共查询到20条相似文献,搜索用时 0 毫秒
1.
K. Sadhana 《Journal of magnetism and magnetic materials》2010,322(23):3729-3736
The nanocrystalline Ni0.53Cu0.12Zn0.35Fe1.88O4 and BaTiO3 powders were prepared using Microwave-Hydrothermal (M-H) method at 160 °C/45 min. The as synthesized powders were characterized using the X-ray diffraction (XRD) and Transmission Electron Microscope (TEM). The size of the powders that were synthesized using M-H system was found to be ∼30 and ∼50 nm for ferrite phase and ferroelectric phases, respectively. The powders were densified using microwave sintering method at 900 °C/30 min. The ferrite and ferroelectric phases were observed from XRD and morphology of the composites was observed with the Scanning Electron Microscope (SEM).The magnetic hysteresis loops were recorded using the Vibrating Sample Magnetometer (VSM).The frequency dependence of real (μ′) and imaginary (μ″) parts of permeability was measured in the range of 1 MHz-1.8 GHz. The permeability decreases with an increase of BaTiO3 content at 1 MHz. The transition temperature (TC) of ferrite was found to be 245 °C. The TC of composite materials decreases with an increase in BaTiO3 content. 相似文献
2.
S.J. Yan L. Zhen C.Y. XuJ.T. Jiang W.Z. ShaoJ.K. Tang 《Journal of magnetism and magnetic materials》2011,323(5):515-520
Fe1−xCox alloy microparticles with size 3-5 μm and novel flower-like shapes were prepared by a simple low temperature reduction method. The electromagnetic properties for the paraffin matrix composites containing Fe1−xCox alloy microparticles were measured using a vector network analyzer in the 2-18 GHz frequency range. As a consequence of large surface- and shape-anisotropy energy for the flower-like shaped 3D microstructures, the strong natural resonance around 8-12 GHz and remarkable dielectric relaxation were observed in the complex permittivity and permeability spectrum, which are dominant in the enhanced electromagnetic wave absorption (EMA) performance. It was found that both the electromagnetic parameters of complex permittivity and permeability and the intensity and location of absorption band were remarkably dependent on the Co/Fe molar ratio. The enhanced EMA performance was obtained in these Fe1−xCox-paraffin (x=0.4, 0.5, and 0.6) composites system. For the Fe0.5Co0.5 alloy, the reflection loss (RL) exceeding −20 dB was obtained in the broad frequency range of 5.4-18 GHz with a thin sample thickness of between 1.0 and 2.9 mm. In particular, an optimal RL of −59 dB was obtained at 3.61 GHz with a thin thickness of 3.6 mm for the Fe0.4Co0.6 sample. The Fe1−xCox alloy microparticles may be attractive candidates for applications of microwave absorption materials with a wide frequency range and strong absorption in the high frequency region. 相似文献
3.
B.K. BammannavarL.R. Naik 《Journal of magnetism and magnetic materials》2012,324(6):944-948
Magnetoelectric (ME) composites consisting of ferrite phase (x) Ni0.5Zn0.5Fe2O4+ferroelectric phase (1−x)Pb Zr0.8Ti0.2O3 (Lead Zirconate Titanate—PZT) in which x (mol%) varies between 0 and 1 (0.0≤x≤1.0) was synthesized by double sintering ceramic method. The presence of constituent phases of ferrite, ferroelectric and their composites was confirmed by X-ray diffraction studies. The hysteresis measurement was used to study magnetic properties such as saturation magnetization (MS) and magnetic moment (μB). The existence of single domain (SD) particle in the ferrite phase and mixed (SD+MD) particle in the composites was studied from AC susceptibility measurements. ME voltage coefficient for each mol% of ferrite phase was measured as a function of applied DC magnetic field and at the same time influence of magnetic field on ME response and resistivity of composites was studied. The maximum ME voltage coefficient of 0.84 mV/cm Oe was observed for 15% of ferrite phase and 85% of ferroelectric phase in the composites. 相似文献
4.
