The crystal structure of the minor phase, named superstructure II, existing in multiferroic compound BiMnO3 has been studied by electron diffraction and high-resolution transmission electron microscopy. Domains of maj...The crystal structure of the minor phase, named superstructure II, existing in multiferroic compound BiMnO3 has been studied by electron diffraction and high-resolution transmission electron microscopy. Domains of major and minor phases coexisting in BiMnO3 were observed in high-resolution electron microscope images. The unit cell of minor phase was determined to be triclinic with the size 4×4×4 times as large as the distorted perovskite subcell. The [111] and [101] projected structure maps of the minor phase have been derived from the corresponding images by means of the image processing. A possible rough three-dimensional （3D） structure model was proposed based on the 3D structural information extracted from the two projected structure maps. Since there is no inversion centre in the proposed model, the minor phase may contribute to the ferroelectric property of BiMnO3.展开更多
Perovskite BiMnO_3 samples are successfully synthesized by the co-precipitation method at relatively low pressure and moderate temperature.The temperature dependences of resistivity are measured and systematically inv...Perovskite BiMnO_3 samples are successfully synthesized by the co-precipitation method at relatively low pressure and moderate temperature.The temperature dependences of resistivity are measured and systematically investigated.It is shown that the electrical resistivity increases sharply with the decrease of temperature above 210 K and the fitted results demonstrate that the thermally activated conduction model is the dominant conduction mechanism for the electron transport behaviors in this temperature region.A dual conducting mechanism,i.e.,the variable range hopping and thermal activated conduction,is suggested to be responsible for the transport behaviors of BiMnO_3 in the region of 180-200 K.Moreover,the resistivity increases slightly with the decrease of temperature below 180 K and the transport is governed by the variable range hopping mechanism.展开更多
We study the elastic constants and electronic properties of orthorhombic Bi Mn O3 under uniaxial strain along the c-axis using the first-principles method. It is found that, beyond the range –0.025 〈ε〈 0.055, the ...We study the elastic constants and electronic properties of orthorhombic Bi Mn O3 under uniaxial strain along the c-axis using the first-principles method. It is found that, beyond the range –0.025 〈ε〈 0.055, the predicted stiffness constants c ij cannot demand the Born stability criteria and the compliance constant s44 shows abrupt changes, which accompany phase transition. In addition, the results for magnetism moments and polycrystalline properties are also reported. Additionally, under compressive strain, a band gap transition from the indirect to the direct occurs within0：019 〈ε〈0：018. Furthermore, the response of the band gap of orthorhombic BiMnO3 to uniaxial strain is studied.展开更多
Magnetic ferroelectrics are one of the most important functional materials. The present bottleneck lim- iting applications of them is lacking of high-temperature single-phased ferromagnetic-ferroelectric multiferroics...Magnetic ferroelectrics are one of the most important functional materials. The present bottleneck lim- iting applications of them is lacking of high-temperature single-phased ferromagnetic-ferroelectric multiferroics with strong magnetoelectric coupling effect. Here, those progresses of the mechanism for coexistence of ferroelectric and magnetic order, experimental and theoretical studies on single-phased magnetic ferroelectrics, and the relationship between magnetic structure and crystal symmetry are summarized. With examples of BiFeO3, BiMnO3 and Bi2FeCrO6, the difficulties encountered in this field are analyzed. At last, some prospects to develop high-temperature single-phased ferromagnetic-ferro- electric multiferroics are also presented.展开更多
基金supported by the National Natural Science Foundation of China (Grant No 50672124)Ministry of Science and Technology (MOST) of China (Grant Nos 2005CB724402 and 2007CB925003)
文摘The crystal structure of the minor phase, named superstructure II, existing in multiferroic compound BiMnO3 has been studied by electron diffraction and high-resolution transmission electron microscopy. Domains of major and minor phases coexisting in BiMnO3 were observed in high-resolution electron microscope images. The unit cell of minor phase was determined to be triclinic with the size 4×4×4 times as large as the distorted perovskite subcell. The [111] and [101] projected structure maps of the minor phase have been derived from the corresponding images by means of the image processing. A possible rough three-dimensional （3D） structure model was proposed based on the 3D structural information extracted from the two projected structure maps. Since there is no inversion centre in the proposed model, the minor phase may contribute to the ferroelectric property of BiMnO3.
基金Supported by the Key Research Project of Shaanxi University of Science and Technology under Grant Nos 2016GBJ-12 and2016BJ-59
文摘Perovskite BiMnO_3 samples are successfully synthesized by the co-precipitation method at relatively low pressure and moderate temperature.The temperature dependences of resistivity are measured and systematically investigated.It is shown that the electrical resistivity increases sharply with the decrease of temperature above 210 K and the fitted results demonstrate that the thermally activated conduction model is the dominant conduction mechanism for the electron transport behaviors in this temperature region.A dual conducting mechanism,i.e.,the variable range hopping and thermal activated conduction,is suggested to be responsible for the transport behaviors of BiMnO_3 in the region of 180-200 K.Moreover,the resistivity increases slightly with the decrease of temperature below 180 K and the transport is governed by the variable range hopping mechanism.
文摘We study the elastic constants and electronic properties of orthorhombic Bi Mn O3 under uniaxial strain along the c-axis using the first-principles method. It is found that, beyond the range –0.025 〈ε〈 0.055, the predicted stiffness constants c ij cannot demand the Born stability criteria and the compliance constant s44 shows abrupt changes, which accompany phase transition. In addition, the results for magnetism moments and polycrystalline properties are also reported. Additionally, under compressive strain, a band gap transition from the indirect to the direct occurs within0：019 〈ε〈0：018. Furthermore, the response of the band gap of orthorhombic BiMnO3 to uniaxial strain is studied.
基金supported by the National Natural Science Foundation of China (Grant No. 10304021)National Basic Research Program of China (Grant No. 2007CB924900)+2 种基金Foundation for the Author of National Excellent Doctoral Dissertation of China (FANEDD-200744)Shanghai Pujiang Program (Grant No. 07pj14087)Program for New Century Excellent Talents in University (NCET-07-0624)
文摘Magnetic ferroelectrics are one of the most important functional materials. The present bottleneck lim- iting applications of them is lacking of high-temperature single-phased ferromagnetic-ferroelectric multiferroics with strong magnetoelectric coupling effect. Here, those progresses of the mechanism for coexistence of ferroelectric and magnetic order, experimental and theoretical studies on single-phased magnetic ferroelectrics, and the relationship between magnetic structure and crystal symmetry are summarized. With examples of BiFeO3, BiMnO3 and Bi2FeCrO6, the difficulties encountered in this field are analyzed. At last, some prospects to develop high-temperature single-phased ferromagnetic-ferro- electric multiferroics are also presented.
