Multiferroics simultaneously exhibit several order parameters such as ferroelectricity and antiferromagnetism, representing an appealing class of multifunctional material. As the only multiferroics above room temperature, BiFeO3 (BFO) becomes an attractive choice for a wide variety of applications in the areas of sensors and spintronic devices. The coexistence of several order parameters brings about novel physical phenomena, for example, the magnetoelectric coupling effect. It allows the reversal of ferroelectric polarization by a magnetic field or the control of magnetic order parameter by an electric field. Heterostructure interface plays an important role in enhancing the ferroelectric and magnetic properties of multiferroic materials. Furthermore, the magnetoelectric coupling at the interface between the antiferromagnetism BFO and a ferromagnetic film has the close relation with achieving a functional multiferroic-ferromagnetic heterostructure. In order to determine the relationship between the multiferroic property and the interface experimentally, we prepare the Bi0.8Ba0.2FeO3(BBFO)/La2/3Sr1/3MnO3(LSMO) heterostructure on an SrTiO3(STO) substrate by pulsed laser deposition, and the structure characteristics and ferroelectric and magnetic properties are investigated. X-ray diffraction analysis shows that BBFO and LSMO films are epitaxially grown as single-phase. The further study by high-resolution transmission electron microscopy determines that the BBFO film has a tetragonal structure. The ferroelectric and magnetic measurements show that the magnetic and the ferroelectric properties are simultaneously improved, and the maximum values of the remnant polarization (2Pr) and the saturation magnetization of the heterostructure at room temperature are about 3.25 C/cm2 and 112 emu/cm3, respectively. The reasons for enhancing the ferroelectric and ferromagnetic properties of heterostructure are demonstrated by X-ray photoelectron spectrum that shows being unrelated to the valence states of Fe element. On the contrary, interface effect plays a major role. In addition, the magnetic resistivities and dielectric properties of BBFO/LSMO heterostructure are investigated at temperatures in a range of 50 K to 300 K, finding that magnetoresistance (MR) and magnetodielectric (MD) are respectively about -42.2% and 21.9% at 70 K with a magnetic field of 0.8 T, and the transition of magnetic phase takes place near 180 K. Furthermore, the temperature dependences of magnetodielectric and magnetoloss (ML) present opposite tendencies, suggesting that magnetodielectric is caused by Maxwell-Wagner effect and the magnetoresistance. Experimental results reveal that heterogeneous interface effect shows the exceptional advantages in enhancing multiferroic property and magnetoelectric coupling effect of complex heterostructure material. It is an effective way to speed up the application of multiferroic materials.

The transport properties and magnetoresistance of electron-doped manganate / insulator composites (La 0.8 Te 0.2 MnO 3 ) 1−x /(ZrO 2 )x (x = 0, 0.3, and 0.5) are investigated. It is found that the metal-insulator transition temperature of this system shifts to a lower value as the ZrO 2 content increases. The introduction of ZrO 2 enhances both the domain scattering and electron relative scattering in the metal transport region. In the adiabatic small polaron hopping transport region, the thermal activation energy seems invariable regardless of the ZrO 2 content. The application of a magnetic field promotes the charge transportation capabilities of the composites, and the magnetoresistance is enhanced with an increase of the ZrO 2 content. This could be attributed to the more remarkable modification effect of magnetic field on ordering degree in the composites than in pure La 0.8 Te 0.2 MnO 3 .

The photovoltaic effect and the good rectifying behavior are observed in La0.88Te0.12MnO3(LTMO)/Si heterostructure fabricated by a pulsed laser deposition method. The photovoltage increases quickly to a maximum value at about 394 μs and then decreases gradually. The maximum photovoltage is about 13.7 mV at T = 80 K. The maximum photovoltage decreases with temperature increasing, which is attributed to the stronger thermal fluctuation. A nonlinear decrease of the maximum photovoltage in the photovoltages-temperature curve is observed, which is mainly caused by the change in the band structure of the LTMO layer due to the metal-insulator transition.

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