共查询到19条相似文献,搜索用时 953 毫秒
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利用脉冲激光沉积方法在Si(100)上制备了Cox-C1-x颗粒膜,并研 究了其正磁电阻 效应.实验结果表明,样品在室温下的正磁电阻效应要远远高于低温下的正磁电阻效应;Co 0.02-C0.98样品具有最大的室温正磁电阻效应,在外加磁场B=1T时 ,其磁电阻 率MR=22%;随着Co含量的增加,Cox-C1-x颗粒膜的正磁电阻效应呈 减小趋势.样品 的MR-B的曲线与传统的多
关键词:
正磁电阻效应
x-C1-x颗粒膜')" href="#">Cox-C1-x颗粒膜
脉冲激光沉积 相似文献
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研究了溶胶-凝胶法制备氧化物巨磁电阻材料的工艺,制备了La0.7Sr0.3< /sub>CrxMn1-xO3(x=0,0.10,0.15)和La0.7Sr0.3FexMn1-xO3(x=0.05,0.10,0.16)两 系列的单相钙钛矿锰氧化物多晶样品,并研究了Cr,Fe替代La0.7Sr0.3 sub>MnO3中部分Mn后对其结构、磁性和巨磁电阻性质的影响.观察到La0.7 Sr0.3Cr0.15Mn0.85O3和La0. 7Sr0.3Fe0.05Mn0.95O3两个样品的 电阻-温度曲线都出现了双峰.定性讨论了可能产生双峰的机制.随Cr(或Fe)替代量的增加, 材料的居里温度很快下降,铁磁性减弱,导电性降低,巨磁电阻效应增强.但与Fe掺杂相比 ,相同数量的Cr掺杂对材料的影响要小.
关键词:
巨磁电阻效应
溶胶-凝胶工艺
电阻-温度曲线
金属绝缘体转变 相似文献
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采用脉冲电子束沉积技术,在Si(100)单晶衬底上沉积庞磁电阻La0.67Ca0.33MnO3颗粒薄膜,并对它的磁学性能和电学输运性能进行了表征.研究晶界对庞磁电阻薄膜的物理性能的影响,结果表明,晶界的存在使得晶粒之间的耦合变弱,在变温磁化过程中表现出团簇玻璃态行为,金属—绝缘体转变温度(Tp)远远低于铁磁—顺磁转变温度(Tc).低温下电子输运具有弱局域化行为.在低磁场下,晶界的存在掩盖了La0.67Ca0.33MnO3的本征磁电阻行为.
关键词:
脉冲电子束沉积
晶界
磁学和电学输运性能
庞磁电阻 相似文献
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Xuebin Zhu Hechang Lei Xiangde Zhu Gang Li Wenhai Song Yuping Sun Shixue Dou 《Journal of magnetism and magnetic materials》2009,321(13):2009-2014
Grain size effects on magnetic and transport properties for heavily Sr-doped A-type antiferromagnetic La0.4Sr0.6MnO3 ceramics were studied. It was observed that with decrease in grain size, surface ferromagnetism could be introduced due to bond-breaking at surfaces. With decrease in grain size, the surface ferromagnetism was enhanced, and the phase transition order distinguished from the Arrott plot was a second one. The surface-induced ferromagnetism was insulating as judged from transport properties. With decrease in grain size, magnetoresistance was largely improved for both high magnetic and low magnetic fields. Under a 500 Oe magnetic field, the magnetoresistance is improved from 0.2%, 0.1%, 0.03% and 0.02% for the sample with grain size of 150 nm at 10, 100, 200 and 300 K, respectively, to 3%, 2.3%, 0.43% and 0.12% for the sample with grain size of 20 nm at 10, 100, 200 and 300 K. It was interesting to find that large magnetoresistance could be induced due to the surface ferromagnetism in A-type antiferromagnetic La0.4Sr0.6MnO3 nanoparticles, which suggested that it was possible to search for manganites with relatively high low-field magnetoresistance in nanostructured A-type antiferromagnetic materials. 相似文献
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Paolo Allia Federica Celegato Paola Tiberto Franca Albertini Simone Fabbrici 《Journal of magnetism and magnetic materials》2010,322(14):1898-1903
Fe-Pt thin films were deposited by rf sputtering on an MgO substrate heated at different temperatures to induce the formation of the perpendicular Fe-Pt L10 phase with a different grain morphology on the nanometer scale. All films are characterized by a mazelike pattern of FePt nanograins with interconnected bases. MFM images and magnetization curves indicate that all samples have a strong perpendicular magnetic anisotropy arising from (0 0 1) growth. The temperature behaviour of the electrical resistance indicates that a percolating path exists for conduction electrons in the mazelike pattern. The magnetoresistance was measured as a function of magnetic field (applied longitudinally) and temperature in the ranges −70 kOe<H<+70 kOe and 4 K<T<150 K, respectively. All samples display a complex behaviour of the electrical resistance as a function of applied field. The role of the different magnetoresistance effects (both intrinsic and extrinsic) measured in these FePt thin films is elucidated. 相似文献
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D. A. Balaev S. I. Popkov K. A. Shaikhutdinov M. I. Petrov D. M. Gokhfeld 《Physics of the Solid State》2014,56(8):1542-1547
