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1.
铁基超导体的发现开启了探索超导材料的新一轮热潮。最新发现的铁基超导体KxFe2-ySe2有着许多不同寻常的性质。此材料中明显存在相分离,材料中主要的部分是具有反铁磁性质的绝缘相K<sub<2</sub<Fe<sub<4</sub<Se<sub<5</sub<,,超导相只占少量体积。但是超导相在物理上很重要,因为根据理论计算,该材料中不存在空穴型费米面,这样该领域中被广泛接受的S<sup<±</sup<; 配对图像似乎受到挑战。相分离的存在致使此材料中相关研究的难度非常大。该文介绍了此材料中超导相的探索和研究,确认了此材料的超导相是以三维网络状的细丝形态存在,并提出超导的母体相可能是每8个Fe位置有一个Fe空位形成的√8× √10这种有序平行四边形结构,称为K<sub<2</sub<Fe<sub<7</sub<Se<sub<8</sub<相。 相似文献
2.
Kiichirou?Koyasu Wilko?Westh?user Marco?Niemietz Jan?Heinen Gerd?Gantef?r 《Applied Physics A: Materials Science & Processing》2009,96(3):679-684
Using time-resolved photoelectron spectroscopy, the decay channels of AuO2− and Au2O2− following photoexcitation with 3.1-eV photons have been studied. For AuO2−, a state with a rather long lifetime of 30 ps has been identified. Its decay path could not be determined but photodesorption
can be excluded. For Au2O2−, the spectra indicate O2 desorption after 3.1-eV photoexcitation on a time scale of 1 ps. While comparing these results on Au
n
O2− with analogous data on Ag
n
O2− clusters, a discernible pattern emerges: for dissociatively bound O2(AuO2−, Ag3O2−), there are long-living excited states which do not decay by oxygen desorption, while for molecular chemisorption (Au2O2−, Ag2O2−, Ag4O2−, Ag8O2−), the 3.1-eV photoexcitation triggers fast O2 desorption with a high quantum yield. 相似文献
3.
N. A. Kalanda G. G. Gorokh M. V. Yarmolich A. A. Lozovenko E. Yu. Kanyukov 《Physics of the Solid State》2016,58(2):351-359
A method has been developed for fabricating nanoporous matrices based on anodic aluminum oxide for the deposition of ferromagnetic nanoparticles in them. The modes of deposition of strontium ferromolybdate thin films prepared by the ion-plasma method have been worked out, and the magnetic and magnetoresistive properties, structure, and composition of the films have been investigated. It has been revealed that the microstructure and properties of the strontium ferromolybdate films deposited by ionplasma sputtering depend on the deposition rate and the temperature of the substrate. Based on the measurement of the electrical resistivity of nanoheterostructures in a magnetic field, it has been found that the magnetoresistance reaches 14% at T = 15 K and B = 8 T, which is due to the manifestation of tunneling magnetoresistance. 相似文献
4.
Zn$lt;sub$gt;1-$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;Mg$lt;sub$gt;$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;O薄膜的光致发光特性研究
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采用脉冲激光沉积方法在单晶Si(100)衬底上制备出c轴取向的Zn1-xMgxO单晶薄膜,通过荧光光谱仪研究了薄膜的光致发光特性.实验结果表明,Mg含量增加,Zn1-xMgxO单晶薄膜的紫外发光峰蓝移,发光峰强度减弱,缺陷发光强度增强.同时发现,由于Mg的掺杂,引入了一些束缚能较大的局域束缚态.对于氧气氛下制备的样品,实验发现紫外峰和绿光带发光峰同时增强,但是R值减小,紫外峰红移.对绿光发光机理研究发现,绿光发光带主要与锌空位、氧间隙(Oi)或锌位氧(OZn)等缺陷有关,它是由多个缺陷发光峰组成,各缺陷发光峰强度相对变化导致了绿光发光带的整体移动.
关键词:
1-xMgxO薄膜')" href="#">Zn1-xMgxO薄膜
光致发光
脉冲激光沉积 相似文献
5.
The microwave characteristics of Pb1?x Ca x Fe0.5Nb0.5O3 multiferroics (x = 0.0, 0.4, 0.45, 0.5, 0.55, 0.6), have been investigated as a function of frequency and substitution. The results depict ?13.99 dB reflection loss at 11.65 GHz in composition x = 0.6. Microwave absorption is enhanced with substitution of Ca2+ ions and undoped composition 0.0 behaves as electromagnetic shield. The model governing microwave absorption is discussed and different compositions for electromagnetic applications have been suggested. 相似文献
6.
