排序方式: 共有194条查询结果,搜索用时 62 毫秒
1.
F. Prez-Willard C. Sürgers H. Von Lhneysen P. Pfundstein 《Physica E: Low-dimensional Systems and Nanostructures》2004,22(4):872-880
The electronic transport through nanostructured bismuth nanobridges has been investigated at low temperatures (T<2 K) and in magnetic fields B up to 8.5 T. The samples show reproducible resistance fluctuations as a function of B, superimposed on a large magnetoresistance of up to 50%. In addition, time-dependent resistance fluctuations in zero magnetic field demonstrate the presence of bistable scatterers in the constriction region of our samples, which are described by two-level systems. Their dynamics are shown to be sensitive to subtle modifications of the static scatterer configuration in their vicinity, which cannot be detected in the sample magnetofingerprint. 相似文献
2.
J. -Ph. Jay J. Ben Youssef H. Le Gall 《Journal of magnetism and magnetic materials》2002,240(1-3):287-290
The dynamic response of trilayer magnetoresistive permalloy/Cu/Co films was studied by high-frequency permeability spectra measurements. The resonance frequency is shown to depend on the interlayer copper thickness. This dependence is related to exchange coupling between permalloy and cobalt and the interaction field is estimated using the Landau–Lifschitz–Gilbert model. 相似文献
3.
Viktor A. Nikolaenko Yurii Z. Kovdrya Sergey P. Gladchenko 《Journal of Molecular Liquids》2005,120(1-3):171-174
The magnetotransport in a nondegenerate quasi-one-dimensional (Q1D) electron system over superfluid helium has been investigated experimentally. The measurements are performed in the presence of a perpendicular magnetic field B up to 2.6 T in the temperature range T=0.48–2.05 K in the system of conducting channels of 100–400 nm width. It is shown that the value of longitudinal magnetoresistance ρxx increases with B. In the electron-gas scattering region (T>0.9 ), the behaviour of ρxx agrees with classical Drude law. In the quantum transport regime, the self-consistent Born approximation (SCBA) theory for a 2D electron system over liquid helium describes the experimental data qualitatively. The deviation due to the difference of the experimentally studied Q1D system of the electrons in a parabolic potential well differs from theoretically analysed one. The experimental data agree with the theoretical calculation for the Q1D electron system at the weak magnetic field and the low temperature.
The negative magnetoresistance of the conducting channels has been observed in both the gas- and the ripplon-scattering region. These effects have been explained by weak carrier localization on the gas atoms at high temperature and by display of the quantum magnetotransport features in a mesoscopic system at low temperature. 相似文献
4.
S. Takahashi T. Yamashita H. Imamura S. Maekawa 《Journal of magnetism and magnetic materials》2002,240(1-3):100-102
The effect of spin relaxation on tunnel magnetoresistance (TMR) in a ferromagnet/superconductor/ferromagnet (FM/SC/FM) double tunnel junction is theoretically studied. The spin accumulation in SC is determined by balancing of the spin-injection rate and the spin-relaxation rate. In the superconducting state, the spin-relaxation time τs becomes longer with decreasing temperature, resulting in a rapid increase of TMR. The TMR of FM/SC/FM junctions provides a useful probe to extract information about spin-relaxation in superconductors. 相似文献
5.
Sebastiaan van Dijken Xavier Fain Steven M. Watts Kentaro Nakajima J. M. D. Coey 《Journal of magnetism and magnetic materials》2004,280(2-3):322-326
A detailed study of the in-plane magnetotransport properties of spin valves with one and two Fe3O4 electrodes is presented. Fe3O4/Au/Fe3O4 spin valves exhibit a clear anisotropic magnetoresistance in small magnetic fields but no giant magnetoresistance (GMR). The absence of GMR in these structures is due to simultaneous magnetization reversal in the two Fe3O4 layers. By contrast, a negative GMR effect is measured on Fe3O4/Au/Fe spin valves. The negative GMR is attributed to an electron spin scattering asymmetry at the Fe3O4/Au interface or an induced spin scattering asymmetry in the Au interfacial layers. 相似文献
6.
