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Travelling Salesman Problem (TSP) is a typical NP complete combinatorial optimization problem with various applications. In this paper, a nature inspired meta-heuristic optimization algorithm named as Artificial Immune System Optimization (AISO) algorithm is proposed for solving TSP. There are other approaches for solving this problem, namely Greedy Method, Brunch and Bound (B&B), and Dynamic Programming (DP) but they are not very efficient. The time complexity of Greedy approach is O (n2). However, the Greedy method doesn't always converge to an optimum solution whereas the B&B increases search space exponentially and DP finds out optimal solution in O (n22 n) time. The population based meta-heuristic optimization algorithms such as Artificial Immune System Optimization (AISO) and Genetic Algorithm (GA) provide a way to find solution of the TSP in linear time complexity. The proposed algorithm finds out the best cell (optimum solution) using a Survivor Selection (SS) operator which reduces the search space to ensure that effective information is not lost. Dataset, results and convergence graphs are presented and accuracy of the analysis is briefly discussed.

Designing electrochemically active, stable, and earth-abundant electrocatalysts is essential for boosting oxygen evolution reaction (OER) rates for sustainable hydrogen production. High entropy oxides (HEOs) consist of five or more metal cations, offering ample opportunities to tune their catalytic properties toward high OER efficiency. In this work, we combine theoretical and experimental studies to scrutinize the OER activity and stability for spinel-type HEOs. Our density functional theory calculations unequivocally confirm that randomly mixed metal sites are more thermodynamically stable, while we also show that adsorption energies of the intermediates display widening distributions accompanied by the equatorial strain of active metal-oxygen bonds under mixing. The rapid sol-flame method was successfully employed to synthesize spinel oxides up to five third-row metal cations (Co, Fe, Ni, Cr, and Mn) with high degree of entropy. Such catalyst exhibits the highest OER activity of 309 mV at 10 mA cm− 2 and prolonged durability up to 168 hours under alkaline conditions over less complex mixtures despite partial formation of surface oxyhydroxide. The high-entropy model developed in this work identifies mixed Co3+ active site as the most active center of this system. Overall, this work reveals that a key feature controlling the enhanced activity of high-entropy oxides is related to mixing and resulting strain near the active site.

The overarching goal of the present multiscale investigation is to unearth the kinetics and mechanisms of corrosion of borosilicate glasses in hyper-alkaline (pH = 13) environments as a function of...

Surface reconstruction and electronic transitions were examined. Experiments and computational analysis were conducted to study the surface effects compared to the bulk. Previous results, like XMCD, XAS, and S-TEM, were considered for further analysis.

In this work, we report the presence of surface-densified phases (β-Ni5O8, γ-Ni3O4, and δ-Ni7O8) in LiNiO2 (LNO)- and LiNi0.8Al0.2O2 (LNA)-layered compounds by combined atomic level scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). These surface phases form upon electrochemical aging at high state of charge corresponding to a fully delithiated state. A unique feature of these phases is the periodic occupancy by Ni2+ in the Li layer. This periodic Ni occupancy gives rise to extra diffraction reflections, which are qualitatively similar to those of the LiNi2O4 spinel structure, but these surface phases have a lower Ni valence state and cation content than spinel. These experimental results confirm the presence of thermodynamically stable surface phases and provide new insights into the phenomena of surface phase formation in Ni-rich layered structures.

Surface reconstruction and electronic transitions are examined. XMCD through total fluorescence yield and total electron yield show evidence of density of state differences between bulk and surface. Surface reconstruction was examined via STEM.

