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In this work, the nanostructuration effects on the physical properties of pure and La doped (0.6)BiFeO3‐(0.4)PbTiO3 magnetoelectric nanoparticles were investigated. An exotic magnetic response, mimicking a superparamagneticlike behavior that raised the magnetization to levels never reported before for these materials, is clearly observed. Another important change associated with the nanostructuration is observed in the symmetry of the perovskite-structured materials, which changes from a tetragonal to a rhombohedral one. Transmission electron microscopic and X-ray diffraction results (investigated by the Debye-Scherrer method) revealed uniform nanoparticles of spherical shape, average particle sizes close to 5 nm and with a single structural domain (only one crystallite per particle). The pronounced increase (∼20 times) in the magnetization response of the nanoparticles, compared to microparticle ones, is observed in magnetization curves. A magnetic semiempirical phenomenological model, where noninteracting single-domain magnetic nanoparticles are considered, is used to fit the magnetization curves, revealing the almost absence of surface effects in a typical superparamagneticlike behavior. All these aspects pointing to a material with immense potential for practical applications in spintronics and magnetoelectronics.In this work, the nanostructuration effects on the physical properties of pure and La doped (0.6)BiFeO3‐(0.4)PbTiO3 magnetoelectric nanoparticles were investigated. An exotic magnetic response, mimicking a superparamagneticlike behavior that raised the magnetization to levels never reported before for these materials, is clearly observed. Another important change associated with the nanostructuration is observed in the symmetry of the perovskite-structured materials, which changes from a tetragonal to a rhombohedral one. Transmission electron microscopic and X-ray diffraction results (investigated by the Debye-Scherrer method) revealed uniform nanoparticles of spherical shape, average particle sizes close to 5 nm and with a single structural domain (only one crystallite per particle). The pronounced increase (∼20 times) in the magnetization response of the nanoparticles, compared to microparticle ones, is observed in magnetization curves. A magnetic semiempirical phenomenological model, where noninteracti...

We present a Raman spectroscopy study of the lattice-dynamical properties of the BaxSr1−xTiO3 thin films with x=0.05, 0.1, 0.2, 0.35, and 0.5 in the temperature range of 5–300K. Soft phonon modes were observed, and the temperature dependence of their frequencies and Raman intensities were investigated. The Raman spectra of the BaxSr1−xTiO3 films are compared with the single crystals of the same compositions. The essential differences in the lattice-dynamical properties of the thin films and single crystals are observed, such as the forbidden first-order Raman scattering in the films well above the phase-transition temperature in bulk, hardening of the soft phonon modes in films compared to crystals, and significantly larger range of the soft-mode overdamping in the films. On the other hand, the lattice-dynamics behavior in the BaxSr1−xTiO3 films is found similar to that of the relaxor ferroelectrics. Analogous to the relaxors, the presence of the polar nanoregions existing in the films at the temperatures...

The field distribution, dielectric constant, and loss in a two-phase composite, in which phase A is distributed inside a square matrix of phase B, have been calculated using the finite-element method (FEM). The calculation was carried out by taking into account different shapes for phase A, such as circles, triangles, and rings with different sizes. The modeling by FEM in the dielectric composite indicates that the shape for phase A has an influence on the electric-field distribution. In the case of the triangular shape of phase A, the electric flux condensed on the sharp angles of phase A. In a particular case of a ring for phase A, the electric-field distribution in the composite was quite different from that of circles/triangles due to the shielding effect of flux, and hence the dielectric constant and loss are greatly changed. The calculated values are analyzed and compared with that from the empirical Licktenecher relation. The results indicate that the FEM method can reflect the change in the shape ...

Dielectric properties of Nb2O5(0.92):SiO2(0.08) ceramic were measured in the temperature range of 10–300 K by the cryostat system. Frequency-dependent dielectric loss suggests the relaxation behavior of this material. The relaxation mechanism was analyzed by the Arrhenius relationship and the Cole–Cole plot. Calculated distribution of relaxation time reveals deviation from the pure Debye relaxation.