Hua Su Huaiwu Zhang Xiaoli Tang Yulan Jing Zhiyong Zhong 《Journal of magnetism and magnetic materials》2009,321(18):2763-2766
The composition effects on the dielectric and magnetic properties of NiCuZn-BaTiO3 composites fired at low temperature were investigated. The coexistence of perovskite BaTiO3 and spinel ferrite phases in the composites were observed; no significant chemical reactions occurred between BaTiO3 and NiCuZn ceramics during sintering. The nanosized BaTiO3 powders favored a decrease in grain size. The saturation magnetization, remanent magnetization and real permeability continuously decreased with increasing BaTiO3 content. And the real permittivity continuously increased with the BaTiO3 content. The Q-factor (quality factor) exhibited relatively high values with 20-30 wt% BaTiO3. All composite materials exhibited a low dielectric loss below 100 MHz. Synthetically considerations, the composites with 20-30 wt% BaTiO3 could obtain relatively high real permeability and real permittivity values, and the magnetic and dielectric losses were relatively low, so they were the best candidates to produce LC-integrated chip elements. 相似文献
5.
D.R. Patil 《Journal of Physics and Chemistry of Solids》2007,68(8):1522-1526
Magnetoelectric composites of NiFe2O4 and Ba0.8Sr0.2TiO3 were prepared using conventional double-sintering ceramic method. The phase formation of magnetoelectric composites was confirmed by XRD technique. Variation of dielectric constant and loss tangent at room temperature with frequency in the range 100 Hz-1 MHz has been studied. Also the variation of dielectric constant and loss tangent with temperature and composition at fixed frequencies of 1 kHz, 10 kHz, 100 kHz and 1 MHz is reported. The static value of the magnetoelectric conversion factor was measured as a function of intensity of the magnetic field. The ME voltage coefficient of about 430 μV/cm Oe was observed for 15% NiFe2O4+85% Ba0.8Sr0.2TiO3 composite. All the samples show linear variation of magnetoelectric conversion in the presence of static magnetic field. 相似文献
6.
V. Dorcet P. Marchet G. Trolliard 《Journal of magnetism and magnetic materials》2009,321(11):1762-1766
This study shows that remarkable electric and magnetic properties are encountered within the (1−x)Na0.5Bi0.5TiO3 (NBT)-(x)BiFeO3 (BF) solid solution. Dual ferroelectric and magnetic properties are observed in the BF-rich part of the solid solution implying intrinsic multiferroic character of the compounds. In addition, a relaxation phenomenon is evidenced within the overall compositional domain of the solid solution. This study emphasizes that in the NBT-rich part, the relaxor behaviour is very similar to that of NBT, while beyond x=0.5, it turns to a different mechanism of relaxation probably induced by the presence of oxygen vacancies resulting from the mixed valence of the iron cations. 相似文献
7.
C.S. Xiong Y. Zeng J. Zhang L. Zhang X.W. Cheng L.J. Li 《Physica B: Condensed Matter》2008,403(18):3266-3270
Composite samples (1−x)La0.7Ca0.2Sr0.1MnO3(LCSMO)+x(ZnO) with different ZnO doping levels x have been investigated systematically. The structure and morphology of the composites have been studied by the X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The XRD and SEM results indicate that no reaction occurs between LCSMO and ZnO grains, and that ZnO segregates mostly at the grain boundaries of LCSMO. The magnetic properties reveal that the ferromagnetic order of LCSMO is weakened by addition of ZnO. The results also show that ZnO has a direct effect on the resistance of LCSMO/ZnO composites, especially on the low-temperature resistance. With increase of the ZnO doping level, TP shifts to a lower temperature and the resistance increases. It is interesting to note that an enhanced magnetoresisitance (MR) effect for the composites is found over a wide temperature range from low temperature to room temperature in an applied magnetic field of 3 kOe. The maximum MR appears at x=0.1. The low field magnetoresistance (LFMR) results from spin-polarized tunneling. However, around room temperature, the enhanced MR of the composites is caused by magnetic disorder. 相似文献
8.
