Ferroelectric-ferromagnetic Composites Research Articles

In-situ formation of CoFe2O4 within electrospun PVDF scaffolds to achieve a high β content and high magnetic hyperthermia ability

This study aimed to enhance the piezoelectric and ferromagnetic properties of electrospun poly (vinylidene fluoride) (PVDF) scaffold by in-situ formation of CoFe2O4 (CFO) within the fibers. To evaluate the effects of CFO on the microstructures and properties of the scaffolds, varying amounts of CFO were utilized (x = 0 to 10 wt %). The results demonstrated the successful formation of CFO at the fiber junctions (x < 2), while the agglomerates were formed within the large fibers (2 < x < 10). The in-situ formation of CFO was confirmed by the energy dispersive spectroscopy (EDS) analysis and X-ray diffraction (XRD) patterns. The highest fraction of β phase was achieved at 0.735 and 0.960 for the PVDF-CFO scaffold (x = 1) based on the XRD and Fourier-transform infrared technique (FTIR) results. The dielectric constant, magnetic properties, and piezoelectric sensitivity of the PVDF scaffold were enhanced with the in-situ formation of CFO. The highest coercivity and piezoelectric sensitivity were observed at x = 1. In-vitro analysis of the scaffolds revealed that the highest blood compatibility and antioxidant activity could be achieved through the in-situ formation of 1 wt % of CFO. Eventually, the magnetic hyperthermia ability of scaffolds was evaluated, and the PVDF-CFO scaffolds were recognized as the high potential materials for the hyperthermia treatment according to the specific absorption rate (SAR) of 25–44 W g−1 and intrinsic loss power (ILP) factor of 5–9 nH m2·kg−1. Our findings suggest that by controlling the in-situ formation of CFO within the PVDF electrospun scaffold, the cancer cell eradication process can be performed with a minimum dosage of the ferroelectric-ferromagnetic magnetic composite.

Magnetoelectric coupling and energy harvesting in 2/3Pb(Mg1/3Nb2/3)O3-1/3PbTiO3: CoFe1.97RE0.03O4 (RE = La3+ and Eu3+) composites

The ferroelectric-ferromagnetic composites are attracting attention as the new generation multifunctional device applications owing to the strong magnetoelectric coupling due to piezoelectric and magnetostrictive constituents. This study focuses on coupling between the piezoelectric 2/3Pb(Mg1/3Nb2/3)O3-1/3PbTiO3 and the rare earth (RE = La3+ and Eu3+) substituted magnetostrictive cobalt ferrite (CoFe1.97RE0.03O4) composites. The M−H loop and P-E loop measurements confirm the ferromagnetic and ferroelectric nature of the composites, respectively. The well-saturated hysteresis loop suggests the ferromagnetic nature of composites ascribed to the ferromagnetic ferrites. The P-E loop becomes broad as the ferrite concentration increases, owing to the conducting nature of the ferrite. In both sets of composites, the 80:20 composition shows the maximum αME value, which is ∼ 4.104 mV/cm-Oe for 80PMN-PT:20CFLO and ∼ 3.142 mV/cm-Oe for 80PMN-PT:20CFEO at 1 kHz. Besides, at the resonance frequency (fr) the 90:10 compositions show a higher αME, ∼3118 mV/cm-Oe at 288 kHz for 90PMN-PT:10CFLO and ∼ 2580 mV/cm-Oe at 282 kHz for 90PMN-PT:10CFEO. The energy harvesting application is demonstrated by placing the sample atop the rotating AC axial exhaust fan. The 80PMN-PT:20CFLO composite produced the highest peak-to-peak AC voltage (Vpp) of about 4.24 V. The outcomes of this study show that the studied composites can be employed effectively for energy-harvesting applications.

Structural, dielectric and electro-caloric properties of Ba(Ti,Zr)O3-(La,Sr)MnO3 composite multiferroic