Ca$lt;sub$gt;2$lt;/sub$gt;Si(O$lt;sub$gt;4-$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;N$lt;sub$gt;$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;):Eu$lt;sup$gt;2+$lt;/sup$gt;绿色荧光粉的制备及其发光性能
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利用在Ca-Si-O干凝胶前驱体中添加Si3N4的方法于非还原气氛下合成了含N固溶体Ca2Si(O4-xNx):Eu2+绿色荧光粉. 通过X射线衍射仪、扫描电子显微镜以及荧光分光光度计分别分析了产物的物相结构、颗粒形貌和发光性能. 结果显示,Si3N4与前驱体的混合物在非还原气氛(纯氮气)下于1100℃焙烧后获得含N固溶体Ca2Si(O4-xNx):Eu2+荧光粉,特别是其中Eu3+被还原为Eu2+,产物的晶体结构与βup -Ca2SiO4相一致. Ca2Si(O4-xNx):Eu2+能够被270–400 nm 范围内的紫外线有效激发,其发射光谱呈宽带发射. 随着N含量的增加,发射峰出现一定程度红移(501–504 nm),而且发光强度显著提高. 当Eu2+浓度为0.25 mol%时发光强度达最大值,浓度超过0.25 mol%时,发光强度显著降低,出现浓度猝灭 效应.
关键词:
白光LED
荧光粉
溶胶凝胶法
3N4')" href="#">Si3N4 相似文献
7.
A. V. Kalgin S. A. Gridnev E. S. Grigorjev 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(9):1097-1100
The inverse magnetoelectric effect and internal friction in two-layer composites based on ferromagnetic Tb0.12Dy0.2Fe0.68 and piezoelectric PbZr0.53Ti0.47O3 are studied in an ac electrical field in the frequency range of 52–213 kHz at temperatures of 293 to 400 K. A correlation is found between the internal friction and the efficiency of the inverse magnetoelectric transformation at resonant frequencies. 相似文献
8.
S. I. Vorob’ev D. S. Andrievskii S. G. Barsov A. L. Getalov E. I. Golovenchits E. N. Komarov S. A. Kotov A. Yu. Mishchenko V. A. Sanina G. V. Shcherbakov 《Journal of Experimental and Theoretical Physics》2016,123(6):1017-1024
A comparative μSR study of ceramic samples of the EuMn2O5 and Eu0.8Ce0.2Mn2O5 multiferroics is performed in the temperature range from 15 to 300 K. It is found that the Ce doping of the EuMn2O5 sample slightly reduces the temperature of the magnetic phase transition from T N = 45 K for the EuMn2O5 sample to T N = 42.5 K for the Eu0.8Ce0.2Mn2O5 sample. Below the temperature T N for both samples, there are two types of localization of a thermalized muon with different temperature dependences of the precession frequency of the magnetic moment of the muon in an internal magnetic field. The higher frequency in both samples refers to the initial antiferromagnetic matrix. The behavior of this frequency in Eu0.8Ce0.2Mn2O5 follows the Curie–Weiss law with the exponent β = 0.29 ± 0.02, which differs from the value β = 0.39 standard for 3D Heisenberg magnetics and is observed in EuMn2O5, because of the strong frustration of the doped sample. The temperature-independent low frequency is due to the presence of Mn3+–Mn4+ ferromagnetic pairs located along the b axis of the antiferromagnetic matrix and in the regions of phase separation, which contain such ion pairs and e g electrons recharging them. In both samples, polarization losses are the same (about 20%) and are associated with the formation of Mn4+–Mn4+ + Mu complexes near Mn3+–Mn4+ ferromagnetic pairs. In the temperature interval from 25 to 45 K, the separation of the Eu0.8Ce0.2Mn2O5 structure into two fractions where the relaxation rates of polarization of muons differ by an order of magnitude is revealed. This effect is due to a change in the state of regions of phase separation (1D superlattices) at the indicated temperatures. Such effect in EuMn2O5 is significantly weaker. 相似文献
9.
L. T. Denisova N. V. Belousova N. A. Galiakhmetova V. M. Denisov E. O. Golubeva 《Physics of the Solid State》2018,60(7):1303-1307
Differential scanning calorimetry has been used to study the influence of temperature on the heat capacity of synthesized vanadates Zn2V2O7, (Cu0.56Zn1.44)V2O7, and (Cu1.0Zn1.0)V2O7. It is found that dependences Cp = f(T) have extremes. The thermodynamic properties of Zn2V2O7 have been determined. 相似文献
10.
