Agata Stoch, Jan Maurin, Paweł Stoch, Jan Kulawik and Dorota Szwagierczak
1. Scott, J. F. (2007). Data storage: Multiferroic memories. Nat. Mater., 6, 256-257. DOI: 10.1038/nmat1868.
2. Paik, H., Hwang, H., No, K., Kwon, S., & Cann, D. P. (2007). Room temperature multiferroic properties of single-phase (Bi0.9La0.1)FeO3-Ba(Fe0.5Nb0.5)O3 solid solution ceramics. Appl. Phys. Lett., 90, 042908. DOI: 10.1063/1.2434182.
3. Yuan, G. L., Or, S. W., Liu, J. M., & Liu, Z. G. (2006). Structural transformation and ferroelectromagnetic behavior in single-phase Bi1-xNdxFeO3 multiferroic
Karol Kowal, Elżbieta Jartych, Piotr Guzdek, Agata Lisińska-Czekaj and Dionizy Czekaj
The aim of the present work was to study magnetoelectric effect (ME) in (BiFeO3)x-(BaTiO3)1-x solid solutions in terms of technological conditions applied in the samples fabrication process. The rapidly growing interest in these materials is caused by their multiferroic behaviour, i.e. coexistence of both electric and magnetic ordering. It creates possibility for many innovative applications, e.g. in steering the magnetic memory by electric field and vice versa. The investigated samples of various chemical compositions (i.e. x = 0.7, 0.8 and 0.9) were prepared by the solid-state sintering method under three sets of technological conditions differing in the applied temperature and soaking time. Measurements of the magnetoelectric voltage coefficient αME were performed using a dynamic lock-in technique. The highest value of αME was observed for 0.7BiFeO3-0.3BaTiO3 solid solution sintered at the highest temperature (T = 1153 K) after initial electrical poling despite that the soaking time was reduced 10 times in this case.
Nanocrystalline multiferroic BiFeO3 ceramics was prepared by a novel solution combustion method (SCM). The X-ray diffraction (XRD) studies on structural properties of the synthesized ceramics reveal that the BiFeO3 ceramics has rhombhohedral perovskite structure with an average crystallite size of 15 nm. The ferroelectric P-E hysteresis loop measurement at room temperature shows unsaturated behavior with a partial reversal of polarization. Investigations on temperature dependence of dielectric constant in BiFeO3 demonstrate a clear dielectric anomaly at approximately around 380 °C, which corresponds to antiferromagnetic to paramagnetic phase transition (TN) and also evidences a possible coupling among the electric and magnetic dipoles of BiFeO3. A room temperature variation of dielectric constant “ɛ” and dielectric loss “tan δ” as a function of frequency in the range of 100 Hz — 1 MHz, confirms that both dielectric constant and loss are strong functions of frequency.
N. Moulay, M. Ameri, Y. Azaz, A. Zenati, Y. Al-Douri and I. Ameri
The full potential linear-muffin-tin-orbital method within the spin local density approximation has been used to study the structural, electronic, magnetic and thermodynamic properties of three multiferroic compounds of XFeO3 type. Large values of bulk modulus for these compounds have been obtained, which demonstrates their hardness. The calculated total and partial density of states of these compounds shows a complex of strong hybridized 3d and 4d states at Fermi level. The two degenerate levels eg and t2g clearly demonstrate the origin of this complex. We have also investigated the effect of pressure, from 0 GPa to 55 GPa, on the magnetic moment per atom and the exchange of magnetic energy between the ferromagnetic and antiferromagnetic states. For more detailed knowledge, we have calculated the thermodynamic properties, and determined heat capacity, Debye temperature, bulk modulus and enthropy at different temperatures and pressures for the three multiferroic compounds. This is the first predictive calculation of all these properties.
Mariusz Mazurek, Dariusz Oleszak and Dionizy Czekaj
The aim of the study was to determine the structure and hyperfine interactions of Bim+1Ti3Fem−3O3m+3 multiferroic Aurivillius compounds prepared by mechanical activation process. X-ray diffraction and Mössbauer spectroscopy were applied as complementary methods. After the process of mechanical milling, desired Aurivillius phases were not formed, thus, thermal treatment needed to be applied. Heating the product of mechanical activation up to 993 K allowed to obtain Aurivillius phases with relatively large amount of non-reacted hematite. However, after the material was annealed at an elevated temperature of 1073 K, the content of not fully synthesized hematite was significantly reduced. Mössbauer spectroscopy confirmed that Aurivillius compounds remain in paramagnetic state at room temperature.
