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Journal ArticleDOI

Enhanced magnetoelectric properties of BiFeO3 on formation of BiFeO3/SrFe12O19 nanocomposites

17 Jun 2016-Journal of Applied Physics (AIP Publishing)-Vol. 119, Iss: 23, pp 234102
TL;DR: The presence of pure phases of both BiFeO3 (BFO) and SrFe12O19 (SRF) in Nanocomposites for x = 0.3 and 0.4 has been confirmed by Rietveld analysis of XRD data as mentioned in this paper.
Abstract: Nanocomposites (NCs) comprising (1−x) BiFeO3 (BFO) and x SrFe12O19 (SRF) (x = 0.1, 0.2, 0.3, and 0.4) have been prepared by a sol-gel route. Presence of pure phases of both BiFeO3 (BFO) and SrFe12O19 (SRF) in the NCs for x = 0.3 and 0.4 has been confirmed by Rietveld analysis of XRD data though a minor impurity phase is observed in the case of x = 0.1 and 0.2 NCs. Transmission electron micrographs of the NCs show that particles are mostly spherical with average size of 30 nm. M-H measurements at 300 and 10 K indicate predominantly ferrimagnetic behavior of all the NCs with an increasing trend of saturation magnetization values with increasing content of SRF. Dielectric constant (er) of the NCs at room temperature shows a dispersive behavior with frequency and attains a constant value at higher frequency. er − T measurements reveal an increasing trend of dielectric constant of the NCs with increasing temperature and show an anomaly around the antiferromagnetic transition temperature of BFO, which indicates...
Citations
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Journal ArticleDOI
TL;DR: In this paper, the authors synthesize Nanocomposites (NCs) comprising BiFeO 3 (BFO) and CoFe 2 O 4 (CFO) with nominal composition.
Abstract: Nanocomposites (NCs) comprising BiFeO 3 (BFO) and CoFe 2 O 4 (CFO) with nominal composition, x CoFe 2 O 4 - (1- x ) BiFeO 3 ( x = 0.2, 0.3 and 0.4) have been synthesized adopting a sol-gel route. XRD patterns of the prepared samples exhibit presence of both BFO and CFO crystalline phases. TEM images of the NCs show that particles are mostly spherical with size in the range 15–25 nm. Room temperature Mossbauer spectra of the pristine samples and NCs reveal presence of Fe 3+ ions at different inequivalent sites of BFO and CFO. Room temperature dc magnetization measurements show significant enhancement in magnetization of the NCs compared to that of the pristine BFO. Variation of dielectric constant of the NCs with frequency shows a dispersive behavior in low frequency region which is attributed to grain boundary relaxation in the NCs. e r – T curves of all samples exhibit an anomaly near the antiferromagnetic transition temperature of BFO indicating presence of magnetoelectric (ME) coupling. Variation of capacitance of the NCs in presence of external magnetic field confirms an improvement of ME coupling in BFO after formation of the NCs.

40 citations

Journal ArticleDOI
TL;DR: In this paper, M-type bismuth doped strontium hexaferrite was prepared by the sol-gel auto-combustion method and studied for magnetoelectricity.
Abstract: M-type bismuth doped strontium hexaferrite Sr1 − xBixFe12O19 (x = 0, 0.01, and 0.02) is prepared by the sol-gel auto-combustion method and studied for magnetoelectricity. The lattice of the x = 0.01 sample is found to be highly strained compared to the other two compositions. The enhancement of strain is also accompanied by an increase in magnetization by 6%. Impedance and modulus spectroscopy studies suggest a transition in relaxation mechanism from grain dominated (below 150 K) to grain boundary dominated (above 150 K). The grain related capacitance for x = 0.01 is found to be ∼50 nF, and this value is ∼10 times higher than the other two samples. The linear magnetoelectric coefficient α d (in mV c m − 1 O e − 1) for the parent x = 0 sample is found to be 0.33 at 125 K, and this value decreases gradually to 0.27 at 300 K. The x = 0.01 sample displayed the highest (even 10% higher than the x = 0 sample) value of α d at low temperature. Unfortunately, the increased value of α d is also accompanied by a drastic reduction in its magnitude for temperatures higher than 200 K, due to the increased electrical conduction which in x = 0.01 is ∼94% higher than the parent.