Dielectric and electrocaloric (EC) properties of sol-gel synthesized BaTi0.84Zr0.16O3 (BTZ) and La0.78Sr.0.22MnO3 (LSM) composite in 80:20 molar ratio is reported. We discuss the dielectric analysis based on the electric modulus M*(=1/ϵ*) with the aim to differentiate the orientational and interfacial/carrier contribution and to explain their temperature and frequency dependence. Frequency dependence of imaginary part of M, i.e., M″(ω) of the composite exhibits a broad relaxation peak in MHz range while ϵ″(ω) graph is typical of interfacial/carrier polarization dominated: ϵ″ is as high as 7k at 20 Hz, decreases to 300 at 2 MHz measured at 25°C. M″-max shifts to higher frequencies with the increase in the temperature. The M″-peak, associated with BTZ-dipoles, is fitted using Cole-Cole (CC) equation to estimate the dielectric parameters, static and high-frequency dielectric constants ϵs and ϵꝏ respectively, relaxation time, τ, and the CC parameter, α, which is related to the distribution of relaxation time. Temperature dependence of physical parameters obtained from the fitting reflected the attributes of orientational polarization of the parent BTZ. These analyses indicate that M* is a more suitable parameter to consider for the ferroelectric-ferromagnetic composites.

Anomalous conductivity behavior induced by in situ metastable amorphous phase in BaTiO3/Ni0.5Zn0.5Fe2O4 ceramic composite

The electrical conductivity of ferroelectric-ferromagnetic ceramic composites usually increases monotonously with elevated temperature, which may seriously deteriorate their performance. In this work, we report an anomalous conductivity behavior induced by in situ metastable amorphous phase in a semi-conductive ceramic composite, 0.1BaTiO3(BTO)/0.9Ni0.5Zn0.5Fe2O4(NZFO). The ceramic composites with in situ formed amorphous BTO phase (a-BTO) or crystalline BTO phase (c-BTO) were successfully prepared. The effect of such metastable amorphous phase on the electrical transport properties of the ceramic composite was investigated. A comparative study reveals that a-BTO could act as a buffering phase preventing the electrical conductivity of the composite from monotonous increment above a critical temperature (513 K), whereas such effect does not occur when BTO is pure crystalline. Around 513 K, a change in the activation energy of dc conductivity has been observed for the c-BTO/NZFO sample. Whereas for the a-BTO/NZFO sample, the Arrhenius relation fails to describe its behavior above 513 K owing to decreased conductivity, which is rarely seen in semiconductors. The activation energy of relaxation is identical for both systems, i.e. 0.204 eV, because their dielectric relaxation is dominated by crystalline NZFO phase. The findings of this work are inspiring for the design of novel electronic materials constituted by a crystalline phase and an amorphous phase with adjustable performance.

Enhanced magnetodielectric coupling in strongly ferroic composite oxide film

Lead-free all oxide composite thin films comprising ferromagnetic (FM) and ferroelectric (FE) phases are observed as promising candidates for multifunctional device applications. A series of composites having systematic replacement of FM La0.67Sr0.33MnO3 (LSMO) by FE-Na0.5K0.5NbO3 (NKN), all oxide composite thin films were optimally grown by pulsed laser deposition. While x-ray diffraction confirmed a systematic phase change from a rhombohedral to an orthorhombic structure, almost monodispersed grain size distribution and smooth surface topography were revealed by atomic force microscopy. Two-probe dielectric spectroscopy indicated a pronounced enhancement of real permittivity for 0.4 sample as compared to the pure FM and FE parent compounds. Similarly, an enhancement in the magnetodielectric permittivity revealed high values for intermediate composites. The enhancement in the dielectric and magnetoelectric coupling is suggested to be due to the magnetostriction effect in FM (LSMO), which induces stress that is in turn transferred to the FE (NKN) phase, leading to strong FM–FE coupling. X-ray photoelectron spectroscopy reveals the presence of Mn in +3 and +4 states in the FE–FM composites. The presence of these mixed valence states can be ascribed to the magnetic properties within the composites.

Structural Analysis and Magnetoelectric Sensing in Cobalt Ferrite–BaTiO3 Composites

The fabrication of ferromagnetic–ferroelectric composites is of pronounced importance in science and technology. The efficiency with which magnetostrictive and piezoelectric strain gets transferred among each other decides the extent of coupling between polarization and magnetization. In this study, the solid-state reaction method was used to synthesize CFO-BT composites. X- ray diffraction patterns of CFO-BT composites revealed phase purity of constituent phases, i.e., spinel and tetragonal structures for CFO and BT, respectively. The enhancement in electrical polarization was observed in the CFO-BT composite compared with CFO. The electrical coercivity improved radically from 9 to 5 kV/cm, confirming the larger grain size and its correlation with domains switching. The magnetoelectric coupling was achieved in CFO-40%BT composite by studying the change in polarization with magnetic field which revealed a remarkable change in the maximum polarization from 3.5 to 0.5 μC/cm2 when the applied field changed from 0 to 5000 Gauss.

