共查询到20条相似文献,搜索用时 125 毫秒
1.
Wunderlich J Jungwirth T Kaestner B Irvine AC Shick AB Stone N Wang KY Rana U Giddings AD Foxon CT Campion RP Williams DA Gallagher BL 《Physical review letters》2006,97(7):077201
We observe low-field hysteretic magnetoresistance in a (Ga,Mn)As single-electron transistor which can exceed 3 orders of magnitude. The sign and size of the magnetoresistance signal are controlled by the gate voltage. Experimental data are interpreted in terms of electrochemical shifts associated with magnetization rotations. This Coulomb blockade anisotropic magnetoresistance is distinct from previously observed anisotropic magnetoresistance effects as it occurs when the anisotropy in a band structure derived parameter is comparable to an independent scale, the single-electron charging energy. Effective kinetic-exchange model calculations in (Ga,Mn)As show chemical potential anisotropies consistent with experiment and ab initio calculations in transition metal systems suggest that this generic effect persists to high temperatures in metal ferromagnets with strong spin-orbit coupling. 相似文献
2.
Tan RP Carrey J Desvaux C Grisolia J Renaud P Chaudret B Respaud M 《Physical review letters》2007,99(17):176805
We report on magnetotransport measurements on millimetric superlattices of Co-Fe nanoparticles surrounded by an organic layer. At low temperature, the transition between the Coulomb blockade and the conductive regime becomes abrupt and hysteretic. The transition between both regimes can be induced by a magnetic field, leading to a novel mechanism of magnetoresistance. Between 1.8 and 10 K, a high-field magnetoresistance attributed to magnetic disorder at the surface of the particles is also observed. Below 1.8 K, this magnetoresistance abruptly collapses and a low-field magnetoresistance is observed. 相似文献
3.
Kyoung-Woong Moon Jae-Chul Lee Sug-Bong Choe Kyung-Ho Shin 《Current Applied Physics》2009,9(6):1293-1295
We present an experimental technique to determine the magnetic anisotropy of ferromagnetic nanowires. In the technique, the magnetization state is monitored by measuring the anisotropic magnetoresistance with rotating the external magnetic field. The measured magnetoresistance curves exhibit basically the same curves typically appeared in the torque magnetometric measurements, which are then readily analyzed based on the Stoner–Wohlfarth theory with a single fitting parameter – the magnetic anisotropy. By applying the present technique to Permalloy nanowires, it is shown that the shape anisotropy in real nanowires is significantly influenced by the edge roughness. 相似文献
4.
Electronic transport properties of graphene‐based junctions are considered theoretically in the linear response regime and in terms of the effective continuous electronic model. The junctions under consideration consist of two parts; one part is magnetic, while the other one is non‐magnetic but exhibits strong Rashba spin–orbit coupling. Transport properties of such junctions depend on relative orientation of the magnetization, graphene plane, and direction of charge current. A relatively large anisotropic magnetoresistance, associated with a change in the relative orientation of the magnetization and electric current has been found. This magnetoresistance can be either positive or negative. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
S. T. B. Goennenwein M. Althammer C. Bihler A. Brandlmaier S. Geprgs M. Opel W. Schoch W. Limmer R. Gross M. S. Brandt 《固体物理学:研究快报》2008,2(3):96-98
The possibility to control magnetic properties via electrical fields is investigated in a piezoelectric actuator/ferromagnetic semiconductor thin film hybrid structure. Using anisotropic magnetoresistance techniques, the magnetic anisotropy and the magnetization orientation within the plane of the ferromagnetic film are measured quantitatively. The experiments reveal that the application of an electrical field to the piezoelectric actuator allows to continuously and reversibly rotate the magnetization orientation in the ferromagnet by about 70°. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
Reasmey P. Tan Julian Carrey Marc Respaud Céline Desvaux Philippe Renaud Bruno Chaudret 《Journal of magnetism and magnetic materials》2008
We report on magnetotransport measurements on millimeter-large super-lattices of CoFe nanoparticles surrounded by an organic layer. Electrical properties are typical of Coulomb blockade in three-dimensional arrays of nanoparticles. A large high-field magnetoresistance, reaching up to 3000%, is measured between 1.8 and 10 K. This exceeds by two orders of magnitude magnetoresistance values generally measured in arrays of 3d transition metal ferromagnetic nanoparticles. The magnetoresistance amplitude scales with the magnetic field/temperature ratio and displays an unusual exponential dependency with the applied voltage. The magnetoresistance abruptly disappears below 1.8 K. We propose that the magnetoresistance is due to some individual paramagnetic moments localized between the metallic cores of the nanoparticles, the origin of which is discussed. 相似文献
7.
