共查询到20条相似文献,搜索用时 15 毫秒
1.
Bi1+xCexFeO3 (Ce–BFO) for x=0, 0.05, 0.1, and 0.15 monophasic ceramic samples were successfully synthesized by conventional solid-state reaction routes. The influences of Ce doping on structural, dielectric, ferroelectric, leakage current and capacitive properties of BiFeO3 ceramics were investigated intensively. At higher concentrations of x (x=0.1 and 0.15) the samples showed good crystallinity with almost impurity free phases. No structural phase transformation took place after partial doping of Ce ions and all ceramic bulk samples remain in their rhombohedral structure with space group R3c. The dielectric behavior of the samples improved significantly and the ferroelectric hysteresis loops changed their shape from rounded to a strongly nonlinear typical ferroelectric feature mainly originating from the domain switching and became enhanced with increase in doping concentration of cerium (Ce). Experimental results also suggested that partial doping of higher valence, smaller ionic radius Ce ions in BiFeO3 forces the reduction of oxygen vacancies, resulting in a great suppression of leakage current. It is found that the sharp capacitance peak/discontinuity present in the C–V characteristics of Ce–BFO for different Ce doping concentrations is directly associated with the polarization reversal. Incorporation of excess bismuth in the presence of Ce in BiFeO3 is expected to compensate Bi loss during high temperature sintering and caused structural distortion which also favors enhancement of ferroelectric properties in Ce-doped BFO. 相似文献
2.
Dongxiang ZhouGang Jian Yanan Zheng Shuping GongFei Shi 《Applied Surface Science》2011,257(17):7621-7626
Electrophoretic deposition was utilized for preparation of BaTiO3/CoFe2O4 multiferroic composite thick films on indium-tin oxide substrates. The suspensions for electrophoretic experiments were prepared by dispersing BaTiO3 and CoFe2O4 nanoparticles with different molar ratios into solvents composed of ethanol and acetylacetone. Polyvinyl butyral was added to the suspensions in order to enhance the adhesion and strength of deposit and prevent cracking. The zeta potential values of BaTiO3/CoFe2O4 suspensions were measured to be 26.4-36.9 mV. The experiment results showed that deposited films were obtained only when the applied electric field was larger than a certain critical value. XRD and SEM analysis depicted the presence of constituent phases in composite films. The percolation threshold of composite films was improved through dispersing ferromagnetic phase into ferroelectric phase. Therefore, the ferroelectric properties of composite thick films were maintained when the ferromagnetic properties were enhanced significantly with increasing CFO content. 相似文献
3.
C. Doubrovsky G. André F. Bouquet E. Elkaim M. Li M. Greenblatt P. Foury-Leylekian 《Physica B: Condensed Matter》2012,407(11):1718-1721
RMn2O5 (R=lanthanide, Bi, Y) multiferroic compounds are intensively studied for their potential application in the spintronic field. In these systems, the key issue is to understand the origin of the strong coupling between the ferroelectric and magnetic orders and to investigate the influence of the nature of the R ions in this coupling. While the phase diagram of RMn2O5 compounds with small R size is well established, this of large R size compounds is missing due to the lack of samples originating with difficulties of synthesis. We present in this paper the first investigation of the thermodynamic, structural and magnetic properties of high quality polycrystalline PrMn2O5 samples. Our work shows that PrMn2O5 presents two magnetic transitions corresponding to commensurate magnetic orderings. We also evidence a weak lattice effect coupled to the magnetic order. Our results point out that the physical properties of PrMn2O5 differ from those of the parent compounds with magnetic R ions. 相似文献
4.
Yong Liu Kang-Kai WangLi-Hong Ni Zhao-Hui RenGang Xu Chen-Lu SongGao-Rong Han 《Physics letters. A》2012
The phase transition of BiFeO3 (BFO) from tetragonal to monoclinic induced by pressure was investigated by first-principles method. The sequential monoclinic phase, Ma, which is favorable during low compression with respect to the tetragonal phase, was characterized. The order parameters were calculated in the vicinity of the phase transition, showing that phase transition has a second-order character. The results demonstrated that the pressure-induced tetragonal-to-monoclinic phase transition in BFO is related to the softening behavior of the E mode, which are very helpful in further investigations of the morphotropic phase boundary (MPB) in lead-free materials. 相似文献
5.