Ferromagnetism in the multiferroic alloy systems BiFeO3-BaTiO3 and BiFeO3-SrTiO3: Intrinsic or extrinsic?

Among the different bulk alloys of the room temperature multiferroic compound BiFeO3, alloying with ATiO3 (A = Ba, Sr, Pb) is interesting as they have been reported to induce ferromagnetism under certain conditions. While this makes them interesting as potential multiferroic magnetoelectric materials, there is a lack of clarity on the origin of ferromagnetism in these systems. We have performed a detailed magneto-structural analysis on two alloys, namely, BiFeO3-BaTiO3 and BiFeO3-SrTiO3, and found the systems' propensity for the formation of ferrimagnetic hexaferrite (BaFe12O19 and SrFe12O19) phases. Though insignificantly small to the extent of being undetectable by x-ray powder diffraction, we prove that the ferromagnetic character of the specimen is entirely due to spontaneous precipitation of the hexaferrite grains. While our results suggest that care should be exercised before attributing ferromagnetism in such alloy systems as intrinsic to the perovskite phase, the propensity for the spontaneous precipitation of the hexaferrite phase in these multiferroic alloy systems is encouraging as it provides an opportunity for designing self-grown ferroelectric-ferromagnetic composites with good magnetoelectric coupling.

Low-firing behavior, microstructure, and electromagnetic properties of a ferroelectric-ferromagnetic composite material with multiple doping

A series of BaTiO3-Ni0.62Cu0.25Zn0.16Fe1.98O4 ferroelectric-ferromagnetic composites with Li2CO3-V2O5-Bi2O3 multiple doping were prepared by the solid-state reaction at 900 °C–1000 °C, and the low fired (<961 °C) samples can adapt to the low temperature cofired ceramic (LTCC) technology. The relative density of all sintered composites was higher than 96%, and particularly for the low fired composites, it was in the range of 97.1%–99.5%. The variation of magnetic properties with BaTiO3 content was investigated combining with microstructure and two types of magnetization (demagnetization) processes. A novel method for calculating the microstructure parameter δ∗/D of the multiple doping composite systems has been deduced so that the magnetic circuit model can be used to predict the magnetic properties of the composites, and the experimental results matched well with the fitting curve. The dielectric behavior of the composites has been investigated in non-dispersive region (106∼108 Hz) and dielectric dispersion region (108∼1010Hz). Through combing grain size effect and phase transition, the influence of sintering temperature and BaTiO3 content on permittivity ε′ and dielectric dispersion of the composites have been discussed. In the non-dispersive region, the maximum ε′ of composites (256.07) was obtained in the sample with 90 wt% BaTiO3 (sintered at 950 °C). In the dispersion region, among all composites, both the maximum relaxation frequency 1.24 GHz and maximum resonance frequency 1.16 GHz were obtained in low fired samples.

Microstructure and Properties of the Ferroelectric-Ferromagnetic PLZT-Ferrite Composites

The paper presents the technology of ferroelectric-ferromagnetic ceramic composites obtained from PLZT powder (the chemical formula Pb0.98La0.02(Zr0.90Ti0.10)0.995O3) and ferrite powder (Ni0.64Zn0.36Fe2O4), as well as the results of X-ray powder-diffraction data (XRD) measurement, microstructure, dielectric, ferroelectric, and magnetic properties of the composite samples. The ferroelectric-ferromagnetic composite (P-F) was obtained by mixing and the synthesis of 90% of PLZT and 10% of ferrite powders. The XRD test of the P-F composite shows a two-phase structure derived from the PLZT component (strong peaks) and the ferrite component (weak peaks). The symmetry of PLZT was identified as a rhombohedral ferroelectric phase, while the ferrite was identified as a spinel structure. Scanning electron microscope (SEM) microstructure analysis of the P-F ceramic composites showed that fine grains of the PLZT component surrounded large ferrite grains. At room temperature P-F composites exhibit both ferroelectric and ferromagnetic properties. The P-F composite samples have lower values of the maximum dielectric permittivity at the Curie temperature and a higher dielectric loss compared to the PLZT ceramics, however, the exhibit overall good multiferroic properties.

