共查询到20条相似文献,搜索用时 46 毫秒
1.
DONG Zheng-Chao 《理论物理通讯》2004,41(1):135-140
The tunneling conductance and tunneling magnetoresistance (TMR) are
investigated in ferromagnet/insulator/ferromagnet/insulator/d-wave
superconductor (FM/I/FM/I/d-wave SC) structures by applying an extended
Blonder-Tinkham-Klapwijk (BTK) approach. We study the effects of the
exchange splitting in the FM, the magnetic impurity scattering in the thin
insulator interface of FM/I/FM, and noncollinear magnetizations in adjacent
magnetic layers on the TMR. It is shown (1) that the tunneling conductance
and TMR exhibit amplitude-varying oscillating behavior with exchange
splitting, (2) that with the presence of spin-flip scattering in insulator
interface of FM/I/FM, the TMR can be dramatically enhanced, and (3)
that the TMR depends strongly on the angle between the magnetization of two
FMs. 相似文献
2.
《Journal of magnetism and magnetic materials》2002,251(2):163-168
Taking into account the nonequilibrium spin accumulation, we apply a quantum-statistical approach to study the spin-polarized transport in a two-dimensional ferromagnet/semiconductor/ferromagnet (FM/SM/FM) double tunnel junction. It is found that the effective spin polarization is raised by increasing the barrier strength, resulting in an enhancement of the tunneling magnetoresistance (TMR). The nonequilibrium spin accumulation in SM may appear in both antiparallel and parallel alignments of magnetizations in two FMs, in particular for high bias voltages. The effects of spin accumulation and TMR on the bias voltage are discussed. 相似文献
3.
The influence of the Dresselhaus spin--orbit coupling on the tunnelling magnetoresistance in ferromagnet/ insulator /semiconductor/ insulator /ferromagnet tunnel junctions 下载免费PDF全文
This paper investigates the effect of Dresselhaus spin--orbit
coupling on the spin-transport properties of
ferromagnet/insulator/semiconductor/insulator/ferromagnet
double-barrier structures. The influence of the thickness of the
insulator between the ferromagnet and the semiconductor on the
polarization is also considered. The obtained results indicate that
(i) the polarization can be enhanced by reducing the insulator
layers at zero temperature, and (ii) the tunnelling magnetoresistance
inversion can be illustrated by the influence of the Dresselhaus
spin--orbit coupling effect in the double-barrier structure. Due to
the Dresselhaus spin--orbit coupling effect, the tunnelling
magnetoresistance inversion occurs when the energy of a localized
state in the barrier matches the Fermi energy EF of the
ferromagnetic electrodes. 相似文献
4.
TUNNEL MAGNETORESISTANCE IN THE FERROMAGNETIC TUNNEL JUNCTION WITH FERROMAGNETIC LAYERS OF FINITE THICKNESS SUBJECTED TO AN ELECTRIC FIELD 下载免费PDF全文
Based on the two-band model, we investigate the tunnel magnetoresistance(TMR) in ferromagnet/insulator (semiconductor)/ferromagnet(FM/I(S)/FM) tunnel junction covered on both sides by nonmagnetic metal layers subjected to an electric field. Our results show that TMR oscillates with the thickness of ferromagnetic layers owing to the quantum-size effect and can reach very large value under suitable conditions, which may in general not be reached in FM/I(S)/FM with infinitely thick ferromagnetic layer. Although the electric field causes the change of the oscillation period, phase and amplitude of the TMR, a large TMR is still obtained in some situations with the electric field. Furthermore, the electric field does not change the feature that TMR varies monotonously with the change of magnetization angle of the middle ferromagnetic layer. 相似文献
5.
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
6.