This paper presents detailed steps and procedures for the design of a 4-pole, 0.75-hp, 1500-r.p.m. surface-mounted permanent magnet brush-less DC (SPM-BLDC) motor. The motor has been fabricated at the works of a local manufacturer. The parameters of the machine have been analytically evaluated and subsequently compared to the experimentally determined values. Its practical performance on load has been experimentally evaluated in the laboratory and verified against analytical predictions too. Low-cost M45 electrical steel laminations, as used for commercial induction motors (IMs), have been used from considerations of cost and availability. This also enables direct comparison of important parameters (e.g. torque density, power density and efficiency) between the fabricated prototype and commercially available fractional-hp 3-phase and 1-phase IMs of similar rating. This study is significant since electrical motor manufacturers need not change their stator stamping production line for BLDC motor vis-a-vis IM in case of mass production. Such an approach is hardly reported in the available technical literature. Analytical methods adopted include both conventional hand calculations and finite-element analysis using commercially available software package(s). Excellent agreements between analytical and experimental values uphold the correctness of the design process, precision of fabrication and accuracy of experimental investigations.

This paper presents a novel and exhaustive investigation involving in-depth analysis, performance evaluation and comparative study of two 0.75 hp, 4-pole, 1500 rpm laboratory prototypes of Brushless DC (BLDC) motors of identical nominal ratings with surface and interior permanent magnet rotor structures having the same stator and winding (integral slot distributed winding). Both the motors were designed and developed in the lab. The major electrical variables (such as rated power, speed, voltage, current, number of poles, etc.) and the stator (such as core material, stator lamination, stack length, winding pattern and wire gauge) of the fabricated prototypes have also been kept identical to pin-point the direct influence of the two different rotor configurations (viz., surface vs interior permanent magnet) on the parameters, performance and operation of these BLDC motors. Additionally, to ensure unbiased basis for appropriate comparison, the overall volumes of magnets/pole in both the motors have also been kept similar. A detailed comparison of different quantities like air-gap flux density distribution, THD in induced voltage, torque ripple, losses and efficiency, torque–speed characteristics with field-weakening capability, steady state parameters at different operating conditions, etc. has been conducted for the said motors and the salient points duly highlighted. The vulnerability of the permanent magnets to demagnetisation based on armature reaction, particularly during a sudden fault, has also been investigated in both the cases. The theoretically determined parameters and analytically evaluated performance figures have been verified through standard FEM packages, and later validated experimentally on the fabricated prototypes. Very good mutual agreement has been observed between predicted and experimental values.

Supplementary Material

This paper reports new insights into structural and chemical evolution of surface phases of LiNi0.8Co0.15Al0.05O2 (NCA) held at constant high voltages (up to 4.75 V) as well as high temperatures (6...

Practical utilization of energy densities near the theoretical limit for R3m layered oxide positive electrode materials is dependent on the stability of the electrochemical performance of these materials at or near full delithiation. To develop new chemistries and novel approaches toward the improvement of the electrochemical performance of these materials at such high states of charge, a robust understanding of the failure mechanisms limiting current materials is necessary. Thorough analysis of LixCo1–yAlyO2 and LixNi1–yAlyO2 as well as LixNi0.8Co0.2O2 and LixNi0.8Co0.15Al0.05O2 (1 ≥ x ≥ 0 and 0.2 ≥ y ≥ 0) enabled the identification of key relationships between the transition metal chemistry of the electrode, its structural stability, and cycling characteristics at or near complete delithiation (4.75 V). Extensive characterization of these materials was achieved by a multitude of physical and electrochemical techniques to investigate the relative importance of surface vs bulk phenomena. The resulting in...

© 2017 American Chemical Society. Enabling practical utilization of layered R3m positive electrodes near full delithiation requires an enhanced understanding of the complex electrode-electrolyte interactions that often induce failure. Using Li[Ni0.8Co0.15Al0.05]O2 (NCA) as a model layered compound, the chemical and structural stability in a strenuous thermal and electrochemical environment was explored. Operando microcalorimetry and electrochemical impedance spectroscopy identified a fingerprint for a structural decomposition and transition-metal dissolution reaction that occurs on the positive electrode at full delithiation. Surface-sensitive characterization techniques, including X-ray absorption spectroscopy and high-resolution transmission electron microscopy, measured a structural and morphological transformation of the surface and subsurface regions of NCA. Despite the bulk structural integrity being maintained, NCA surface degradation at a high state of charge induces excessive transition-metal dissolution and significant positive electrode impedance development, resulting in a rapid decrease in electrochemical performance. Additionally, the impact of electrolyte salt, positive electrode surface area, and surface Li2CO3 content on the magnitude and character of the dissolution reaction was studied.