The hysteretic dependences of the magnetoresistance of porous (38% of the theoretical density) granular high-temperature superconductor (HTSC) Bi1.8Pb0.3Sr1.9Ca2Cu3O x have been analyzed in the model of the effective intergranular field. This effective field has been defined by the superposition of the external field and the field induced by magnetic moments of superconducting grains. The magnetic flux compression in an intergranular medium, characterized by the effective field, controls the hysteretic behavior of the magnetoresistance. It has been found that the magnetoresistance hysteresis width for the studied porous HTSC depends on the transport current, in contrast to the superconductor of the same composition with high physical density (more than 90% of the theoretical value). For a porous superconductor, a significant current concentration occurs in the region of the grain boundaries, which is caused by features of its microstructure. A current-induced increase in the effective boundary length results in a decrease in the flux compression, a decrease in the effective field in the intergranular medium, and a magnetoresistance hysteresis narrowing with increasing current. 相似文献
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W. Chérif M. Ellouze A.-F. Lehlooh F. Elhalouani S.H. Mahmood 《Journal of magnetism and magnetic materials》2012
A sample of Pr0.67Sr0.33MnO3 nanoparticles was synthesized by the ball milling method. X-ray diffraction pattern of the sample showed orthorhombic system with Pnma space group. The average crystallite size of 110 nm was obtained by both Scanning Electron Microscopy and X-ray diffraction. Magnetic measurements showed para-to-ferromagnetic transition with a Curie temperature of TC=269 K. Electrical investigations showed that all our samples exhibit a semi-conducting behavior above TC and a metallic-like one at lower temperatures. The sample exhibited a large magnetoresistance of 30% at room temperature in an applied magnetic field of 2 T. The transport and the magnetic properties were interpreted in terms of the existence of magnetic polarons in the sample. 相似文献
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Magnetite particles with different average diameter (Dm) suitable for magnetic fluid hyperthermia (MFH) were synthesized by controlled coprecipitation technique. In this method, the reaction pH was stabilized using the pH buffer and the average particle diameter decreased with increasing reaction pH. The size-dependent magnetic behavior of the magnetite nanoparticles was studied and the optimum size range required for magnetic fluid hyperthermia (MFH) has been arrived at. Among the samples studied, the maximum specific absorption rate of 15.7 W/g was recorded for the magnetite sample with Dm of 13 nm, when exposed to an AC magnetic field strength of 3.2 kA/m and a frequency of 600 kHz. The AC magnetic properties suggested that the size distribution of the sample was bimodal with average particle size less than ∼13 nm. 相似文献
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G. de la González Cruz Yu. G. Gurevich V. V. Kucherenko E. de Ramírez Arellano 《Journal of Experimental and Theoretical Physics》2001,92(2):277-286
We propose a new theoretical method to study galvanomagnetic effects in bounded semiconductors. The general idea of this method is as follows. We consider the electron temperature distribution and the electric potential as consisting of two terms, one of which represents the regular solution of the energy balance equation obtained from the Boltzmann transport equation at steady-state conditions and the Maxwell equation, while the other is the effect of the specimen size that is significant near the contacts (the boundary layer function). With the distribution of the electric potential at the contacts and the electron temperature distribution at the surface of the sample taken into account, we find that the magnetoresistance is different from the one in the standard theory of galvanomagnetic effects in boundless media. We show that, besides the usual quadratic dependence on the applied magnetic field B, the magnetoresistance can exhibit a linear dependence on B under certain conditions. We obtain new formulas for the linear and quadratic terms of the magnetoresistance in bounded semiconductors. This linear contribution of the magnetic field to the magnetoresistance is essentially due to the spatial dependence of the potential at the electric contacts. We also discuss the possibility of obtaining the distribution of the electric potential at the contacts from standard magnetoresistance experiments. Because the applied magnetic field acts differently on carriers with different mobilities, a redistribution of the electron energy occurs in the sample and thus, the Ettingshausen effect on the magnetoresistance must be considered in bounded semiconductors. 相似文献
