Magnetic properties of (Fe$_{1-x}$Co$_x$)$_2$B alloys and the effect of doping by 5$d$ elements
A. Edström, M. Werwiński, Diana Iuşan, J. Rusz, O. Eriksson, K. P. Skokov, I. A. Radulov, S. Ener, M. D. Kuz'min, J. Hong, M. Fries, D. Yu. Karpenkov, O. Gutfle… 展开作者
A. Edström, M. Werwiński, Diana Iuşan, J. Rusz, O. Eriksson, K. P. Skokov, I. A. Radulov, S. Ener, M. D. Kuz'min, J. Hong, M. Fries, D. Yu. Karpenkov, O. Gutfleisch, P. Toson, J. Fidler
我们已经探索，计算和实验，磁性能的\fecob{}合金。计算提供了一个很好的协议与实验方面的饱和磁化强度和磁晶各向异性能在描述钴$_2$ B的一些困难，它被发现，在动态平均场理论处理的全势效应和电子相关性是重要的正确的描述。该材料在$x=0.1$和$x=0.5$之间的钴浓度范围内表现出单轴磁各向异性。磁各向异性的温度依赖性的一个简单的模型表明，复杂的非单调的温度行为主要是由于在带结构的变化，因为交换分裂减少了温度。使用基于密度泛函理论的计算，我们已经探索了整个范围内的5 $d$过渡金属的过渡金属亚晶格的替代掺杂的效果，发现Re或W元素的掺杂应显着提高磁晶各向异性能。实验上，W掺杂没有成功地提高磁各向异性，由于形成其他相。另一方面，掺杂的Ir和Re是成功的，并导致磁各向异性，与理论预测一致。特别地，掺杂2.5~at. Re在Fe/Co位上的磁晶各向异性能与其母体（Fe $_{0.7}$ Co $_{0.3}$）$_2$ B化合物相比增加了50%，这使得该系统例如在永磁体替代材料的背景下或在其中大的磁各向异性是重要的其它领域中令人感兴趣。
英文摘要：
We have explored, computationally and experimentally, the magnetic properties of \fecob{} alloys. Calculations provide a good agreement with experiment in terms of the saturation magnetization and the magnetocrystalline anisotropy energy with some difficulty in describing Co$_2$B, for which it is found that both full potential effects and electron correlations treated within dynamical mean field theory are of importance for a correct description. The material exhibits a uniaxial magnetic anisotropy for a range of cobalt concentrations between $x=0.1$ and $x=0.5$. A simple model for the temperature dependence of magnetic anisotropy suggests that the complicated non-monotonous temperature behaviour is mainly due to variations in the band structure as the exchange splitting is reduced by temperature. Using density functional theory based calculations we have explored the effect of substitutional doping the transition metal sublattice by the whole range of 5$d$ transition metals and found that doping by Re or W elements should significantly enhance the magnetocrystalline anisotropy energy. Experimentally, W doping did not succeed in enhancing the magnetic anisotropy due to formation of other phases. On the other hand, doping by Ir and Re was successful and resulted in magnetic anisotropies that are in agreement with theoretical predictions. In particular, doping by 2.5~at.\% of Re on the Fe/Co site shows a magnetocrystalline anisotropy energy which is increased by 50\% compared to its parent (Fe$_{0.7}$Co$_{0.3}$)$_2$B compound, making this system interesting, for example, in the context of permanent magnet replacement materials or in other areas where a large magnetic anisotropy is of importance.
By performing first principles calculations combined with Boltzmann transport equations, we calculate the thermoelectric power factor (PF) of Bi-Sb-Te and Bi-Te-Se ternary alloys as a function of alloy composition ratio, carrier concentration, and temperature. The point defect formation energy calculations also perform to search potential n-type dopant candidates in ternaries.