Ryszard Skulski, Przemysław Niemiec, Dariusz Bochenek and Artur Chrobak
In this paper we present the results of investigations into ceramic samples of solid solution (1-x)(PbZr0.53Ti0.47O3)- x(PbFe0.5Ta0.503) (i.e. (1-x)PZT-xPFT) with x = 0.25, 0.35 and 0.45. We try to find the relation between the character of dielectric dispersion at various temperatures and the composition of this solution. We also describe the magnetic properties of investigated samples. With increasing the content of PFT also mass magnetization and mass susceptibility increase (i.e. magnetic properties are more pronounced) at every temperature. The temperature dependences of mass magnetization and reciprocal of mass susceptibility have similar runs for all the compositions. However, our magnetic investigations exhibit weak antiferromagnetic ordering instead of the ferromagnetic one at room temperature. We can also say that up to room temperature any magnetic phase transition has not occurred. It may be a result of the conditions of the technological process during producing our PZT-PFT ceramics.
R. Sobiestianskas, B. Vengalis, J. Banys, J. Devenson, A. Oginskis, V. Lisauskas and L. Dapkus
Nondoped BiFeO3 (BFO) and doped Bi0.9La0.1Fe0.9Mn0.1O3 (BLFMO) thin films (d = 200–350 nm) were grown at 650–750 °C by RF sputtering on Si and SrTiO3(100), coated by conductive LaNiO3 films and La2/3Ca1/3MnO3/SrRuO3 bilayers. The complex dielectric permittivity of the films was measured at room temperature in the frequency range from 10 MHz to 10 GHz using parallel plate capacitor structures. Dielectric properties of the polycrystalline BFO films were compared with those of the epitaxial quality BLFMO films, and it was seen that the latter has better microwave performance than the former. The dielectric losses were below 0.05 at 1 GHz frequency, which may be acceptable for microwave applications.
1. Zvezdin, A. K., Logginov, A. S., Meshkov, G. A., & Pyatakov, A. P. (2007). Multiferroics: promising materials for microelectronics, spintronics, and sensor technique. Bull. Russ. Acad. Sci.: Physics, 71(11), 1561-1562. DOI: 10.3103/S1062873807110263.
2. Aurivillius, B. (1949). Mixed bismuth oxides with layer lattices. Ark. Kemi., 54(1), 463-471.
3. Lomanova, N. A., Morozov, M. I., Ugolkov, V. L., & Gusarov, V. V. (2006). Properties of Aurivillius phases in the Bi4Ti3O12-BiFeO3 system. Inorg. Mater
Mohammad Shariq, Davinder Kaur, Vishal Chandel and Mohd Siddiqui
BiFeO3 polycrystalline ceramics was prepared by solid-state reaction method and its structural, optical and magnetic properties were investigated. BiFeO3 was synthesized in a wide range of temperature (825–880 °C) and a well crystalline phase was obtained at a sintering temperature of 870 °C. X-ray diffraction patterns of the samples were recorded and analyzed for the confirmation of crystal structure and the determination of the lattice parameters. The average grain size of the samples was found to be between 1–2 μm. The determined value of direct bandgap of BiFeO3 ceramics was found to be 2.72 eV. The linear behavior of M-H curve at room temperature confirmed antiferromagetic properties of the BiFeO3 (BFO). S shaped M-H curve was obtained at a temperature of 5 K. In the whole temperature measurement range (5–300 K) of M-T, no anomalies were observed due to high Curie temperature and Neel temperature of the BiFeO3.
Phonon properties have been studied using reduced sound velocity of Eu0.5Ba0.5TiO3 (EBTO). To achieve this aim, the anharmonic phonon-phonon interaction and the spin-phonon interaction were used. It was shown that the reduced sound velocity of multiferroic EBTO exhibits a kink at TN = 1.9 K. This anomalously reduced sound velocity can be interpreted as an effect of vanishing magnetic ordering above TN. What’s more, the ferroelectric subsystem cannot be influenced by the magnetic subsystem above TN for TN ≪TC in the EBTO. It was found that the reduced sound velocity decreases as T increases near ferroelectric transition TC. That is to say, the sound velocity softens near ferroelectric transition TC. It is also noteworthy that the reduced sound velocity softens when the RE (the coupling between the ferroelectric pseudo-spins and phonons), V(3) and |V(4)| (the third- and fourth-order atomic force constants of the anharmonic phonons, respectively) increase. These conclusions are all in good accordance with the experimental data and theoretical results.