In this paper, detailed steps and procedures for the design of a fractional slot non-overlapping(concentrated) winding(FSCW) permanent magnet synchronous generator(PMSG) is presented. Here the design of a 2 kVA, 1000 rpm, 230 V machine is done. Analytical calculation steps have been shown. starting with conventional design methods, main dimensions are chosen. Thereafter modern methods of determining pole-slot combination, number of turns per phase, the geometry of the stator and the magnet dimensions are adopted. Thereafter the design has been validated and fine-tuned using standard FEM-based commercially available software package. The parameters of the machine have also been evaluated. Finally, the machine has been fabricated by a local manufacturer and then tested at the lab. The preliminary test results are found to be in good agreement with theoretical predictions which upholds both the design accuracy and precision of fabrication.

Iron oxide nanomaterials participate in redox processes that give them ideal properties for their use as earth-abundant catalysts. Fabricating nanocatalysts for such applications requires detailed knowledge of the deposition and growth. We report the spontaneous deposition of iron oxide nanoparticles on HOPG in defect areas and on step edges from a metal precursor solution. To study the nucleation and growth of iron oxide nanoparticles, tailored defects were created on the surface of HOPG using various ion sources that serve as the target sites for iron oxide nucleation. After solution deposition and annealing, the iron oxide nanoparticles were found to nucleate and coalesce at 400 °C. AFM revealed that the particles on the sp3 carbon sites enabled the nanoparticles to aggregate into larger particles. The iron oxide nanoparticles were characterized as having an Fe3+ oxidation state and two different oxygen species, Fe–O and Fe–OH/Fe–OOH, as determined by XPS. STEM imaging and EDS mapping confirmed that the majority of the nanoparticles grown were converted to hematite after annealing at 400 °C. A mechanism of spontaneous and selective deposition on the HOPG surface and transformation of the iron oxide nanoparticles is proposed. These results suggest a simple method for growing nanoparticles as a model catalyst.

We report the formation of complex core–shell and three-layer Mn–Bi nanoparticles in a single step inert-gas condensation process. These structures have been achieved by controlling the thermal environment of the nanoparticles. High resolution transmission electron microscopy, high-angle annular dark-field imaging in scanning transmission electron microscopy mode, and elemental mapping by energy dispersive spectroscopy have been used to determine the crystal structure and chemical composition of the nanoparticles. These particles exist in two forms: (1) a crystalline Bi core with an amorphous Mn-rich shell, and (2) a crystalline Bi annular shell between two amorphous layers with high Mn concentration. These particles show significant magnetic hysteresis possibly arising from the change in bond length between Mn atoms introduced by Bi atoms in the bonding environment of the Mn atoms.

Bi-substituted iron garnet films are extensively used in the fabrication of nonreciprocal devices in optical telecommunications. The miniaturization of these devices for on-chip integration requires the development of more efficient magneto-optic materials than presently available. Recent evidence has emerged of large near-surface enhancements in the magneto-optic response in these materials. However, their operative mechanisms at the atomic and electronic levels are not as yet understood. We report significant differences in the ionic structure between surface and bulk in bismuth-substituted iron garnet materials. It is found that the unit cell is elongated normal to the surface, thus enlarging the separation between F e 3 + ions. These ions play a central role in the magneto-optic response of this material. A marked displacement of Fe ions creates gaps at the surface that are populated in the bulk. Concomitantly, surface- and bulk-sensitive measurements of spin-polarized 3d F e 3 + states show significant differences in the magnitude of L 2 edge x-ray magnetic circular dichroism, as well as differences in L 3 edge dichroism, which, in the presence of spin-orbit coupling in 3d states, can be assigned to high-energy states. An increase in magnetic circular dichroism correlates with larger Faraday rotation. These findings provide a deeper understanding of the role of the surface in the electronic transitions to excited F e 3 + 3d states, responsible for these nonreciprocal phenomena. Together with the surface reconstruction underlying these effects reported here, they provide a useful tool for the further development of improved materials technologies to advance the integration of nonreciprocal devices in optical circuits.