In this paper, we show that the leakage current properties of BiFeO3 (BFO) thin films have been greatly improved by Zr-doping. In contrast, the magnetic properties of Zr-doped BFO films are affected as a weak ferromagnetism. Beyond the double-exchange interactions arising from the creation of Fe2+, we propose another simple model considering the replacement of the magnetically active Fe3+, time to time, by a non-active Zr4+, which is expected to induce a local ferromagnetic coupling rather than an antiferromagnetic one. 相似文献
6.
使用快速烧结和溶胶-凝胶方法制备了Bi(Fe1-xMnx)O3的块材陶瓷,其x能够达到0.3,因而可以得到较细的粉末. 经X射线衍射谱和拉曼光谱研究发现其结构转变取决于锰的掺杂浓度. 当x=0.05和0.1时,Bi(Fe1-xMnx)O3的结构保持斜方六面体结构;当x=0.3时,Bi(Fe1-xMnx)O3的结构变化到正方六面体结构.在x=0.05和0.1时观测到弱铁磁性,但在x=0.3时观测到强顺磁性. 这显示了Bi(Fe1-xMnx)O3从反铁磁性到顺磁性的磁相变,同时也表明其结构从R3C变化到C222. 在30和140 K, x=0.05和0.1时,观察到Bi(Fe1-xMnx)O3的两个反常现象. 在30 K时,直流磁记忆和缓慢测量Bi(Fe1-xMnx)O3团族的反常现象与冷冻的旋转玻璃系统有关. 相似文献
7.
Qingyu Xu Shengqiang ZhouZheng Wen Di WuTeng Qiu Mingxiang XuKay Potzger Heidemarie Schmidt 《Physics letters. A》2011,375(8):1209-1212
Bi(Fe1 − xMnx)O3 ceramics (x up to 0.3) were prepared by rapid sintering. Weak ferromagnetism with two magnetic anomalies at low temperatures was observed for Bi(Fe0.95Mn0.05)O3 and Bi(Fe0.9Mn0.1)O3. From temperature-dependent magnetic relaxation measurements, the anomalies at 20 K and 100 K are related to the freezing of cluster spin glass. 相似文献
8.
Shuxia Zhang Yingbang Yao Yao Chen Dongliang Wang Xianping Zhang Satoshi Awaji Kazuo Watanabe Yanwei Ma 《Journal of magnetism and magnetic materials》2012
In this work, the effects of magnetic annealing on crystal structure and multiferroic properties of BiFeO3 and Bi0.85Dy0.15FeO3 have been investigated. It is found that the X-ray diffraction patterns of pure BiFeO3 samples are obviously broadened after magnetic annealing, whereas those of Bi0.85Dy0.15FeO3 samples are almost unchanged. Magnetic field annealing did not affect the magnetic properties of these two kinds of samples much. However, ferroelectric properties of the two materials exhibited different behaviors after magnetic field annealing. For pure BiFeO3 samples, the remnant polarizations (Pr) are suppressed; in contrast, for Bi0.85Dy0.15FeO3 samples, Pr is greatly enhanced. Possible mechanisms for the effects of magnetic field annealing have been discussed. 相似文献
9.
The ferroelectric properties of BiFeO3 (BFO) films spray deposited on porous silicon have been studied. The analysis of XRD and FESEM investigations show that the crystalline strain in the BFO films increases with pore size. The BFO films on porous silicon substrate showed improvement in ferroelectric fatigue behavior, remanent polarization and ferroelectric switching time. A maximum memory window of 5.54 V at 1 MHz and a large remanent polarization (Pr) of 13.1 μC/cm2 have been obtained at room temperature. The improvement in the ferroelectric properties of these films has been correlated to the crystalline strain. 相似文献
10.
Fei Fan Mengmeng Duan Bingcheng Luo Changle Chen 《Chinese Journal of Physics (Taipei)》2018,56(5):1903-1908
BiFeO3/LaNiO3 (BFO/LNO) heterostructure was fabricated on quartz substrate via RF sputtering method. The microstructure and surface morphology of the BFO/LNO heterostructure was demonstrated. BFO layer shows good ferroelectric and weak ferromagnetic characters at room temperature. The dielectric constants of the heterostructure under an applied magnetic field 1.2T and zero field are both decreased with increasing frequency at room temperature and the dielectric constant under the applied magnetic field is larger, which is attributed to the coupling between the electric and magnetic dipoles, and further demonstrated in the framework of the Ginzburg-Landau theory for second phase transition. Additionally, the photoconductivity of the heterostructure under blue-laser illumination was observed, and the photoconductivity increase with the enhanced power of the blue-laser. 相似文献
11.
