnetic to weak ferromagnetic change. Composition dependent P versus E ferroelectric hysteresis loop measurements confirmed the enhanced ferroelectric nature of the samples. An enhanced value of energy storage density (13.71 mJ/cm3 and 34.86 mJ/cm3) was achieved for BFMO3 and BFMO5 samples. The frequency dependent and magnetic field dependent measurements of P versus E hysteresis and dielectric anomaly near the magnetic transition temperature confirmed qualitative, as well as quantitative, magnetoelectric (ME) coupling, including the maximum value of ME coupling coefficient (α ≈ 3.36584 mVcm−1 Oe−1 at a field of 2696 Oe) obtained for the BFMO5 sample. Enhanced values of dielectric and impedance parameters were observed in the Mn modified BFO samples.

Relaxation mechanism, conductivity and magnetoelectric properties of (Nd1/2Li1/2)(Fe2/3Mo1/3)O3 multiferroics

Relaxation mechanism, conductivity and magnetoelectric properties of (Nd1/2Li1/2)(Fe2/3Mo1/3)O3 multiferroic have been investigated systematically. This material was synthesized by a solid-state reaction route. Thermogravimetric analysis is enforced to perceive the percentage of weight change with rise in temperature in order to obtain the calcination temperature of the material. The preliminary structural study using X-ray diffraction data reveals the orthorhombic structure of the material. The complex plot of impedance data helped to distinguish the involvement of grain as well as grain boundary effects towards the overall electrical properties of the compound. Temperature-dependent electrical conductivity plots exhibit the presence of thermally activated conduction mechanism of the compound. The magnetic field dependence of magnetization (M–H loop) showed the presence of ferromagnetic nature of the material. The value of magnetoelectric coupling coefficient of prepared material is found to be 2.7 mV Cm−1 Oe−1.

Laminate composite magnetoelectric multiferroics optimized by global derivative-free optimization method

The magnetoelectric multiferroics where magnetism and ferroelectricity coexist in one material have recently attracted renewed interest due to its potential applications in novel functional devices. Natural multiferroic single-phase compounds are rare and an alternative approach to obtain a magnetoelectric (ME) effect is through multilayered composites of a ferroelectric and a ferromagnetic material. An applied electric field creates a piezoelectric strain in the ferroelectric, which produces a corresponding strain in the ferromagnetic material and a subsequent change in magnetization. Various efforts to improve the value of ME coupling coefficient α have been made by modifying preparation techniques of the samples, by the proper choice of materials or different structures and by choosing different thickness of the samples. In this study, we have applied numerical optimization for arriving at the solution for maximum ME coupling coefficient α of a laminar ME composite by making use of the anisotropy of the ferroelectric phase. We have used a global derivative-free optimization method based in directional direct search coupled with specific multistart strategies for setting up the optimization problem. The effective ME couping coefficients αij∼ are computed using the asymptotic homogenization method. Optimal composite microstructure with a range of the constituent ferroelectric single-crystal configurations that enhances the overall α is identified. Optimal composite would have the [001]-axis of the ferroelectric phase oriented out-of-plane of the lamina. Yet the elasticity of the composite is found to be anisotropic at the optimal orientations of the ferroelectric phase. Stress-mediated enhancement of the ME coupling is demonstrated using the analysis of the inplane elastic stiffness of the composite.

Synthesis and characterization of (100-x) Ba0.82Sr0.03Ca0.15Zr0.10Ti0.90O3 + (x) Mg0.25Cu0.25Zn0.5Mn0.05Fe1.95O4 composites with improved magnetoelectric voltage coefficient