通过求解Bogoliubov-deGennes方程,利用推广的Bonder-Tinklam-Klapwijk方法,计算铁磁/绝缘层/铁磁/绝缘层/超导结构中的微分电导(G)和散粒噪声(S)。研究发现系统中的微分电导和散粒噪声都随中间铁磁层厚度作两种不同周斯的振荡,其中通过增强铁磁材料中的交换劈裂和铁磁/超导界面的势垒强度,短周期分量可从长周期中分离出来,反之通过降低铁磁层中的交换劈裂和铁磁/超导界面的势垒强度,长周期分量可从短周期中分离出来,这一结果表明G和S中的两种不同周期的振荡分量分别来自入射电子与铁磁/超导界面处的Andreev反射和正常电子反射的量子干涉效应。 相似文献
7.
Chunxu Bai 《Physics letters. A》2008,372(5):725-729
Spin-polarized transports of relativistic electrons through graphene-based ferromagnet/insulator/ferromagnet (FG/IG/FG) single junctions have been investigated theoretically. Large oscillating tunnel magnetoresistance (TMR) has been found in monolayer and bilayer FG/IG/FG junctions. The oscillating amplitudes of TMR do not decrease with the increase of the thickness and the height of barrier, in contrast to the exponential decay in conventional ferromagnet/insulator/ferromagnet single junction. The physical origin for such a phenomenon has also been analyzed. It is anticipated to apply such a phenomenon to design the spin-polarized electron device based on the graphene materials. 相似文献
8.
Spin transport properties in ferromagnet/superconductor junctions on topological insulator 下载免费PDF全文
The spin-dependent Andreev reflection is investigated theoretically by analyzing the electronic transport in a thin-film topological insulator (TI) ferromagnet/superconductor (FM/SC) junction. The tunneling conductance and shot noise are calculated based on the Dirac-Bogoliubov-de Gennes equation and Blonder-Tinkham-Klapwijk theory. It is found that the magnetic gap in ferromagnet can enhance the Andreev retro-reflection but suppress the specular Andreev reflection. The gate potential applied to the electrode on top of superconductor can enhance the two types of reflections. There is a transition between the two types of reflections at which both the tunneling conductance and differential shot noise become zero. These results provide a method to realize and detect experimentally the intra-band specular Andreev reflection in thin film TI-based FM/SC structures. 相似文献
9.
We have studied the tunneling conductance in ferromagnet/insulator/p-wave superconductor junctions, taking into account the
rough interface scattering effect. We find that there exist zero-bias conductance peaks and single-minimum structure in tunneling
spectroscopy. As the exchange energy increases, the Andreev reflection is always suppressed and the differential conductance
decreases. The differential conductance depends on the barrier strength and the roughness at the interface.
Supported by the Natural Science Foundation of Jiangsu Higher Education Institutions, China (Grant No. 06KJB140009) 相似文献
10.
Sun Guoya Xing D.Y. Shen R. Lin H.Q. 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):33-38
The Nambu spinor Green's function approach is applied to calculating the density of states (DOS) and superconducting order
parameter in normal-metal/insulator/ferromagnet/superconductor (NM/I/FM/SC) junctions. It is found that the s-wave superconductivity and ferromagnetism can coexist near the FM/SC interface, which is induced by proximity effect. On
the SC side, the spin-dependent DOS appears both within and without the energy gap. On the FM side, the superconducting order
parameter displays a damped oscillation and the DOS exhibits some superconducting behavior. The calculated result for the
DOS in FM for “0 state” and “π state” can reproduce recent tunneling spectra in Al/Al2O3/PdNi/Nb tunnel junctions.
Received 1st July 2002 Published online 19 November 2002 相似文献
11.
S. A. Ignatenko 《Technical Physics》2006,51(11):1398-1404
A two-band s-d model based on the Green function method has been developed for calculating the conductivity and tunnel magnetoresistance of ferromagnet/insulator/ferromagnet structures. It is shown that s-d scattering at the interface between the ferromagnet and the insulator in Fe/Al2O3/Fe increases the tunnel magnetoresistance. The spin polarization of the current decreases thereby and even becomes negative, which is mainly due to scattering of strongly localized d electrons to the s band, followed by tunnelling through the insulator. 相似文献
12.