R. Nigam A. V. Pan S. X. Dou 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,74(4):429-436
We investigate in detail the dc magnetization and nonlinear ac susceptibility behavior of the superconducting ferromagnet
RuSr2Eu1.5Ce0.5Cu2O10-
δ (Ru1222) to develop a comprehensive understanding of the spin glass and superparamagnetism in this material.
The structural properties of the system result in the formation of magnetic (ferromagnetic) clusters of different sizes, shapes
and properties.
The magnetic clustering of the system leads to observation of various features in dc magnetization and ac susceptibility consistent
with superparamagnetism and cluster spin glass states, which can coexist or stand alone, depending on the temperature range
considered.
Experimental results of magnetic measurements in combination with their analysis have enabled us to explain and distinguish
these phenomena, as well as to propose a temperature dependent scenario of the system behavior. 相似文献
11.
The effect of simultaneous Sr substitution at the Ba and Y sites has been studied in the Sr0.75Y0.75Ba1.5Cu3O7–dsystem. Attempts to replace 25% Y and 25% Ba have been successful and superconductivity was observed above 78 K for Sr0.75Y0.75Ba1.5Cu3O7–d compound with high oxygen content, i.e., O6.76, and having orthorhombic crystal symmetry. The compound was treated in argon gas at 800°C to reduce the oxygen content and to induce some structural changes. The Sr0.75Y0.75Ba1.5Cu3O6.1 compound thus obtained has tetragonal symmetry and low oxygen content, O6.1. It has also shown superconductivity at 28 K. The paper presents a careful comparison of the structural and electrical properties and infrared absorbance spectra of the two compounds with the same metallic composition, Sr0.75Y0.75Ba1.5Cu3, but with different oxygen content and crystal symmetry. The study clearly establishes the occurrence of superconductivity in tetragonal Sr-substituted (both at Y and Ba sites in) YBCO. 相似文献
12.
13.
High field electrical switching on blown films of MoO3(60%)–P2O5(40%), MoO3(50%)–WO3(10%)–P2O5(40%), and MoO3(45%)–WO3(15%)–P2O5(40%) having different thicknesses was studied and compared. Switching was observed using two terminal samples. S-type current–voltage
characteristic (current-controlled negative resistance—CCNR) with memory was observed in molybdenum–phosphate glasses, but
N-type characteristic (voltage-controlled negative resistance—VCNR) with threshold in tungsten–molybdenum–phosphate glasses
was observed. The important observation was that with the addition of WO3 to binary MoO3–P2O5 led to a change of I–V characteristic from CCNR with memory to VCNR with threshold. The measurements of density and molar volume showed linear relation
between MoO3 content and density which decreased with the increase of MoO3 content. The samples’ thickness had no significant effect on threshold voltage. The attained results also indicated that
the electrode material had no effect on switching property of devices. The switching behavior of the devices did not show
any dependence on the polarity of the applied voltage. In terms of the effect of heat on the switching behavior of molybdenum–phosphate
glasses, it was found that threshold voltage decreases with increasing of temperature. Finally, the switching phenomenon was
explained by thermal (formation of crystalline filaments) and electronic models. 相似文献
14.
V. I. Murav’ev 《Physics of the Solid State》2004,46(5):853-857
The parameters of hyperfine interactions in Pb3+F 8 ? F a ? tetragonal clusters of MeF2 crystals (Me=Ca, Sr, Ba) are interpreted. The contributions of the spin polarization to the parameters of the proper hyperfine interaction and additional (ligand) hyperfine interactions are calculated in the approximation of weak binding between a charge-compensating ion F a ? and a cubic fragment in the tetragonal cluster. It is demonstrated that correct inclusion of the contributions from the spin polarization to the ligand isotropic hyperfine interaction for the F a ? ion leads to anomalously large parameters of this interaction for MeF2 crystals. These results are in agreement with experimental data. 相似文献
15.
