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(La1-xYx)2/3Ca1/3MnO3(x=0.195)系统中的磁电阻行为 总被引:1,自引:0,他引:1
本文实验上探讨了 (La1-xYx)2/3Ca1/3MnO3(x=0.195)窄带系统不同磁场下的磁电阻行为.实验表明,最大磁电阻效应随磁场增加而实质性提高,例如,7T磁场下最大磁电阻效应高达1.8×105%.同时,我们在远远低于半导体-金属转变温度下也观察到明显的磁电阻效应.文中就磁电阻的起因进行了讨论,特别是基于最近提出的自旋-极化子模型,对实验数据进行了定量的比较性分析,结果表明,该模型虽能预言实验的主要特征,但理论预言随磁场增加而明显偏离实验. 相似文献
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阐述了巨磁电阻效应的机理,利用AA002系列巨磁电阻(GMR)器件测量了单个巨磁电阻的阻值与磁场磁感应强度的关系以及AA002系列巨磁电阻(GMR)器件的输出电压与外磁场的关系,研究了巨磁电阻效应的特性,并设计了巨磁电阻器件在物理实验教学中的实用性比较广泛的系列实验. 相似文献
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锰氧化物具有内禀的多尺度非均匀性,这与同时活跃的多个自由度--自旋、电荷、晶格和轨道--非线性耦合,以及多种相互作用的共存密切相关.更重要的是, 这种极为特殊的物理现象可能是庞磁电阻效应的微观起源--铁磁金属相在磁场作用下的逾渗而驱动的磁电阻效应.另一方面,在某组分导电逾渗阈值附近的磁电阻显著增强效应,是高自旋极化氧化物颗粒体系所具有的普遍现象之一.因此,针对各种高自旋极化氧化物的非均匀和颗粒复合体系,逾渗驱动磁电阻增强效应的研究具有重要的学术意义和应用价值,其中输运网络理论为重要的理论研究.在充分认识电磁输运微观机制的基础之上,通过调控输运网络的结构,探讨逾渗驱动磁电阻增强的必要条件,可以找出实现可控性高且幅值较大的磁电阻的新途径、新方法.本文主要基于电阻网络模型,综述高自旋极化氧化物材料中多相共存体系的磁输运性质研究的主要背景和发展现状,充分结合相关的实验结果,介绍逾渗驱动磁电阻效应增强的物理机制,以及各类电输运网络的构建,并展望未来的发展. 相似文献
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锰氧化物具有内禀的多尺度非均匀性,这与同时活跃的多个自由度——自旋、电荷、晶格和轨道——非线性耦合,以及多种相互作用的共存密切相关。更重要的是,这种极为特殊的物理现象可能是庞磁电阻效应的微观起源——铁磁金属相在磁场作用下的逾渗而驱动的磁电阻效应。另一方面,在某组分导电逾渗阈值附近的磁电阻显著增强效应,是高自旋极化氧化物颗粒体系所具有的普遍现象之一。因此,针对各种高自旋极化氧化物的非均匀和颗粒复合体系,逾渗驱动磁电阻增强效应的研究具有重要的学术意义和应用价值,其中输运网络理论为重要的理论研究。在充分认识电磁输运微观机制的基础之上,通过调控输运网络的结构,探讨逾渗驱动磁电阻增强的必要条件,可以找出实现可控性高且幅值较大的磁电阻的新途径、新方法。本文主要基于电阻网络模型,综述高自旋极化氧化物材料中多相共存体系的磁输运性质研究的主要背景和发展现状,充分结合相关的实验结果,介绍逾渗驱动磁电阻效应增强的物理机制,以及各类电输运网络的构建,并展望未来的发展。 相似文献
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研究磁性半导体中负磁电阻产生机理对正确理解载流子与磁性离子间的sp.d磁交换作用是非常重要的.通过变温(10-300K)磁输运和变温(5-300K)磁化率实验研究了一系列不同Mn含量非简并P型Hgl-xMn。Te单晶佃〉0.17)的负磁电阻和顺磁增强效应.实验结果表明其负磁电阻与温度的关系和磁化率与温度的关系基本一致,两者都包含一个呈指数型变化的温度函数exp(-K/T).根据磁性半导体的杂质能级理论,非简并P型H譬1-xMnxTe单晶在低磁场范围内出现负磁电阻效应的主要物理机理为外磁场的磁化效应使得受主杂质或受主型束缚磁极化子的有效电离能减小. 相似文献
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V. V. Rylkov B. A. Aronzon A. S. Lagutin V. V. Podol’skii V. P. Lesnikov M. Goiran J. Galibert B. Raquet J. Léotin 《Journal of Experimental and Theoretical Physics》2009,108(1):149-158
We have studied the magnetotransport properties of p-InMnAs layers in strong (up to 30 T) pulsed magnetic fields. The p-InMnAs layers were obtained by laser plasma deposition with subsequent annealing by radiation of a pulsed ruby laser. Under anomalous Hall effect conditions in a strong magnetic field (above 20 T), the Hall resistance in the paramagnetic region of temperatures is greater than that in the ferromagnetic region (below 40 K). It has also been established that, at helium temperatures, the negative magnetoresistance exhibits saturation in a field of about 10 T, whereas the anomalous Hall effect is saturated at about 2 T. At T ≈ 4 K, the resistance in a field of 10 T exhibits a more than tenfold decrease. The results are explained by a mesoscopically inhomogeneous distribution of the acceptor (Mn) impurity, a local ferromagnetic transition, and a percolation character of the conductivity of p-InMnAs films in a state close to the insulator-metal phase transition. The characteristic scale of magnetoelectric inhomogeneity in the system is evaluated based on an analysis of mesoscopic fluctuations of the nondiagonal component of the magnetoresistance tensor. 相似文献
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B. A. Aronzon A. B. Granovskii S. N. Nikolaev D. Yu. Kovalev N. S. Perov V. V. Ryl’kov 《Physics of the Solid State》2004,46(8):1482-1486
The Hall effect and magnetoresistance in Cr(50 Å)/Co(200 Å) bilayer films prepared by ion sputtering on a silicon substrate are investigated at room temperature. The planar Hall effect revealed in the bilayer films differs from the planar Hall effect observed usually in that it is symmetric with respect to the sign of the change in the rotation angle of the magnetic moment in the film plane. Under conditions where the symmetric planar Hall effect is realized, the change in the Hall resistance is more than 10% and exceeds the anisotropic magnetoresistance by two orders of magnitude. The hysteresis loops are measured at different orientations of magnetic fields. The planar Hall effect is studied in a weak longitudinal magnetic field. The results obtained demonstrate that the symmetric planar Hall effect is associated with the multidomain structure of the cobalt film in Cr/Co bilayer composites. 相似文献
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Yu. N. Ovchinnikov 《Journal of Experimental and Theoretical Physics》2000,90(6):1058-1062
The influence of a magnetic field on the effective conductivity of a system with a chessboard structure is studied under conditions of the Hall effect. It is shown that in this case a new physical effect occurs, involving an oscillatory dependence of the charge density at the interfaces on passage through the bifurcation point. The system possesses considerable magnetoresistance. 相似文献