Y.R. DaiQingyu Xu Xiaohong ZhengShijun Yuan Ya ZhaiMingxiang Xu 《Physica B: Condensed Matter》2012,407(3):560-563
BiFe1−xNixO3 ceramic powders with x up to 0.10 have been prepared by the sol-gel technique. The band gap of BiFeO3 is 2.23 eV, and decreases to 2.09 eV for BiFe0.95Ni0.05O3 and BiFe0.90Ni0.10O3. The Mössbauer spectra show sextet at room temperature, indicating the magnetic ordering and the presence of only Fe3+ ions. Superparamagnetism with blocking temperature of 31 K for BiFe0.95Ni0.05O3 and 100 K for BiFe0.90Ni0.10O3 was observed. Enhanced magnetization at room temperature have been observed (1.0 emu/g for BiFe0.95Ni0.05O3 and 2.9 emu/g for BiFe0.90Ni0.10O3 under magnetic field of 10,000 Oe), which is one order larger than that of BiFeO3 (0.1 emu/g under magnetic field of 10,000 Oe). The enhanced magnetization was attributed to the suppression of the cycloidal spin structure by Ni3+ substitution and the ferrimagnetic interaction between Fe3+ and Ni3+ ions. 相似文献
12.
The leakage current behaviours of polycrystalline BiFeO3 thin films are investigated by using both conductive atomic force microscopy and current-voltage characteristic measurements. The local charge transport pathways are found to be located mainly at the grain boundaries of the films. The leakage current density can be tuned by changing the post-annealing temperature, the annealing time, the bias voltage and the light illumination, which can be used to improve the performances of the ferroelectric devices based on the BiFeO3 films. A possible leakage mechanism is proposed to interpret the charge transports in the polycrystalline BiFeO3 films. 相似文献
13.
Li-Qin Yan Fen Wang Yuelei Zhao Tao Zou Jun Shen Young Sun 《Journal of magnetism and magnetic materials》2012
The exchange bias phenomenon has been investigated in multiferroic Eu0.75Y0.25MnO3. The material shows a weak ferromagnetism with cone spin configuration induced by external magnetic field below 30 K. Consequently, the electric polarization coming from the cycloid spin order below 30 K can be suppressed by external magnetic fields. The magnetic hysteresis loops after cooling in a magnetic field exhibit characteristics of exchange bias below the spin glassy freezing temperature (Tg)∼16 K. The exchange bias field, coercivity field, and remanent magnetization increase with increasing cooling magnetic field. The exchange bias effect is ascribed to the frozen uncompensated spins at the antiferromagnetism/weak ferromagnetism interfaces in the spin-glass like phase. 相似文献
14.
Amit KumarK.L. Yadav 《Physica B: Condensed Matter》2011,406(9):1763-1766
The mixed spinel-perovskite composites of xMnFe2O4-(1-x)BiFeO3 with x=0, 0.1, 0.2, 0.3 and 0.4 were prepared by solid state reaction method. The structure and grain size were examined by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The XRD results showed that the composites consisted of spinel MnFe2O4 and perovskite BiFeO3 phases after being calcined at the temperature 950 °C for 2 h. The grain size ranged from 0.8 to 1 μm. Magnetization was found to increase with increasing concentration of ferrite content. The variation of dielectric constant and dielectric loss with frequency showed dispersion in the low frequency range. Magnetocapacitance was also observed in the prepared composites, which may be the sign of magnetoelectric coupling in the synthesized composites at room temperature. 相似文献
15.
Ceramics of YMnO3 and its Fe substituted YMn(0.93)Fe(0.07)O3 solid solution were synthesized by solid state reaction of the oxides at 1200 °C. Hexagonal phase was identified in both cases by X-ray powder diffraction. Rietveld refinement of cell parameters showed an increase of the parameter values for the solid solution. Dielectric permittivity measurements versus temperature showed a phase transition at 655 °C for yttrium manganite, however, for the solid solution no phase transition was detected on heating up to 700 °C. Dielectric loss measurements showed higher slope changes and better defined local maxima for the solid solution than for the pure phase. 相似文献
16.
Bi1–xBaxFeO3 (0.0≤x≤0.25) ceramics are prepared by chemical synthesis route. At room temperature, antiferromagnetic BiFeO3 is converted to ferromagnetic on doping Ba. A large change in the magnetization is observed around 370 °C which is close to the Neel temperature (TN) of parent compound. Another magnetic transition is also observed near 600 °C. Spin canting or impurity phase could be a probable reason for the origin of ferromagnetism in both cases. Ferroelectric and magnetic transitions of the compounds shift towards higher temperature with Ba-doping concentration. Anomaly in the dielectric constant is also observed near the TN of BiFeO3. The composition x=0.15 shows the maximum magnetic moment at room temperature while better fatigue resistance and maximum magnetoelectric coupling are observed for x=0.20 composition. 相似文献
17.