Heusler alloys with Mn and Co have been found to exhibit interesting electronic and magnetic properties. Mn$_2$CoAl is well known SGS compound while Mn$_2$CoGa has weak half metallic character. By using plane wave pseudo-potential method, we studied the effect of Fe and Cr doping on half-metalicity and magnetism of these compounds. The doping destroys the SGS nature of Mn$_2$CoAl while the small-scale doping enhance the half-metallicity of Mn$_2$CoGa making it perfect half-metal. In case of Mn$_2$CoAl, the doping decrease the band gap while increase in band width is noticed for Mn$_2$CoGa. The…
For (CoCrFeMn)$_{100-x}$Al$_{x}$ high-entropy alloys, we investigate the phase evolution with increasing Al-content (0 $\le$ x $\le$ 20 at.%). From first-principles theory, the Al-doping drives the alloy structurally from FCC to BCC separated by a narrow two-phase region (FCC+BCC), which is well supported by our experiments. We highlight the effect of Al-doping on the formation enthalpy and electronic structure of (CoCrFeMn)$_{100-x}$Al$_{x}$ alloys. As chemical short-range order (SRO) in multicomponent alloys indicates the nascent local order (and entropy changes), as well as expected low-tem…
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 …
Spintronics is the fast growing field that will play a key role in optimizing power consumption, memory, and processing capabilities of nanoelectronic devices. Heusler alloys are potential candidates for application in spintronics due to their room temperature (RT) half-metallicity, high Curie temperature, low lattice mismatch with most substrates, and strong control on electronic density of states at Fermi level. In this work, we investigate the effect of {substitutional doping and disorder} on the half-metallicity, phase stability, and magnetism of Heusler alloys using density functional the…
Using density functional theory based calculations, we have carried out in-depth studies of effect of Co substitution on the magnetic properties of Ni and Pt-based shape memory alloys. We show the systematic variation of the total magnetic moment, as a function of Co doping. A detailed analysis of evolution of Heisenberg exchange coupling parameters as a function of Co doping has been presented here. The strength of RKKY type of exchange interaction is found to decay with the increase of Co doping.
Based on high-throughput density functional theory calculations, we investigated the effects of light interstitial H, B, C, and N atoms on the magnetic properties of cubic Heusler alloys, with the aim to design new rare-earth free permanent magnets. It is observed that the interstitial atoms induce significant tetragonal distortions, leading to 32 candidates with large ($>$ 0.4 MJ/m$^3$) uniaxial magneto-crystalline anisotropy energies (MAEs) and 10 cases with large in-plane MAEs. Detailed analysis following the the perturbation theory and chemical bonding reveals the strong MAE originates fro…
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…
Ge with a quasi-direct band gap can be realized by strain engineering, alloying with Sn, or ultrahigh n-type doping. In this work, we use all three approaches together to fabricate direct-band-gap Ge-Sn alloys. The heavily doped n-type Ge-Sn is realized with CMOS-compatible nonequilibrium material processing. P is used to form highly doped n-type Ge-Sn layers and to modify the lattice parameter of P-doped Ge-Sn alloys. The strain engineering in heavily-P-doped Ge-Sn films is confirmed by x-ray diffraction and micro Raman spectroscopy. The change of the band gap in P-doped Ge-Sn alloy as a func…
