Dielectric relaxation and magneto-dielectric effect in polycrystalline Bi0.9Ca0.1FeO2.95
TL;DR: In this paper, temperature, frequency, and magnetic field dependent dielectric properties of polycrystalline Bi0.9Ca0.1FeO2.95 were investigated.
Abstract: We have investigated temperature, frequency, and magnetic field dependent dielectric properties of polycrystalline Bi0.9Ca0.1FeO2.95. Two dielectric anomalies, near 65 K and 260 K, were observed with the anomaly near 65 K exhibiting distinct frequency dependence as the peak temperature shifts with increasing frequency. The low-temperature dielectric relaxation data that can be fitted to a Vogel-Fulcher expression yielding a characteristic relaxation time of ∼10−8 s are four orders larger than that of pure BiFeO3 which may be the resultant of the chemical pressure induced by Ca doping. We also observed a switchable magneto-dielectric response in Bi0.9Ca0.1FeO2.95 at room temperature.
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TL;DR: X-ray photoelectron spectroscopy confirms the shifting of the binding energy of the Bi 4f orbital, establishing Eu substitution at the Bi site, and calculation of the area under the Fe(2+)/Fe(3+) (2p) and O (1s) XPS spectra gives approximate values of the oxygen vacancies.
Abstract: The influence of oxygen vacancies on the dielectric relaxation behavior of pure and Eu-substituted BiFeO3 nanoparticles synthesized by a sol–gel technique has been studied using impedance spectroscopy in the temperature range of 90 °C to 180 °C. The electric relaxation time and activation energy of the oxygen vacancies can be calculated from the Arrhenius equation, and found to be 1.26 eV and 1.76 eV for pure and Eu-substituted BiFeO3, respectively. Substitution induces structural disorder and changes in the Fe–O–Fe bond angle, leading to alteration of the magnetic properties, observed from magnetic studies and evaluated using Rietveld refinement of the XRD patterns. X-ray photoelectron spectroscopy (XPS) confirms the shifting of the binding energy of the Bi 4f orbital, establishing Eu substitution at the Bi site. Calculation of the area under the Fe2+/Fe3+ (2p) and O (1s) XPS spectra gives approximate values of the oxygen vacancies.
155 citations
TL;DR: In this article, the effects of Eu and Sr codoped on the structural, morphological, magnetic and ferroelectric properties of pure BiFeO3 and Eu-Sr co-substituted BFO samples were systematically investigated.
59 citations
TL;DR: In this article, a prominent peak in the variation of dielectric constant in Ca2+ doped BiFeO3 ceramics near the antiferromagnetic to paramagnetic phase transition is reported.
42 citations
TL;DR: In this article, diffuse reflectance spectra of the polycrystalline BiFeO3, Bi0.9Ba0.05Ca0.95, and Bi 0.1FeO2.95 samples were used to demonstrate crystal-field spectroscopy, which enabled them to explore local distortion in the non-centrosymmetric FeO6 octahedron, and also to study chemical pressure effect on the band gap and d-d transition band energies.
Abstract: We have investigated diffuse reflectance spectra of the polycrystalline BiFeO3, Bi0.9Ba0.05Ca0.05FeO2.95, and Bi0.9Ca0.1FeO2.95 samples to demonstrate crystal-field spectroscopy, which enabled us to explore local distortion in the non-centrosymmetric FeO6 octahedron, and also to study chemical pressure effect on the band gap and d-d transition band energies. The energy values of band gap and d-d transition bands of the doped BiFeO3 samples were found to red-shift with the reduced unit cell volume. Absorption spectroscopic studies of the BiFeO3 samples reveal that nature of the band gap is a direct. Raman spectroscopy study also reveals that the softening/hardening of the certain Raman modes in BiFeO3 upon substitution of Ca. The chemical pressure induced changes in the band gap and d-d band energies, and the Raman modes of the Ca doped BiFeO3, which also found to enhance its magnetic and magnetoelectric properties.
32 citations
TL;DR: In this article, a single phase multiferroics BiFeO3 (BFO), Bi 0.99 Sm 0.01 FeO 3 (Sm1) and Sm 1Co1 were successively synthesized by tartaric acid assisted sol-gel method and X-ray diffraction patterns analyzed through Rietveld refinement method confirmed substitution driven structural distortion.
27 citations
References
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TL;DR: A ferroelectric crystal exhibits a stable and switchable electrical polarization that is manifested in the form of cooperative atomic displacements that arises through the quantum mechanical phenomenon of exchange.
