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1.
La2/3Ca1/3MnO3中的输运机制与CMR效应 总被引:8,自引:3,他引:8
研究了超大磁阻材料La2/3Ca1/3MnO3的磁电特性,发现由电阻测量得到的绝缘体.金属相变与由磁化曲线得到的顺磁-铁磁相变温区完全一致,均随磁场的增强推向高温区。结果证明样品输运行为的变化起因于磁结构的变化,在Tc附近产生超大巨磁电阻效应。 相似文献
2.
Ti2O3 thin films have been prepared through atomic layer deposition and subjected to electrical resistivity measurements as a function of temperature. The as-prepared films were stable for up to three weeks. In Ti2O3 thin films, the insulator-metal transition is observed at ∼80 K, with nearly 3–4 orders of magnitude change in resistivity. The anomalous increase in electrical resistivity in the films is in accordance with the two-band model. However, the energy interval between the bands depending on the crystallographic c/a ratio leads to a change in electrical resistivity as a function of temperature. 相似文献
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实验研究了La2/3CamMnO3样品零磁场下的电阻率和低磁场下的磁化强度随温度的变化行为.结果表明,除了居里温度(Tc)外还存在另一特征温度Tonset,高于Tonset的样品为典型的顺磁绝缘体,而低于Tc的样品为典型的铁磁金属,但在Lonset和Tc之间,样品的磁化率大大偏离居里一外斯定律,同时其导电特性显示出明显的反常.对观察到的不寻常导电特性,根据铁磁金属集团在顺磁绝缘体背景上随机分布的假设,进行了分析与探讨。 相似文献
4.
Abstract High pressure electrical measurements were conducted in the antiferromagnetic insulator CoI, using a miniature Diamond Anvil Cell (DAC). The existence of a Mott Transition predicted from high pressure 129I Mgssbauer Spectroscopy (MS)1 has been verified. At about 8 GPa the system becomes metal1ic as evidenced by the temperature behavior of the conductivity. The conductivity at room temperature, however, still increases with increasing pressure, leveling off at 11 GPa. The metallic behavior in the 8 -11 GPa is explained by coexistence of metallic and insulating clusters via a percolating process. Above 11 GPa the material is completely metallic. This mechanism is consistent with the MS findings. 相似文献
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Rui Zhang Dr. Wanli Yang Lepeng Zhang Dr. Tiantian Huang Linkui Niu Peiran Xu Prof. Zhimin Chen Prof. Xin Chen Prof. Weida Hu Prof. Ning Dai 《Chemphyschem》2023,24(11):e202300059
Oxygen defects are among essential issues and required to be manipulated in correlated electronic oxides with insulator-metal transition (IMT). Besides, surface and interface control are necessary but challenging in field-induced electronic switching towards advanced IMT-triggered transistors and optical modulators. Herein, we demonstrated reversible entropy-driven oxygen defect migrations and reversible IMT suppression in vanadium dioxide (VO2) phase-change electronic switching. The initial IMT was suppressed with oxygen defects, which is caused by the entropy change during reversed surface oxygen ionosorption on the VO2 nanostructures. This IMT suppression is reversible and reverts when the adsorbed oxygen extracts electrons from the surface and heals defects again. The reversible IMT suppression observed in the VO2 nanobeam with M2 phase is accompanied by large variations in the IMT temperature. We also achieved irreversible and stable IMT by exploiting an Al2O3 partition layer prepared by atomic layer deposition (ALD) to disrupt the entropy-driven defect migration. We expected that such reversible modulations would be helpful for understanding the origin of surface-driven IMT in correlated vanadium oxides, and constructing functional phase-change electronic and optical devices. 相似文献
8.
Manjunatha Pattabi 《Pramana》2002,58(5-6):1141-1145
Aging, which manifests itself as an irreversible increase in electrical resistance in island metal films is of considerable
interest from both academic as well as applications point of view. Aging is attributed to various causes, oxidation of islands
and mobility of islands followed by coalescence (mobility coalescence) being the main contenders. The effect of parameters
like substrate temperature, substrate cleaning, residual gases in the vacuum chamber, ultrasonic vibration of the substrate,
suggest that the mobility coalescence is responsible for the aging in island metal films. Electron microscopy studies show
evidence for mobility of islands at high substrate temperatures. The comparison of aging data of island silver films deposited
on glass substrates in ultra high vacuum and high vacuum suggests that the oxidation of islands, as being responsible for
aging in these films, can be ruled out. Further, under certain conditions of deposition, island silver films exhibit a dramatic
and drastic fall in electrical resistance, marking the insulator-metal transition. This interesting transition observed in
a conservative system — after the stoppage of deposition of the film — is a clear evidence for mobility coalescence of islands
even at room temperature. The sudden fall in resistance is preceded by fluctuations in resistance with time and the fluctuations
are attributed to the making and breaking of the percolation path in the film. 相似文献
9.
Strain-induced insulator–metal transition in ferroelectric BaTiO_3(001) surface:First-principles study
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The electronic properties of TiO_2-terminated BaTiO_3(001) surface subjected to biaxial strain have been studied using first-principles calculations based on density functional theory. The Ti ions are always inward shifted either at compressive or tension strains, while the inward shift of the Ba ions occurs only for high compressive strain, implying an enhanced electric dipole moment in the case of high compressive strain. In particular, an insulator–metal transition is predicted at a compressive biaxial strain of 0.0475. These changes present a very interesting possibility for engineering the electronic properties of ferroelectric BaTiO_3(001) surface. 相似文献
10.
用溶胶-凝胶法并经过1450℃后处理而制备出名义组分为La2/3(Ca1-xMgx)1/3MnO3 (0≤x≤60%)多晶样品.磁化测量表明,除磁转变温度因Mg掺杂而稍有降低外,磁性质整体上和不含Mg样品无本质上的差别.未加磁场下阻温关系测量表明,即使Mg含量高达60%,实验上仍观察到绝缘体到金属的转变.特别有意义的结果是,适当的Mg掺杂可明显提高转变温度附近的磁电阻效应,例如,在Mg掺杂量为30~40%的样品中,1T磁场下观察到的磁电阻甚至比不含Mg样品在5T磁场下得到的值还要大. 相似文献