Co-thickness and oxidation states effect on magnetic anisotropy in Co/MgO heterostructure

Interfacial magnetism and magnetic anisotropy constant ($K_i$) in Co/MgO heterostructure have been studied using ab-initio density functional calculations. It is found that interfacial Co spin magnetic moment shows a strong interdependence on Co-O bond lengths and a reasonable spin-polarization of ～80% is established as a function of Co layers. Our results revealed a saturated positive (out-of-plane) $K_i$ of +2.80 mJ/m² at ≥12 Co layers (～1.6 nm Co thickness), which is associated with orbital magnetic moment difference in [100] and [001] direction along with a strong hybridization between $d_{xy}$ and $d_{x^2?y^2}$ orbitals through orbital angular momentum operator $\stackrel{?}{L_z}$. Furthermore, it is shown that the $K_i$ magnitude almost remains constant and weakens in the case of under- and over-oxidations in the interfacial MgO and Co layers, respectively. Interestingly, $K_i$ improved for oxygen migrated interface due to enhanced $d_{xy}$ and $d_{x^2?y^2}$ orbitals coupling. The disordered interfaces stability is checked by analyzing the formation energy. Hence, the present findings disclose that the higher Co thickness in ordered Co/MgO structure supports to out-of-plane [001] (positive) $K_i$, which could be useful for its technological implementation in high-density magnetic data storage devices with high thermal stability.     

Spin-polarized zero-energy states in BN/C core–shell quantum dots

Boron-nitride (BN) domains in graphene or graphene domains in BN monolayer offer additional freedoms for tuning the electronic properties of these BN/C nanostructures, which is quite crucial for the applications in nanoscale devices. Based on first-principles calculations combined with a simple Hubbard model, we show that the electron zero-energy states (ZESs) of BN/graphene core–shell quantum dots (QDs) in triangular shapes can be well tuned by varying the size and topology of each domain. The net spin of the systems is dominated by the graphene segment which can be described by a Lieb?s theorem. We also demonstrated that a π-electron Hubbard model within a mean-field approximation is implementable in dealing with the electron spin-polarization of BN/C hetero-structured graphene-like materials. This provides an efficient theoretical approach for the BN/C systems where electron spin-polarization is involved.     

Spin-polarization dependent carrier recombination dynamics and spin relaxation mechanism in asymmetrically doped (110) n-GaAs quantum wells

Carrier recombination and electron spin relaxation dynamics in asymmetric n-doped (110) GaAs/AlGaAs quantum wells are investigated with time-resolved pump-probe spectroscopy. The experiment results reveal that the measured carrier recombination time depends strongly on the polarization of pump pulse. With the same pump photon flux densities, the recombination time of spin-polarized carriers is always longer than that of the spin-balanced carriers except at low pump photon flux densities, this anomaly originates from the polarization-sensitive nonlinear absorption effect. Differing from the traditional views, in the low carrier density regime, the D'yakonov–Perel' (DP) mechanism can be more important than the Bir–Aronov–Pikus (BAP) mechanism, since the DP mechanism takes effect, the spin relaxation time in (110) GaAs QWs is shortened obviously via asymmetric doping.     

Effect of the -function potential on the electron transport in a magnetic nanostructure

In this paper, the spin-dependent electron transport is studied in detail in a magnetic nanostructure with a δ-function potential. It is shown that the large spin-polarization can be achieved in such a device, and the degree of the spin-polarization strongly depends on the height of the δ-function potential. It is also shown that the conductance-polarization apparently has the bigger oscillatory magnitudes with the height of δ-function potential increasing. These interesting features will be more helpful for developing new types of devices.     

An SCF XαSW study of the electronic structure and X-ray and photoelectron spectra of Fe(II) and Fe(III) hexacyano complexes in a cluster approach

The electronic structure of the hexacyano complexes [Fe(CN)₆]^4– and [Fe(CN)₆]^3– as clusters of the cyanide complex salts has been calculated by the SCF XSW method. Theoretical photoelectron, X-ray emission and absorption spectra have been constructed. The contribution of the resonance emission to the X-ray emission spectra has been estimated. On the basis of detailed comparison of the theoretical and experimental spectra an assignment of the fine structure of the spectra has been proposed.     

电子定域化函数的含义与函数形式

电子定域化函数(ELF)是研究电子结构的重要工具.本文介绍了电子定域性的概念,从电子对密度和动能密度两个角度详细讨论了ELF的物理意义与其函数形式的联系,并将ELF推广到自旋极化形式.通过实例分析,指出了参考项在ELF 中起到了关键性作用.对两种自旋极化形式的ELF 的比较发现:CheckDen 和TopMoD程序中使用的形式并不合理,明显低估了单电子区域的定域性.最后指出了一些文献由于对ELF函数的错误理解而在引用时出现的错误.     

Effect of the -doping on the electron transport in a structure modulated by the magnetic barriers

The effect of the δ-doping on the electron transport has been theoretically studied in a structure modulated by the magnetic barriers. The results show that the transmission probability and the electron conductance can be dramatically suppressed by the weight of the δ-doping. However, the spin-injection efficiencies are obviously enhanced. In addition, the transmission probability and the spin-polarization both show a periodic profile with the increase of L₂. These interesting features will be more helpful for developing new types of devices.     

Spin-dependent electron transport in a magnetic nanostructure with the δ-doping

We report on a theoretical study of spin-dependent electron transport in a magnetic nanostructure with the δ-doping. It is revealed that the transmission probability, the electron conductance and the spin-polarization obviously depend on the weight of the δ-doping. It is also revealed that the transmission probability and the spin-polarization (PT) both show a periodic profile with the increase of the length L₂. These interesting phenomena will be more helpful for understanding the experimental physical phenomena in δ-doping and for making new types of devices.     

LaNi5电子与能量结构的全电子计算

在全电子水平上,基于广义梯度近似(GGA)密度泛函和全势能线性缀加平面波方法(FLAPW),计算给出了LaNi5的晶体结构、能带结构、电子密度、状态密度(DOS),以及势能结构;并比较分析了自旋极化(Spin-Polarization)对这些性质的影响.全电子计算的晶体结构与实验结果符合得很好;考虑自旋极化后,仅计算出能量约为降低,而对优化结构的影响不明显.?     

Polarization and dichroism in atomic Auger spectroscopy following absorption of circularly polarized light

Spin resolved Auger current is shown to be different for the absorption of left and right circularly polarized light. This current is produced in non-radiative spontaneous decay of photoexcited atoms or of excited atomic photoions. Circular dichroism in such polarized Auger electrons exists even in the absence of spin-orbit interaction. Physical and geometrical conditions, necessary for the occurrence of dichroic effects in atomic Auger spectroscopy, have been obtained. Calculations for Ba and Xe show that the effect is substantially large and can be readily observed.