16 citations

Journal ArticleDOI
TL;DR: In this paper, the magnetodielectric properties of multiferroic composites were evaluated using powders of BiFeO3 and SrFe12O19 that were mixed, pressed at 800 MPa, and sintered at 700 °C for 4h.
Abstract: Multiferroic composites xBiFeO3:(1-x) SrFe12O19 (0.5 ≤ x ≤ 1, Δx = 0.1) were produced by mixing powders of BiFeO3 and SrFe12O19 obtained by high energy ball milling assisted with heat treatment. To study their multiferroic properties, the ferromagnetic, dielectric and magnetodielectric behavior was evaluated for each composite. The composites were produced using powders of BiFeO3 and SrFe12O19 that were mixed, pressed at 800 MPa, and sintered at 700 °C for 4 h. XRD analysis confirms the presence of both ferroic phases, BiFeO3 and SrFe12O19, and small amounts of the secondary phase, Bi2Fe4O9 (mullite). The quantity of this secondary phase increases with the concentration of strontium hexaferrite. The remanent magnetization values are 17.9 emu/g and 2.54 emu/g for x = 0.5 and x = 0.9, respectively. The coercive field does not change with the composition; it exhibits a nearly constant value of 5.5 kOe for all the samples containing strontium hexaferrite. The addition of strontium hexaferrite produces diminution of the relative permittivity (ξr) and dielectric losses (tan δ). At 5 MHz, the composite with x = 0.9 shows the highest relative permittivity (16.78), and a diminution of dielectric loses of 43.88% due to the higher resistivity of the strontium hexaferrite. The magnetodielectric measurements showed an increase in the relative permittivity of the composites due to a reduction of the resistivity in agreement with the Maxwell-Wagner behavior when a magnetic field was applied. This study show evidence for magnetoresistive behavior by pure bismuth ferrite at room temperature, which has not been previously reported.

6 citations

Journal ArticleDOI
TL;DR: In this paper, the structural, microstructural, and broadband dielectric and magnetic properties of double perovskite oxides were investigated, and the properties of the compound were correlated qualitatively to the multiple valence state of the cobalt ions.
Abstract: In this work, we investigate the structural, microstructural, and broadband dielectric and magnetic properties of Sr3YCo4–xAlxO10+δ (x = 0, 0.1, 0.3, 0.5, and 1.0; δ ≤ 1) double perovskite oxides in detail. The compounds were synthesized through solid-state reaction, and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The broadband dielectric and magnetic properties of the compounds were correlated qualitatively to the multiple valence state of the cobalt ions. The real part of permittivity was found to decrease with increase in Al3+ concentration from 117.3 (x = 0) to 37 (x = 1.0) (at 900 MHz), while the dielectric loss increased from 0.36 to 1.51. The real part of permeability decreased from 1.01 for x = 0 to 0.93 for x = 1.0 (at 900 MHz) accompanied by a decrease in the magnetic loss factor from 0.43 to 0.11. The broadband electromagnetic response was found to be in good agreement with the results obtained from XPS analysis. Impedance analysis revealed that the compounds exhibit a capacitive behavior, which can be attributed to the interfacial polarization due to the pore–grain interfaces. Further, room-temperature magnetic measurements revealed that the ferromagnetic nature of the parent compound diminished with the substitution of aluminum ions as a result of the reduction in oxygen vacancy ordering, which was also evident from FTIR analysis.

2 citations

References
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Journal ArticleDOI
15 Jul 2005-Science
TL;DR: Magnetoelectric multiferroics combine ferromagnetic magnetization and ferroelectricity in the same phase and have tremendous potential for applications, not only because they possess the properties of both parent phenomena, but also because coupling between ferromagnetism and electric polarization can lead to additional novel effects as discussed by the authors.
Abstract: Magnetoelectric multiferroics combine ferromagnetism (a spontaneous magnetization that can be switched by a magnetic field) and ferroelectricity (a spontaneous electric polarization that can be switched by an electric field) in the same phase They have tremendous potential for applications, not only because they possess the properties of both parent phenomena, but also because coupling between ferromagnetism and ferroelectricity can lead to additional novel effects In their Perspective, Spaldin and Fiebig discuss the factors behind the recent resurgence of interest in magnetoelectric multiferroics, describe some exciting results emerging from the current research activities, and point to important challenges and directions for future work