Abstract: A ferroelectric crystal exhibits a stable and switchable electrical polarization that is manifested in the form of cooperative atomic displacements. A ferromagnetic crystal exhibits a stable and switchable magnetization that arises through the quantum mechanical phenomenon of exchange. There are very few 'multiferroic' materials that exhibit both of these properties, but the 'magnetoelectric' coupling of magnetic and electrical properties is a more general and widespread phenomenon. Although work in this area can be traced back to pioneering research in the 1950s and 1960s, there has been a recent resurgence of interest driven by long-term technological aspirations.
6,813 citations
Abstract: Recent research activities on the linear magnetoelectric (ME) effect?induction of magnetization by an electric field or of polarization by a magnetic field?are reviewed. Beginning with a brief summary of the history of the ME effect since its prediction in 1894, the paper focuses on the present revival of the effect. Two major sources for 'large' ME effects are identified. (i) In composite materials the ME effect is generated as a product property of a magnetostrictive and a piezoelectric compound. A linear ME polarization is induced by a weak ac magnetic field oscillating in the presence of a strong dc bias field. The ME effect is large if the ME coefficient coupling the magnetic and electric fields is large. Experiments on sintered granular composites and on laminated layers of the constituents as well as theories on the interaction between the constituents are described. In the vicinity of electromechanical resonances a ME voltage coefficient of up to 90?V?cm?1?Oe?1 is achieved, which exceeds the ME response of single-phase compounds by 3?5 orders of magnitude. Microwave devices, sensors, transducers and heterogeneous read/write devices are among the suggested technical implementations of the composite ME effect. (ii) In multiferroics the internal magnetic and/or electric fields are enhanced by the presence of multiple long-range ordering. The ME effect is strong enough to trigger magnetic or electrical phase transitions. ME effects in multiferroics are thus 'large' if the corresponding contribution to the free energy is large. Clamped ME switching of electrical and magnetic domains, ferroelectric reorientation induced by applied magnetic fields and induction of ferromagnetic ordering in applied electric fields were observed. Mechanisms favouring multiferroicity are summarized, and multiferroics in reduced dimensions are discussed. In addition to composites and multiferroics, novel and exotic manifestations of ME behaviour are investigated. This includes (i) optical second harmonic generation as a tool to study magnetic, electrical and ME properties in one setup and with access to domain structures; (ii) ME effects in colossal magnetoresistive manganites, superconductors and phosphates of the LiMPO4 type; (iii) the concept of the toroidal moment as manifestation of a ME dipole moment; (iv) pronounced ME effects in photonic crystals with a possibility of electromagnetic unidirectionality. The review concludes with a summary and an outlook to the future development of magnetoelectrics research.
4,315 citations
TL;DR: The discovery of ferroelectricity in a perovskite manganite, TbMnO3, where the effect of spin frustration causes sinusoidal antiferromagnetic ordering and gigantic magnetoelectric and magnetocapacitance effects are found.
Abstract: The magnetoelectric effect--the induction of magnetization by means of an electric field and induction of polarization by means of a magnetic field--was first presumed to exist by Pierre Curie, and subsequently attracted a great deal of interest in the 1960s and 1970s (refs 2-4). More recently, related studies on magnetic ferroelectrics have signalled a revival of interest in this phenomenon. From a technological point of view, the mutual control of electric and magnetic properties is an attractive possibility, but the number of candidate materials is limited and the effects are typically too small to be useful in applications. Here we report the discovery of ferroelectricity in a perovskite manganite, TbMnO3, where the effect of spin frustration causes sinusoidal antiferromagnetic ordering. The modulated magnetic structure is accompanied by a magnetoelastically induced lattice modulation, and with the emergence of a spontaneous polarization. In the magnetic ferroelectric TbMnO3, we found gigantic magnetoelectric and magnetocapacitance effects, which can be attributed to switching of the electric polarization induced by magnetic fields. Frustrated spin systems therefore provide a new area to search for magnetoelectric media.
3,769 citations
TL;DR: Novel device paradigms based on magnetoelectric coupling are discussed, the key scientific challenges in the field are outlined, and high-quality thin-film multiferroics are reviewed.
Abstract: Multiferroic materials, which show simultaneous ferroelectric and magnetic ordering, exhibit unusual physical properties — and in turn promise new device applications — as a result of the coupling between their dual order parameters. We review recent progress in the growth, characterization and understanding of thin-film multiferroics. The availability of high-quality thin-film multiferroics makes it easier to tailor their properties through epitaxial strain, atomic-level engineering of chemistry and interfacial coupling, and is a prerequisite for their incorporation into practical devices. We discuss novel device paradigms based on magnetoelectric coupling, and outline the key scientific challenges in the field.
3,472 citations
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