Fe_3Si是一种铁磁材料，在磁性隧道结中有可能应用。当掺杂有Mn时，材料显示出复杂的磁性行为，如较早的实验所示。采用KKR格林函数方法，在密度泛函理论（DFT）中对合金Fe（3-x）Mn（x）Si（0 < x < 1）进行了研究.在相干势近似（CPA）中描述了化学无序。与实验结果一致，Mn原子与Fe原子呈铁磁性排列，随着Mn浓度的增加，磁化强度和居里温度均下降，$x$ .在费米能级处计算的自旋极化P随x强烈变化，从x=0（有序Fe 3Si）处的P=-0.3到x=0.28处的P=0，再到x>0.75时的P=+1;即，在高Mn浓度下，体系是半金属的。我们讨论了磁矩、交换作用、居里温度和自旋极化率的变化趋势。
英文摘要：
Fe3Si is a ferromagnetic material with possible applications in magnetic tunnel junctions. When doped with Mn, the material shows a complex magnetic behavior, as suggested by older experiments. We employed the Korringa-Kohn-Rostoker (KKR) Green function method within density-functional theory (DFT) in order to study the alloy Fe(3-x)Mn(x)Si, with 0 < x < 1. Chemical disorder is described within the coherent potential approximation (CPA). In agreement with experiment, we find that the Mn atoms align ferromagnetically to the Fe atoms, and that the magnetization and Curie temperature drop with increasing Mn-concentration $x$. The calculated spin polarization P at the Fermi level varies strongly with x, from P=-0.3 at x=0 (ordered Fe3Si) through P=0 at x=0.28, to P=+1 for x>0.75; i.e., at high Mn concentrations the system is half-metallic. We discuss the origin of the trends of magnetic moments, exchange interactions, Curie temperature and the spin polarization.
Electronic structure and spin polarization of Fe$_{1-x}$Mn(Co,Ni)$_x$S$_2$ alloys from first principles
用密度泛函方法研究了T=Mn，Co，Ni取代对FeS $_2$合金化的影响.本文研究了铁磁合金Fe $_{1-x}$ T $_x$ S $_2$的$x=\frac{1}{4},\frac{1}{2},\frac{3}{4}$浓度和纯化合物的基态。的电子结构进行了讨论，以确定候选人的半金属，这是感兴趣的自旋电子学应用的目标。我们发现有趣的候选人在高浓度的Mn掺杂的FeS $_2$和低浓度的Ni掺杂的材料。对于Mn合金，我们还注意到接近低自旋到高自旋的转变。对于Co掺杂的材料，我们再现了在整个浓度范围内的半金属度的众所周知的发现。
Aluminum nitride is piezoelectric and exhibits spontaneous polarization along the $c$-axis, but the polarization cannot be switched by applying an electric field. Adding Sc to AlN enhances the piezoelectric properties, and can make the alloy ferroelectric. We perform a detailed first-principles analysis of spontaneous and piezoelectric polarization. Comparisons between explicit supercell calculations show that the virtual crystal approximation produces accurate results for polarization, but falls short in describing the phase stability of the alloy. We relate the behavior of the piezoelectric …
In this report, structural, electronic, magnetic and transport properties of quaternary Heusler alloys CoRuMnGe and CoRuVZ (Z = Al, Ga) are investigated. All the three alloys are found to crystallize in cubic structure. CoRuMnGe exhibits L2$_1$ structure whereas, the other two alloys have B2-type disorder. For CoRuMnGe and CoRuVGa, the experimental magnetic moments are in close agreement with the theory as well as those predicted by the Slater-Pauling rule, while for CoRuVAl, a relatively large deviation is seen. The reduction in the moment in case of CoRuVAl possibly arises due to the anti-si…
Direct evidence for minority spin gap in the Co2MnSi Heusler alloy
半金属磁体由于其在费米能级上的全自旋极化和低的磁化阻尼而在自旋电子学领域引起了极大的兴趣。Heusler合金Co_2MnSi具有很高的居里温度和约0.7eV的少数自旋能隙，因此具有很好的应用前景。在Co2 MnSi的表面处，观察到少数自旋通道中的间隙，导致100%的自旋极化。然而，这个差距是0.3 eV以下的费米能级和少数自旋状态观察到费米能级。我们表明，少数自旋间隙的费米能量，但可以恢复无论是通过改变合金的化学计量比，或通过覆盖表面的Mn，MnSi或MgO。这导致极小的阻尼系数，其值低至7 x 10-4。
The corrosion property of Nickel-titanium (NiTi) shape memory alloy is investigated during forward martensitic transformation between 40C and 0C. The Differential Scanning Calorimetry technique is used to find the forward and reverse martensitic transformation temperatures. NiTi shows the present of martensitic phase at near room temperature by cooling from 80C. The change in corrosion behavior is monitored by electrochemical Open Circuit Potential (OCP) during phase transformation. Cyclic potentiodynamic polarization method is used to identify the corrosion compound of NiTi. Corrosion rate at…
Parameters of the energy gap and, consequently, electronic, magnetic and galvanomagnetic properties in different X$_2$YZ Heusler alloys can vary quite strongly. In particular, half-metallic ferromagnets (HMFs) and spin gapless semiconductors (SGSs) with almost 100% spin polarization of charge carriers are promising materials for spintronics. The changes in the electrical, magnetic and galvanomagnetic properties of the Co$_2$YSi (Y = Ti, V, Cr, Mn, Fe) and Co$_2$MnZ Heusler alloys (Z = Al, Si, Ga, Ge) in possible HMF and/or SGS states were followed and their interconnection was established. Sig…
The evolution of the optical phonons in layered semiconductor alloys SnSe1-xSx is studied as a function of the composition by using polarized Raman spectroscopy with six different excitation wavelengths (784.8, 632.8, 532, 514.5, 488, and 441.6 nm). The polarization dependences of the phonon modes are compared with transmission electron diffraction measurements to determine the crystallographic orientation of the samples. Some of the Raman modes show significant variation in their polarization behavior depending on the excitation wavelengths. It is established that the maximum intensity direct…
