共查询到17条相似文献,搜索用时 459 毫秒
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用紫外光电子能谱和同步辐射光电子能谱研究了Sm掺杂C60薄膜的价带电子结构.Sm的价电子大部分转移给C60,化学键以离子性为主.对于任何化学配比都没有观察到费米边,所以Sm富勒烯超导相在室温下为半导体性质.获得了很接近单相Sm2.75C60的样品在费米能级附近的电子态密度分布.固溶相的光电子发射与Sm2.75C60有明显区别.SmxC60关键词:
60的Sm填隙化合物')" href="#">C60的Sm填隙化合物
价带光电子能谱
电子结构 相似文献
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通过磁输运测量研究了Al0.22Ga0.78N/GaN二维电子气的电子相干散射中的弱局域和反弱局域化现象.在外加弱磁场的情况下,该系统表现出正-负磁阻的变化,说明在Al0.22Ga0.78N/GaN异质结中存在晶体场引起的电子自旋-轨道散射.同时讨论了二维电子气中不同的散射时间对温度的依赖关系,实验得到的非弹性散射时间与温度成反比,表明非弹性散射机理主要来源于小能量转移的电子-电子散射.
关键词:
二维电子气
弱局域
磁阻 相似文献
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文中报道非晶Cu33Y67低温电阻和磁阻的测量结果。这种合金是在He气氛中以熔化-自旋技术制备的。相互作用效果可以为4.5K以下的低温电阻提供一个-T1/2形式的贡献。在稍高的温度,其变化规律也可以通过相互作用和弱定域化的联合来解释。上至1.8T的磁阻测量揭示出一个具有自旋-轨道散射较强影响的弱定域化效果。Cu33Y67的磁阻测量值比弱定域化预言的大。如果把弱定域化的理论预言强度增大3倍,则可以在
关键词: 相似文献
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利用射频磁控溅射技术在MgO(001)单晶基片上沉积了一系列Ba0.94La0.06SnO3薄膜,并对薄膜的结构和电输运性质进行了系统研究.所有薄膜均表现出简并半导体(金属)导电特性:在T>Tmin的高温区(Tmin为电阻最小值对应的温度),薄膜的电阻率随温度的升高而升高,并且与温度的平方呈线性关系.在T min的低温区域,薄膜的电阻率随温度降低而上升,并且电阻率随lnT呈线性变化,均匀无序系统中的电子-电子相互作用、弱局域效应以及Kondo效应均不能解释这种现象.经过定量分析,发现电阻率在低温下lnT的依赖关系源于颗粒间电子的库仑相互作用.同时,在Ba0.94La0.06SnO3薄膜中也观察到霍尔系数RH与lnT呈线性关系,并且该线性关系也定量的符合金属颗粒体系中库仑相互作用的理论.薄膜断面高分辨透射电子显微镜结果表明,虽然薄膜整体呈现外延结构,但其中... 相似文献
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本文采用密度泛涵理论对富勒烯C40分子进行了结构优化,得到了稳定构型,然后构建了以金原子面为电极的电子输运模型.使用非平衡格林函数方法对构建的电子输运模型进行了电子输运性质的计算,得到了电子透射谱和伏安曲线,并分析了分子器件产生电子输运性质的原因.研究结果发现:C40富勒烯的化学活性明显强于富勒烯C60和C32分子,在一些分子能级处,该分子为一个良导体. 相似文献
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对Heusler 合金Cu2VAl多晶甩带样品进行了磁性与输运性质方面的研究. 实验 发现Cu2VAl在温度T为210K附近发生铁磁—顺磁相变,为弱铁磁体. 输运性质的 测量表 明在72K时电阻因局域杂质超导相变而发生突变,电子和声子之间的散射是主要的散射机 理. 居里温度TC以下存在侧跃导致的反常霍尔效应,并且7K附近的相变导致霍 尔电阻率发生异常.
关键词:
磁性
输运
2VAl')" href="#">Cu2VAl 相似文献
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Yufang WangXuewei Cao Hyon U. HanGuoxiang Lan 《Journal of Physics and Chemistry of Solids》2002,63(11):2053-2056
Samarium-fullerene intercalation compounds of nominal composition SmxC60 (x=1,2,…,6) have been synthesized by a solid-state reaction method. We obtain a Sm2.75C60 superconducting phase with orthogonal structure and a Sm6C60 phase with body-centered cubic structure. The broadening and weakening of Raman peaks of the SmxC60 compounds are due to the distortion of C60 and electron-phonon interaction. The Raman measurements reveal that the distortion of C60 decrease in SmxC60 (x=3,4,5) exposed to air, although the fulleride solids have transformed into an amorphous state. The Raman results also show that the distortion of C60 is still very large in the Sm6C60 exposed to air, or the C60 molecules have been destroyed and become some amorphous carbide. 相似文献
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N. IbrahimA.K. Yahya S.S. RajputS. Keshri M.K. Talari 《Journal of magnetism and magnetic materials》2011,323(16):2179-2185
La0.85−xSmxAg0.15MnO3 (x=0−0.2) ceramics were prepared using the conventional solid-state synthesis method to investigate the effect of Sm3+ substitution on magnetic and electrical transport properties. Magnetic susceptibility versus temperature measurements showed all samples exhibit ferromagnetic to paramagnetic transition with Curie temperature, Tc decreasing from 283 K (x=0) to 164 K (x=0.2) with increasing Sm3+. The observed slope in susceptibility, χ′ versus temperature curves below Tc indicates the possible presence of FM and AFM phases in the metallic region. In addition, a deviation from the Curie-Weiss law above Tc in 1/χ′ versus T curves indicates the existence of a Griffith's phase in the x=0.05−0.2 samples due to the Sm3+ ion substitution. The Griffith temperature, TG was found to decrease from 295 K (x=0.05) to 229 K (x=0.2). Electrical resistivity measurements of the samples in zero field showed transition from metallic behavior to insulating behavior as the temperature was increased. For x=0, two metal-insulator, MI transition peaks were observed at Tp1=282 K and at Tp2=250 K. Both peaks shifted to lower temperatures with the increase in Sm3+. The relative resistivity of the first peak to the second peak decreases with increasing Sm3+ for x>0.05 while at x=0.2 the Tp1 peak was strongly suppressed. Magnetoresistance, MR was observed to weaken with Sm3+ substitution. The metallic region of the ρ(T) curve of the x=0−0.15 samples was fitted to the model of electron-electron and electron-magnon scattering while the insulating region was fitted to the variable range hopping, VRH model. The resistivity behavior indicated that the substitution of Sm3+ weakened the double exchange process and enhanced the Jahn-Teller effect. Our results indicated that the Tp1 peak is strongly related to the double-exchange mechanism while the Tp2 peak is suggested to originate from magnetic inhomogeneity. 相似文献
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T. LahiriT. Pal Majumder 《Physica B: Condensed Matter》2011,406(23):4417-4422