The La0.833K0.167MnO3:Ag2O and the La0.833K0.167MnO3:SrTiO3 samples are fabricated by the sol–gel method. The microstructure, magnetic and transportation properties have been systematically studied. X-ray diffraction patterns show that the La0.833K0.167MnO3:Ag2O (abbreviated as LKMO/Ag) sample is a two-phase composite and consists of a magnetic La0.833K0.167MnO3 (abbreviated as LKMO) perovskite phase and a nonmagnetic Ag metal phase, while the structure of the La0.833K0.167MnO3:SrTiO3 (abbreviated as LKMO/STO) sample is a homogeneous solid solution phase. Comparing with the pure LKMO sample, the room temperature magnetoresistance (MR) effect for the LKMO/Ag sample is enhanced significantly due to the addition of Ag metal. The MR ratio increases from ∼25% for the pure LKMO sample to 65% for the LKMO/Ag sample under a higher field of 5.5 T at 300 K. For the LKMO/STO sample, however, the room temperature MR effect is weakened dramatically and is almost close to zero due to the addition of SrTiO3 insulator. In the low temperature regime below the Curie temperature, the MR behaviors are different from that of the room temperature; that is, the MR effect is decreased for the LKMO/Ag sample and increased for the LKMO/STO sample with temperature decrease. In fact, the low-field (μ0H=0.5 T) MR decreases from 32% to 5% for the LKMO/Ag sample, while increasing from 0.07% to 25% for the LKMO/STO sample with decreasing temperature from 300 to 4 K. The relative change between the intrinsic and the extrinsic MR, and varied roles of the spin-polarized-tunneling and the spin-dependent scattering mechanisms in different temperature regimes are employed to interpret the anomalous transport behaviors. 相似文献
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8.
L.F. KissV. Franco M. CsontosL. Péter C.F. CondeA. Conde T. KeményJ. Tóth L.K. VargaI. Bakonyi 《Journal of magnetism and magnetic materials》2011,323(6):699-707
The magnetoresistance (MR) was measured at 200, 250 and 300 K in magnetic fields up to B=12 T for a nanocrystallized Fe63.5Cr10Nb3Cu1Si13.5B9 alloy. Both the longitudinal (LMR) and transverse (TMR) component of the magnetoresistance decreased from B=0 to about 0.1 T. This could be ascribed to a giant MR (GMR) effect due to spin-dependent scattering of conduction electrons along their path between two Fe-Si nanograins via the non-magnetic matrix. Such a scattering may occur if the nanograin moments are not or only weakly coupled in the absence of a strong exchange coupling (due to the high Cr content in the matrix) and/or only weak dipole-dipole coupling is present (due to sufficiently large separations between the nanograins). For larger fields, the GMR saturated and a slightly nonlinear increase in MR with B was observed due to a contribution by the residual amorphous matrix. The anisotropic MR effect (AMR≡LMR−TMR) was negative for all fields and temperatures investigated. By measuring the MR of melt-quenched Fe100−xSix solid solutions with x=15, 18, 20, 25 and 28, the observed AMR could be identified as originating from the Fe-Si nanograins having a D03 structure. 相似文献
9.
We present an experimentalist's view of the theory and published data for the magnetoresistance (MR) of a multilayer composed of alternating ferromagnetic (F) and non-magnetic (N) metals measured with current flow perpendicular to the layer planes (CPP-MR). We explain the advantages of this geometry for determining the fundamental quantities underlying spin-polarized transport, describe the different techniques developed to measure the CPP-MR, summarize the salient features of the models used to analyze experimental data, and describe tests of those models. We then review what has been learned so far about spin-dependent scattering anisotropy and spin relaxation in F-metals and at F/N interfaces, specific resistances of F/N interfaces, the temperature dependence of spin-polarized transport parameters, and mixing of the spin-polarized electron currents. After a brief overview of some new directions, we conclude with a list of questions still to be answered. 相似文献
10.
Jun Zhang Fangwei Wang Panlin Zhang Xiangdong Sun Qiwei Yan 《Journal of magnetism and magnetic materials》1998,190(3):1085
Magnetic and electric properties of layered perovskites Nd2−2xSr1+2xMn2O7 (x=0.3, 0.4 and 0.5) are sensitive to the doping content x. The sample with x=0.5 is antiferromagnetic (AFM) and insulating. On decreasing x, the AFM ordering is suppressed and a canted AFM or weak ferromagnetic (FM) ordering appears, and the resistivity decreases. The sample with x=0.4 still shows insulating behavior, but a metal–insulator transition is observed for x=0.3. By suggesting the presence of a competition between AFM super-exchange interaction and FM double-exchange interaction, the doping dependence of magnetic and electric properties can be understood. 相似文献