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The Hall effect and magnetoresistance of a mesoscopic system having a four-probe ring geometry are calculated in a tight-binding
model, either ordered or disordered, as function of magnetic flux and Fermi energy. The changes induced in the spectrum by
the magnetic field affect differently the Aharonov-Bohm (AB) oscillating pattern of the two resistances: after the gap reaches
the Fermi energy, the Hall effect remains bounded while the magnetoresistance increases exponentially with the sample size.
The results are shown to depend significantly on the number and geometry of the probes. 相似文献
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The Hall effect and magnetoresistance of a mesoscopic system having a four-probe ring geometry are calculated in a tight-binding model, either ordered or disordered, as function of magnetic flux and Fermi energy. The changes induced in the spectrum by the magnetic field affect differently the Aharonov-Bohm (AB) oscillating pattern of the two resistances: after the gap reaches the Fermi energy, the Hall effect remains bounded while the magnetoresistance increases exponentially with the sample size. The results are shown to depend significantly on the number and geometry of the probes. 相似文献
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A. G. Pogosov M. V. Budantsev R. A. Lavrov A. E. Plotnikov A. K. Bakarov A. I. Toropov 《JETP Letters》2005,81(9):462-466
Commensurability oscillations of thermopower in a square antidot lattice are observed. The oscillations are attributed to the geometrical resonances of the classical electron motion in a magnetic field and are much more pronounced than the corresponding magnetoresistance oscillations. The off-diagonal component of the thermopower tensor (the Nernst-Ettingshausen effect) changes sign at resonances. Additional measurements of magnetoresistance verify the correctness of the method used for thermopower measurements and provide information on the temperature distribution in the sample. 相似文献
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V. I. Kadushkin 《Russian Physics Journal》1979,22(5):506-510
Shubnikovde Haas oscillations of the transverse magnetoresistance and of the Hall effect are analyzed. The magnetic field dependence of the monotonic components of the transverse magnetoresistance and conductivity are determined. It is found that these dependences do not follow the saturation law usually assumed to hold in a strong magnetic field. It is shown that the reason is the magnetic field dependence of the Hall angle and of the carrier effective mass.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 60–65, May, 1979.The author is grateful to Yu. A. Bykovskii, under whose guidance the experiments were performed, to V. F. Elesin for indicating the present problem, and to L. G. Iofee for help in handling the experimental results. 相似文献
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磁性颗粒膜法拉第转角的研究 总被引:2,自引:2,他引:0
在外磁场作用下,复合介质的法拉第磁光效应依赖于颗粒膜电介质张量。而复合介质的电介质张量的计算相当复杂。运用了有效介质近似理论,利用非均匀复合介质的有效电场等于单个颗粒中局域场的平均值的自恰条件,由电介质张量εe方程及自洽条件导出了计算磁性颗粒膜系统磁光法拉第转角的解析公式。并应用导出的关系,以Cu金属颗粒为例,讨论了颗粒膜中金属颗粒含量及对应的基质、离子浓度、颗粒形状对法拉第转角的影响,结果表明,利用有效介质近似理论计算的结果与实验结果一致。 相似文献
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A. A. Sinchenko Yu. I. Latyshev A. P. Orlov A. A. Ivanov P. Monceau 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):199-204
We have measured the Hall effect and the transverse
magnetoresistance in NbSe3 single crystals. In the liquid helium
temperature range we observed an absolute negative magnetoresistance
(NMR) — the value of the resistance under magnetic field being much
lower than that at zero field — in NbSe3 single crystals with a
thickness less than 5 μm with the magnetic field oriented in the
(b, c) plane. We show that this NMR effect is observed in the
magnetic field range in which the Hall constant changes its sign.
The results are qualitatively explained by the change of the surface
scattering contribution to the magnetoconductance in the magnetic
field range near the Hall voltage zero crossing. 相似文献
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The transverse redistribution of carriers that occurs in a 2D system under the effect of a tangential electric field and a magnetic field possessing a tangential component is studied. It is shown that the redistribution of carriers gives rise to a Hall voltage across isolated electrodes positioned above and under the quantum film. This voltage is determined by the 2D conductivity tensor and the transverse static electric polarizability of the 2D layer. The additional contribution that appears in the vertical Hall voltage because of the electron spin orientation induced by magnetic field and the spin-orbit interaction of electrons with the quantum well potential is determined. 相似文献