This paper presents detailed steps of parameter estimation and performance analysis of two interior permanent magnet(IPM) motors that have been designed in the laboratory and are in the winding stage at the works of a small local machines manufacturer. The parameters have been estimated using standard FEM packages and through analytical calculations under different operating conditions. The estimated parameters are used to evaluate the performance (such as torque, speed, efficiency) of the IPM motor. The effect of saliency on the motor performance has been highlighted. The effect of parameter variations on the performance of the machine has also been presented. The field weakening capability of the IPM motor has been studied too. The analytical and FEM-based results are presented for two laboratory designed IPM motor prototypes (5kW, 8 pole, 750rpm and 0.75hp, 4 pole, 1500rpm IPM motors).

Bulk magnetic materials with the noncentrosymmetric cubic B20 structure are fascinating due to skyrmion spin structures associated with Dzyaloshinskii–Moriya interactions, but the size of skyrmions are generally larger than 50 nm. The control of such spin structures in the 10 nm size ranges is essential to explore them for spintronics, ultra-high-density magnetic recording, and other applications. In this study, we have fabricated MnSi nanoparticles with average sizes of 9.7, 13.1 and 17.7 nm and investigated their structural and magnetic properties. X-ray diffraction and transmission electron microscope studies show that the MnSi nanoparticles crystallize in the cubic B20 structure. Field-dependent dc susceptibility data of the MnSi samples with average particle sizes of 17.7 and 13.1 nm show anomalies in limited field (about 25–400 Oe) and temperature (25 K–43 K) ranges. These features are similar to the signature of the skyrmion-like spin structures observed below the Curie temperature of MnSi. Our results also show that this anomalous behavior is size-dependent and suppressed in the smallest nanoparticles (9.7 nm), and this suppression is interpreted as a confinement effect that leads to a truncation of the skyrmion structure.

Core–shell nanoparticles are known to form in binary systems using a one-step gas-condensation deposition process where a large, positive enthalpy of mixing provides the driving force for phase separation and a difference in surface energy between component atoms creates a preferential surface phase leading to a core–shell structure. Here, core–shell nanoparticles have been observed in systems with enthalpy as low as −5 kJ mol−1 and a surface energy difference of 0.5 J m−2 (Mo–Co). This suggests that surface energy dominates at the nanoscale and can lead to phase separation in nanoparticles. The compositions and size dependence of the core–shell structures are also compared and no core–shell structures are observed below a critical size of 8 nm.

This paper presents steps and procedures of designing a closed loop speed controller for a surface mounted permanent magnet(SM-PM) brush-less DC machine(BLDC). The closed-loop speed control technique has been implemented using Hall-effect position sensor. The BLDC motor control algorithm has been modelled and simulated first. The same has been thereafter practically implemented on a 0.75 hp, 1500 r.p.m BLDC motor that was designed and developed as a lab prototype. Both the simulation and the experimental results are in excellent in agreements.

Enabling practical utilization of layered R3̅m positive electrodes near full delithiation requires an enhanced understanding of the complex electrode-electrolyte interactions that often induce failure. Using Li[Ni

Prospects for diamond-structured magnetic Si are investigated experimentally, by model calculations, and numerically. Our theoretical analysis, using bond-orbital, Vienna ab-initio simulation package, and SIESTA calculations, suggest that some diamond-Si imperfection may carry a magnetic moment. In particular, for tetrahedral Si5 clusters, we calculate a magnetic moment of 4 μB per cluster. These moments are more likely to be observed in nanoparticles, as compared with thin films, due to the larger surface-to-volume ratios of the former and to their more versatile atomic surface structure. Experimentally, we have prepared Si nanoparticles by cluster deposition and found a small magnetization of 2.9 emu/cm3 at 10 K.