We provide a hydrodynamical approach utilizing time dependent Landau-Ginzburg model (L-G) and the Cahn-Hilliard model (C-H) to investigate antiferroelectric liquid crystals (AFLCs) exhibiting different chiral phases between paraelectric smectic A (SmA?) phase and antiferroelectric smectic CA? phase (SmCA?). Introducing conserved and non-conserved order parameters in C-H and L-G models, we have predicted the appearance of a chiral smectic C (SmC?) phase and a ferrielectric SmCFI1? phase (three layers SmCA?) in an antiferroelectric phase sequence. The three layers periodicity for SmCFI1? phase is studied in detail with a non-uniform layer interactions among smectic layers with strong experimental support. Finally, we provide some theoretical basis for the non-uniformity of our proposed layer interactions. 相似文献
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Manjusha Battabyal 《Solid State Communications》2004,131(5):337-342
A detailed investigation of the electrical resistivity of a series of monovalent (Ag) doped polycrystalline La1−xAgxMnO3 pellets with x ranging from 0.05 to 0.30 and measured over the temperature range between 10 and 350 K is reported. La1−xAgxMnO3 compounds have been prepared by a novel pyrophoric technique. XRD analysis of our samples indicates single phasic nature for samples with Ag content ≤0.15, while samples with higher Ag content (x≥0.2) show presence of both magnetic perovskite and non-magnetic Ag phases. A sharp insulator-metal transition with TMI close to room temperature arising out of the paramagnetic to ferromagnetic transition, and a large magneto-resistance (MR=∼16%) near TMI has been observed for all the Ag doped samples. Between TC(Tp1) and 350 K, all the samples show activated conduction following the Emin-Holstein theory of adiabatic small polaron hopping, while at lower temperatures, in the ferromagnetic regime resistivity appears to be governed by various electron scattering processes. Between 20 and 50 K, a distinct minimum for both H=0 and has been observed, which is explained in terms of inelastic scattering and electron-electron interactions. 相似文献
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The structure, transport and magnetic properties of (La0.8Sr0.2)1−xMnO3 (0≤x≤0.30) polycrystalline perovskite manganites have been investigated. For all the samples the Curie temperatures, Tc, remain nearly unchanged (329±3 K). Resistivity versus temperature curves for the samples show a double-peak behavior. A significant magnetoresistance (MR) effect and different temperature dependences of the MR ratios of the samples are observed. The shapes of the MR-T curves of the samples can be adjusted by changing x. For the x=0.30 sample, a nearly constant MR ratio of (9.5±0.5)% is obtained over the temperature range from 205 to 328 K. 相似文献
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The effect of Pr-doping on structural, electronic transport, magnetic properties in perovskite molybdates Sr1−xPrxMoO3 (0≤x≤0.15) has been investigated. The Pr-doping at Sr-site does not change the space group of the samples, but decreases the lattice parameter a. The magnitude of resistivity ρ increases initially (x≤0.08) and then decreases with further increasing Pr-doping level x and ρ(T) behaves as T2 and T dependence in the low-temperature range blow T* and high-temperature range of 150 K<T<350 K, related to the electron-electron (e-e) and electron-phonon (e-ph) scattering, respectively. The magnetic susceptibility χ value of the sample increases with increasing x and the χ(T) curve for all samples can be well described by the model of exchange-enhanced paramagnetism. The specific heat magnitude in the low-temperature region increases with increasing Pr-doping level. The specific heat value agrees with the classical Dulong-Petit phonon specific heat, Ccl=3kBrNA=124.7 J/mol K in the high-temperature region and the temperature dependence of the specific heat can be well described by the formula Cp(T)/T=γe+βpT2 in the low-temperature range. These behaviors can be explained by the competition between the increase in the density of state (DOS) at Fermi energy level and the disorder effect due to Pr-doping. 相似文献
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The electrical and magnetoresistant properties of La0.67(Ca0.65Ba0.35)0.33MnO3/Agx (abbreviated by LCBMO/Agx) have been studied. The results show that Ag addition causes a decrease of resistivity dramatically and especially induces a large enhancement of room temperature magnetoresistance (MR). The room temperature MR ratio for x=0.27 sample in 10 kOe magnetic field is 41%, almost 20 times larger than that for x=0 sample. This enhancement is related to that the Curie temperature (Tc) of the sample is near room temperature, as well as the significant reduction of resistivity. The good fits of experimental results for x=0.27 sample to Brillouin function indicate that the MR behavior in the Ag added LCBMO is induced by the spin-dependent hopping of the electrons between the spin clusters, which is an intrinsic property of the CMR materials. 相似文献