Magnetic enhancement of ferroelectric polarization in a self-grown ferroelectric-ferromagnetic composite

Ferroelectric-ferromagnetic multiferroic composites are of great interest both from the scientific and technological standpoints. The extent of coupling between polarization and magnetization in such two-phase systems depends on how efficiently the magnetostrictive and electrostrictive/piezoelectric strain gets transferred from one phase to the other. This challenge is most profound in the easy to make 0-3 ferroelectric-ferromagnetic particulate composites. Here we report a self-grown ferroelectric-ferromagnetic 0-3 particulate composite through controlled spontaneous precipitation of ferrimagnetic barium hexaferrite phase ($\mathrm{BaF}{\mathrm{e}}_{12}{\mathrm{O}}_{19}$) amid ferroelectric grains in the multiferroic alloy system $\mathrm{BiFe}{\mathrm{O}}_{3}\ensuremath{-}\mathrm{BaTi}{\mathrm{O}}_{3}$. We demonstrate that a composite specimen exhibiting merely \ensuremath{\sim}1% hexaferrite phase exhibits \ensuremath{\sim}34% increase in saturation polarization in a dc magnetic field of \ensuremath{\sim}10 kOe. Using modified Rayleigh analysis of the polarization field loop in the subcoercive field region we argue that the substantial enhancement in the ferroelectric switching is associated with the reduction in the barrier heights of the pinning centers of the ferroelectric-ferroelastic domain walls in the stress field generated by magnetostriction in the hexaferrite grains when the magnetic field is turned on. Our study proves that controlled precipitation of the magnetic phase is a good strategy for synthesis of 0-3 ferroelectric-ferromagnetic particulate multiferroic composite as it not only helps in ensuring a good electrical insulating character of the composite, enabling it to sustain high enough electric field for ferroelectric switching, but also the factors associated with the spontaneity of the precipitation process ensure efficient transfer of the magnetostrictive strain/stress to the surrounding ferroelectric matrix making domain wall motion easy.

Multiferroic properties of ferromagnetic and ferroelectric coupled Mn-Zn ferrite-BaTiO3 composite

ABSTRACTThe magneto-dielectric properties can be tuned through ferromagnetic–ferroelectric composites with different Mn0.9Zn0.1FeO4 to BaTiO3 ratio. The two phenomena can couple and interact with each other when they exist simultaneously due to induced electric polarization in the magnetic order. The composites were synthesized using the nanoparticles of Mn0.9Zn0.1Fe2O4 and BaTiO3 with different composition by sintering at 1000°C. The X-ray diffraction confirms the coexistence of ferromagnetic and ferroelectric phases. The surface micrographs show variations in the porosity along with two types of inter grain connectivity. The magnetic and ferroelectric hysteresis loops confirm the magneto-electric coupling presents in the composites.

Voltage-Impulse-Induced Nonvolatile Control of Inductance in Tunable Magnetoelectric Inductors

Tunable inductors are important for $i\phantom{\rule{0}{0ex}}n$ $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ performance optimization of electronics. Compared to traditional components, voltage-controlled magnetoelectric inductors based on ferromagnetic-ferroelectric composites are efficient and highly integrated. Previous efforts have exploited the linear piezoelectric effect, a volatile behavior, but here the authors use the large residual strain induced by ferroelastic domain switching to realize a $n\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}v\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}e$ inductor with 250% tunability. This work expands the horizons of multiferroic devices, power electronics, and rf/microwave systems, for academia and industry.

Cold pressing of ferroelectric-ferromagnetic layered composites for nonlinear forming lines of high-voltage impulse generators

Cold pressing of ferroelectric-ferromagnetic layered composites for nonlinear forming lines of high-voltage impulse generators

Tunable Electromagnetic and Microwave Absorption Properties of Ba3Co2Fe24O41/P(VDF-TrFE) Composites

The electromagnetic and microwave absorption properties of polymer-based Ba3Co2Fe24O41/P(VDF-TrFE) composites were investigated. The effective complex permeability and permittivity of the two-phase composites can be manipulated by either varying the Ba3Co2Fe24O41 content or applying the dc magnetic field ( H dc). The composite containing 90 wt% Co2Z obtains a maximum reflection loss (RL) due to a proper impedance match and relatively high magnetic loss. In addition, it is found that the position of RL peak was tuned from 5.5 to 7 GHz with H dc up to 50 mT, whereas the intensity obtains a remarkable enhancement of 67% at 15 mT. These results reveal great potential for the applications of ferroelectric–ferromagnetic composites with tunable microwave absorption.