Amorphous Fe32Ni52Zr3B13, prepared by rapid solidification, undergoes crystallization during high-energy mechanical milling. The resulting structure consists of face-centered cubic (fcc) FeNi and Zr3Ni20B6 nanocrystallites. Structural evolution and defect analysis of as-solidified Fe32Ni52Zr3B13 ribbons with different milling times is investigated. From the differential thermal analysis (DTA) curve of amorphous ribbons, exothermic peaks were observed at 415 °C and 475 °C corresponding to the crystallization of fcc Zr3Ni20B6 phase and fcc FeNi phase, respectively. However, high-energy mechanical milling induces the formation of FeNi within the first 2 h of mechanical milling. Further milling induces the crystallization of Zr3Ni20B6. Doppler broadening positron annihilation spectroscopy (DBPAS) was used to investigate vacancy-type defects. The milling-induced crystallization appears to be related to enhanced vacancy-type defect concentrations allowing growth of pre-existing Fe(Ni) nuclei. The milling and enhanced vacancy concentration also de-stabilizes the glass, leading to decreased crystallization temperatures for both phases, and ultimately eliminating the glass transition altogether.

Four nanoparticle compositions, Fe–21, 35, 47, and 67 at. % Au, have been prepared to study the phase stability and solid-state transformation in confined Fe–Au nanoalloys. The formation of two phases, predicted from bulk thermodynamics, has been suppressed in all compositions. Instead, a single phase solid solution forms after heat treatment at 600 °C and slow cooling. However, bulk phase relationships, signified by the precipitation of α-Fe upon cooling, was observed in larger particles (>20 nm) with composition Fe–35 at. % Au. The suppression of the phase transformation/precipitation in small particles is explained thermodynamically, as the free energy decrease associated with the phase transformation does not exceed the increase in energy due to the introduction of an interphase interface (grain boundary) within the cluster. A general equation has been derived to predict the critical cluster size below which transformations are inhibited, which agrees well with the observed experimental results.

Microstrip patch antenna has extensive applications in areas requiring light weight and low profile antenna sub system. Differential Evolution (DE) algorithm and Cuckoo Search (CS) algorithm are modern optimization algorithms used here for determining the design parameters of microstrip antenna. In literature, there does not exist any direct relation between the bandwidth of a microstrip patch antenna with its design parameters. In this paper, a relationship between bandwidth and geometrical parameters of co-ax fed microstrip patch antenna has been established using Curve fitting model. The investigation is performed for microwave frequencies over a certain range. A comparative study is performed between the results obtained for bandwidth enhancement by optimizing the patch length, patch width and the position of feed using DE and CS algorithms.

Mn-based silicides are fascinating due to their exotic spin textures and unique crystal structures, but the low magnetic ordering temperatures and/or small magnetic moments of bulk alloys are major impediments to their use in practical applications. In sharp contrast to bulk Mn5Si3, which is paramagnetic at room temperature and exhibits low-temperature antiferromagnetic ordering, we show ferromagnetic ordering in Mn5Si3 nanoparticles with a high Curie temperature (Tc ≈ 590 K). The Mn5Si3 nanoparticles have an average size of 8.6 nm and also exhibit large saturation magnetic polarizations (Js = 10.1 kG at 300 K and 12.4 kG at 3 K) and appreciable magnetocrystalline anisotropy constants (K1 = 6.2 Mergs/cm(3) at 300 K and at 12.8 Mergs/cm(3) at 3 K). The drastic change of the magnetic ordering and properties in the nanoparticles are attributed to low-dimensional and quantum-confinement effects, evident from first-principle density-functional-theory calculations.