SrBi2Ta2O9 thin films on various bottom electrodes/substrates such as Pt/TiO2/SiO2/Si (Pt) and LaNiO3/Pt/TiO2/SiO2/Si (LNO) were grown using the pulsed laser deposition technique. X-ray diffraction studies revealed that as-grown (at 500 °C) films were crystallized in the layered structure after annealing at 800 °C. Films grown on platinized silicon exhibited maximum value of remanent polarization (2Pr∼21.5 μC/cm2) with coercive field (Ec) of ∼67 kV/cm. The dielectric constant and dissipation factor also decreased with the introduction of a 50 nm conducting LaNiO3 oxide electrode at the interface of Pt and SBT thin films, which might be contributed by the high resistive oxide electrode layers. The dc leakage characteristics of the films were studied at elevated temperatures and the data were fitted with the Schottky emission model. The barrier heights of the films grown on Pt and LNO substrates were estimated to be 1.27 and 1.12 eV with optical dielectric constants of 6.3 and 17, respectively. The reductio...

The polarization and strain behavior of Ba(Ti1−xZrx)O3 (x=0–0.3) ceramics are studied. The unipolar strain levels of ∼0.18% at 40 kV/cm and of ∼0.25% at ∼120 kV/cm with small hysteresis were obtained for the ceramics with 0.03⩽x⩽0.08. The remnant polarization is ∼13–18 μC/cm2 for 0.03⩽x⩽0.08 and below 2 μC/cm2 for 0.15⩽x⩽0.3 at room temperature. The electromechanical coupling coefficient K33=56.5% and the piezoelectric stain coefficient d33=236 pC/N were obtained for the ceramics with x=0.05. These results indicated that the Ba(Ti1−xZrx)O3 system is a promising lead-free high strain material for applications.

The thermal expansion coefficients of a single crystal and ceramic of Nb2O5 are measured in the temperature range of −200–500 °C by the dilatometer technique. Both single crystals and ceramics of Nb2O5 and Nb2O5(1−x):xTiO2 show negative thermal expansion in this temperature range. Some contribution to the result could be due to the presence of the Magneli phases. The main phase transition temperature, which also matches with the dielectric anomaly, occurs at ≈150 °C.

The effect of dc bias on dielectric properties of cadmium pyroniobate Cd2Nb2O7 ceramics is studied in this article. Without dc bias, two obvious dielectric peaks around 80 and 180 K are observed; by applying dc bias, the two peaks are greatly suppressed and finally eliminated at 15 kV/cm, however, a peak with no frequency dispersion shows up at 192 K. The results show high electric-field tunability of the dielectric constant with a low dielectric loss at radio frequencies. The electric-field dependence of the dielectric constant around 80 K can be well described by the modified Devonshire relation including the Langevin-type cluster term, i.e., e(E)=e1−e2E2+e3E4+(Pjxj/e0)[cosh(Exj)]−2. The fit parameters indicate that the polar cluster carries polarization P=∼0.28–0.65 mC/m2 with the cluster size of L=∼24–30 nm.

In this study, the phase transition behavior of the BaTiO3–BaZrO3 system was studied using micro-Raman scattering and dielectric measurement techniques. BaZrxTi1−xO3 ceramics were prepared for x=0.00, 0.05, 0.08, 0.15, 0.20, and 1.00 compositions using a solid-state reaction technique. A single-phase perovskite structure of the ceramics was identified by the x-ray diffraction technique. The basic phase transition temperatures in these compositions were studied in the temperature range of 70–575 K. The tetragonal to cubic transition temperature was found to decrease with increasing Zr content. The orthorhombic to tetragonal transition temperature that increases with an initial increase in Zr content merges with the tetragonal–cubic transition for x⩾0.15 compositions. Raman spectra of rhombohedral and orthorhombic phases could not be distinguished. Excellent agreement between the crystallographic transition temperatures obtained by both techniques suggested that Zr substituted octahedra were uniformly distr...

