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Journal ArticleDOI

Vibrational, magnetic, and dielectric behavior of La-substituted BiFeO3-PbTiO3

30 Dec 2011-Journal of Applied Physics (American Institute of Physics)-Vol. 110, Iss: 12, pp 123529
TL;DR: In this article, the magnetic and ferroelectric ordering in La-substituted (Bi1−xLax) 0.5Pb0.5O3 was investigated using Raman, magnetization, and polarization measurements as a function of temperature.
Abstract: Phonons and magnetic and ferroelectric ordering in La-substituted (Bi1−xLax)0.5Pb0.5Fe0.5Ti0.5O3 for samples with 0.0 ≤ x ≤ 0.5 are investigated using Raman, magnetization, and polarization measurements as a function of temperature. The system is tetragonal for pure Bi0.5Pb0.5Fe0.5Ti0.5O3 with a large c/a ratio. The anisotropy is reduced when Bi is partially replaced by La (0 ≤ x ≤ 0.5), and it turns cubic for x ≥ 0.4. All the properties are found to change significantly with changes in the c/a ratio. Evidence of spin-glass-like magnetic ordering at low temperature is found in the case of x = 0.2. A mechanism for the systematic change of magnetic ordering temperature as a function of doping is also discussed. The phonon frequencies and line widths exhibit discontinuous changes across the tetragonal-cubic transition. Large polarization and forbidden Raman scattering in the cubic phase are explained on the basis of symmetry breaking due to the formation of a polar nano region, which leads to relaxor behavior.
Citations
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Journal ArticleDOI
TL;DR: In this article, the authors presented the impedance spectroscopy of ternary solid solutions of BiFeO3, TbFeO 3, and PbTiO3 by solid-state reaction method.
Abstract: In this paper we present the impedance spectroscopy of ternary solid solutions of BiFeO3, TbFeO3 and PbTiO3, prepared by solid-state reaction method. The preliminary structural studies were carried out by x-ray diffraction technique, showing the formation of polycrystalline sample with ABO3 type of perovskite structure with hexagonal symmetry for Bi0.8Tb0.1Pb0.1Fe0.9Ti0.1O3system at room temperature. Dielectric and impedance study of this ceramic has been characterized in the temperature range 175 - 325 0C and frequency range 100 Hz - 1 MHz. The maximum ferroelectric transition temperature (Tc) of this system was in the range 210 - 225 0C with the dielectric constant having maximum value ~2480 at 1 kHz. The complex impedance graph exhibited one impedance semicircle arc at all reported temperatures, which indicates that the impedance response is a Cole-Cole type relaxation. Single semicircle indicate that the grain effect of the bulk in ceramic. The bulk resistance of the material decreases with increasing temperature showing negative temperature showing a typical semiconducting property, i.e. negative temperature coefficient of resistance (NTCR) behavior.

133 citations

Journal ArticleDOI
TL;DR: In this article, structural phase analysis by XRD suggested that pure bismuth ferrite stabilized in rhombohedral crystal symmetry (space group R3c ) and orthorhombic (Pbnm ) phase fraction was observed in co-substituted samples which increase with the increase in substitution percentage.

109 citations

Journal ArticleDOI
TL;DR: In this article, polycrystalline BiFeO3 and rare earth substituted Bi0.9R0.1FeO 3 (BRFO, R=Y, Ho and Er) compounds were prepared by rapid solid state sintering technique.

102 citations


Cites background from "Vibrational, magnetic, and dielectr..."

  • ...An appearance of weak ferromagnetism in BRFO is accounted due to the enhancement of Dzyaloshinskii–Moriya (DM) interactions [30]....

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Journal ArticleDOI
TL;DR: In this article, a series of lead-free perovskite solid solutions of Na0.5Bi 0.5TiO3 (NBT)-x BaSnO3(BSN) for 0.15 have been synthesized using a high-temperature solid-state reaction route.
Abstract: A series of lead-free perovskite solid solutions of (1 − x) Na0.5Bi0.5TiO3(NBT)—x BaSnO3(BSN), for 0.0 ≤ x ≤ 0.15 have been synthesized using a high-temperature solid-state reaction route. The phase transition behaviors are studied using dielectric and Raman spectroscopic techniques. The ferroelectric to relaxor phase transition temperature (TFR) and the temperature corresponding to maximum dielectric permittivity (Tm) are estimated from the temperature-dependent dielectric data. Dielectric studies show diffuse phase transition around ~335°C in pure NBT and this transition temperature decreases with increase in x. The disappearance of x-dependence of A1 mode frequency at ~134 cm−1 for x ≥ 0.1 is consistent with rhombohedral-orthorhombic transition. In situ temperature dependence Raman spectroscopic studies show disappearance and discontinuous changes in the phonon mode frequencies across rhombohedral (x < 0.1)/orthorhombic (x ≥ 0.1) to tetragonal transition.