The tunnel magnetoresistance (TMR) in an Aharonov–Bohm interferometer with two quantum dots inserted in its arms, which is attached to ferromagnetic leads with parallel and antiparallel magnetic configurations, is theoretically studied by means of the nonequilibrium Green’s function technique. We pay particular attention to the influence of an applied magnetic flux on the characteristics of the TMR. In the linear response regime (the external bias voltage V→0) and when the electrons are free from intradot Coulomb interaction, the magnetic flux only changes the peak or dip positions of the TMR. But in the presence of intradot Coulomb repulsion, its peak or dip positions, signs and magnitude are tuned by the magnetic flux. For the nonlinear response regime (V≠0), the TMR is symmetric with respect to zero bias voltage and the magnetic flux can influence its magnitude, signs and the peak positions regardless of the existence of intradot Coulomb interaction. The behavior of the TMR is interpreted in terms of the quantum interference (Fano) effect. 相似文献
8.
P.D. Grigoriev 《Physica B: Condensed Matter》2012,407(11):1932-1936
It is shown that in rather strong magnetic field the interlayer electron conductivity is exponentially damped by the Coulomb barrier arising from the formation of polaron around each localized electron state. The theoretical model is developed to describe this effect, and the calculation of the temperature and field dependence of interlayer magnetoresistance is performed. The results obtained agree well with the experimental data in GaAs/AlGaAs heterostructures and in strongly anisotropic organic metals. The proposed theory allows to use the experiments on interlayer magnetoresistance to investigate the electron states, localized by magnetic field and disorder. 相似文献
9.
Yong-Hong Kong Mao-Wang Lu Wei-Hua Tang Gui-Lian Zhang 《Solid State Communications》2007,142(3):143-147
We theoretically investigate the giant magnetoresistance (GMR) effect in general magnetically modulated semiconductor nanosystems, which can be realized experimentally by depositing two parallel ferromagnetic strips on the top of a heterostructure. Here the exact magnetic profiles and arbitrary magnetization direction of ferromagnetic strips are emphasized. It is shown that a considerable GMR effect can be achieved in such nanosystems due to the significant transmission difference for electrons tunneling through parallel and antiparallel magnetization configurations. It is also shown that the magnetoresistance ratio is strongly influenced by the magnetization direction of ferromagnetic strips in nanosystems, thus possibly leading to tunable GMR devices. 相似文献
10.
The colossal magnetoresistance effect in magnetic semiconductors based on lanthanum manganites has been investigated in terms of the model allowing for the effects of p-d hybridization and electronelectron Coulomb correlations. The influence of an external magnetic field on spin fluctuations has been considered under the conditions where the chemical potential is in a narrow heavy-fermion band formed in the hybridization gap. It has been shown that, in the vicinity of the Curie point T C, the strong spin anharmonicity leads to an anomalously strong suppression of spin fluctuations by the external magnetic field, a phenomenon contributing significantly to the formation of colossal negative magnetoresistance. 相似文献
11.
Stefan Krompiewski 《Central European Journal of Physics》2011,9(2):369-371
This contribution reports on charge and spin transport through graphene nanoribbons (GrNs) and carbon nanotubes (CNTs). The
paper focuses on the giant magnetoresistance effect in these materials, and their potential usefulness for spintronic applications.
As examples, the following devices are shortly discussed: GrNs in the ballistic transport regime, a CNT-based Schottky-barrier
field effect transistor (CNT SB-FET), as well as CNT quantum dots in the Coulomb blockade limit. 相似文献
12.