In this article, we report the successful growth of Ba(Ti1−xZrx)O3 (x=0.05–0.2) single-crystal fibers by the laser-heated pedestal growth technique. A single-phase perovskite structure of the materials has been identified by the x-ray diffraction technique. The phase diagram for Ba(Ti1−xZrx)O3 single crystals is established for x⩽0.2. Dielectric properties as function of temperature and frequency and room-temperature hysteresis loops are measured. The remnant polarization (Pr) and coercive fields (Ec) are obtained and compared for both single crystals and ceramics. The small dielectric relaxation has been observed for the lower-temperature phase transition (around 40 °C at 1 kHz) of the sample with x=0.08. The relaxation times follow the Arrhenius law with τ0=0.4×10−13 s and Erelax=0.53 eV. A common feature of the low-temperature relaxation mode in the sample is also observed, which follows the Arrhenius law with the τ0=0.8×10−10 s and Erelax=0.46 eV.

High dielectric constant (Ta2O5)1−x(TiO2)x ceramics for x=0.00, 0.05, 0.08, and 0.11 were prepared and studied utilizing micro-Raman scattering and x-ray diffraction techniques. The modification in the lowest frequency phonon mode of pure Ta2O5 with increasing TiO2 content in these ceramics was assigned as Ta–Ti vibrations originating from the interaction between TiO6 octahedra and TaOn5-2n or Ta6O12+6 clusters. Raman spectra, in the range −200–900 °C, reveal a softening of this mode with increasing temperature followed by a structural transformation. A triclinic to monoclinic phase (Hmon′) transition was observed at about 300, 360, 450, and 540 °C for x=0.00, 0.05, 0.08, and 0.11, respectively. It was also found that reannealing at 1150 °C for 12 h transforms these ceramics from triclinic to a metastable monoclinic phase Hmon, which was found to be an irreversible process.

This article reports a study on the dielectric relaxation processes of Cd2Nb2O7 compound. Three dielectric relaxation modes I, II, and III were reexamined. By using the Cole–Cole equation fitting of the frequency dependence of dielectric constant and loss, we obtained more precise relaxation time data, compared to the data reported in the literature. The results indicate that the relaxation time for mode I follows the Arrhenius law with one slope rather than two slopes as reported in the literature in the frequency range of 102–105 Hz. However, the parameters obtained from the Arrhenius law fit are not physically reasonable. More physically reasonable parameters can be obtained by fitting the relaxation time to the empirical Vogel [Z. Phys. 22, 645 (1921)]–Fulcher [J. Am. Ceram. Soc. 8, 339 (1925)] relation with essentially the same fitting quality. A comparison of Cd2Nb2O7 with well known triglycine sulphate (TGS) is made. The similarity between the dielectric response of Cd2Nb2O7 and TGS is emphasized. ...

The effect of dc electric field and post-treatment on the dielectric properties of SrTiO3 single crystals are reported. Both the dielectric constant and the loss tan δ decrease after post-treatment in flowing oxygen environment for 26 h at 1100 °C. The possible physical mechanism is briefly discussed. The dielectric behavior under dc electric field is measured. The rounded dielectric constant peak is induced by application of dc bias, and the corresponding dielectric loss is presented, which show more complicated behavior and usually are missing in the literature. In this work, it is found that the temperature (Tm) of the dielectric constant maximum shifts to higher temperatures with increasing dc electric field E, and follows the Tm∼E2/3 relation, indicating an induced ferroelectric-like behavior with the second-order phase transition under dc bias.

