Magnetic-barrier Nanostructure Research Articles

Improved airy function formalism for the study of anti-parallel double δ-magnetic-barrier nanostructure under the modulation of the applied bias

The Goos–Hänchen (GH) shift and the spin polarization are theoretically investigated under the anti-parallel double [Formula: see text]-magnetic-barrier nanostructure model by applying a bias using Airy’s function formalism and transfer-matrix technique, which is an improvement on previous calculation. The results show the magnitude and sign of GH shift and spin polarization can be easily changed by modulating the applied bias. The closer the applied bias to the critical value is, the more intensive GH shift and spin polarization will be. Furthermore, two critical values come through modulating the strength of magnetic fields, and an intensive GH shift and a spin polarization also exist near each critical value. These findings can provide a practical approach to designing and fabricating spin beam filters or splitters modulated by applied bias.

Lateral shift in a spin-orbit-coupling modulated magnetic-barrier nanostructure

Spin-dependent Goos–Hänchen（GH）effect of the electron in a magnetic barrier nanostructure modulated by the spin-orbit coupling (SOC) is investigated. Two kinds of intrinsic SOCs (Rashba and Dresselhaus types) are taken into account, and spin-dependent lateral shifts are obtained by the transfer matrix method and the stationary phase approximation. The spin-dependent lateral shift is found to be related closely to the SOC. Both magnitude and sign of the spin-polarised lateral shift can be controlled by properly adjusting the strength of Rashba or Dresselhaus SOC. These interesting features can provide an alternative approach to manipulate spin-polarised electrons in the semiconductor, and such a nanostructure can serve as a controllable spatial spin splitter for spintronics applications.

Spin filtering in a $$\updelta $$ δ -magnetic-barrier nanostructure modulated by Rashba and Dresselhaus spin–orbit couplings

We theoretically investigated the electron-spin transport properties of an antiparallel double \(\updelta \)-magnetic-barrier nanostructure modulated by spin–orbit coupling (SOC), which could be fabricated experimentally by depositing two ferromagnetic stripes with horizontal magnetization on the top and bottom of an InAs/Al\(_{x}\)In\(_{1-x}\)As semiconductor heterostructure. Both Rashba and Dresselhaus SOCs were taken into account, and the transmission coefficient, conductance, and spin polarization calculated analytically by means of the improved transfer matrix method. The electron-spin transport through this nanosystem is found to be strongly dependent on the SOC. The electron-spin polarization is also found to vary with the strength of the SOC, potentially enabling tunable spin filters for use in spintronic applications.

Manipulable wave-vector filtering in a δ -doped magnetic-barrier nanostructure

Abstract We theoretically explore the control of the wave-vector filtering (WVF) effect in a realistic magnetic-barrier nanostructure with a δ -doping, which can be experimentally realized by depositing a ferromagnetic stripe on the top of a GaAs / Al x Ga 1 − x As heterostructure. It is shown that an obvious WVF effect still exists when a δ-doping is introduced into the device. It is also shown that the degree of the WVF effect can be controlled by tuning the weight and/or the position of the δ-doping.

Tunable spin spatial splitter based on a [formula omitted]-doped realistic magnetic-barrier nanostructure

We theoretically investigate a tunable δ-potential effect on a spin spatial splitter, which can be realized experimentally by depositing a ferromagnetic stripe with a vertical magnetization on top of semiconductor heterostructure and using atomic-layer doping technique. With the help of stationary phase method, the δ-doping dependent spin-polarized lateral displacement is numerically calculated by means of the improved transfer-matrix technique. Both amplitude and sign of the spin polarized lateral displacement are found to vary dramatically with the weight and/or location of the δ-doping. Thus, a structurally tunable spin spatial splitter can be achieved for spintronic applications.

