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With the help of the transfer-matrix method, we theoretically investigate the effect of the [Formula: see text]-doping on the magnetoresistance (MR) effect in a magnetic nanostructure, which can be realized by depositing two ferromagnetic strips on the top and bottom of a nanostructure and using the atomic layer doping technique. It is shown that an obvious MR effect can be obtained in this device, and it can be tuned by the position and weight of the [Formula: see text]-doping. This device can be used as a [Formula: see text]-doping-dependent MR device for magneto electronics applications.

We theoretically investigate the electron transport properties in a nanostructure modulated by a ferromagnetic stripe (FM) and a Schottky metal stripe (SM) as well as a [Formula: see text]-doping with the help of transfer-matrix method. It is found that the position and the weight of the [Formula: see text]-doping, the width of the SM and the electrical potential, all play an important role in the electron transmission probability and the spin polarization. Therefore, we can control the electron transport properties through adjusting the SM and the [Formula: see text]-doping. These interesting phenomena may be very helpful for designing the spintronic devices.

With the help of the scattering-matrix method, the quantum states of ballistic electrons and conductance, as well as resistance are studied in a four-terminal junction of narrow wire with various widths. We find that these observable quantities are highly sensitive to the geometries of junctions and differ from the conventional structure with the same width. In particular, the predicted quantization conductance phenomena are striking and are also in self-consistency with calculated scattering probabilities, relating to electronic subbands and transmission states.

The zero-field splitting D of the 8 S 7/2 ground singlet for the tetragonal Gd 3+ center in La 2-x Sr x CuO 4 is theoretically studied from the superposition model. Meanwhile, the g factor is also quantitatively investigated from the approximation formula including admixture of the ground 8 S 7/2 and the excited 6 L 7/2 ( L=P , D, F, G) states via the spin-orbit coupling interactions. The calculated zero-field splitting and g factor are in reasonable agreement with the experimental data. It is found that the significant zero-field splitting can be ascribed to the average impurity-ligand bonding angles [≈ (θ1 + θ2)/2 ≈ 62°] related to the four-fold axis larger than that (≈ 54.74°) of the cubic case. Nevertheless, the experimental g factor close to 2 may be largely due to the very slight admixture of the ground 8 S 7/2 and the excited 6 L 7/2 states via the spin-orbit coupling interactions.

The EPR g factors g // and g ⊥ for the six-coordinated Cu 2+(1) site in YBa 2 Cu 3 O 6+x are theoretically investigated from the perturbation formulas for a 3 d 9 ion in tetragonally elongated octahedra. The related tetragonal crystal-field parameters Ds and Dt are determined from the superposition model and the structural data for the Cu 2+(1) site, by considering the effective elongation of the oxygen octahedron due to the Jahn-Teller effect of the Cu 2+ cluster. Based on the calculations, the effective elongation (≈ 15%) of the ligand octahedron is obtained for the signals at 100K. As for the EPR signals at room temperature, the elongation declines to merely 4%, corresponding to the smaller anisotropy Δ g (= g // - g ⊥). The theoretical results for the g factors are in good agreement with the observed values, and the local tetragonal distortion due to the Jahn-Teller effect is discussed.

We present a numerical study of the influence of junction-geometries and disorder on quantum-mechanical transmission by considering the presence of an impurity in a wide-narrow-wide (W-N-W) quantum-wire junction. The device is modeled as an electron waveguide of finite cross section. Transmission and reflection probabilities as well as conductance are computed by using model expansions of the wave function together with a waveguide-matching technique. The calculations show that the transmission of the two-dimensional electron gas through the W-N-W geometry is highly sensitive to geometries of junction and can be suppressed by the presence of a repulsive or attractive impurity potential. Furthermore, the depression effect becomes more visible if the absolute value of potential strength becomes bigger.

In this paper, we investigated the spin-dependent electron transport in a nonmagnetic nanostructure under the influence of the [Formula: see text]-doping which can be experimentally doped in the nanostructure with metal-organic chemical vapor deposition or molecular beam epitaxy. The numerical results indicate that the large spin polarization nearly 100% can be achieved in such a structure without the external magnetic field due to spin–orbit interactions and it can be controlled not only by the barrier, but also by the [Formula: see text]-doping. These interesting finds are very valuable for designing the [Formula: see text]-doping-tunable spintronic device based on the nonmagnetic nanostructure.

We theoretically present the spin-dependent electron transport in a two-dimensional electron gas (2DEG) with finite width modulated by magnetic–electric barriers. It is found that the transmission probability and the spin polarization are strongly dependent on the height of the electric barrier, the energy of the incident electron, the distance between the two magnetic fields, and the width of the 2DEG. These may be useful for making the practical devices.