Single crystals of quaternary solid solution compositions of A-site filled tungsten bronze-type α(Ba1−xSrx)Nb2O6:β(Na1−yKy)NbO3 (where α:β=2:1, 9:2, x=0.75, 0.60, and y=0.50, 0.40, and 0.25) have been grown by the laser heated pedestal growth technique, both along the a axis and the c axis. The crystal growth studies, the crystallographic parameter analysis, the dielectric properties as well as the thermal expansion behavior of the as grown single crystals are reported. Compositions with low ratios of Ba and Na in the 2:1 section plane have high polarizability, low dielectric loss, and ferroelectric relaxor characteristics.

Strontium titanate sol was prepared using strontium ethyl haxanoate and titanium isopropoxide. The sol was then spin coated on fused silica, p-type single-crystal silicon wafers (100) and stainless-steel substrates and annealed to give polycrystalline, transparent, and crack-free films. The surface morphology and structural properties of the films were studied using scanning electron microscopy and x-ray diffraction, respectively, and differential thermal analysis was used to observe structural transition. The dielectric measurements were conducted on films with metal–insulator–metal and metal–insulator–semiconductor configurations. Capacitance–voltage (C–V) measurements were carried out and the effect of the annealing temperature was studied. The dielectric constant and loss tangent at 1 MHz at room temperature were found to be 105 and 0.02, respectively, for 1.1 μm thick films. These measurements were also carried out at low temperatures down to 20 K. There are indications for a phase transition from a ...

The longitudinal (LO) and transverse (TO) A1 vibrational modes have been measured between 30 and 1200 cm−1 as a function of temperature (30–1240 K) for both KTiOPO4 (KTP) and KTiOAsO4 (KTA). KTP and KTA exhibit an obviously different Raman spectra in the frequency region 400–650 cm−1 (with respect to KTA). This middle‐frequency difference is attributed to the substitution ions in XO4 group (X=P or As) modifing the force constant of crystal. The relative intensities of the low‐frequency bands increase dramatically with increasing temperature due to high mobility of K+ ion. There is no typical soft‐mode like behavior in the measured frequency range. A higher symmetric structure taking place above Tc has been confirmed by the disappearance of the A1g(LO) stretching modes of TiO6 group. Comparison of each frequency belonging to the symmetry A1, A2, B1, and B2 measured along the [110] phonon direction shows complex difference. The vibrational frequencies of various symmetries were also obtained.

Several near quasicongruent undoped YVO4 single crystals grown by the Czochralski (CZ) technique as well as near stoichiometric YVO4 single crystals grown by the top‐seeded solution growth technique, were investigated by micro‐probe Raman spectroscopy using unpolarized argon–ion laser light. The line broadening effects of the Raman active mode at 379 cm−1 indicate that all CZ grown crystals possess wider peak widths than near stoichiometric YVO4. In the latter case a value of 9.23 cm−1 was measured for full width at half‐maximum. Although the annealing process in O2 can improve the oxygen stoichiometry in the originally slightly oxygen deficient CZ grown YVO4 crystals, certain remaining peak broadening effects demonstrate a Y–V related stoichiometry problem by both lower (external) and higher frequency (internal) modes. Radial inhomogeneous distributions were observed in CZ specimens by the shift of external Raman modes at 157 and 162 cm−1 frequencies. In addition, nonassigned low intensity extra Raman peaks appeared over 1000 cm−1 frequencies in all CZ grown samples. The above detected changes in Y–V–O stoichiometry demonstrate a complex phase system around the homogeneity region of quasicongruent YVO4 specimens and enable a more realistic and unified interpretation of the segregated defects and stoichiometry changes in CZ grown YVO4 single crystals than previously available.

Selected tensor property coefficients of the nonlinear optical crystal LiB3O5 are reported. The full set of pyroelectric, dielectric, and thermal expansion coefficients were measured as a function of temperature. The five independent piezoelectric coefficients, the full set of electromechanical coupling coefficients, along with the compliance constants, were measured at room temperature. The material was found to be quite anisotropic in most property coefficients. The piezoelectric and electromechanical coupling coefficients were reasonably low, and comparisons are made between LiB3O5 and other borate crystals. The material showed strong ionic conductivity along the 〈001〉 direction, with a calculated activation energy for Li transport of 0.43 eV.

