The formation of the magnetic moment in C- and N-doped MgO is the result of a delicate interplay between Hund's coupling, hybridization and Jahn-Teller distortion. The balance depends on a number of environmental variables including electron doping. We investigate such a dependence by self-interaction corrected density functional theory and we find that the moment formation is robust with respect to electron doping. In contrast, the local symmetry around the dopant is more fragile and two different geometries can be stabilized. Crucially the magnetic moment is always extremely localized, making any carrier mediated picture of magnetism in d^0 magnets unlikely.
Electronic and magnetic structure of epitaxial NiO/Fe$_3$O$_4$(001) heterostructures grown on MgO(001) and Nb-doped SrTiO$_3$(001)
我们研究了一些磁铁矿基薄膜的基本化学，电子和磁性。主要研究了MgO（001）和Nb-SrTiO $_3$（001）衬底上生长的NiO/Fe $_3$ O $_4$（001）双层薄膜。我们比较的结果与纯Fe $_3$ O $_4$（001）薄膜。结果发现，磁铁矿层被氧化，Fe $^{3+}$占主导地位的表面由于磁赤铁矿（$γ$ -Fe $_2$ O $_3$）的形成，这减少了磁铁矿层的厚度。从约20 nm的层厚度上的阳离子分布接近于化学计量的Fe $_3$ O $_4$。在NiO和Fe $_3$ O $_4$之间的界面处，我们发现Ni处于二价态，在Ni 2 p核心水平X射线光电子能谱中具有NiO典型的明确的光谱特征。通过XMCD可以排除明显的NiFe $_2$ O $_4$中间层的形成。磁光克尔效应测量揭示了显着更高的矫顽场相比，MgO（001）和45 $^{\circ}$旋转磁易轴上生长的磁铁矿薄膜。我们讨论了磁性层的自旋磁矩，发现磁矩随薄膜厚度的增加而增加。在较低的厚度下，在Nb-SrTiO $_3$上生长的NiO/Fe $_3$ O $_4$薄膜的自旋磁矩显著降低。20 nm或更高的厚度导致自旋磁矩接近块状磁铁矿的自旋磁矩。
Fluoride doping into SiO2-MgO-CaO bioactive glass nanoparticles: bioactivity, biodegradation and biocompatibility assessments
Faculty of Materials Science and Engineering, K. N. Toosi University of Technology（材料科学与工程系，K.N.托基理工大学）；Cellular and Molecular Research Center, Basic Health Sciences Institute, Shahrekord University of Medical Sciences（细胞与分子研究中心，基础健康科学研究所，沙赫鲁德医科大学）
Doping is an effective way to modify the electronic property of two-dimensional (2D) materials and endow them with new functionalities. However, wide-range control of the substitutional doping concentration with large scale uniformity remains challenging in 2D materials. Here we report in-situ chemical vapor deposition growth of vanadium (V) doped monolayer molybdenum disulfide (MoS2) with widely tunable doping concentrations ranging from 0.3 to 13.1 at%. The key to regulate the doping concentration lies in the use of appropriate V precursors with different doping abilities, which also generat…
In this paper, we have analysed the electronic and mechanical properties of Nitrogen(N) doped (6,1) SWCNTs based on first-principles and Molecular dynamic (MD) simulation. A schematic N-doping on SWCNT was performed along zigzag(zz) and armchair(ac) direction. Armchair doping is considered parallel to the tube axis while the zigzag is along the cross-section perpendicular to the tube axis. In doping pattern (both zz and ac) we have observed the variation in electronic properties for even number of N-doping and odd number of N-doping. To study the mechanical properties we have adopted ab-initio…
The crystal structure of MoS$_2$ with strong covalent bonds in plane and weak Van der Waals interactions out of plane gives rise to interesting properties for applications such as solid lubrication, optoelectronics, and catalysis, which can be enhanced by transition-metal doping. However, the mechanisms for improvement and even the structure of the doped material can be unclear, which we address with theoretical calculations. Building on our previous work on Ni-doping of the bulk 2H phase, now we compare to polytypes (1H monolayer and 3R bulk), to determine favorable sites for Ni and the dopin…
