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.

Two gold (I) complexes 1 and 2 were designed, synthesized and structurally characterized by NMR, IR as well as elemental analysis. Fluorescence studies show that the two compounds exhibit very weak photoluminescence in pure organic solvents (dimethylsulfoxide or N,N-dimethyl formamide), enhanced fluorescences are observed after the addition of water, which indicate that the aggregation-induced emission (AIE) characteristics of these complexes. The solid-state fluorescence of complexes 1 and 2 can be significantly increased by grinding the solid samples. The recovery of the fluorescence intensity of these ground powders was detected after exposure the samples to organic solvent vapors. This phenomenon suggested the reversible mechanochromism behaviors of comounds 1 and 2. The powder X-ray diffracton (XRD) results displayed the morphology transition between the crystalline and amorphous states before and after the grinding of the sample. The AIE and reversible mechanochromism characteristics of complexes 1 and 2 made them can be potentially used for "smart" materials.