Based on a magnetic relaxation model, an approach that includes the spin dynamics is proposed and applied to describe the magnetoelectric (ME) effect frequency dependence for a 0–3 type composite at low temperatures. Our results show that the ME coefficient, in low temperatures, for PMN-PT/CFO ( (1−x)Pb(Mg1/3Nb2/3)−xPbTiO3/CoFe2O4) composite has a step-like behavior on the hysteresis loop for frequency of 1 kHz, contrasting with the results at low frequencies (10 Hz). This approach assumes that the ferromagnetic and ferroelectric phases are coupled through the interactions of the spins of the ferromagnetic phase with the composite phonons by spin/lattice relaxation.

The preparation of Ba(Mg1/3Ta2/3)O3 (BMT) ceramics and the first successful growth of BMT single crystals by the laser heated pedestal growth technique (LHPG) is reported. The single crystal has a simple cubic perovskite structure in comparison to the ordered hexagonal structure normally found in ceramics of the same phase. The dielectric properties of single crystals are examined, the dielectric Q value increases with the increase in B‐site ordering, while the dielectric constant κ is relatively independent of ordering. Our results also show that BMT is a candidate substrate for high Tc superconductor thin films as it has one of the highest Q values known for the oxide perovskite family, along with its matching thermal expansion coefficient α=9.0×10−6/ °C and twin‐free cubic perovskite structure with a=4.0877 A. BMT single crystals grown by the LHPG technique are probably the highest melting oxide compounds grown to date.

Ferroelectric-relaxor behavior of Ba(Ti0.7Zr0.3)O3 ceramics is studied in the temperature range from 150 to 450 K. A broad dielectric peak with a high-dielectric maximum exhibits frequency dispersion. The dielectric relaxation rate follows the Vogel–Fulcher relation with E=0.21 eV and TVF=199.6 K. The polarization hysteresis loops were observed with a remnant polarization of 10 μC/cm2 at 175 K. The high-dielectric constant and high-polarization properties are expected to find practical applications at low temperatures.

The temperature dependence of the complex refractive indices of SbSI, MoS2, and BiVO4 have been investigated using spectroscopic ellipsometry. The wavelength of maximum temperature dependence was identified for an in depth study of the sensitivity of the reflectance coefficient to a small ac temperature modulation. It was found feasible to detect temperature changes of 10−3, 10−2, and 10−2 °C by monitoring the reflectance coefficient of SbSI, MoS2, and BiVO4, respectively, using null ellipsometry. It is thus possible to use the pyro‐optic phenomena for long wavelength infrared imaging, analogous to pyroelectrics.

The room‐temperature transverse electro‐optic, rc, coefficient, halfwave voltage, Vπ, and temperature dependence of the birefringence, Δn0(T), were determined for Sr0.61Ba0.39Nb2O6 single‐crystal fibers produced by the laser‐heated pedestal growth technique. The effect cerium doping, 0.034 at. %, had on the measured properties is also reported. Concurrent measurements on a Czochralski‐grown Sr0.61Ba0.39Nb2O6 single crystal enabled comparison of the single‐crystal fibers to a bulk‐grown single crystal. The growth rate of the Sr0.61Ba0.39Nb2O6 single‐crystal fibers was approximately an order of magnitude greater than the Czochralski‐grown Sr0.61Ba0.39Nb2O6 single crystal. The effect the rapid growth rate had on the optical properties is also discussed.

Low‐temperature (10–300 K) dielectric and pyroelectric properties of morphotropic‐phase‐boundary lead‐barium‐niobate tungsten‐bronze ferroelectric single crystals have been investigated. Strong ‘‘Debye‐like’’ dielectric dispersion, along a nonpolar direction (perpendicular to the polarization direction), has been observed and characterized by dielectric spectrum techniques. A direct charge measurement method has been used to study the low‐temperature pyroelectric properties in polar and nonpolar directions. A ‘‘frozen‐in’’ polarization component in a nonpolar direction is also reported. The low‐temperature relaxation effects are explained by the internal reorientation polarization perturbation and a thermally agitated local dipole fluctuation model.