Multiferroic composites having the nominal composition (100-x) [Ba0.82Sr0.03Ca0.15Zr0.10Ti0.90O3] (BSCZTO) + (x) [Mg0.25Cu0.25Zn0.5Mn0.05Fe1.95O4] (MCZMFO) (where x = 5, 10, 20, 40, 60, 80 and 100 wt %) were synthesized by solid state sintering method. The structural, morphological and magnetic properties of the composites were elucidated through X-ray diffractometer (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electronic Microscopy (SEM), Energy Dispersive Analysis of X-ray (EDAX) and vibrating sample magnetometer (VSM). XRD and FTIR analyses revealed that MCZMFO and BSCZTO phases coexist with cubic spinel and tetragonal perovskite structure without interacting with each other. The lattice constant of MCZMFO and BSCZTO phases in the composites increases with increase of MCZMFO phase due to increased inner stress. SEM and EDAX analyses reveal a homogeneous microstructure with uniform dispersion of MCZMFO grains and presence of Mg, Cu, Zn, Mn, Fe, O, Ba, Sr, Ca, Zr and Ti elements respectively. At low frequencies, the dielectric dispersion for x = 80 and 100 wt % composites is due to interfacial polarization emanating from the interface of the two phases. At higher frequencies, the electron hopping does not follow the fast variation of the alternating applied electric field as a consequence the dielectric constant remains constant. The electrical conductivity exhibits that the conduction mechanism is in conformity with electron hopping model. The real part of the initial permeability increases except for x = 20 wt % composites and the peak of Q-factor spreads with the MCZMFO content in the composites. Two semicircular arcs have been observed for x = 80 and 100 wt % (MCZMFO) composites which corresponds to both grain and grain boundary contribution to electrical properties. Electric modulus study reveals the satisfactory polaron hopping and the presence of negligibly small electrode effect contribution. The magnetic properties increases with increase of MCZMFO phase in the composites. The maximum magnetoelectric coupling coefficient is found to be 1.74 V cm−1Oe−1 for x = 20 wt % composites and this value is significantly larger than those reported particulate composite in literature and as well as the close proximity to the theoretical value (2.4 V cm−1Oe−1). This significant large value of magnetoelectric coupling coefficient makes BSCZTO/MCZMFO composites potential candidates for multifunctional devices applications.

Magneto-electric response in Pb substituted M-type barium-hexaferrite

Pb-substituted barium hexaferrite with chemical formula, Ba1−xPbxFe12O19 (x=0.0, 0.1, 0.2, 0.3, 0.4) were prepared by co-precipitation method and citric acid was used as the organic precipitating agent. The samples were characterized by X-ray (XRD), scanning electron microscopy (SEM), Polarization versus Electric field (P-E) loop tracers and vibrating sample magnetometer (VSM). XRD analysis confirms the single hexagonal phase formation for all the compounds and indicates that all Pb ions are situated into the lattice of barium ferrite. Images of scanning electron microscopy show that the grains are regular and well defined structures. P-E loops shows that the value of remnant polarization and saturation polarization increases up to x=0.2 and then decreases with increasing the Pb doping contents. Magnetization versus field (M-H) curves shows that the coercivity first increases and then decreases with the increase in Pb content with maximum value of coercivity (1270.38 Gauss) for x=0.2 sample. Magnetoelectric quadratic coefficient β has been measured by the dynamic magnetoelectric method at room temperature. The maximum value of magneto-electric coupling coefficient is 5.27×10−4μV/cm-Oe2 at 3500Oe for x=0.3 sample.

Improvement in magnetoelectric and other physical properties of BSZT-NZF composites by microwave sintering

A comparative study of conventional (CS) and microwave sintered (MS) magnetoelectric (ME) composites with compositional formula 0.90Ba0.9Sr0.1Zr0.04Ti0.96O3+0.10Ni0.8 Zn0.2Fe2O4 (BSZT-NZF) was done. The present report is on the achievement of comparable properties achieved by microwave sintering of the composites at an expense of less energy and time as compared to conventional sintering. The value of magnetoelectric coupling coefficient ‘α’ was found to be increased by 12.5% by microwave sintering. The value of α was 1.6 and 1.8 mV/cm-Oe for CS and MS composite sample respectively. The dielectric, ferroelectric and magnetic properties were found to be improved for MS composite sample.