Magnetization reversal process in thin Co nanowires 总被引:2,自引:0,他引:2
B. Hausmanns T. P. Krome G. Dumpich E. F. Wassermann D. Hinzke U. Nowak K. D. Usadel 《Journal of magnetism and magnetic materials》2002,240(1-3):297-300
The magnetoresistance of single Co nanowires of various widths is investigated at low temperatures applying magnetic fields μ0H up to 4.5 T. The in-plane longitudinal magnetoresistance shows pronounced features at coercive fields Hc explained by the anisotropic magnetoresistance indicating the magnetization reversal process. Monte Carlo simulations present the magnetization distribution during the reversal process, revealing different mechanisms depending on the wire width. 相似文献
13.
Cheng XM Urazhdin S Tchernyshyov O Chien CL Nikitenko VI Shapiro AJ Shull RD 《Physical review letters》2005,94(1):017203
While magnetoresistance (MR) has generally been found to be symmetric in applied field in nonmagnetic or magnetic metals, we have observed antisymmetric MR in Co/Pt multilayers. Simultaneous domain imaging and transport measurements show that the antisymmetric MR is due to the appearance of domain walls that run perpendicular to both the magnetization and the current, a geometry existing only in materials with perpendicular magnetic anisotropy. As a result, the extraordinary Hall effect gives rise to circulating currents in the vicinity of the domain walls that contributes to the MR. The antisymmetric MR and extraordinary Hall effect have been quantitatively accounted for by a theoretical model. 相似文献
14.
V. O. Vas’kovskii K. G. Balymov A. A. Yuvchenko A. V. Svalov A. N. Sorokin N. A. Kulesh 《Technical Physics》2011,56(7):981-985
The magnetization reversal and magnetoresistance of two-layer exchange-coupled Fe19Ni81/Tb-Co films are studied. Amorphous
Tb
x
Co100 − x
layers with 30 < x < 35 are found to have a uniaxial magnetic anisotropy and a rather high coercive force, which ensures magnetic biasing of
the adjacent permalloy layers. In addition, the permalloy layers subjected to selective annealing exhibit a significant anisotropic
magnetoresistance and a small magnetic hysteresis. These properties make it possible to consider the developed film structure
as an effective magnetoresistive medium. This structure is used to form magnetic sensor samples that have an odd transfer
function in the absence of external magnetic biasing. 相似文献
15.
Rüster C Gould C Jungwirth T Sinova J Schott GM Giraud R Brunner K Schmidt G Molenkamp LW 《Physical review letters》2005,94(2):027203
We report the discovery of a very large tunneling anisotropic magnetoresistance in an epitaxially grown (Ga,Mn)As/GaAs/(Ga,Mn)As structure. The key novel spintronics features of this effect are as follows: (i) both normal and inverted spin-valve-like signals; (ii) a large nonhysteretic magnetoresistance for magnetic fields perpendicular to the interfaces; (iii) magnetization orientations for extremal resistance are, in general, not aligned with the magnetic easy and hard axis; (iv) enormous amplification of the effect at low bias and temperatures. 相似文献
16.
We investigated spin-dependent transport in magnetic tunnel junctions made of III-V Ga(1-x)Mn(x)As electrodes and II-VI ZnSe tunnel barriers. The high tunnel magnetoresistance (TMR) ratio up to 100% we observed indicates high spin polarization at the barrier/electrodes interfaces. We found anisotropic tunneling conductance having a magnitude of 10% with respect to the direction of magnetization to linearly depend on the magnetic anisotropy energy of Ga(1-x)Mn(x)As. This proves that the spin-orbit interactions in the valence band of Ga(1-x)M(x)As are responsible for the tunnel anisotropic magnetoresistance (TAMR) effect. 相似文献
17.
