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Bi1-xMgxFeO3 (BMFO, x = 0, 0.02, 0.04, 0.06 and 0.08) multiferroic films were directly synthesized on flexible stainless steel (FSS), save the bottom electrode process, by means of sol–gel spin-coating technology. The effects of different bending conditions on ferroelectric, dielectric and leakage-current properties of BMFO films were investigated. The leakage-current densities of BiFeO3 (BFO, x = 0) and BMFO (x = 0.06) films were 5.86 × 10−4 and 3.73 × 10−7 A/cm2, which shows that the BMFO (x = 0.06) has more than three orders of magnitude lower than that of BFO film. The residual polarization (2 Pr) can be enhanced from 120 to 140 μC/cm2. The proper doping of Mg in BiFeO3 film could provide an effective method for reducing the leakage-current values as well as boosting the ferroelectric properties. In this study, the leakage-current mechanism of low electric field and high electric field of BMFO film is analyzed and established. In addition, the flexible BMFO film maintains practical ferroelectric and leakage-current properties at retention time of 106 s under different symmetry bending conditions. These results indicate that the BFMO film will be very practical in opto-electronic and storage device applications.

We investigate transformations of space modulated structure in BiFeO3films induced by change of magnetic anisotropy, strain, or temperature and applied magnetic field. We show that critical field of the transition between incommensurate and commensurate structures is lower in films as compared with single crystals. There are two incommensurate phases at H∥[111]: plane and conical cycloidal phases with the second order transition between them. An important feature of this transition is softening of spin wave activation mode localized on spin cycloid. Cycloidal spin wave spectrum contains a countable number of branches, thus BiFeO3can be considered as a magnonic crystal. [ABSTRACT FROM PUBLISHER]

Magnetoelectric (ME) xLaCaMnO-(1 − x)BiNdTiO (LCMO-BNT) composite thin films have been prepared by a sol-gel process and spin-coating technique. The effects of LCMO content on the microstructure, leakage current density, ferroelectric properties, fatigue endurance and ME voltage coefficient of LCMO-BNT thin films derived by sol-gel method were studied. It was found that the composite thin films have better fatigue endurance properties and lower leakage current densities compared with pure BNT thin films, as well as large ME voltage coefficients. [ABSTRACT FROM AUTHOR]

Abstract: Epitaxial LuFe2O4 thin films are deposited on sapphire substrate by pulsed-laser deposition. Different growth conditions are tackled and it is found that substrate temperature is the most critical condition for the film growth; while below 750°C the film crystallization is poor. The Lu:Fe ratio is also found to be important in forming the LuFe2O4 phase in the films; while higher content of Fe oxide than that of stoichiometric LuFe2O4 in the target is favorable for the formation of the LuFe2O4 phase. However, impurity phases such as Fe3O4 and Fe2O3 are induced in the film with a Fe oxide enriched target. A large dielectric tunability under electric field is revealed in the film; while the dielectric tunability decreases as the frequency increases, and eventually the dielectric tunability disappears above 500MHz. [ABSTRACT FROM AUTHOR]

Abstract: Epitaxial orthorhombic YMnO3 thin films, (001) oriented, have been grown by pulsed laser deposition on (001)SrTiO3 substrates. Their crystal structure and magnetic response have been studied in detail. Although bulk o-YMnO3 is antiferromagnetic, our magnetic measurements reveal intriguing thermal hysteresis between the zero-field-cooled and field-cooled curves below the onset of the antiferromagnetic ordering temperature, thus signaling a more complex magnetic structure with net ferromagnetic moments. We discuss on the possible origin of this net magnetization and we have found a correlation of the magnetic response with the strain state of the films. We propose that substrate-induced strain modifies the subtle competition of magnetic interactions and leads to a non-collinear magnetic state that can thus be tuned by strain engineering. [Copyright &y& Elsevier]

(00 l)-oriented Pb(Zr0.5Ti0.5)O3/CoFe2O4 (PZT/CFO) multilayer thin films were fabricated with a change in stacking periodicity. When the periodicity increased, a size effect on both ferroelectric and ferromagnetic properties was observed. This result indicates the existence of a passive layer at the PZT/CFO interface. Consequently, the magnetoelectric coupling was significantly degraded with increasing stacking periodicity. From transmission electron microscopy analysis, in addition to slight interdifussion, a highly roughened interface structure is believed to be responsible for the formation of the passive layer. [Copyright &y& Elsevier]

The effects of CoFe2O4 content on the microstructure, leakage current density, fatigue endurance and magnetoelectric (ME) voltage coefficient of multiferroic Bi3.15Nd0.85Ti3O12–CoFe2O4 thin films fabricated by a chemical solution deposition method were studied. It was found that the composite films have lower leakage current densities and better fatigue endurance properties compared with pure Bi3.15Nd0.85Ti3O12 film, and the composite films possess large ME voltage coefficients. The mechanism concerning the dependence of properties on CoFe2O4 content is discussed. [Copyright &y& Elsevier]

Abstract: We present a thermodynamic analysis and phase field modeling of self-assembled multiphase nanostructures produced by phase transformations in constrained layers. Due to coherency between the phases, the elastic interactions between them and between each phase and the substrate layer play an important role in the formation of the nanostructures. It has been shown that a variety of morphologies of heterophase nanostructures can be obtained depending on the crystallographic characteristics of transformations, elastic properties of the phases, relative fractions of the phases, and the thickness of the film. The results obtained by phase-field modeling agree well with predictions of an analytical thermodynamic model. The final equilibrium structures are determined by thermodynamic parameters and do not depend on the transformation path and, therefore, the phase-field approach developed in this paper can be expanded to finding equilibrium multiphase coherent nanostructures created as a result of solid–solid or solid–liquid transformations as well as during co-deposition on a substrate. [Copyright &y& Elsevier]

Bi1-xMgxFeO3 (BMFO, x = 0, 0.02, 0.04, 0.06 and 0.08) multiferroic films were directly synthesized on flexible stainless steel (FSS), save the bottom electrode process, by means of sol–gel spin-coating technology. The effects of different bending conditions on ferroelectric, dielectric and leakage-current properties of BMFO films were investigated. The leakage-current densities of BiFeO3 (BFO, x = 0) and BMFO (x = 0.06) films were 5.86 × 10−4 and 3.73 × 10−7 A/cm2, which shows that the BMFO (x = 0.06) has more than three orders of magnitude lower than that of BFO film. The residual polarization (2 Pr) can be enhanced from 120 to 140 μC/cm2. The proper doping of Mg in BiFeO3 film could provide an effective method for reducing the leakage-current values as well as boosting the ferroelectric properties. In this study, the leakage-current mechanism of low electric field and high electric field of BMFO film is analyzed and established. In addition, the flexible BMFO film maintains practical ferroelectric and leakage-current properties at retention time of 106 s under different symmetry bending conditions. These results indicate that the BFMO film will be very practical in opto-electronic and storage device applications. [ABSTRACT FROM AUTHOR]