Microstrip line feed Microstrip Antenna (MSA) geometrical design parameters are Patch Width, Inset Feed Position and Patch length. Cuckoo Search algorithm (CS) is a recent optimization algorithm creating its application in the electromagnetic community for evolving the design parameters of microstrip antenna. Cuckoo Search algorithm (CS) has been employed in this paper to calculate the design parameters of the microstrip line feed microstrip antenna for a reaspective target frequencies and return loss. Same investigation is made for different microwave frequencies (1–18 GHz) and at dielectric constant 2.4. Simulations have been done using IE3D software. The results suggests Cuckoo search algorithm outperforms Differential Evolution (DE)in terms of quality of solution and convergence speed.

Microstrip Antenna (MSA) found widespread applications in satellite communications, wireless and microwave systems, direct broadcast systems; due to their reduced cost and compact-planar structure. Differential Evolution (DE) algorithm is a recent evolutionary computing technique. In this paper, we have implemented DE algorithm to optimize the resonant frequencies of the inset line fed rectangular microstrip patch antenna considering their geometrical design parameters like patch length, patch width and the length of the inset fed as an unknown variables. Simulations have been done for different microwave frequencies (3 to 18 GHz) for the optimized antennas.

Nanoscale magnets with characteristic dimensions in the range of 1–100 nm are important in several areas of nanoscience and technology. First, this length scale spans the typical important dimensions of exchange lengths and domain-wall widths, which means that significant control of magnetic properties can be obtained by varying grain or particle dimensions. Second, the nonequilibrium synthetic processes used for clusters, particles, and films, often lead to new real-space crystal structures with completely novel spin structures and magnetic properties. Third, a basic-science challenge in this class of matter involves the spin-polarized quantum mechanics of many-electron systems containing 10–10 000 atoms. Finally, the materials under study may have important future applications in high-density data storage, ultra-small spintronic devices, or high-energy magnetic materials. In this article, we discuss our recent work on novel Fe-Au nanoclusters, MnAu-Mn coreshell structures, and complex high-anisotropy Co-rich intermetallic compound clusters. We also present new results on Fe-based alloys including the magnetic properties of semiconducting FeSi2 nanoclusters and spin correlations in FeGe nanocluster films. V C 2015 AIP Publishing LLC.

A very rapid growth in wireless communication demands antennas with wider bandwidth range to carry out various applications. In this context, ultra wide-band (UWB) technology has gathered a lot of interest because of its substantial bandwidth. In this paper, a novel Differential Evolution (DE) based optimization technique has been proposed to design a UWB printed square monopole antenna. The errors for desired lower band edge frequency and bandwidth are minimized to obtain the parameters of the antenna. These results have been compared with that of Genetic Algorithm (GA) and Particle Swarm Optimization (PSO). Simulation results are given to show the performance of the proposed technique. A 2:1 VSWR bandwidth of 7.2 GHz (4.2–11.4 GHz) is achieved with the help of Differential Evolution (DE).

The technique of feeding a microstrip antenna with a microstrip line through an aperture is gathering a lot of interest in communication and radar systems used for defence applications. This is due to the fact that this feeding technique has many adjustable parameters in the form of aperture length, width, and stub parameters. This paper presents a study on the effect of aperture dimensions and stub length on the voltage-standing wave ratio bandwidth of an aperturecoupled microstrip antenna. Without any additional matching network, optimal impedance matching of the antenna has been achieved using genetic algorithm. In the algorithm, each chromosome consists of three binary encoded genes, one for aperture length, second one for aperture width and the last one for stub length. Finally, the algorithm determines the parameters of the antenna that provides the minimum value of the average reflection coefficient. The investigation is made at different microwave frequency ranges and it extends up to Ku band. The results show that the percentage of fractional bandwidth improves for higher design frequencies and has a maximum of 13.2 per cent for centre frequency of 17.5 GHz. Experimental results are presented for a particular range of frequency and the accuracy of the analysis is briefly discussed.