DONG Zheng-Chao 《理论物理通讯》2004,41(5):775-780
The tunneling spectroscopy and shot noise in ferromagnet/insulator/triplet-superconductor (FM/I/triplet-SC) structures are studied by taking into account the roughness interfacial barrier and exchange splitting in the FM. For the triplet-SC of
Sr2RuO4,
we consider two-dimensional f-wave order parameter symmetries having nodes within the RuO2
plane, which reasonably describe both thermodynamic and thermal conductivity data. It is shown that the ferromagnetic exchange splitting gives rise to a decrease in the differential
conductance, the average current, and the shot noise power, while the noise power-to-current ratio is increased; the interface roughness is found to lead to a decrease in the differential
conductance and the average current, and an increase in the noise power-to-current ratio. 相似文献
13.
H. B. Wang Y. K. Li Z. H. Yang J. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(3):405-409
We report a theoretical study on the interfacial electron transport
in the ferromagnet/two-dimensional electron gas (FM/2DEG) hybrid
junction at zero bias, where the Rashba spin-orbit interaction
(RSOI) is considered in 2DEG region. It is shown that a nonzero
charge current can spontaneously flow in the interface of the
junction due to broken time reversal symmetry and spin-dependent
scattering of electron at interface. This interfacial charge current
can be modulated by system parameters such as the magnetization of
FM, RSOI strength, and interface barrier, moreover, it can be
optimized as the magnetization of FM in 2DEG plane is perpendicular
to interface whereas it can vanish as the FM magnetization is
parallel to interface. 相似文献
14.
《Current Applied Physics》2019,19(12):1362-1366
Based on a spin drift-diffusion model, we theoretically investigate the spin-orbit torque in ferromagnet/normal metal/insulator trilayers with considering the Rashba interfacial spin-orbit coupling at the normal metal/insulator interface. We find that the spin-orbit torque shows the opposite normal-metal-thickness dependences for the bulk spin-orbit coupling effect in the normal metal layer and for the interfacial spin-orbit coupling effect at the normal metal/insulator interface, offering a way to disentangle these two spin-orbit coupling effects. Moreover, we show that the conventional interpretation based on the bulk spin-orbit coupling effect overestimates the spin Hall angle and underestimates the spin diffusion length of the normal metal layer, when the interfacial contribution is non-negligible. Our result, a concise analytic expression of the spin-orbit torque considering both bulk and interface spin-orbit coupling effects, will be useful to design and interpret experiments on spin-orbit torque experiments in ferromagnet/normal metal/insulator trilayers. 相似文献
15.
The tunneling conductance in topological insulator (TI) ferromagnet/p-wave superconductor (FM/pS) junction is studied based on the Blonder–Tinkham–Klapwijk (BTK) theory. The Fermi energy mismatch between FM and pS as well as the finite quasiparticle lifetime are considered. Three kinds of pairings px, py, and px+ipy-waves for pS are chosen. It is found that the spectrum strongly depend on the magnetic gap, the gate potential, the quasiparticle lifetime as well as the type of the pair potential symmetry. The pair potential symmetry drastically affects the formation of the zero-energy bound states dependent on the magneto effect or the Fermi energy mismatch effect. The finite quasiparticle lifetime effect can suppress the Andreev resonant scattering process at eV=Δ0 and smear the dips in the conductance. 相似文献
16.
运用拓展的BTK理论研究了拓扑绝缘层上铁磁/铁磁超导隧道结的磁效应和塞曼效应,同时考虑了铁磁体和铁磁超导体之间的费米能级错配效应.研究发现:在该系统中塞曼效应和邻近效应可以共存;铁磁体和铁磁超导体之间的费米能级错配效应能够增强系统中发生在eV=Δ处的Andreev谐振散射过程和邻近效应. 相似文献
17.