Technology and dielectric properties of the PLZT-NZF composites

ABSTRACTThe aims of the study were to design and obtain ferroelectric-ferromagnetic ceramic composites based on ferrite powder and PLZT powder. The synthesis of the composition of the PLZT material of chemical formula Pb0.98La0.02(Zr0.90Ti0.10)0.995O3 was carried out by conventional technology. The composite constituted 90% of PLZT powder and 10% of ferrite powder (Ni0.64Zn0.36Fe2O4).The article presents the technology and the results of a XRD measurement, a microstructure and the dielectric properties of the composite samples. This type of multiferroic materials and ferroelectric-ferrimagnetic composites can be used to develop a new class of transducers/sensors integrating electro-magnetic interaction in a single device.

Internal friction phenomena in composites based on PZT-type ferroelectric powder and ferrites

The aim of the work was to determine the phenomena of internal friction (mechanical losses) occurring in ferroelectric-ferromagnetic composites created based on PZT-type ferroelectric powder and ferrite. The composites were obtained using ceramic powders – multi-component PZT-type solid solutions with ferroelectric properties. Their magnetic component included zinc-nickel powder Ni0.64Zn0.36Fe2O4. 30 × 10 × 1 mm3 test specimens were obtained using free sintering. Temperature Q -1(T) and amplitude Q -1(ε) internal friction dependencies were determined. Wide high temperature maxima were observed with regard to the internal friction temperature dependencies obtained for the tested specimens. The conducted measurements of amplitude (isothermal) dependencies of internal friction Q -1(ε) for the tested composites have allowed for interpreting the previously observed maximum on the temperature dependencies of internal friction.

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.

Ferroelectric–Ferromagnetic Ceramic Composites Based on PZT with Added Ferrite

The study presents a ferroelectric–ferromagnetic composite based on a doped PZT‐type and ferrite powders. Ferroelectric powder (in amount of 90 wt‐%) was based on multicomponent PZT‐type materials, while nickel–zinc ferrite Ni1–xZnxFe2O4 (in amount of 10 wt‐%) served as the magnetic component of the composite. The syntheses of the ferroelectric–ferromagnetic composite's components were performed using solid‐phase sintering, while final densification of the synthesized powder was achieved using free sintering. X‐ray analysis of the composite confirmed the presence of strong maxima originating from particular PZT‐type material phases, as well as weak peaks from the Ni0.64Zn0.36Fe2O4 ferrite, without foreign phases. The microstructure of the fracture of the ferroelectric–ferromagnetic composites shows that the ferrite grains on the surface of the ferroelectric component are distributed heterogeneously. Magnetic studies have characterized composite as a soft ferromagnetic material. The study indicated the influence of the magnetic subsystem on the electrical properties. In the two‐phase PBZTMC–NZF ceramic composite, the magnetic component causes the decrease in electric permittivity and increased value of the dielectric losses.

Controlled self-assembly of multiferroic core-shell nanoparticles exhibiting strong magneto-electric effects

Ferromagnetic-ferroelectric composites show strain mediated coupling between the magnetic and electric sub-systems due to magnetostriction and piezoelectric effects associated with the ferroic phases. We have synthesized core-shell multiferroic nano-composites by functionalizing 10–100 nm barium titanate and nickel ferrite nanoparticles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst. The core-shell structure was confirmed by electron microscopy and magnetic force microscopy. Evidence for strong strain mediated magneto-electric coupling was obtained by static magnetic field induced variations in the permittivity over 16–18 GHz and polarization and by electric field induced by low-frequency ac magnetic fields.

Ferroelectric–Ferromagnetic Composites Based on PZT Type Powder and Ferrite Powder

Abstract A ferroelectric-ferromagnetic composites based on PZT powder have been obtained in presented work. The main aim of combination of ferroelectric and magnetic powders was to obtain material showing both electric and magnetic properties. Ferroelectric ceramic powder (in amount of 90%) was based on the doped PZT type solid solution while magnetic component of the composite was nickel-zinc ferrite Ni1-x ZnxFe2O4 (in amount of 10%). The synthesis of components of ferroelectric-ferromagnetic composite was performed using the solid phase sintering. Final densification of synthesized powder has been done using free sintering. For obtained of ferroelectric-ferromagnetic composites the XRD, the microstructure, EDS, dielectric, magnetic, internal friction and electrical hysteresis loop investigations were performed. Obtained results shown the correlations between the magnetic subsystem and the electrical subsystem of the ferroelectric-ferromagnetic composites. Such properties of obtained composites give the possibility to use them in memory applications of new type.