This paper presents detailed steps and procedure for the design of a permanent magnet brush-less DC machine(PM-BLDC). Here the design(both the armature circuit and the PM field) is done for a 4-pole 0.75 hp, 1500 rpm surface mounted BLDC(SPM-BLDC). First the design and the performance analysis of the machine has been done by hand calculation. The results are then fine tuned and verified using a standard finite element analysis(FEM) software. Parameters of the machine have also been calculated. The designed BLDC motor also have been fabricated.

We report a facile synthesis of hard magnetic L10-FePtAu nanoparticles by coreduction of Fe(acac)3, Pt(acac)2 (acac = acetylacetonate) and gold acetate in oleylamine. In the current reaction condition, NP sizes are controlled to be 5.5 to 11.0 nm by changing the amount of Au doping. When the Au composition in the NPs is higher than 14%, the hard magnetic NPs are directly obtained without any annealing. The highest coercivity of 12.15 kOe at room temperature could be achieved for the NPs with 32% Au doping, which is much higher than the coercivities reported by the previous studies on solution-synthesized FePt nanoparticles. The reported one-pot synthesis of L10-FePtAu NPs may help to build superstrong magnets for magnetic or data-storage applications.

Formation of chemically ordered compounds of Fe and Au is inhibited in bulk materials due to their limited mutual solubility. However, here we report the formation of chemically ordered L12-type Fe3Au and FeAu3 compounds in Fe-Au sub-10 nm nanoparticles, suggesting that they are equilibrium structures in size-constrained systems. The stability of these L12-ordered Fe3Au and FeAu3 compounds along with a previously discovered L10-ordered FeAu has been explained by a size-dependent equilibrium thermodynamic model. Furthermore, the spin ordering of these three compounds has been computed using ab initio first-principle calculations. All ordered compounds exhibit a substantial magnetization at room temperature. The Fe3Au had a high saturation magnetization of about 143.6 emu/g with a ferromagnetic spin structure. The FeAu3 nanoparticles displayed a low saturation magnetization of about 11 emu/g. This suggests a antiferromagnetic spin structure, with the net magnetization arising from uncompensated surface spins. First-principle calculations using the Vienna ab initio simulation package (VASP) indicate that ferromagnetic ordering is energetically most stable in Fe3Au, while antiferromagnetic order is predicted in FeAu and FeAu3, consistent with the experimental results.

We present simple, self-assembled, and robust fabrication of ultrahigh density cobalt nanowire arrays. The binary Co-Al and Co-Si systems phase-separate during physical vapor deposition, resulting in Co nanowire arrays with average diameter as small as 4.9 nm and nanowire density on the order of 10(16)/m(2). The nanowire diameters were controlled by moderating the surface diffusivity, which affected the lateral diffusion lengths. High resolution transmission electron microscopy reveals that the Co nanowires formed in the face-centered cubic structure. Elemental mapping showed that in both systems the nanowires consisted of Co with undetectable Al or Si and that the matrix consisted of Al with no distinguishable Co in the Co-Al system and a mixture of Si and Co in the Co-Si system. Magnetic measurements clearly indicate anisotropic behavior consistent with shape anisotropy. The dynamics of nanowire growth, simulated using an Ising model, is consistent with the experimental phase and geometry of the nanowires.

High-anisotropy arc-melted and field-annealed Mn100−x Bi x (x = 50–65) alloys have been investigated. Samples predominantly consist of low-temperature phase (LTP) MnBi and elemental Bi, where the LTP volume fraction and sample magnetization decrease with increasing x. All samples are hard ferromagnetic at room temperature and demonstrate a structural and magnetic phase transition at 630 K. For Mn35Bi65, the highest values for coercivity (4.6 kOe), magnetization remanence ratio (0.97), and energy product (4.9 MGOe) are measured at 540 K, near the melting point of bismuth. We explain the trend in magnetic properties as a consequence of c-axis alignment of MnBi grains facilitated by the molten Bi during magnetic field annealing.