Investigations of the polarization mechanisms in tungsten bronze relaxor ferroelectrics, Pb1–xBaxNb2O6 (PBN[(1−x) %]), in particular, of the morphotropic phase boundary compositions have been carried out for both ceramics and bulk crystals by means of electrical, thermal, optical, and electron‐microscopic methods. Relations of phase‐transition behavior with compositional and polarizational fluctuations have been carefully studied. Instead of a sharp boundary composition, it is found that a rather wide composition range, 1−x≊0.63±0.03 in Pb1−xBaxNb2O6, corresponds to the orthorhombic and tetragonal morphotropic phase boundary. It is demonstrated with the help of optical conoscopic interference figures that for the near‐morphotropic phase boundary single crystal PBN of tetragonal symmetry, the polarization vector can be switched orthogonally to an orthorhombic phase simply by the application of an electric field, which authenticates optically the 90° polarization rotation. A transmission electron microscope study in the temperature range from −180 °C to room temperature revealed the presence of incommensurate ferroelastic domains in the morphotropic phase boundary composition PBN crystals. In light of the above observed experimental data, the polarization mechanisms of the morphotropic phase‐boundary compositions are discussed in terms of qualitative thermodynamics.

It is still a challenging problem to obtain technologically useful materials displaying strong magnetoelectric coupling at room temperature. In the search for new effects and materials to achieve this kind of coupling, a nonlinear magnetoelectric effect was proposed in the magnetically disordered relaxor ferroelectric materials. In this context, the aluminum iron oxide (AlFeO3), a room temperature ferroelectric relaxor and magnetic spin glass compound, emerges as an attractive lead-free magnetoelectric material along with nonlinear magnetoelectric effects. In this work, static, dynamic, and temperature dependent ferroic and magnetoelectric properties in lead-free AlFeO3 and 2 at. % Nb-doped AlFeO3 multiferroic magnetoelectric compositions are studied. Pyroelectric and magnetic measurements show changes in ferroelectric and magnetic states close to each other (∼200 K). The magnetoelectric coefficient behavior as a function of Hbias suggests a room temperature nonlinear magnetoelectric coupling in both sing...

Epitaxial Tl2Ba2CaCu2O8 superconducting films have been successfully grown on the dielectric Sr2(AlTa)O6 (SAT) buffer layers. X‐ray diffraction data showed that the films were highly c‐axis oriented with a rocking curve full width half maximum as narrow as 0.3°. The films also had an excellent in‐plane epitaxy with Tl2Ba2CaCu2O8[100] aligned with SAT[100] and MgO[100] of the substrate. The zero resistance temperature Tc of the superconducting films ranged from 95 to 103 K and the transport critical current density Jc in zero field was 3×105 A/cm2 at 77 K.

Sr2(AlTa)O6 thin films (2000–3000 A) have been deposited on MgO (001) substrates using pulsed laser deposition (PLD). X‐ray‐diffraction analysis shows that the Sr2(AlTa)O6 grows with the c axis highly oriented normal to the substrate plane and very good in‐plane epitaxy. The subsequently deposited YBa2Cu3O7−x films using PLD on Sr2(AlTa)O6 buffered MgO substrates exhibit excellent epitaxial growth with a narrow rocking curve width and a small φ scan peak width. The critical temperature Tc0 of 90–92 K has been achieved reproducibly and the critical current density is over 2.7×106 A/cm2 at 77 K.