Based on the nearly-free-electron approximation, the bias dependencies of electron transport properties of ferromagnet/ferromagnetic insulator (semiconductor)/ferromagnet junctions have been studied. Resonances appear in electron transmission probability. These resonances cause oscillations in the zero-temperature tunnel current and the resonances occur in tunnel conductance. Tunnel magnetoresistance (TMR) is an oscillatory function of bias. The TMR can reach a value as high as 100%. The bins dependencies of electron transport properties relate to the magnetic configurations of the junctions. 相似文献
18.
M. J. Ma M. B. A. Jalil S. G. Tan D. E. Koh 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,82(1):37-46
We theoretically study the spin-polarized transport
through double barrier magnetic tunnel junction (DBMTJ) consisting
of the quantum dot sandwiched by two ferromagnetic (FM) leads. The
tunneling current through the DBMTJ is evaluated based on the
Keldysh nonequilibrium Green’s function approach. The self-energy
and Green’s function of the dot are analytically obtained via the
equation of motion method, by systematically incorporating two
spin-flip phenomena, namely, intra-dot spin-flip, and spin-flip
coupling between the lead and the central dot region. The effects of
both spin-flip processes on the spectral functions, tunneling
current and tunnel magnetoresistance (TMR) are analyzed. The
spin-flip effects result in spin mixing, thus contributing to the
spectral function of the off-diagonal Green’s function components ( Gs[`(s)] r )\left( {G_{\sigma \bar \sigma }^r } \right). Interestingly, the spin-flip coupling
between the lead and dot enhances both the tunneling current and the
TMR for applied bias above the threshold voltage V
th
. On the
other hand, the intra-dot spin-flip results in an additional step in
the I-V characteristics near V
th
. Additionally, it
suppresses the tunneling current but enhances the TMR. The opposing
effects of the two types of spin-flip on the tunneling current means
that one spin-flip mechanism can be engineered to counteract the
other, so as to maintain the tunneling current without reducing the
TMR. Their additive effect on the TMR enables the DBMTJ to attain a
large tunneling current and high TMR for above threshold bias
values. 相似文献
19.
We present a general formula for tunneling conductance in ballistic ferromagnet/ferromagnetic insulator/superconductor junctions where the superconducting state has the opposite spin pairing symmetry. The formula shows, correctly, that ferromagnetism has been induced by the effective mass difference between up- and down-spin electrons. This effectively mass mismatched ferromagnet and a standard Stoner ferromagnet have been employed in this paper. As an application of the formulation, we have studied the tunneling effect for junctions including a spin-triplet p-wave superconductor, where we choose a normal insulator for the insulating region, although our formula can be used for a ferromagnetic insulator. Then, we have been able to devote our attention to features of a ferromagnetic metal. The conductance spectra show a clear difference between the two ferromagnets depending upon the method of normalization of the conductance. In particular, an essential difference is seen in the zero-bias conductance peaks, reflecting the characteristics of each ferromagnet. From the obtained results, we suggest that the measurements of the tunneling conductance in the junction provide us with useful information about the mechanism of itinerant ferromagnetism in metals. 相似文献
20.
A recent theoretical estimation indicated that the NM/FI/FI/NM double spin-filter junction (DSFJ, here the NM and FI represent the nonmagnetic electrode and the ferromagnetic insulator (semiconductor) spacer, respectively) could have very high tunneling magnetoresistance (TMR) at zero bias. To meet the requirement in research and application of the magnetoresistance devices, we have calculated the dependences of tunneling magnetoresistance of DSFJ on the bias (voltage), the thicknesses of ferromagnetic insulators (semiconductors) and the average barrier height. Our results show that except its very high value, the TMR of DSFJ does not decrease monotonously and rapidly with rising bias, but increase slowly at first and decrease then after having reached a maximum value. This feature is in distinct contrast to the ordinary magnetic tunnel junction FM/NI/FM (FM and NI denote the ferromagnetic electrode and the nonmagnetic insulator (semiconductor) spacer, respectively), and is of benefit to the use of DSFJ as a magnetoresistance device. 相似文献