Yu-Jie WuXiao-Kun Chen Jing ZhangXiao-Jia Chen 《Journal of magnetism and magnetic materials》2012,324(7):1348-1352
Bi1−xYxFeO3 (x=0-0.2) powders were prepared to study the effect of Y substitution on their structural and magnetic properties. A structural symmetric breaking from the rhombohedral R3c to orthorhombic Pnma at around x=0.10 was identified across a ferroelectric-paraelectric phase. A parabolic dependence of the magnetization upon substitution was obtained with a maximum at the phase transition boundary and a switching behavior for x=0.20. The composition-driven magnetic structure evolution was proposed to account for the magnetic properties in Bi1−xYxFeO3. 相似文献
9.
D.T. Zhang W.T. Geng M. Yue W.Q. Liu J.X. Zhang J.A. Sundararajan Y. Qiang 《Journal of magnetism and magnetic materials》2012
MnxBi100−x (x=48, 50, 55 and 60) alloys were prepared by the induction melting technique, and subjected to melt spinning and subsequent ball milling. XRD shows that the as-milled powders were mainly composed of LTP MnBi. Increasing melt spinning speed and reducing annealing treatment time can restrain the segregation of Mn from MnBi liquid during the peritectic reaction, which increases the LTP MnBi content. High energy ball milling results in the coercivity increase of MnBi powders. With increasing milling time, the coercivity increases initially and then decreases gradually. After ball milling for 4 h, the coercivity of the MnxBi100−x powders is 11.4 kOe for x=48 and 14.8 kOe for x=55. The optimal composition of Mn48Bi52 with more LTP has an M2.2 T of 49.98 emu/g and an Mr of 33.57 emu/g. 相似文献
10.
The structural, electronic structure, elastic and optical properties of the AlCu(Se1−xTex)2 compounds have been investigated by using a first-principles method based on density functional theory. The lattice constants of the quaternary compounds AlCu(Se1−xTex)2 increase with the increasing of Te composition. The calculated lattice constants for the ternary compounds i.e. AlCuSe2 and AlCuTe2 are in good agreement with the experimental data. The band structures show that the compounds have direct band gap and the band gaps are found to vary nonlinearly with composition. The total and part density of states of the quaternary AlCu(Se1−xTex)2 compounds are discussed. The calculated elastic constants indicate that all of the AlCu(Se1−xTex)2 compounds are mechanically stable. The bulk modulus B, shear modulus G, Young’s modulus E and Poisson’s ratio ν can be obtained by using the Voigt-Reuss-Hill averaging scheme. The B/G ratios of the AlCu(Se1−xTex)2 compounds indicate that AlCu(Se0.8Te0.2)2 is ductile and the others are brittle. The Debye temperature of the AlCu(Se1−xTex)2 compounds decreases a little with increasing Te content except the compound with x = 0.4. The dielectric functions, refractive index, extinction coefficient, absorption spectrums and energy-loss function of the AlCuSe2 and AlCuTe2 are also calculated and discussed in this work. 相似文献
11.
The magnetic property of double doped manganite Nd0.5(1+x)Ca0.5(1−x)Mn(1−x)CrxO3 with a fixed ratio of Mn3+:Mn4+=1:1 has been investigated. For the undoped sample, it undergoes one transition from charge disordering to charge ordering (CO) associated with paramagnetic (PM)-antiferromagnetic (AFM) phase transition at T<250 K. The long range AFM ordering seems to form at 35 K, rather than previously reported 150 K. At low temperature, an asymmetrical M-H hysteresis loop occurs due to weak AFM coupling. For the doped samples, the substitution of Cr3+ for Mn3+ ions causes the increase of magnetization and the rise of Tc. As the Cr3+ concentration increases, the CO domain gradually becomes smaller and the CO melting process emerges. At low temperature, the FM superexchange interaction between Mn3+ and Cr3+ ions causes a magnetic upturn, namely, the second FM phase transition. 相似文献
12.