Effect of 3d Transition Metal Doping (Mn, Fe, Co, Ni) on the Electronic and Magnetic Properties of Pd Alloys at Low Impurity Concentrations: An Ab initio Study
Effect of Niobium Doping on the Crystal Structure and Hydrogen Sorption Properties of TiFe: Combined Synchrotron X-ray Diffraction and Extended X-ray Absorption Fine Structure Study
University of Stavanger（斯塔万格大学）；Institute for Energy Technology（能源技术研究所）
Surface bubbling and helium retention of pure aluminum and a solid solution of aluminum-gallium(Ga) alloy exposed to low-energy He plasma has been investigated with the fluence of 1.8E24 He/m2 at room temperature . Surface morphology observations show that after irradiation, the average size of He bubbles on Al-1.8 at.% Ga alloy is around 1.8 micro metre, smaller than that on pure Al. Ga doping noticeably increases the area density of the bubble. The thermal desorption spectroscopyshows that the release amount of He in Al-1.8 at.% Ga alloy is 1.77E21 He/m2, nearly three orders of magnitude hig…
The electronic structure and intrinsic magnetic properties of $\text{Fe}_2\text{AlB}_2$-related compounds and their alloys have been investigated using density functional theory. For $\text{Fe}_2\text{AlB}_2$, the crystallographic $a$ axis is the easiest axis, which agrees with experiments. The magnetic ground state of $\text{Mn}_2\text{AlB}_2$ is found to be ferromagnetic in the basal $ab$ plane, but antiferromagnetic along the $c$ axis. All $3d$ dopings considered decrease the magnetization and Curie temperature in $\text{Fe}_2\text{AlB}_2$. Electron doping with Co or Ni has a stronger effec…
ZrCo alloy is promising to substitute uranium for handling hydrogen isotope storage in thermonuclear reactor. The alloying substitution of Zr in ZrCo with Hf or Ti can enhance the ability of anti-disproportionation. In this work, Zr$_{0.75}$Hf$_{0.25}$Co and Zr$_{0.75}$Ti$_{0.25}$Co were considered in the framework of density functional theory, aimed to investigate the properties of the alloying substitution of Zr with Hf or Ti in ZrCo. Our results found that the optimized lattice constants of the alloying substitutions, Zr$_{0.75}$Hf$_{0.25}$Co and Zr$_{0.75}$Ti$_{0.25}$Co, are smaller than Z…
Ordered W-doped Ta2O5 nanotube arrays were grown by self-organizing electrochemical anodization of TaW alloys with different tungsten concentrations and by a suitable high temperature ammonia treatment, fully converted to W:Ta3N5 tubular structures. A main effect found is that W doping can decrease the band gap from 2 eV (bare Ta3N5) down to 1.75 eV. Ta3N5 nanotubes grown on 0.5 at% W alloy and modified with (CoOH)x as co-catalyst show ~33% higher photocurrents in photoelectrochemical (PEC) water splitting than pure Ta3N5.
Structure and gap of low-$x$ (Ga$_{1-x}$In$_x$)$_2$O$_3$ alloys
用密度泛函理论研究了纯的和In取代的$β$ -Ga $_2$ O $_3$的电子和局域结构性质。我们的主要结果是In在Ga $_2$ O $_3$中的结构能量学导致大多数位置基本上不能被In取代，从而在该相中将In的最大含量降低到12 - 25%之间。我们还发现，掺杂的间隙变化基本上是由于“化学压力”，即掺杂的体积变化。
Structural and electronic properties of superconducting Heusler alloy Ni$_{2}$Nb$_{1+x}$Sn$_{1-x}$: \textit{Ab initio} approach
采用\textit{ab initio}计算方法，系统地研究了NiPDMATHABMN Nb $_{1+x}$ Sn $_{1-x}$（$x$ = 0，0.25，0.50）的结构和电子性质.在这里，投影仪增广波方法（PAW）中实现的维也纳\textit{ab initio}模拟包（VASP）内的广义梯度近似（GGA）的交换相关功能已被使用。本文报道了Ni $_{2}$ Nb Sn和Ni $_{2}$ Nb $_{1.25}$ Sn $_{0.75}$虽然没有结构转变，但Ni $_{2}$ Nb $_{1.5}$ Sn $_{0.5}$可以从立方L2 $_{1}$相转变为四方结构。在非化学计量比合金中，立方晶格参数随着Nb在Sn位点处的掺杂而减小。合金在所有结构中均处于顺磁相。Ni和Nb的3d态之间的杂化引发了四重态畸变。由于立方L2 $_{1}$相中的Nb掺杂，在费米能（EPDMATHABMW）（N（EPDMATHABMW））处的总态密度（DOS）存在显著变化。N（EPDMATHABMW）随着Nb掺杂的增加而增加。但在Ni-$_{2}$-$_{1.5}$的结构转变过程中，N（E-$_{F}$）降低.超导临界温度（TPDMATHABMX）也随Nb在立方相中的掺杂和四角畸变而变化，因为TPDMATHABMX非常依赖于N（EPDMATHABMW）。