The magnetoelectric coupling effect in multiferroic composites based on PZT–ferrite

In the multiferroic materials, the dielectric and magnetic properties are closely correlated through the coupling interaction between the ferroelectric and magnetic order. We attempted to determine the values of magnetoelectric coupling coefficient , from the temperature dependences of the dielectric permittivity for the ferroelectric–ferromagnetic composite PZT–ferrite type, namely PSZTC–NiZn and PBZTN–NiZn. The main component of the ferroelectric–ferromagnetic composite was PZT type powder (with ferroelectric properties), which was synthesized using sintering of a mixture of simple oxides in solid phase. The second element of the ferroelectric–ferromagnetic composite was the ferrite powder (with ferromagnetic properties). Ferrite powder was synthesized using calcination. Next, the mixed components were synthesized using sintering of the mixture of simple oxides in a solid phase (compaction by a free sintering method). The temperature dependences of the dielectric permittivity ( ε ) for the different frequencies and for both multiferroic composites were investigated. Based on dielectric measurements and theoretical considerations, the values of the magnetoelectric coupling coefficient were specified. • The magnetoelectric effect at two different ferroelectric–ferromagnetic composites based on a PZT and nickel–zinc ferrite. • Multiferroics composite incorporate both ferroelectric and magnetic phases. • The mechanism of the magnetoelectric coupling between ferroelectric and magnetic properties, in multiferroic composites, is caused by the strain. • The determination of the magnetoelectric coupling coefficient based on a theoretical model and the measurements of dielectric permittivity.

Phase transition and magneto-electric coupling of BiFeO3–YMnO3 multiferroic nanoceramics

We report the crystal structure, dielectric, magnetic, and magneto-electric properties of (1−x) BiFeO3-xYMnO3 (0.00 ≤ x ≤ 0.2) multiferroic nanoceramics prepared by auto-combustion technique. YMnO3 substitution is found to induce a structural phase transition from R3c to R3c+Pbnm after x ≈ 0.1 using Rietveld refinement technique. Field emission scanning electron micrographs show decrease in grain size with increase in YMnO3 content. The dielectric permittivity and loss tangent are found to be increased with composition x. The anomalies noticed from the temperature dependent dielectric analysis reveal the signature of magneto-electric coupling in the system. A decrease in magnetic ordering temperature as a function of composition is found from dielectric study. At room temperature, the dielectric permittivity of all the YMnO3 modified samples decrease with increasing magnetic field. The maximum value of magneto-electric coupling coefficient (ε(H)-ε(0))/ε(0) is found to be ∼ −5.5% at H = 2 T for x = 0.2. The behaviour of the magnetic hysteresis loop observed at room temperature suggests the suppression of space modulated spin structure.

Room-temperature magnetoelectric properties of Fe doped BaZr0.05Ti0.95O3

To explore the magnetoelectric effect in lead free bulk ceramics, solid solutions of BaZr0.05(FexTi1−3x/4)0.95O3 have been synthesized using conventional solid state reaction route with x = 0.000 to 0.020 in steps of 0.005. A small amount of Fe content shows an immense effect on properties of barium zirconium titanate. Room temperature X-ray diffraction studies substantiate the formation and purity of these polycrystalline samples in an orthorhombic crystal system. Temperature dependent dielectric study revealed a decrease in ferroelectric Curie temperature with a decrease in dielectric constant values as x varied from 0.000 to 0.020. Ferroelectricity is still maintained and well saturated loops are observed with Fe substitution at these levels; although the remnant polarization Pr values decrease substantially with increasing Fe content. The best value of magnetoelectric coupling coefficient (α) at room temperature is found to be 145.30 mV/cm.Oe for x = 0.015 sample. In conclusion, in a non-Pb based simple perovskite system a reasonably large magnetoelectric coupling is demonstrated.