Jijing XuGuijuan Ji Haifeng ZouYanhua Song Shucai Gan 《Journal of magnetism and magnetic materials》2011,323(1):156-161
Sm-substituted barium hexaferrites, Ba3−xSmxCo2Fe24O41 (x=0-0.25), were prepared by a conventional ceramic sintering method. The microstructure, complex permittivity, complex permeability and static magnetic properties of the samples were studied using powder X-ray diffraction, field emission scanning electron microscopy, vector network analyzer and vibrating sample magnetometry. The results reveal that by introducing a relatively small amount of Sm3+ instead of Ba2+ an important modification of both structure and high-frequency electromagnetic properties can be obtained. Doping of Sm3+ suppressed the grain growth and gave rise to a decrease of the grain size. As the Sm content increases, the static magnetic properties continuously increase. The real part and imaginary part of complex permittivity initially increase with Sm content, and then decreases when x>0.10. The imaginary part of complex permeability decreases after Sm3+ is doped. There is no obvious change in the real part of the complex permeability for different Sm contents. The reasons are discussed using electromagnetic theory. 相似文献
13.
In this work carbonyl iron/La0.6Sr0.4MnO3 composites were prepared to develop super-thin microwave absorbing materials. The complex permittivity, permeability and microwave absorption properties are investigated in the frequency range of 8-12 GHz. An optimal reflection loss of −12.4 dB is reached at 10.5 GHz with a matching thickness of 0.8 mm. The thickness of carbonyl iron/La0.6Sr0.4MnO3 absorber is thinner, compared with conventional carbonyl iron powders with the same absorption properties. The bandwidth with a reflection loss exceeding −7.4 dB is obtained in the whole measured frequency range with the thickness of 0.8 mm. The excellent microwave absorption properties are attributed to a better electromagnetic matching established by the combination of the enhanced dielectric loss and nearly invariable magnetic loss with the addition of La0.6Sr0.4MnO3 nanoparticles in the composites. Our work indicates that carbonyl iron/La0.6Sr0.4MnO3 composites may have an important application in wide-band and super-thin electromagnetic absorbers in the frequency range of 8−12 GHz. 相似文献
14.
H. LiK.F. Cai Y. Du H.F. WangS.Z. Shen X.L. LiY.Y. Wang C.W. Zhou 《Current Applied Physics》2012,12(1):188-192
AgPb18SbTe20−xSex (x = 1, 2, 4) bulk materials were prepared by combining hydrothermal synthesis and melting. Thermoelectric properties were measured from room temperature up to 773K. The materials showed n-type conduction and exhibited degenerate semiconductor behavior. The power factors of the materials varied greatly with increase of Se content (x). Partial substitution of Se for Te in AgPb18SbTe20 resulted in remarkable reduction of thermal conductivity in the whole temperature range and increase of power factor at lower temperatures; therefore, the dimensionless figure of merit, ZT, was enhanced below 600K. A maximum ZT value of ∼0.82 is obtained at 523K for the AgPb18SbTe18Se2 sample. 相似文献
15.
Oxidative (δ>0) nonstoichiometry in the perovskite ‘LaMnO3+δ’ has been known to be manifested not with O interstitials but rather with cation vacancies of equal amounts at the two cation sites, La and Mn, i.e. La1−xMn1−yO3 with x=y. Here, we report the fabrication of samples with record-high cation-vacancy concentrations (x>0.12 or δ>0.4) by means of a variety of high-pressure oxygenation techniques. Linear (negative) dependence of the cell volume on x was observed within the whole x range investigated, down to 56.9 Å3 (per formula unit) for a sample oxygenated at 5 GPa and 1100 °C using Ag2O2 as an excess oxygen source. With increasing degree of cation deficiency in La1−xMn1−xO3, the ferromagnetic transition temperature was found to follow a bell shape with respect to x exhibiting a maximum of ∼250 K about x≈0.1. For moderately oxygenated samples large magnetoresistance effect was evidenced. 相似文献
16.
C.S. ZhangL. Yang 《Journal of magnetism and magnetic materials》2012,324(8):1469-1472
Core-shell Co(1−x)NixFe2O4/polyaniline nanoparticles, where the core was Co(1−x)NixFe2O4 and the shell was polyaniline, were prepared by the combination of sol-gel process and in-situ polymerization methods. Nanoparticles were investigated by Fourier transform spectrometer, X-ray diffraction diffractometer, Scanning electron microscope, Differential thermal analysis and Superconductor quantum interference device. The results showed that the saturation magnetization of pure Co(1−x)NixFe2O4 nanoparticles were 57.57 emu/g, but Co(1−x)NixFe2O4/polyaniline composites were 37.36 emu/g. It was attributed to the lower content (15 wt%), smaller size and their uneven distribution of Co(1−x)NixFe2O4 nanoparticles in the final microsphere composites. Both Co(1−x)NixFe2O4 and PANI/Co(1−x)NixFe2O4 showed superparamagnetism. 相似文献
17.
The samples with the Mn3+/Mn4+ ratio fixed at 2:1 La(2+x)/3Sr(1−x)/3Mn1−xCrxO3 (0≤x≤0.20) have been prepared. The magnetic, electrical transport, and magnetoresistance properties have been investigated. Remarkable transport and colossal magnetoresistance (CMR) effect, as well as cluster glass (CG) behaviors have been clearly observed in the samples studied. It was found that the Curie temperature Tc and insulator−metal transition temperature Tp1 are strongly affected by Cr substitution. The experiment observations are discussed by taking into account the variety of tolerance factors t; the effects of A-site radius 〈rA〉 and the A-site mismatch effect (σ2). 相似文献
18.
HaiChuan Chen JianPing Long Lijun Yang XueSong Wei KaMa Huang 《Physica B: Condensed Matter》2012,407(18):3705-3708
The lattice constants, band structure and dielectric properties of Ca1−xSrxTiO3 (0<x<1) (CSTO) have been studies by using the first-principles implemented with the GGA-PBEsol method. The calculation results shows that the lattice constants of CSTO obeys the Vegard model while the energy gap of CSTO shows a decreasing trend with the changing molar fraction x. The real and imaginary parts of the dielectric function and the static dielectric constant of the CSTO, optical permittivity and the static refractive index, are given to support the potential applications of the compounds in the future. 相似文献
19.
B.S. Wang W.J. LuS. Lin J.C. LinP. Tong B.C. ZhaoW.H. Song Y.P. Sun 《Journal of magnetism and magnetic materials》2012,324(5):773-781
The effects of Mn substitutions on the crystal structure, magnetic properties, and magnetocaloric effect (MCE) of antiperovskite Sn1−xCMn3+x (0≤x≤0.40) have been investigated detailedly. Both the Curie temperature (TC) and the magnetizations at 40 kOe decrease with increasing x firstly for x≤0.10, and then increase with increasing x further. The type of magnetic transition changes from first-order to second-order around x=0.10 with increasing x. Chemical composition-dependent MCE is also studied around TC. With increasing x, the maximal magnetic entropy changes decrease and the magnetic phase transitions broaden. Accordingly, the relative cooling power (RCP) increases with increasing x, reaching the largest values of ∼0.56 J/cm3 (∼75 J/kg) and ∼1.66 J/cm3 (∼221 J/kg) with the magnetic changes of 20 kOe and 48 kOe, respectively. Considering the large RCP, inexpensive, and innoxious raw materials, these serial samples Sn1−xCMn3+x are suggested to be potential room-temperature magnetic refrigerant materials. 相似文献
20.
Dinesh Varshney R. Sapkale Meenu Varshney 《Journal of Physics and Chemistry of Solids》2011,72(8):945-953
A theoretical study of the elastic properties in diluted magnetic semiconductors Hg1−xMnxS (x=0.02 and 0.07) using an effective interionic interaction potential (EIoIP) in which long-range Coulomb interactions, charge transfer mechanism (three body interaction) and the Hafemeister and Flygare type short-range overlap repulsion extending up to the second neighbor ions and the van der Waals (vdW) interaction is considered. Particular attention is devoted to evaluate Poisson's ratio ν, the ratio RS/B of S (Voigt averaged shear modulus) over B (bulk modulus), elastic anisotropy parameter, elastic wave velocity, average wave velocity and thermodynamic property as Debye temperature is calculated. By analyzing Poisson's ratio ν and the ratio RS/B we conclude that Hg1−xMnxS is brittle in zinc blende (B3). To our knowledge this is the first quantitative theoretical prediction of the pressure dependence of ductile (brittle) nature of Hg1−xMnxS compounds and still awaits experimental confirmations. 相似文献