Local structure around Fe ions on multiferroic Pb(Fe1/2Nb1/2)O-3 ceramics probed by x-ray absorption spectroscopy

Local structure around Fe ions on Pb(Fe1/2Nb1/2)O-3 ceramics was probed by x-ray absorption spectroscopy in order to settle the controversies about its structure. It is observed that the shell structure around Fe atoms exhibits a monoclinic local symmetry at 130 and 230 K, tetragonal local symmetry at room temperature, and cubic local symmetry at 410 K. Independently of the coordination, temperature, or symmetry, Fe-O mean bond-length does not vary significantly. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4709490]FAPESPFAPESP [Proc. 2008/04025-0, 2010/11187-6]CNPqCNP

Magnetoelectric intrinsic coupling in PFW based perovskites

Magnetic, electric and mechanical properties can be strongly coupled in multiferroic materials. However, only few models were developed to describe electro-magneto-mechanical coupling effects on them. We report the influence of the strain induced phase transitions on the enhancement of the magnetoelectric intrinsic properties in multiferroic Pb[(Fe2/3W1/3)((1-x))Ti-x]O-3 (x = 0.17,0.20) ceramics. We argue that when both ferroelectric and antiferromagnetic transitions temperatures are closer together, the magnetoelectric intrinsic and extrinsic responses increase. Colossal magnetoelectric intrinsic response was found for Pb(Fe2/3W1/3)(0.83)Ti0.17O(3)

Dielectric Study at Microwave Frequencies of Phase Transitions in Multiferroic Ceramics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Multiferroic ceramic solid solutions between the ferroelectric relaxor Pb(Fe2/3W1/3)O-3 (PFW) and "normal" ferroelectric PbTiO3 (PT) - PFW-PT have been synthesized by a modified B-site precursor method and characterized by microwave dielectric measurements. A dielectric dispersion occurring in the frequency range of 100MHz-3GHz and in a broad range of temperatures showed to be a powerful tool to detect electrostrictive and magnetostrictive effects. Anomalies in the temperature dependence of the dielectric parameters (f(R) (characteristic frequency) and the dielectric strength Delta epsilon (characteristic of the dispersion)) have been observed at T-N and T-C for all samples, indicating that the coupling between the ferroelectric and antiferromagnetic orders occurs "via strain" and confirming the high sensitivity of microwave dielectric measurements to probe weak transitions in bulk ceramics.16511341139Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [Proc. 2008/04025-0, 2010/11187-6

Magnetic and Electric Orderings and Intrinsic Magnetoelectric Coupling in Pb(Fe,W)O-3 Based Ceramics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)In this work structural, electric, dielectric, and anelastic properties of single phase high density (> 97%) (1-x) PFW-xPT ceramics, with 0 <= x <= 0.30, are investigated. The experimental results show that the temperatures, in which magnetic (T-N) or electric (T-FE) ordering occur, can be interchanged by PbTiO3 addition. Correlations between the experimental results allow to estimate intrinsic ferromagnetoelectroelastic coefficients at the temperatures, where the multiferroic state exist. The intrinsic magnetoelectric coefficient is maximum for compositions, in which the temperatures for magnetic and ferroelectric ordering coincide, no matter in what sequence the orderings (FE or AFM) occur.44215060Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [Proc. 2008/04025-0, 2010/11187-6

Colossal intrinsic magnetoelectric effect in Pb(Fe2/3W1/3)(0.83)Ti0.17O3

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Dielectric and magnetic properties were investigated in Pb(Fe2/3W1/3)(0.83)Ti0.17O3 ceramics. The dielectric constant in these samples exhibits colossal changes at the magnetic ordering temperature under the presence of bias external electric fields, which presents a close connection with magnetoelectrics effects (ME), confirming the possibility to control magnetic proprieties with electric fields. The ferroelectromagnetoelastic coefficient was determined from the dielectric response as a function of the electric field. The analysis of magnetic and dielectric susceptibilities based on the Landau-Devonshire thermodynamic formalisms indicates that the ME effects is a contribution of intrinsic ME coupling and a field dependent term. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748819]1019Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [Proc. 2008/04025-0, 2010/11187-6