Revealing the origin of the vertical hysteresis loop shifts in an exchange biased Co/YMnO(3) bilayer
J Barzola-Quiquia A Lessig A Ballestar C Zandalazini G Bridoux F Bern P Esquinazi 《J Phys Condens Matter》2012,24(36):366006
We have investigated exchange bias effects in bilayers composed of the antiferromagnetic o-YMnO(3) and ferromagnetic Co thin film by means of SQUID magnetometry, magnetoresistance, anisotropic magnetoresistance and the planar Hall effect. The magnetization and magneto-transport properties show pronounced asymmetries in the field and magnetization axes of the field hysteresis loops. Both exchange bias parameters, the exchange bias field H(E)(T) as well as the magnetization shift M(E)(T), vanish around the Néel temperature T(N)???45?K. We show that the magnetization shift M(E)(T) is also measured by a shift in the anisotropic magnetoresistance and planar Hall resistance having a similar temperature dependence as the one obtained from magnetization measurements. Because the o-YMnO(3) film is highly insulating, our results demonstrate that the M(E)(T) shift originates at the interface within the ferromagnetic Co layer. To show that the main results obtained are general and not because of some special characteristics of the o-YMO(3) layer, similar measurements were done in Co/CoO micro-wires. The transport and magnetization characterization of the micro-wires supports the main conclusion that these effects are related to the response of the ferromagnetic Co layer at the interface. 相似文献
18.
Domain wall pinning in narrow ferromagnetic ring structures probed by magnetoresistance measurements
Kläui M Vaz CA Rothman J Bland JA Wernsdorfer W Faini G Cambril E 《Physical review letters》2003,90(9):097202
We present a magnetoresistance study of magnetization reversal and domain wall pinning effects in a mesoscopic narrow ferromagnetic Permalloy ring structure containing notches. The size and strength of the attractive pinning potential created by a notch is measured and the resistance minimum at remanence is found to occur when a single transverse domain wall is pinned at the notch, in agreement with the results of numerical simulations of the anisotropic magnetoresistance. When a field is applied in the direction corresponding to a potential well edge, a novel magnetic state with a very wide domain wall is stabilized, giving rise to a characteristic signature in the magnetoresistance at such angles. 相似文献
19.
Q. Chen H. -K. Zhao 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(2):237-248
We have investigated the spectral density of shot noise for an ultra-small quantum dot(QD) system in the Coulomb blockade
regime when irradiated with microwave fields (MWFs) by employing a nonequilibrium Green’s function technique. The shot noise
is sensitive to Coulomb interaction, and the photon-assisted Coulomb blockade behaviour strongly modifies the mesoscopic transport.
We have calculated the first and second derivatives of shot noise in the strong and weak coupling regimes to compare the theoretical
results with existing experimental results. In the strong coupling regime, the first and second derivatives of shot noise
display Fano type peak-valley structures around the charging channel 2E
c
due to Coulomb interaction. When the magnitudes of the MWFs are sufficiently large, the system displays channel blockade
due to photon irradiation. The photon-assisted and Coulomb blockade steps in the noise — as well as the resonant behaviour
in the differential noise — are smeared by increasing temperature. The Coulomb interaction suppresses the shot noise, but
the ac fields can either suppress the shot noise(balanced case) or enhance the shot noise(unbalanced case). The suppression
of shot noise caused by ac fields in the balanced case is greater than that caused by Coulomb interaction in our system. Super-Poissonian
shot noise may be induced due to the compound effects of strong Coulomb interaction and photon absorption-emission processes. 相似文献
20.
V. V. Val’kov S. V. Aksenov E. A. Ulanov 《Journal of Experimental and Theoretical Physics》2014,119(1):124-137
Quantum transport of electrons through a magnetic impurity located in an external magnetic field and affected by a substrate is considered using the Keldysh diagram technique for the Fermi and Hubbard operators. It is shown that in a strongly nonequilibrium state induced by multiple reflections of electrons from the impurity, the current-voltage (I–V) characteristic of the system contains segments with a negative conductivity. This effect can be controlled by varying the anisotropy parameter of the impurity center as well as the parameters of coupling between the magnetic impurity and metal contacts. The application of the magnetic field is accompanied by an increase in the number of Coulomb steps in the I–V curve of the impurity. The effect of appreciable magnetoresistance appears in this case. We demonstrate the possibility of switching between magnetic impurity states with different total spin projection values in the regime of asymmetric coupling of this impurity with the contacts. 相似文献