We investigate the effect of Al doping on the magnetic properties of the alloy CoFeB. Comparative measurements of the saturation magnetization, the Gilbert damping parameter $α$ and the exchange constant as a function of the annealing temperature for CoFeB and CoFeAlB thin films are presented. Our results reveal a strong reduction of the magnetization for CoFeAlB in comparison to CoFeB. If the prepared CoFeAlB films are amorphous, the damping parameter $α$ is unaffected by the Al doping in comparison to the CoFeB alloy. In contrast, in the case of a crystalline CoFeAlB film, $α$ is found to be…
Synergistic doping of the grain interior and grain boundary alters deformation mechanisms and enables extreme strength in nanocrystalline Ni-Cr-Y alloys
University of California, Irvine（加州大学尔湾分校）；Stony Brook University（石溪大学）；Oak Ridge National Laboratory（橡树岭国家实验室）；Johns Hopkins University（约翰斯·霍普金斯大学）
The band gap engineering of group IV semiconductors has not been well explored theoretically and experimentally, except for SiGe. Recently, GeSn has attracted much attention due to the possibility of obtaining a direct band gap in this alloy, thereby making it suitable for light emitters. Other group IV alloys may also potentially exhibit material properties useful for device applications, expanding the space for band gap engineering in group IV. In this work the electronic band structure of all group IV semiconductor alloys is investigated. Twelve possible A:B alloys, where A is a semiconduct…
Transition metal dichalcogenides offer unprecedented versatility to engineer 2D materials with tailored properties to explore novel structural and electronic phase transitions. In this work, we present the atomic-scale evolution of the electronic ground state of a monolayer of Nb$_{1-δ}$Mo$_δ$Se$_2$ across the entire alloy composition range (0 < $δ$ < 1) using low-temperature (300 mK) scanning tunneling microscopy and spectroscopy (STM/STS). In particular, we investigate the atomic and electronic structure of this 2D alloy throughout the metal to semiconductor transition (monolayer NbSe$_2$ to…
Microstructural origin of the simultaneous enhancements in strength and ductility of a nitrogen-doped high-entropy alloy
Soochow University（苏州大学）；Research Institute of Aero-Engine, Beihang University（北京航空航天大学发动机研究院）；Center for Advancing Materials Performance from the Nanoscale (CAMP-Nano) and Hysitron Applied Research Center in China (HARCC), and Center for Alloy Innovation and Design (CAID), State Key Lab for Mechanical Behavior of Materials, Xi’an Jiaotong University（西安交通大学材料行为科技重点实验室、纳米尺度材料性能提升中心（CAMP-Nano）、海塞特中国应用研究中心（HARCC）及合金创新与设计中心（CAID））；Max Planck Institute for Sustainable Materials（马普可持续材料研究所）；Institute for Materials Science, University of Stuttgart（斯图加特大学材料科学研究所）；ICAMS, Ruhr-Universität Bochum（波鸿鲁尔大学综合材料与结构科学研究所）；State Key Laboratory of Powder Metallurgy, School of Materials Science and Engineering, Central South University（中南大学材料科学与工程学院粉末冶金国家重点实验室）；Department of Materials, Royal School of Mine, Imperial College London（帝国理工学院皇家矿业学院材料系）
We studied the stable magnetic structure of ordered Nd$_{6}$Fe$_{14-x}$Ga$_x$ ($x = 0, 1)$ alloys, which appears in the grain-boundary (GB) phase of Nd-Fe-B permanent magnets, using first-principles techniques. Slight Ga doping ($x = 1$) was shown to contribute to the stabilization of an anti-ferromagnetic (AF) state, whereas the non-doped case ($x = 0$) was revealed to favor ferromagnetic state rather than AF state with a slight energy difference.