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A single artificial grain boundary in La0.67Ba0.33MnO3 (LBMO) thin film has been prepared by depositing the film on a bicrystal substrate using laser ablation technique. We investigated the magnetic field dependence of magnetoresistance and conductance-voltage characteristics of the grain boundary at 77 K. A decrease of nonlinearity of current-voltage characteristics was observed upon application of magnetic field. The results are explained by assuming the presence of two different types of parallel conducting channels (metallic and highly resistive) across the grain boundary. The analysis of the results reveals that the application of magnetic field suppresses magnetic disorders at the grain boundary region and increases metallic conduction channels across the grain boundary. The temperature dependence of the conduction noise of the bicrystal grain boundary was measured at 0 and 1.5 kG magnetic field and compared with a microbridge on the LBMO film having no grain boundary. The presence of the grain boundary was found to enhance noise by one order of magnitude. The noise of a bicrystal grain boundary showed a decrease in the presence of 1.5 kG magnetic field for T<210 K. This decrease of noise confirms that the application of a magnetic field induces more metallic channels across the grain boundary. 相似文献
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The structure, magnetic properties and magnetostriction of Fe81Ga19 thin films have been investigated by using X-ray diffraction analysis, scanning electron microscope (SEM), vibrating sample magnetometer and capacitive cantilever method. It was found that the grain size of as-deposited Fe81Ga19 thin films is 50–60 nm and the grain size increases with increase in the annealing temperature. The remanence ratio (Mr/Ms) of the thin films slowly decreases with increase in the annealing temperature. However, the coercivity of the thin films goes the opposite way with increase in the annealing temperature. A preferential orientation of the Fe81Ga19 thin film fabricated under an applied magnetic field exists along 〈1 0 0〉 direction due to the function of magnetic field during sputtering. An in-plane-induced anisotropy of the thin film is well formed by the applied magnetic field during the sputtering and the formation of in-plane-induced anisotropy results in 90° rotations of the magnetic domains during magnetization and in the increase of magnetostriction for the thin film. 相似文献
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Thickness dependent modifications in the structure and microstructure and their effect on the transport and magnetotransport in chemical solution deposition (CSD) grown La0.7Pb0.3MnO3 (LPMO) manganite thin films grown on single crystalline LaAlO3 (LAO) (1 0 0) substrates have been studied. X-ray diffraction (XRD) measurements show the reduction in the microstrain at the film-substrate interface with increasing thickness. Increase in grain size and island like grain growth with the reduction in surface roughness as a function of film thickness has been observed from the microstructural studies using atomic force microscopy (AFM) and lateral force microscopy (LFM) measurements. Improvement in the surface to volume ratio (D−1) resulting in the modifications in transport and magnetotransport properties of the LPMO films has been discussed in detail in the light of thickness dependent microstructural effects on the resistivity and magnetoresistance (MR) behavior. The variations in intrinsic and extrinsic MR with D−1 show an interesting interplay between them, which can be explained on the basis of thickness dependent grain size, grain boundary density and grain boundary nature. 相似文献