Colossal Intrinsic Magnetoelectric Effect In Pb(fe 2/3w 1/3) 0.83ti 0.17o 3

Dielectric and magnetic properties were investigated in Pb(Fe 2/3W 1/3) 0.83Ti 0.17O 3 ceramics. The dielectric constant in these samples exhibits colossal changes at the magnetic ordering temperature under the presence of bias external electric fields, which presents a close connection with magnetoelectrics effects (ME), confirming the possibility to control magnetic proprieties with electric fields. The ferroelectromagnetoelastic coefficient was determined from the dielectric response as a function of the electric field. The analysis of magnetic and dielectric susceptibilities based on the Landau-Devonshire thermodynamic formalisms indicates that the ME effects is a contribution of intrinsic ME coupling and a field dependent term. © 2012 American Institute of Physics.1019Eerenstein, W., Mathur, N.D., Scott, J.F., Multiferroic and magnetoelectric materials (2006) Nature, 442 (7104), pp. 759-765. , DOI 10.1038/nature05023, PII NATURE05023Smolenskii, G.A., (1982) Usp. Fiz. Nauk, 137, p. 415. , 10.3367/UFNr.0137.198207b.0415Wang, J., Neaton, J.B., Zheng, H., Nagarajan, V., Ogale, S.B., Liu, B., Viehland, D., Ramesh, R., Epitaxial BiFeO 3 multiferroic thin film heterostructures (2003) Science, 299 (5613), pp. 1719-1722. , DOI 10.1126/science.1080615Kimura, T., Kawamoto, S., Yamada, I., Azuma, M., Takano, M., Tokura, Y., (2003) Phys. Rev. B, 67, pp. 180401R. , 10.1103/PhysRevB.67.180401Fiebig, M., Revival of the magnetoelectric effect (2005) Journal of Physics D: Applied Physics, 38 (8), pp. R123-R152. , DOI 10.1088/0022-3727/38/8/R01Fiebig, M., Spaldin, N.A., (2009) Eur. Phys. J. B, 71, p. 293. , 10.1140/epjb/e2009-00266-4Fraygola, B., Coelho, A.A., Garcia, D., Eiras, J.A., (2011) Mater. Res., 14, p. 434. , 10.1590/S1516-14392011005000075Eiras, J.A., Fraygola, B., Garcia, D., (2010) Key Eng. Mater., 434-435, p. 307. , 10.4028/www.scientific.net/KEM.434-435.307Szwagierczak, D., Kulawik, J., Influence of MnO 2 and Co 3O 4 dopants on dielectric properties of Pb(Fe 2/3W 1/3)O 3 ceramics (2005) Journal of the European Ceramic Society, 25 (9), pp. 1657-1662. , DOI 10.1016/j.jeurceramsoc.2004.05.022, PII S0955221904002584Mitoseriu, L., Marré, D., Siri, A.S., Nanni, P., (2003) Appl. Phys. Lett., 83, p. 5509. , 10.1063/1.1632033Park, J.H., Shin, H.H., Jang, H.M., (2008) Phys. Rev. B, 77, p. 212409. , 10.1103/PhysRevB.77.212409Mitsek, A.I., Smolenskii, G.A., (1963) Sov. Phys. Solid State, 4, p. 2620Chupis, I.E., (2010) Low Temp. Phys., 36, p. 477. , 10.1063/1.3462535Skinner, S., (1970) IEEE Trans. Parts Mater. Packag., 6, p. 68. , 10.1109/TPMP.1970.1136257Khomskii, D., (2009) Physics, 2, p. 20. , 10.1103/Physics.2.2

Magnetic ordering and instability investigation of multiferroic Pb(Fe2/3W1/3)O-3 ceramics by microwave dielectric spectroscopy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The microwave dielectric and magnetic properties of Pb(Fe2/3W1/3)O-3 multiferroic ceramics were investigated. A dielectric dispersion occurring in the frequency range 100 MHz-3 GHz and in a broad temperature range showed itself to be a powerful tool to detect magnetostrictive effects. The experimental results revealed the following remarkable features: the temperature dependence of f(R) (characteristic frequency) and the dielectric strength Delta epsilon (characteristic of the dispersion) enabled us to identify not only the para-ferroelectric (T-C approximate to 180 K) but also the para-antiferromagnetic (T-N approximate to 340 K) phase transitions, while magnetic measurements revealed the para-antiferromagnetic ordering and a weak superexchange interaction (T-N2 similar to 15 K). Additionally, both characterizations confirmed the existence of structural or magnetic instabilities around 250 K. (C) 2011 Elsevier Ltd. All rights reserved.1512318101813Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP