共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
Z.H. Wang D.Y. Geng J. Li W. Liu Z.D. Zhang 《Journal of magnetism and magnetic materials》2010,322(20):3000-3003
The characterization and magnetic properties of YFe12−xMox (x=2.0, 2.5 and 3.0) with the ThMn12-type structure, and the magnetocaloric effect of YFe9.5Mo2.5 were investigated. A directional growth was observed in YFe10Mo2 alloy. A broad peak in the zero-field-cooling (ZFC) magnetization curve of the YFe12−xMox compounds is ascribed to the existence of ferromagnetic clusters with different site moments and scattered orientations of the moments. The broad range of the peak is reduced with increasing Mo content. A weak peak is observed near 190 K in the ZFC curve of YFe9Mo3, which is associated with the 8i sites being mostly occupied by Mo atoms. YFe9.5Mo2.5 has a magnetic entropy change of −1.09 J/kg K for a field change of 5 T at 277 K. 相似文献
3.
The magnetization and electrical resistivity of Mn3−xFexSnC (0.5≤x≤1.3) were measured to investigate the behavior of the complicated magnetic phase transitions and electronic transport properties from 5 to 300 K. The results obtained demonstrate that Fe doping at the Mn sites of Mn3SnC induces a more complicated magnetic phase transition than that in its parent phase Mn3SnC from a paramagnetic (PM) state to a ferrimagnetic (FI) state consisting of antiferromagnetic (AFM) and ferromagnetic (FM) components, while, with the change of Fe-doped content and magnetic field, there is a competition between the AFM component and FM component in the FI state. Both the Curie temperature (TC) and the saturated magnetization Ms increase with increasing x. The FM component region becomes broader with further increasing Fe-doped content x. The external magnetic field easily creates a saturated FM state (and increased TC) when . Fe doping quenches the negative thermal expansion (NTE) behavior from 200 to 250 K reported in Mn3SnC. 相似文献
4.
The structural parameters with stability upon Si incorporation and elastic, electronic, thermodynamic and optical properties of Ti3Al1−xSixC2 (0≤x≤1) are investigated systematically by the plane wave pseudopotential method based on the density functional theory (DFT). The increase of some elastic parameters with increasing Si-content renders the alloys to possess higher compressive and tensile strength. The Vickers hardness value obtained with the help of Mulliken population analysis increases as x is increased from 0 to 1. The solid solutions considered are all metallic with valence and conduction bands, which have a mainly Ti 3d character, crossing the Fermi level. The temperature and pressure dependences of bulk modulus, normalized volume, specific heats, thermal expansion coefficient, and Debye temperature are all obtained through the quasi-harmonic Debye model with phononic effects for T=0−1000 K and P=0−50 GPa. The obtained results are compared with other results available. Further an analysis of optical functions for two polarization vectors reveals that the reflectivity is high in the visible–ultraviolet region up to ∼10.5 eV region showing promise as a good coating material. 相似文献
5.
In order to design the optimal component structure of transmission-mode (t-mode) Ga1−xAlxN photocathode, the optical properties and quantum efficiency of Ga1−xAlxN photocathodes are simulated. Based on thin film principle, optical model of t-mode Ga1−xAlxN photocathodes is built. And the quantum efficiency formula is put forward. Results show that Ga1−xAlxN photocathodes can satisfy the need of detectors with “solar blind” property when the Al component is bigger than 0.375. There is an optimal thickness of Ga1−xAlxN layer to get highest quantum efficiency, and the optimal thickness is 0.3 μm. There is close relation between absorptivity and quantum efficiency, which is in good agreement with the “three-step” model. This work gives a reference for the experimental research on the Ga1−xAlxN photocathodes. 相似文献
6.
Using quantum mechanics GASTEP software package based on the first principle density function theory, the electronic structure and optical properties of Ga1−xAlxAs at different Al constituent are calculated. Result shows that with the increase of Al constituent, the band gap of Ga1−xAlxAs increases and varies from direct band gap to indirect band gap; the absorption band edge and the absorption peak move to high-energy side; the static reflectivity decreases. With the increasing of the incident photon energy, Ga1−xAlxAs shows metal reflective properties in certain energy range. With the increasing of Al constituent, static dielectric constant decreases and the intersection of dielectric function and the x-axis move towards high-energy side; the peak of energy loss function move to low-energy side and the peak value reduces. 相似文献
7.
A.G. Kuchin 《Journal of magnetism and magnetic materials》2010,322(15):2215-2218
Magnetic properties of the single-crystalline Lu2Fe17−xMnx compounds, in which x=0, 0.5, and 2, with the Th2Ni17-type crystal structure are reported. The Lu2Fe17−xMnx compounds with x=0 and 0.5 are ferromagnets at low temperatures and antiferromagnets at high temperatures. The compound with x=2 is always a ferromagnet. The easy-plane magnetic anisotropy in the Lu2Fe17−xMnx ferromagnets drastically weakens with increase in Mn content up to x=2. The temperature dependence of the first magnetic anisotropy constant was obtained and compared with the single-ion model prediction. 相似文献
8.
C.C. LiB.S. Wang S. LinJ.C. Lin P. TongW.J. Lu Y.P. Sun 《Journal of magnetism and magnetic materials》2011,323(17):2233-2237
The structural, magnetic and electrical transport properties of Zn-doped antiperovskite compounds Ga1−xZnxCMn3 (0≤x≤0.30) have been investigated. After partial substitution of Zn for Ga, the Curie temperature increases monotonously and the ground antiferromagnetic (AFM)-ferromagnetic intermediate (FI) phase transition is gradually suppressed. With increasing the doping level x, the saturated magnetizations decreases gradually firstly for x≤0.20, then increases with increasing x. The electrical transport properties of Ga1−xZnxCMn3 are studied at different magnetic fields. Enhanced giant magnetoresistance (GMR) was observed around the AFM-FI transition. With increasing x, the maximal values and peak widths of GMR increase. Particularly, for x=0.20, GMR reaches a maximum value of 75%, spanning a temperature range of 80 K at 50 kOe and displays the behavior of strongly depending on the magnetization history. The possible origins are discussed. 相似文献
9.
The exchange interactions (JBB and JAB are the intra and the inter-sublattice exchange interactions between neighbouring spins, respectively) are obtained by using the general expressions of canting angle and critical temperature obtained by mean field theory of Li0.5Fe2.5−2xAlxCrxO4. The expression of magnetic energy of Li0.5Fe2.5−2xAlxCrxO4 is obtained for different spin configurations and dilution x. The saturation magnetisation of Li0.5Fe2.5-2xAlxCrxO4 is obtained with different values of dilution x. The magnetic phase diagram of Li0.5Fe2.5-2xAlxCrxO4 materials is obtained by high temperature series expansions (HTSEs). The critical exponent associated with the magnetic susceptibility of Li0.5Fe2.5−2xAlxCrxO4 is deduced. 相似文献
10.
Akinori Kan Hirotaka OgawaYuki Inami Tohru Moriyama 《Physica B: Condensed Matter》2011,406(17):3170-3174
Bismuth layer-structured (Bi7−xSrx)(Fe3−xTi3+x)O21 (BSFT) ceramics were synthesized and the ferroelectric properties and crystal structure were investigated. X-ray powder diffraction profiles and refinement of the lattice parameters indicated single phase BSFT was obtained in the composition range 0-1.5. The lattice parameter b of BSFT remained almost constant, while a slight decrease in the lattice parameter a was observed by the Sr and Ti substitution for Bi and Fe, respectively, which indicated an increase in the orthorhombicity. The dependence of the BSFT lattice parameter on temperature implied a phase transition from the orthorhombic to the tetragonal phase, which was in good agreement with the Curie temperature. The remnant polarization Pr, of BSFT was significantly improved by the Sr and Ti substitution for Bi and Fe, and ranged from 9 to 16 μC/cm2, although no remarkable variation in the coercive field Ec was observed. As a result, a well-saturated P-E hysteresis loop of BSFT ceramic was obtained at x=0.5 with a Pr of 30 μC/cm at an applied voltage of 280 kV/cm. 相似文献
11.
Tanjore V. Jayaraman Mark A. KotenJeffrey E. Shield 《Journal of magnetism and magnetic materials》2011,323(15):2037-2041
The magnetocaloric properties of melt-spun Gd-B alloys were examined with the aim to explore their potential application as magnetic refrigerants near room temperature. A series of Gd100−xBx (x=0, 5, 10, 15, and 20 at%) alloys were prepared by melt spinning. With the decrease in Gd/B ratio, Curie temperature (TC) remains constant at ∼293 K, and saturation magnetization, at 275 K, decreases from ∼100 to ∼78 emu/g. Negligible magnetic hysteresis was observed in these alloys. The peak value of magnetic entropy change, (−ΔSM)max, decreased from ∼9.9 J/kg K (0-5 T) and ∼5.5 J/kg K (0-2 T) for melt-spun Gd to ∼7.7 J/kg K (0-5 T) and ∼4.0 J/kg K (0-2 T), respectively for melt-spun Gd85B15 and Gd80B20 alloys. Similarly, the refrigeration capacity (q) decreased monotonously from ∼430 J/kg (0-5 T) for melt-spun Gd to ∼330 J/kg (0-5 T) for melt-spun Gd80B20 alloy. The near room temperature magnetocaloric properties of melt-spun Gd100−xBx (0≤x≤20) alloys were found to be comparable to few first-order transition based magnetic refrigerants. 相似文献
12.
Eiki Niwa Chie UematsuErina Miyashita Takeshi OhzekiTakuya Hashimoto 《Solid State Ionics》2011,201(1):87-93
Preparation of LaNi1 − xFexO3, which is one of the candidate materials of solid oxide fuel cell cathode, current collecting layer and interconnect coating was examined with Pechini method and solid state reaction method. Single phase LaNi1 − xFexO3 with large Ni content has successfully been prepared by low temperature sintering as 750 °C with Pechini method, whereas large amount of raw materials has remained with solid state reaction method by sintering at the same temperature. It can be ascribed to more homogenous cation distribution in raw powder material prior to sintering with Pechini method. It has also been revealed that LaNi1 − xFexO3 with x lower than 0.3 is thermodynamically unstable in air above 1000 °C. LaNi0.6Fe0.4O3 showed superior property as cathode material with high electrical conductivity, thermodynamic stability and appropriate sintering property. 相似文献
13.
The samples of Cu1−xPtxFeO2 (0 ≤ x ≤ 0.05) delafossite have been synthesized by solid-state reaction method to investigate their optical and electrical properties. The properties of electrical resistivity and Seebeck coefficient were measured in the high temperature ranging from 300 to 960 K, and the Hall effect and the optical properties were measured at room temperature. The obtained results of Seebeck showed the samples are p-type conductor. The optical properties at room temperature exhibited the samples are transparent visible light material with optical direct gap 3.45 eV. The low electrical resistivity, hole mobility and carrier density at room temperature displayed value ranging from 0.29 to 0.08 Ω cm, 1.8 to 8.6 cm2/V s and 1.56 × 1018 to 4.04 × 1019 cm−3, respectively. The temperature range for transparent visible light is below 820 K because the direct energy gap contains value above 3.1 eV. Consequently, the Cu1−xPtxFeO2 delafossite enhance performance for materials of p-type transparent conducting oxide (TCO) with low electrical resistivity. 相似文献
14.
Mansoor FarbodMorteza Zargar Shoushtari Saeed Parhoodeh 《Physica B: Condensed Matter》2011,406(2):205-210
In this paper we have introduced a simple method for the fabrication of aluminum doped zinc oxide (AZO) nanoparticles. The Zn1−xAlxO nanoparticles with different concentrations of Al (x=0.01, 0.03, 0.06, 0.09, 0.12) were fabricated successfully by this method. The samples were analyzed by the use of several techniques such as SEM, EDX, XRD, PL and UV-vis spectroscopy. The SEM images showed that the fabricated nanoparticles had spherical shapes. The XRD patterns of the samples indicated that the Al atoms substituted in the Zn positions in the crystal lattice of ZnO and there were some changes in the lattice parameters. A blue shift in the λmax of the absorption and a red shift in the λmax of the emission were observed. The results also indicated that the amount of shifts had a direct relationship with the changes in the lattice parameters. 相似文献
15.
Intense red phosphors, AgGd1−xEux(W1−yMoy)2O8 (x=0.0-1.0, y=0.0-1.0), have been synthesized through traditional solid-state reaction and characterized by X-ray diffraction (XRD) and photoluminescence (PL). XRD results reveal that AgGd1−xEuxW2O8 synthesized at 1000 °C has a tetragonal crystal structure, which is named as high temperature phase (HTP) AgGdW2O8. All phosphors compositions with Eu3+ show red and green emission on excitation either in the charge-transfer or Eu3+ levels. Analysis of the emission spectra with different Eu3+ concentrations reveal that the optimum dopant concentration for Eu3+ is x=0.6 in the HTP AgGd1−xEuxW2O8 (x=0.0-1.0). Studies on the AgGd0.4Eu0.6(W1−yMoy)2O8 (y=0.0-1.0) and AgGd1−xEux(W0.7Mo0.3)2O8 (x=0.0-1.0) show that the emission intensity is maximum for compositions with y=0.3 and x=0.5, respectively, and a decrease in emission intensity is observed for higher y or x values. The Mo6+ and Eu3+ co-doped AgGd(WO4)2 phosphors show higher emission intensity in comparison with the singly Eu3+-doped AgGd(WO4)2 in UV region. The intense emission of the tungstate/molybdate phosphors under 394 and 465 nm excitations, respectively, suggests that these materials are promising candidates as red-emitting phosphors for near-UV/blue GaN-based white LED for white light generation. 相似文献
16.