Jian-Jun Gu Guo-Liang ZhaoFu-Wei Cheng Jin-Rong HanLi-Hu Liu Hui-Yuan Sun 《Physica B: Condensed Matter》2011,406(23):4400-4403
Multiferroic thin films with the general formula TiO2/BiFe1−xMnxO3 (x=0.00, 0.05, 0.10 and 0.15) (TiO2/BFMO) were synthesized on Au/Ti/SiO2/Si substrates using a chemical solution deposition (CSD) method assisted with magnetron sputtering. X-ray diffraction analysis shows the thin films contained perovskite structures with random orientations. Compared with BFMO films, the leakage current density of the TiO2/BFMO thin films was found to be lower by nearly two orders of magnitude, and the remnant polarizations were increased by nearly ten times. The enhanced ferroelectric properties may be attributed to the lower leakage current caused by the introduction of the TiO2 layer. The J-E characteristics indicated that the main conduction mechanism for the TiO2/BFMO thin film was trap-free Ohmic conduction over a wide range of electric fields (0-500 kV/cm). In addition, ferromagnetism was observed in the Mn doped BFO thin films at room temperature. The origin of ferromagnetism is related to the competition between distortion of structure and decrease of grain size and decreasing net magnetic moment in films due to Mn doping. 相似文献
18.
P. Barahona O. Pea A.B. Antunes C. Campos G. Pecchi Y. Moreno C. Moure V. Gil 《Journal of magnetism and magnetic materials》2008,320(14):e61-e64
Partial substitution of manganese by cobalt in rare-earth perovskites REMnO3 leads to unusual magnetic phenomena because of the simultaneous presence of Mn3+, Mn4+, Co2+ and Co3+ species. The magnetic nature of the RE cation plays a fundamental role in the magnetic properties. We present herein two specific families: for RE=La the magnetic behavior of the |Co+Mn| network is observed, while for Gd its strong magnetic moment interacts with the transition metals, leading to a spin reversal state. Magnetic interactions are maximized at x=0.50, as if two regimes exist: for x<0.5 Co substitutes Mn in the REMnO3 manganite, and for x>0.5 Mn substitutes Co in the RECoO3 cobaltite. 相似文献
19.
Konstantinos KoumpourasIosif Galanakis 《Journal of magnetism and magnetic materials》2011,323(17):2328-2333
Using ab-initio calculations, we study the properties of the multiferroic BiFeO3 compounds in the perfect cubic perovskite lattice structure. We show that the appearance of magnetism is energetically favorable. Except the ferromagnetic structure, there are three possible antiferromagnetic arrangements, which are close in energy, and for large values of the lattice constant a G-type antiferromagnetism is the most stable magnetic order. Fe atoms are responsible for the spin magnetic moments while the values of the induced spin moments at the other sites depend strongly on the local environment of the atoms. There is a significant charge transfer from the Fe and Bi atoms towards the p-states of O atoms. 相似文献
20.
P. Priyadharsini A. Pradeep B. Sathyamoorthy G. Chandrasekaran 《Journal of Physics and Chemistry of Solids》2014
Room temperature multiferroic properties of BiFeO3 (BFO), Bi0.9La0.1FeO3 ((La)BFO) and Bi0.9La0.075Ce0.025FeO3 ((La,Ce)BFO) nanoparticles have been reported in this paper. XRD (X-ray diffraction) analyses of the nanoparticles show a decrease in the lattice constants and cell volume with the substitution of La and Ce. It is evident from the SEM (scanning electron microscope) micrographs that the (La,Ce) co-doped sample possesses dense microstructure made of smaller particles. Raman study accounts for the weakening of the strong hybridization between Bi-O by the substitution of La and Ce ions. This is also accompanied by an increase in the remanent magnetization, dielectric constant, and ferroelectric polarization. BFO nanoparticles show exchange bias effect under an applied magnetic field while the (La)BFO and (La,Ce)BFO samples show no trace of such effect. Ac-conductivity of (La,Ce) co-doped sample is observed to be several orders lesser in magnitude than bulk BFO ceramics. These results are interpreted by means of the subtle change in the structure, suppression of the spin cycloid and reduction of oxygen vacancies in the doped samples. 相似文献