65 citations

Journal ArticleDOI
TL;DR: The magnetoelectric composites of spinel ferrite Ni0.75Zn0.25Fe2O4 and BiFeO3 (BFO) have been prepared via hybrid processing route and significant enhancements have been observed in physical observables such as grain size, dielectric constant, magnetization and polarization in ferroelectric hysteresis loops.
Abstract: The magnetoelectric composites of spinel ferrite Ni0.75Zn0.25Fe2O4 (NZF) and BiFeO3 (BFO) with general formula xNi0.75Zn0.25Fe2O4 + (1 − x)BiFeO3 (x = 0, 0.10, 0.20, and 0.30) have been prepared via hybrid processing route. Subsequently, the effects of addition of NZF on structural, dielectric, magnetic, magnetoelectric, and optical properties of BFO have been investigated, and significant enhancements have been observed in physical observables such as grain size, dielectric constant, magnetization, and polarization in ferroelectric hysteresis loops. The variation of magnetization with temperature indicates the presence of spin glass behavior along with the ferromagnetic component. The magnetoelectric coupling is found with a value of magnetocapacitance to be 4.6 % for 30 mol% addition of NZF. The optical properties of the composites are also studied using UV–Vis diffuse reflectance spectroscopy, Photoluminescence spectroscopy, and FTIR spectroscopy.

54 citations


Cites background from "Vibrational, magnetic, and dielectr..."

  • ...The temperature at which this effect is shown is known as irreversible temperature (Tirr), and this is where the irreversible magnetization (Mirr = MFC–MZFC) becomes non zero [49]....

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References
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Journal ArticleDOI
TL;DR: In this article, the most characteristic properties of spin glass systems are described, and related phenomena in other glassy systems (dielectric and orientational glasses) are mentioned, and a review summarizes recent developments in the theory of spin glasses, as well as pertinent experimental data.
Abstract: This review summarizes recent developments in the theory of spin glasses, as well as pertinent experimental data. The most characteristic properties of spin glass systems are described, and related phenomena in other glassy systems (dielectric and orientational glasses) are mentioned. The Edwards-Anderson model of spin glasses and its treatment within the replica method and mean-field theory are outlined, and concepts such as "frustration," "broken replica symmetry," "broken ergodicity," etc., are discussed. The dynamic approach to describing the spin glass transition is emphasized. Monte Carlo simulations of spin glasses and the insight gained by them are described. Other topics discussed include site-disorder models, phenomenological theories for the frozen phase and its excitations, phase diagrams in which spin glass order and ferromagnetism or antiferromagnetism compete, the Ne\'el model of superparamagnetism and related approaches, and possible connections between spin glasses and other topics in the theory of disordered condensed-matter systems.

3,926 citations

Journal ArticleDOI
TL;DR: In this paper, a ferroelastic monodomain single crystal of BiFeO3 at space group R3c is described as a rhombohedrally distorted simple cubic perovskite cell.
Abstract: A ferroelec. and ferroelastic monodomain single crystal of BiFeO3 at space group R3c is rhombohedral, with a 5.57874(16), c 13.8688(3) .ANG.; arh 5.6343 .ANG., arh 59.348 Deg; d. (calcd.) = 8.337 for Z = 6. Final R = 2.4, Rw = 1.9% for 422 reflections. The structure can be described as a rhombohedrally distorted simple cubic perovskite cell. The O octahedron is distorted with min. and max. O-O distances of 2.710(7) and 3.015(9) .ANG., resp., and rotated by about +- a = 13.8(3) Deg around the 3-fold axis. The Fe atom is shifted away from the center of the deformed octahedron by .apprx.0.134(7) .ANG. along the 3-fold axis. The Bi atom is shifted with respect to 2 neighboring octahedron centers by .apprx.0.540(7) .ANG. along the 3-fold axis. The ferroelec. poling mechanism was analyzed: atom displacements were calcd. for 60, 120 and 180 Deg switching of Ps and found to be 0.44, 0.62 and 0.82 .ANG. for Fe. Av. oxygen displacements for +a (-a) rotated octahedra were 0.87 (0.89) 1.13 (1.24) and 1.34 (1.53) .ANG.. Av. Bi shifts were <0.06 .ANG.. As the displacements increase in the order 60, 120 and 180 Deg switching of Ps, the 180 Deg reversal must have a very high activation energy and will be avoided.

1,184 citations

Journal ArticleDOI
TL;DR: In this article, the transport properties of aliovalent-ion-doped BiFeO3 (BFO) thin films have been studied in order to identify the cause of high leakage currents.
Abstract: Transport properties of aliovalent-ion-doped BiFeO3 (BFO) thin films have been studied in order to identify the cause of high leakage currents Doping of 2at% Ti4+ ions increased the dc resistivity by more than three orders of magnitude In contrast, doping of 2+ ions such as Ni2+ reduced the dc resistivity by two orders of magnitude Current–voltage (I–V) characteristics indicated that the main conduction mechanism for pure and Ni2+ doped BFO was space charge limited, which was associated with the free-carriers trapped by the oxygen vacancies, whereas in the Ti4+ doped BFO, field-assisted ionic conduction was dominant

970 citations

Journal ArticleDOI
TL;DR: In this paper, the phase pure BiFeO3 was synthesized using the oxide mixing technique followed by leaching with dilute nitric acid, and X-ray diffraction pattern indicated that the sample is phase pure.
Abstract: The difficulties in synthesizing phase pure BiFeO3 are well known. In this letter we are reporting the optimized synthesis conditions for obtaining phase pure BiFeO3 ceramic. The oxide mixing technique followed by leaching with dilute nitric acid has been used for the synthesis. X-ray diffraction pattern indicated that the sample is phase pure. Scanning electron microscopy along with energy dispersive x-ray fluorescence analysis confirmed the chemical homogeneity of the sample. No segregation of the impurity phase in the matrix was detected. Moreover, Bi/Fe atomic ratio is observed to be ∼1. The ferroelectric transition of the sample at 836 °C has been detected by differential thermal analysis.

738 citations