In this manuscript, X-ray and high-resolution neutron powder diffraction investigations, associated with Rietveld refinements, magnetic hysteresis curves and a modeling of electron-density distributions around the ions, are used to describe the driving forces responsible for tuning the ferroic states in La doped (0.6)BiFeO3-(0.4)PbTiO3 compositions. The intrinsic relations between the ferroic orders and the structural arrangements (angles, distances and electron-density distributions around the ions) are revealed, helping in the understanding of some aspects comprising the ferroic properties of perovskite-based displacive multiferroic compounds.

Multiferroic Bismuth Ferrite (BiFeO3) thin films with varying excess bismuth (Bi) concentration were grown by chemical solution deposition technique. Room temperature multiferroic properties (ferromagnetism, ferroelectricity, and piezoelectricity) of the deposited BiFeO3 thin films have been studied. High resolution X-ray diffraction and Raman spectroscopy studies reveal that the dominant phases formed in the prepared samples change continuously from a mixture of BiFeO3 and Fe2O3 to pure BiFeO3 phase and, subsequently, to a mixture of BiFeO3 and Bi2O3 with increase in the concentration of excess Bi from 0% to 15%. BiFeO3 thin films having low content (0% and 2%) of excess Bi showed the traces of ferromagnetic phase (γ-Fe2O3). Deterioration in ferroic properties of BiFeO3 thin films is also observed when prepared with higher content (15%) of excess Bi. Single-phased BiFeO3 thin film prepared with 5% excess Bi concentration exhibited the soft ferromagnetic hysteresis loops and ferroelectric characteristics with remnant polarization 4.2 μC/cm2 and saturation magnetization 11.66 emu/g. The switching of fine spontaneous domains with applied dc bias has been observed using piezoresponse force microscopy in BiFeO3 thin films having 5% excess Bi. The results are important to identify optimum excess Bi concentration needed for the formation of single phase BiFeO3 thin films exhibiting the improved multiferroic properties.

Lanthanum and neodymium titanate A2Ti2O7 (A=La, Nd) single‐crystal fibers were grown via the laser‐heated pedestal growth technique. The single‐crystal fibers were 600 μm in diameter and 3–4 cm in length. The piezoelectric, k23 and d23, and elastic compliance, s33, coefficients were measured using the standard resonance‐antiresonance technique. From a comparison of the measured coefficients to poled single crystal data in the literature, it is concluded that the La2Ti2O7 single‐crystal fiber grew in a single domain state.

The effect of Bi excess (0 to 15%) and subsequently Mn doping (0 to 20%) on the structural, ferroelectric, and magnetic properties of BiFeO3 (BFO) thin films deposited by chemical solution deposition technique on low cost substrates are reported in the present work. No significant changes in crystallographic structure of BFO were observed with 5% excess Bi. With further increasing the Bi concentrations (> 10%), however, rhombohedral phase transformation occurs with appearance of the other Bi excess phases. Piezoresponse force microscopy studies show that the BFO thin film having 5% excess Bi and 10% Mn yields good ferroelectric behavior. The ferromagnetic behavior of 10% Mn doped BFO thin film is confirmed with vibrating sample magnetometer studies. The results indicate that the 10% Mn doped BFO thin films deposited by chemical solution deposition technique on low cost substrate exhibit very good multiferroic properties, suitable for magnetic memories applications.

Rising demands in design of metamaterials requires better understanding of coupling phenomena in composite systems. Materials exhibiting product properties have effective magnitude of physical constants surpassing those of naturally existing materials. In this manuscript, we conduct numerical modeling of laminated terfenol-D/PZT/terfenol-D magnetoelectric composites with sandwich structure coupled through elastic interactions across the bonding layer. Developed magnetoelectric model couples the piezoelectric and magnetostriction constitutive equations with Langevin theory for simulating the saturated elastic response in composites. Simulated results were found to be in good agreement with the experimental results. Based upon the developed model we predict 17% improvement of magnetoelectric coefficient for sandwich structure through proper rotation of polarization in individual layers. (C) 2010 American Institute of Physics. [doi:10.1063/1.3387815] National Science Foundation (U.S.) - Grant No. DMR-0407462