2,523 citations

Journal ArticleDOI
TL;DR: In this article, the authors highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system and summarize various strategies used to combine the two types of order.
Abstract: Multiferroics, defined for those multifunctional materials in which two or more kinds of fundamental ferroicities coexist, have become one of the hottest topics of condensed matter physics and materials science in recent years. The coexistence of several order parameters in multiferroics brings out novel physical phenomena and offers possibilities for new device functions. The revival of research activities on multiferroics is evidenced by some novel discoveries and concepts, both experimentally and theoretically. In this review, we outline some of the progressive milestones in this stimulating field, especially for those single-phase multiferroics where magnetism and ferroelectricity coexist. First, we highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system. Subsequently, we summarize various strategies used to combine the two types of order. Special attention is paid to three novel mechanisms for multiferroicity generation: (1) the ferroelectricity induced by the spin orders such as spiral and E-phase antiferromagnetic spin orders, which break the spatial inversion symmetry; (2) the ferroelectricity originating from the charge-ordered states; and (3) the ferrotoroidic system. Then, we address the elementary excitations such as electromagnons, and the application potentials of multiferroics. Finally, open questions and future research opportunities are proposed.

1,243 citations

Journal ArticleDOI
TL;DR: In this article, the authors highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system, and summarize various strategies used to combine the two types of orders.
Abstract: Multiferroics, defined for those multifunctional materials in which two or more kinds of fundamental ferroicities coexist, have become one of the hottest topics of condensed matter physics and materials science in recent years. The coexistence of several order parameters in multiferroics brings out novel physical phenomena and offers possibilities for new device functions. The revival of research activities on multiferroics is evidenced by some novel discoveries and concepts, both experimentally and theoretically. In this review article, we outline some of the progressive milestones in this stimulating field, specially for those single phase multiferroics where magnetism and ferroelectricity coexist. Firstly, we will highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system. Subsequently, we will summarize various strategies used to combine the two types of orders. Special attentions to three novel mechanisms for multiferroicity generation: (1) the ferroelectricity induced by the spin orders such as spiral and E-phase antiferromagnetic spin orders, which break the spatial inversion symmetry, (2) the ferroelectricity originating from the charge ordered states, and (3) the ferrotoroidic system, will be paid. Then, we will address the elementary excitations such as electromagnons, and application potentials of multiferroics. Finally, open questions and opportunities will be prospected.

1,088 citations

Journal ArticleDOI
TL;DR: In this article, X-ray diffraction showed that Bi1−xBaxFeO3 was single phase up to x=0.25 and exhibited magnetism and ferroelectricity simultaneously at room temperature.
Abstract: Ba doped BiFeO3 compounds were prepared by a solid-state reaction. X-ray diffraction showed that Bi1−xBaxFeO3 was single phase up to x=0.25. These samples exhibited magnetism and ferroelectricity simultaneously at room temperature. The magnetoelectric coupling was evidenced by the increase of the dielectric constant with the increase of the applied magnetic field. For Bi0.75Ba0.25FeO3 with ΔH=8kOe, the values of [er(H)−er(0)]∕er(0) are 1.7% and 1% for 80 and 300K, respectively.

372 citations

Journal ArticleDOI
TL;DR: Magnetoelectric compounds with the general formula have been synthesized as mentioned in this paper, which show the coexistence of ferroelectricity and magnetism, possess high dielectric constant and exhibit magnetoelectrous coupling at room temperature.
Abstract: Magnetoelectric compounds with the general formula, ${\mathrm{Bi}}_{09\ensuremath{-}x}{R}_{x}{\mathrm{La}}_{01}{\mathrm{FeO}}_{3}$ $(R=\mathrm{Gd},$ Tb, Dy, etc), have been synthesized These show the coexistence of ferroelectricity and magnetism, possess high dielectric constant and exhibit magnetoelectric coupling at room temperature Such materials may be of great significance in basic as well as applied research

367 citations