From electronic-structure-based thermodynamic linear-response, we establish chemical ordering behavior in complex solid solutions versus how Gibbs' space is traversed -- applying it on prototype refractory A2 Ta-Nb-Mo-W high-entropy alloys. Near ideal stoichiometry, this alloy has anomalous, intricate chemical ordering tendencies, with long-ranged chemical interactions that produce competing short-range order (SRO) with a crossover to spinodal segregation. This atypical SRO arises from canonical band behavior that, with alloying, create features near the Fermi-surface (well-defined even with d…
Research of Mechanical Properties of Ni-Ti-Nb Alloyson Low Temperature and Restriction Behavior
对经过冷拉、非真空热处理和真空热处理的Ni-Ti-Nb合金进行了低温力学性能测试，并对Ni 47 Ti44 Nb 9合金进行了限制回复和非限制回复的力学性能对比，分析了它们之间的力学性能变化规律。试验表明，真空热处理后的合金力学性能优于其它两种合金（非真空热处理+冷拉），限制回复合金的应力曲线没有明显的屈服带，且限制回复合金的应力高于非限制回复合金，而限制回复合金的应力低于非限制回复合金的应力。
Magnetic properties of ultra-thin 3d transition-metal binary alloys I: spin and orbital moments, anisotropy, and confirmation of Slater-Pauling behavior
Present work reports a detailed investigation on the magnetoresistance and magnetocaloric behavior of Ni and Cr-doped Mn$_5$Si$_3$ alloys with general formula Mn$_{5-x}$A$_x$Si$_3$ (where A = Ni/Cr; $x$ = 0, 0.05, 0.1 and 0.2). Both pure (undoped) and doped alloys show a reasonably large amount of magnetoresistance (MR). Doping at Mn-site, both by Ni and Cr, results in a monotonic decrease in MR values. Magnetocaloric effect (MCE), on the other hand, is found to be interesting, and all the alloys show both conventional and inverse MCE around the magneto-structural transition temperature. Among…
Alloy engineering of excitonic properties in TMD monolayers
Foundation for Research and Technology-Hellas（希腊研究与技术基金会）；Univ Toulouse, INSA, CNRS, LPCNO（图卢兹大学、国立应用科学学院、法国国家科学研究中心、低压与纳米电子物理实验室）；Department of Materials Science and Engineering, University of Crete（克里特大学材料科学与工程系）；Research Center for Materials Nanoarchitectonics, National Institute for Materials Science（日本国立材料研究所材料纳米架构研究中心）；Research Center for Electronic and Optical Materials, National Institute for Materials Science（日本国立材料研究所电子与光学材料研究中心）；Department of Inorganic Chemistry, University of Chemistry and Technology Prague（布拉格化工大学无机化学系）；Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement, Ministry of Education, School of Physics and Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology（北京理工大学物理学院教育部先进光电子量子结构与测量重点实验室及北京市纳米光子学与超精细光电系统重点实验室）；Institut Universitaire de France（法兰西学院）
Deformation behavior of Mg-8.5wt.%Al alloy under reverse loading investigated by in-situ neutron diffraction and elastic viscoplastic self-consistent modeling
The structural and magnetic behavior of Mn-site doped intermetallic manganese silicide alloys of nominal compositions Mn$_{5-x}$A$_x$Si$_3$ ($x$ = 0.05, 0.1, 0.2 and A = Ni, Cr) have been investigated with a focus to the inverted hysteresis behavior and thermomagnetic irreversibility. Room temperature x-ray powder diffraction data confirm that all the doped alloys crystallize in hexagonal $D8_8$ type structure with space group $P6_3/mcm$. The doped alloys are found to show paramagnetic (PM) - collinear antiferromagnetic (AFM2) - noncollinear antiferromagnetic (AFM1) transitions during cooling …
Theory of local electric polarization and its relation to internal strain: impact on the polarization potential and electronic properties of group-III nitrides
Alloying elements play an important role in the design of plasma facing materials with good comprehensive properties. Based on first-principles calculations, the stability of alloying element W and its interaction with vacancy defects in Ta-W alloys are studied. The results show that W tends to distribute dispersedly in Ta lattice, and is not likely to form precipitation even with the coexistence of vacancy. The aggregation behaviors of W and vacancy can be affected by their concentration competition. The increase of W atoms has a negative effect on the vacancy clustering, as well as delays th…
The compressive mechanical behavior of a dual phase cobalt alloy (Al$_{14}$Co$_{41}$Cr$_{16}$Fe$_{11}$Ni$_{18}$) is reported in this communication. An uncommon triple yielding phenomenon is observed in the as-cast condition. Microstructural studies suggest that the observed behavior may be due to a stress/strain-induced martensitic phase transformation.
Fe based alloys are commonly used in almost every sector of human life. For different reasons, the surfaces of the real parts are prepared using different methods, e.g., mirror-like polishing, grit-blasting, etc. The purpose of the present work is to answer the question how the surface preparation influences the oxidation behavior of Fe-based alloys. To answer this question, a high purity model alloy, Fe 5 wt Al, was isothermally oxidized in a thermogravimetrical furnace. The post-exposure analysis included SEM/EDS (WDS) and XRD. The surface roughness was determined by a contact and laser prof…