OptiMat Alloys: a FAIR, living database of multi-principal element alloys enabled by a conversational agent
Empa - Swiss Federal Laboratories for Materials Science and Technology（瑞士联邦材料科技研究所）；National Centre for Computational Design and Discovery of Novel Materials MARVEL, Empa（MARVEL新型材料计算设计与发现国家中心）
Modeling the Equilibrium Vacancy Concentration in Multi-Principal Element Alloys from First-Principles
École Polytechnique Fédérale de Lausanne（洛桑联邦理工学院）；Institute of Materials, École Polytechnique Fédérale de Lausanne（洛桑联邦理工学院材料研究所）；Laboratory of materials design and simulation (MADES), Institute of Materials, École Polytechnique Fédérale de Lausanne（洛桑联邦理工学院材料研究所材料与模拟实验室）；National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne（洛桑联邦理工学院新材料计算设计与发现国家中心）
Nanocrystalline Al-Mg alloys are used to isolate the effect of grain boundary doping on the strength of nanostructured metals. Mg is added during mechanical milling, followed by low homologous temperature annealing treatments to induce segregation without grain growth. Nanocrystalline Al -7 at.% Mg that is annealed for 1 h at 200 °C is the strongest alloy fabricated, with a hardness of 4.56 GPa or approximately three times that of pure nanocrystalline Al. Micropillar compression experiments indicate a yield strength of 865 MPa and a specific strength of 329 kN m/kg, making this one of the stro…
The generalized stacking fault (SFE) energy curves of pure gold (Au) and its binary alloys with transition metals are determined from density functional theory (DFT). Alloy elements Ag, Al, Cu, Ni, Ti, Zr, Zn, In, Ga, Sn, Mn, Cd, Sn, Ta and Cr are substituted into Au at concentrations up to 4%. A comparison of various proposed methodologies to calculate SFEs is given. The intrinsic SFE decreases for all alloying elements from its value for pure Au, but SFE energies (both stable and unstable) vary strongly with the distance of the alloying element from the stacking fault region, and with alloy …
The ferromagnetic Heusler alloy $Ni_2MnGa$ had been of major interest in the past few years because of its magnetic properties which can be easily tuned. The $Ni_2MnGa$ Heusler alloys are intermetallic alloy with $L2_1$ structure. Here we report a detailed investigation of the effect of doping of Co and Mn in Ni2MnGa. Magnetic properties and electronic structure of $Ni_{2-x}Co_xMnGa_{1-y}Mn_y$ Heusler alloys have been studied by using Green's function-based KKR-CPA method based DFT calculations. We will show the magnetization can be tuned depending on the Co and Mn occumencies. We will also di…
Impurity diffusion in Zr is potentially important for many applications of Zr alloys, and in particular for their use of nuclear reactor cladding. However, significant uncertainty presently exists about which elements are vacancy vs. interstitial diffusers, which can inhibit understanding and prediction of their behavior under different temperature, irradiation, and alloying conditions. Therefore, first-principles calculations based on density functional theory (DFT) have been employed to predict the temperature-dependent dilute impurity diffusion coefficients for 14 substitutional alloying el…
Grain boundaries have been shown to dramatically influence the behavior of relatively simple materials such as monatomic metals and binary alloys. The increased chemical complexity associated with multi-principal element alloys is hypothesized to lead to new grain boundary phenomena. To explore the relationship between grain boundary structure and chemistry in these materials, hybrid molecular dynamics/Monte Carlo simulations of a faceted Σ11 <110> tilt boundary, chosen to sample both high- and low-energy boundary configurations, are performed in face-centered cubic CrFeCoNiCu and CrFeCoNi equ…
FeCrAl alloys are proposed and being intensively investigated as alternative accident tolerant fuel (ATF) cladding for nuclear fission application. Herein, the influence of major alloy elements (Cr and Al), reactive element effect and heating schedules on the oxidation behavior of FeCrAl alloys in steam up to 1500°C was examined. In case of transient ramp tests, catastrophic oxidation, i.e. rapid and complete consumption of the alloy, occurred during temperature ramp up to above 1200°C for specific alloys. The maximum compatible temperature of FeCrAl alloys in steam increases with raising Cr a…
Atomistic simulations can provide useful insights into the physical properties of multi-principal-element alloys. However, classical potentials mostly fail to capture key quantum (electronic-structure) effects. We present a deep 3D convolutional neural network (3D CNN) based framework combined with a voxelization technique to design interatomic potentials for chemically complex alloys. We highlight the performance of the 3D CNN model and its efficacy in computing potentials using the medium-entropy alloy TaNbMo. In order to provide insights into the effect of voxel resolution, we implemented t…
Multi-principal element alloys (MPEAs), inclusive of high entropy alloys (HEAs), continue to attract significant research attention owing to their potentially desirable properties. Although MPEAs remain under extensive research, traditional (i.e. empirical) alloy production and testing is both costly and time-consuming, partly due to the inefficiency of the early discovery process which involves experiments on a large number of alloy compositions. It is intuitive to apply machine learning in the discovery of this novel class of materials, of which only a small number of potential alloys has be…