BiFeO3/Zn1−xMnxO (x = 0-0.08) bilayered thin films were deposited on the SrRuO3/Pt/TiO2/SiO2/Si(1 0 0) substrates by radio frequency sputtering. A highly (1 1 0) orientation was induced for BiFeO3/Zn1−xMnxO. BiFeO3/Zn1−xMnxO thin films demonstrate diode-like and resistive hysteresis behavior. A remanent polarization in the range of 2Pr ∼ 121.0-130.6 μC/cm2 was measured for BiFeO3/Zn1−xMnxO. BiFeO3/Zn1−xMnxO (x = 0.04) bilayer exhibits a highest Ms value of ∼15.2 emu/cm3, owing to the presence of the magnetic Zn0.96Mn0.04O layer with an enhanced Ms value. 相似文献
17.
A. Omri M. Bejar M. Sajieddine E. Dhahri E.K. Hlil M. Es-Souni 《Physica B: Condensed Matter》2012,407(13):2566-2572
Structural, magnetic and magnetocaloric properties of manganites series with the AMn1−xGaxO3 (A=La0.75Ca0.08Sr0.17 and x=0, 0.05, 0.1 and 0.2) composition have been investigated to shed light on Ga-doping influence. Solid-state reaction method was used for preparation. From XRD study, all samples are found single phase and crystallize in the orthorhombic structure with the Pnma space group. The variation of the magnetization M vs. temperature T, under an applied magnetic field of 0.05 T, reveals a ferromagnetic–paramagnetic transition for all samples. The experimental results indicate that TC decreases from 336 to 135 K with increasing Ga substitution. Magnetocaloric effect (MCE) was estimated, in terms of isothermal magnetic entropy change (−ΔSM), using the M(T, μ0H) data and employing the thermodynamic Maxwell equation. The maximum entropy change and Relative Cooling Power (RCP) show non-monotonic behaviors with increasing the concentration of Gallium. In fact, the maximum value of ΔSMmaxof AMn1−xGaxO3 for x=0.00 and 0.2 samples is found to be, respectively, 2.87 and 1.17 J/kg/K under an applied magnetic field change of 2 T. For the same applied magnetic field (μ0H=2 T), the RCP values are found to vary between 97.58 and 89 J/kg. 相似文献
18.
The band structure and optical properties of the CdSexTe1−x ternary mixed crystals have been studied using the pseudopotential formalism under an improved virtual crystal approximation approach. Quantities such as, energy gaps, band-gap bowing parameters, electron effective mass and dielectric constants are calculated. Our results agree well with the available data in the literature. The composition dependence of all studied quantities has been expressed by quadratic polynomial forms. 相似文献
19.
Yu-jie Zhang Hong-guo Zhang Hong-wei Zhang Jing-lan Chen Guang-heng Wu 《Journal of magnetism and magnetic materials》2010,322(15):2251-809
A series of rare-earth doped BiFeO3 samples, Bi1−xRxFeO3 (x=0-1, R=La, Nd, Sm, Eu and Tb), were prepared in this work. X-ray diffraction analysis showed that the structure of rare-earth doped BiFeO3 was transformed from rhombohedral lattice to orthorhombic one by increasing x. The lattice constants and unit-cell volume decreased with the increasing of the doping content, while both the Néel temperature and magnetization were enhanced. A magnetic phase transition was observed at about 35 K for BiFeO3. The variation of the magnetization with temperature depended on applied field strength and magnetizing history, which was explained according to the antiferromagnetic exchange interaction between Fe and R sites in Bi1−xRxFeO3(x>0). The magnetocrystalline anisotropy contributed by Fe sublattice gave rise to a large coercivity in BixNd1−xFeO3 with an orthorhombic structure. 相似文献
20.
Fangting Lin 《Journal of magnetism and magnetic materials》2010,322(14):2081-493
Fe-doped (Ba1−xSrx)TiO3 ceramics were prepared by solid-state reaction, and ferromagnetism was realized at room temperature. The microstructure and magnetism were modified by the Sr concentration control (0≤x≤75 at%) at a fixed Fe concentration, and the relevant magnetic exchange mechanism was discussed. All the samples are shown to have a single perovskite structure. When increasing the Sr concentration, the phase structure is transformed from a hexagonal perovskite into a cubic perovskite, with a monotonic decrease in lattice parameters induced by ionic size effect. The room-temperature ferromagnetism is expected to originate from the super-exchange interactions between Fe3+ on pentahedral and octahedral Ti sites mediated by the O2− ions. The increase in Sr addition modifies two main influencing factors in magnetic properties: the ratio of pentahedral to octahedral Fe3+ and the concentration of oxygen vacancies, leading to a gradually enhanced saturation magnetization. The highest value, obtained for Fe-doped (Ba0.25Sr0.75)TiO3, is an order of magnitude higher than that of the Fe-doped BaTiO3 system with similar Fe concentration and preparation conditions, which may indicate (Ba1−xSrx)TiO3 as a more suitable matrix material for multiferroic research. 相似文献