Two-dimensional (2D) materials with robust magnetism have drawn immense attention for their promising applications in spintronics. Recently, intrinsic ferromagnetic vanadium triiodide (VI3) has been synthesized experimentally. To enhance its spintronic property, we modified VI3 by interstitial doping with 3d transition metals (TM) and used first-principles calculations to investigate the geometric structure, formation energy, electronic property, and magnetism of pristine VI3 and 3d TM-doped VI3 monolayer. Among eight transition metal (Sc-, Ti-, V-, Cr-, Mn-, Fe-, Co-, and Ni-) doped VI3 mater…
Using Density functional theory (DFT) in conjunction with a solvation model we have investigated the phenomenon of eletrode-electrolyte interaction at the electrode surface and its consequences on the electrochemical properties like the charge storage and total capacitance of doped and substituted oxygen functionalised Ti$_{3}$C$_{2}$ supercapcitor electrode. We have studied nitrogen doped, nitrogen substituted and molybdenum substituted Mxenes in acidic electrolyte H$_{2}$SO$_{4}$ solution. By considering nitrogen doping at different sites, we found that the greatest capacitance is obtained f…
While doping is widely used for tuning physical properties of perovskites in experiments, it remains a challenge to exactly know how doping achieves the desired effects. Here, we propose an empirical and computationally tractable model to understand the effects of doping with Fe-doped BaTiO$_{3}$ as an example. This model assumes that the lattice sites occupied by Fe ion and its nearest six neighbors lose their ability to polarize, giving rise to a small cluster of defective dipoles. Employing this model in Monte-Carlo simulations, many important features like reduced polarization and the conv…
In this paper, the effect of B and N doping on the phonon induced thermal conductivity of graphene has been investigated. This study is important when one has to evaluate the usefulness of electronic properties of B and N doped graphene. We have performed the calculations by employing density functional perturbation theory(DFPT) to calculate the inter-atomic forces=force constants of pristine/doped graphene. Thermal conductivity calculations have been carried out by making use of linearized Boltzmann transport equations (LBTE) under single-mode relaxation time approximation (RTA). The thermal …
Sulfur and nitrogen dual doped graphene have been extensively investigated in the field of oxygen reduction reaction, supercapacitors and batteries, but their magnetic and absorption performance have not been explored. Besides, the effects of doping sequence of sulfur and nitrogen atoms on the morphology, structural property and the corresponding microwave absorption performance of the dual doped graphene remain unexplored. In this work, nitrogen and sulfur dual doped graphene with different doping sequence were successfully prepared using a controllable two steps facile thermal treatment meth…
Metal-ion doping can effectively regulate the metal-insulator transition temperature in $\mathrm{VO}_2$. Experiments found that the pentavalent and hexavalent ion doping dramatically reduces the transition temperature while the trivalent ion doping increases the transition temperature and induces intermediate phases. Based on the phase-field model of the metal-insulator transition in $\mathrm{VO}_2$ we developed previously, we formulate a Landau potential of the metal-ion-doped $\mathrm{VO}_2$ taking account of the effects of doping on the electron correlation and lattice structure. The effect…
Stoner factors of doped 122 Fe-based superconductors: First principles results
本文研究了不同掺杂122铁基超导体（BaFe $_2$ As $_2$，SrFe $_2$ As $_2$）的Stoner因子随掺杂浓度的变化规律。我们的第一性原理电子结构计算表明，对于Co/Ru（电子或等电子）掺杂在Fe位或P掺杂在As位的结果在减少的Stoner因子随着掺杂浓度的增加。相反，在Na/K（空穴）掺杂的情况下，在Ba位点处，Stoner因子对于更高的掺杂浓度增强。这可以被认为是在这些系统中的“磁波动”的高度的指标。我们发现，Stoner因子唯一地跟随着磷族元素高度z $_{As}$ /Fe-As键长随各种掺杂的变化。我们计算的费米面解释了不同掺杂122系统的Stoner因子行为的差异;费米面嵌套程度越大，Stoner因子值越大，反之亦然。