直接带隙Ge$lt;sub$gt;1-$lt;em$gt;x$lt;/em$gt;$lt;/sub$gt;Sn$lt;sub$gt;$lt;em$gt;x$lt;/em$gt;$lt;/sub$gt;本征载流子浓度研究
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通过合金化改性技术, Ge可由间接带隙半导体转变为直接带隙半导体. 改性后的Ge半导体可同时应用于光子器件和电子器件, 极具发展潜力. 基于直接带隙Ge1-xSnx半导体合金8带Kronig-Penny模型, 重点研究了其导带有效状态密度、价带有效状态密度及本征载流子浓度, 旨在为直接带隙改性Ge半导体物理的理解及相关器件的研究设计提供有价值的参考. 研究结果表明: 直接带隙Ge1-xSnx合金导带有效状态密度随着Sn组分x的增加而明显减小, 价带有效状态密度几乎不随Sn组分变化. 与体Ge半导体相比, 直接带隙Ge1-xSnx合金导带有效状态密度、价带有效状态密度分别低两个和一个数量级; 直接带隙Ge1-xSnx合金本征载流子浓度随着Sn组分的增加而增加, 比体Ge半导体高一个数量级以上.
关键词:
1-xSnx')" href="#">Ge1-xSnx
直接带隙
本征载流子浓度 相似文献
16.
C. Hess E.M. Ahmed U. Ammerahl A. Revcolevschi B. Büchner 《The European physical journal. Special topics》2010,188(1):103-112
We investigate the transport properties of La1.8−xEu0.2SrxCuO4 (x = 0.04, 0.08, 0.125, 0.15, 0.2) with a special focus on the Nernst effect in the normal state. Various anomalous features
are present in the data. For x = 0.125 and 0.15 a kink-like anomaly is present in the vicinity of the onset of charge stripe order in the LTT phase, suggestive
of enhanced positive quasiparticle Nernst response in the stripe ordered phase. At higher temperature, all doping levels except
x = 0.2 exhibit a further kink anomaly in the LTO phase which cannot unambiguously be related to stripe order. Moreover, a
direct comparison between the Nernst coefficients of stripe ordering La1.8−xEu0.2SrxCuO4 and superconducting La2−xSrxCuO4 at the doping levels x = 0.125 and x = 0.15 reveals only weak differences. Our findings make high demands on any scenario interpreting the Nernst response in
hole-doped cuprates. 相似文献
17.
笔者有幸观摩了一堂第七届全国中学物理青年教师教学大赛录像课——由天津市南开中学贾双老师执教的“自由落体运动”,感受颇多.这是一堂在新课程理念下有意义、有效率、有生成性且非常精彩的课.现重现最精彩的教学片段. 相似文献
18.
19.
Jiaming Li Feifei Wang Xiaomei Qin Min Xu Wangzhou Shi 《Applied Physics A: Materials Science & Processing》2011,104(1):117-122
In the present work, (1−x)(0.935Bi0.5Na0.5TiO3–0.065BaTiO3)–xKNbO3 (BNT–BT–KN, BNT–BT–100xKN) ceramics with x ranging from 0 to 0.1 were prepared by the conventional ceramic fabrication process. A large electrostrictive coefficient
of ∼10−2 m4 C−2 is obtained with the composition x ranging from 0.02 to 0.1, which is close to the well-known electrostrictive material Pb(Mg1/3Nb2/3)O3. Under an electric field of 4 kV/mm, the electrostrictive strain can reach as high as 0.08%. Besides, the electric field
induced strain behavior indicates a temperature independent behavior within the temperature range of 20 to 150°C. The large
electrostrictive strain is suggested to be ascribed to the formation of non-polar (NP) phase developed by the KNbO3 substitution, and the high electrostrictive coefficient of BNT–BT–KN ceramics makes them great candidates to be applied in
the new solid-state actuators. 相似文献
20.
MC与$lt;i$gt;M$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;+1$lt;/sub$gt;$lt;i$gt;AC$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;$lt;/sub$gt;稳定性与电子特征的第一性原理研究
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研究MC与Mn+1ACn(M=Sc, Ti, V, Cr, Mn; A=Al, Si, P, S; n=1, 2, 3)结构的稳定性与电子特征有利于探究三元层状结构Mn+1ACn稳定性的内在原因和设计新型Mn+1ACn结构. 第一性原理计算研究表明, M-3d与C-2p轨道间的电子转移对MC与Mn+1ACn 的形成焓有较大影响. 供电子能力较强的前过渡金属可以形成稳定的MC结构. 计算结果显示, MC结构是缺电子体系, 其趋向于与具有一定供电子能力的MA结构结合形成Mn+1ACn. 与M2PC和M2SC 相比, M2AlC和M2SiC可以更为容易地被分离成二维 M2C结构.
关键词:
MAX相结构
第一性原理
电子结构
过渡金属碳化物 相似文献