Spin-polarized transport in a δ-doped magnetic-barrier nanostructure

We theoretically investigate the electron spin transport properties through a δ -doped magnetic-barrier nanostructure, which can be realized experimentally by depositing two identical ferromagnetic stripes with the opposite in-plane magnetization on the top of a semiconductor heterostructure in parallel configuration and by using atomic layer doping technique. The δ -doping dependent transmission, conductance and spin polarization are calculated exactly by analytically solving Schrödinger equation of the spin electron. It is found that the electronic spin-polarized behavior in this device can be manipulated by changing the weight and/or the position of the δ -doping. Therefore, such a device can be used as a controllable spin filter, which may be helpful for spintronics applications. • Spin-polarized transport in a δ -doped magnetic-barrier nanostructure is explored. • Both magnitude and sign of spin polarization depend on the δ -doping. • A controllable spin filter can be achieved for spintronics applications.

Electric control of spin-dependent Goos–Hänchen shift in a magnetically modulated semiconductor nanostructure

Abstract We theoretically investigate how to manipulate spin-dependent Goos–Hanchen (GH) shifts by an applied bias in a realistic magnetic-barrier nanostructure, which is experimentally created by depositing a ferromagnetic stripe with perpendicular magnetization on the top of heterostructure. GH shifts of transmitted electron beams are calculated numerically with the help of the stationary phase method. It is shown that both magnitude and sign of spin polarization in GH shifts are closely relative to the applied bias, which can give rise to a bias-controllable spin beam splitter.

Voltage-controllable spin beam splitter based on realistic magnetic-barrier nanostructure

We report a theoretical investigation on the Goos–Hänchen (GH) effect of spin electron beams in realistic magnetic-barrier (MB) nanostructures under an applied voltage, which can be experimentally created by lithographic patterning of ferromagnetic (FM) or superconducting films. GH shifts of spin electron beams are calculated numerically for the InAs material system, with the help of the stationary phase method. It is shown that a significant spin polarization effect can be induced by such MB nanostructures with symmetric magnetic field profiles. It also is shown that both magnitude and sign of the spin polarization is closely relative to the electric barrier (EB) produced by a constant voltage applied to the metallic FM stripe of system. These interesting properties may provide an alternative way to spin injection into the semiconductor, and such nanostructures can serve as voltage-tunable spin beam splitters.

Spin-electron beam splitters based on magnetic barrier nanostructures

With the help of stationary phase method, we investigate the Goos-Hänchen (GH) effect of electrons in nanostructures consisting of realistic magnetic barriers (MB) created by lithographic patterning of ferromagnetic (FM) or superconducting films. Due to intrinsic symmetry, only nanostructures with symmetric magnetic field possess a considerable spin-dependent GH effect, and GH shifts of transmitted spin beams are found to depend upon the incident angle and the incident energy of electrons as well as the size and position of the FM stripe. These interesting properties may provide an effective scheme to realize spin injection into semiconductor and also give rise to a type of spin beam splitters based on MB nanostructures.

Lateral shifts of spin electron beams in antiparallel double [formula omitted] nanostructure

We investigate the Goos–Hänchen (GH) effect of spin electron beams in a magnetic-barrier (MB) nanostructure consisting of antiparallel double δ-MBs, which can be experimentally realized by depositing two ferromagnetic (FM) stripes on top and bottom of the semiconductor heterostructure. GH shifts for spin electron beams across this type of MB nanostructures, is derived exactly, with the help of the stationary phase method. It is shown that GH shifts depend strongly on the spin directions for double δ-MBs with unidentical magnetic strengths, giving rise to a considerable spin polarization effect. It also is shown that spin polarization of GH shifts is closely relative to the separation and magnetic-strength difference of two δ-MBs. These interesting properties may provide an alternative scheme to spin-polarize electrons into the semiconductor, and the devices can serve as tunable spin beam splitters.

A magnetoresistance device based on a magnetic-barrier nanostructure

A magnetoresistance device is proposed in a two-dimensional electron gas modulated by a magnetic barrier, which can be realized experimentally by the deposition of two parallel ferromagnetic strips on the top and bottom of a GaAs heterostructure. A considerable magnetoresistance effect is found in this device, due to the significant difference between electronic transmissions through parallel and antiparallel magnetization configurations.

Bias-tunable electron–spin polarization in an antiparallel double [formula omitted]-magnetic-barrier nanostructure

We present a theoretical study of spin-dependent electron transport in an antiparallel double δ-magnetic-barrier nanostructure with an applied bias. It is shown that large spin-polarized current can be achieved in such a device with unidentical strength between two δ-magnetic-barriers. It also is shown that the degree of electron–spin polarization is strongly dependent upon the applied bias. These interesting properties may provide an alternative scheme to spin-polarize electrons into semiconductors, and this device may be used as a bias-tunable spin filter.

Electron-spin polarization in anti-parallel double [formula omitted]-magnetic-barrier nanostructures

We present a theoretical study on spin-dependent transport of electrons in any anti-parallel double δ -magnetic-barrier nanostructure, which can be experimentally realized by depositing a ferromagnetic stripe on the surface of a semiconductor heterostructure. A general fomula of tranmission probability for electrons tunneling through this kind of nanostructures, is obtained. It is shown that large spin-polarized current can be achieved in such a device. It also is shown that the degree of electron-spin polarization is strongly dependent upon magnetic-strength difference of two δ -barriers. These interesting properties may provide an alternative scheme to spin-polarize electrons into semiconductors, and this device may be used as a tunable spin-filter.

Spin filtering in magnetic/semiconductor hybrid nanostructures

We study theoretically the spin-dependent electron transport in realistic magnetic-barrier nanostructures, which can be experimentally realized by depositing a magnetized ferromagnetic stripe with arbitrary magnetization direction on the surface of a semiconductor heterostructure. It is shown that highly spin-polarized current can be achieved in this kind of nanostructures. It is also shown that the spin polarity of the electron transport can be switched by adjusting the magnetized angle of the ferromagnetic stripe in the system. These interesting properties may provide an alternative scheme to spin-polarize electrons into semiconductors and may be used as a spin-filter.

Electron-spin polarization in both magnetically and electrically modulated nanostructures

We investigate theoretically the spin-dependent transport properties of electrons in realistic magnetic-electric-barrier (MEB) nanostructures produced by the deposition, onto a heterostructure, of a metallic ferromagnetic stripe. We find the degree of electron-spin polarization to be closely tied to the voltage applied to the stripe, despite the fact that this voltage in itself induces no spin-polarization effect. As a positive (negative) voltage is applied, the electron-spin polarization shifts in the low- (high-) energy direction and increases (decreases). Our results imply that the degree of electron-spin polarization can be tuned through the applied voltage. This implication might prove useful in the design and application of spintronic devices based on magnetic-barrier nanostructures. PACS Nos.: 73.40.Gk, 73.23.-b, 75.70.Cn

Electric-field and magnetic-field effects on electronic tunneling through magnetic-barrier nanostructures

We have theoretically investigated electric-field and magnetic-field effects on electronic transport properties in nanostructures consisting of realistic magnetic barriers created by lithographic patterning of ferromagnetic or superconducting films. The results indicate that the characteristics of transmission resonance are determined not only by the magnetic configuration and the incident wave vector but also strongly by the applied electric and magnetic fields. It is shown that transmission resonance shifts towards the low-energy region by applying the electric field, and that with increasing the electric field transmission resonance is suppressed for the entire incident wave vector in the magnetic nanostructures with antisymmetric magnetic profile, while for the magnetic nanostructures with symmetric magnetic profile transmission resonance is enhanced for certain incident wave vector. It is also shown that both transmission and conductance shift towards high-energy direction and are greatly suppressed with the increase of the external magnetic field.

Spin polarization of electrons tunneling through magnetic-barrier nanostructures

We present a theoretical investigation of the spin-dependent transport properties of electrons in nanostructures consisting of realistic magnetic barriers created by a lithographic patterning of ferromagnetic or superconducting films. It is shown that a significant electron-spin polarization effect can be induced by such magnetic-barrier nanostructures with a symmetric magnetic field. It is also shown that an applied bias voltage or an external magnetic field can greatly change the degree of the electron-spin polarization in magnetic-barrier nanostructures. When the applied bias voltage increases, the electron-spin polarization shifts toward the low-energy end and gradually decreases, while, with an increase of the external magnetic field, the electron-spin polarization shifts toward the high-energy direction and successively enlarges. It is also found that the degree of the electron-spin polarization can be tuned with the electric barrier induced by a constant voltage applied to the metallic stripe of system.