Conduction Electrons Research Articles

The Relationship between Electrical Conductivity and Electromigration in Liquid Metals

The phenomena of electrical conductivity and electromigration in metallic systems are related, since in both cases the basic physical process is the scattering of conduction electrons by metal ions. Numerous searches have been made for equations connecting the conductivity with electromigration. In the case of a liquid metal, when using the Drude–Sommerfeld (DS) conductivity equation, it was not possible to obtain a quantitative relationship between these phenomena, which would be correct. Attempts to find such a relationship when taking into account the N. Mott correction (g-factor) in the DS equation were unsuccessful. This article proposes a different correction (b-factor) to the DS equation, which takes into account the possibility of varying the momentum transferred by the conduction electron to a metal ion during the scattering. This correction allows to establish a quantitative relationship between conductivity and electromigration as well as between electromigration in various binary systems with common components, in agreement with the experiment. The proposed theory describes well, in particular, two- and multi-component metal systems of any concentration (the consistency rule for triangles A–B, B–C, C–A). The value of the b-factor smoothly changes depending on the heat of vaporization of the metal, per unit volume.

Engineering Interface Defects and Interdiffusion at the Degenerate Conductive In2O3/Al2O3 Interface for Stable Electrodes in a Saline Solution.

A low-temperature Al2O3 deposition process provides a simplified method to form a conductive two-dimensional electron gas (2DEG) at the metal oxide/Al2O3 heterointerface. However, the impact of key factors of the interface defects and cation interdiffusion on the interface is still not well understood. Furthermore, there is still a blank space in terms of applications that go beyond the understanding of the interface's electrical conductivity. In this work, we carried out a systematic experimental study by oxygen plasma pretreatment and thermal annealing post-treatment to study the impact of interface defects and cation interdiffusion at the In2O3/Al2O3 interface on the electrical conductance, respectively. Combining the trends in electrical conductance with the structural characteristics, we found that building a sharp interface with a high concentration of interface defects provides a reliable approach to producing such a conductive interface. After applying this conductive interface as electrodes for fabricating a field-effect transistor (FET) device, we found that this interface electrode exhibited ultrastability in phosphate-buffered saline (PBS), a commonly used biological saline solution. This study provides new insights into the formation of conductive 2DEGs at metal oxide/Al2O3 interfaces and lays the foundation for further applications as electrodes in bioelectronic devices.

Voltage fluctuations and probe frequency jitter in electric force microscopy of a conductor.

Electric force microscopy probes the statistics of electric field fluctuations from a sample surface, both through measurement of the noncontact friction exerted on the oscillating charged probe and by determination of the power spectrum of stochastic probe frequency fluctuations, referred to as "jitter." Here we calculate the frequency jitter power spectrum determined over a conducting sample of finite thickness, whose response is characterized by a dielectric function that is wavevector-dependent. These calculations complement previous predictions of the coefficient of noncontact friction in an electric force microscopy measurement for the same model, and also previous predictions of the jitter power spectrum for a dielectric continuum. The inclusion both of a finite sample thickness and a wavevector-dependent dielectric response can significantly enhance the magnitude of the predicted jitter spectrum for a conductor, relative to a simpler model of an infinitely thick dielectric continuum. These calculations provide a baseline prediction of the jitter power spectrum generated by the dynamics of conduction electrons in a metal sample.

Synthesis of Ni Nanosheets by Template-Free Method and Their Application in Conductive and Magnetic Flexible Electrons.

Two-dimensional Ni nanosheets are synthesized by the template-free method using Na3CA as an orientation agent in liquid phase, and then the conductive Ni nanosheet ink is prepared for conductive circuits on flexible electronics. The thickness of the Ni nanosheets is about 800 nm, and the diameter is about 100 μm. Na3CA plays a structural guiding role to form Ni nanocrystals, promoting the self-assembly of Ni nanocrystals into Ni nanosheets effectively. The laminar stackable patterns of the Ni nanosheet circuits increase the contact area of the Ni nanosheets and improve the stability of the conductors under stress. Ni nanosheets can bend with the folding of the structure, while the mutual constraints between their layers promote the circuit to remain stable during the bending state. Therefore, the Ni nanosheet circuits display excellent conductive performance during the tiled and bent stages. In addition, Ni nanosheet/Ag nanowire composites are prepared to enhance conductivity to meet higher demands. Moreover, the experimental results of its application in magnetic guided switch closure circuits show that Ni nanosheet/Ag nanowire composites have the potential to participate in both conductive and magnetic field applications simultaneously.

Topological Hall Effect in (Mn1−xFex)3.25Ge (x = 0.4) Hexagonal Magnet

Topologically protected nontrivial spin structures attract significant interest in condensed matter physics for their utilization in low‐power‐consumption spintronics devices, memory devices, etc. The topological Hall effect (THE) is an additional Hall resistivity in the system arising from real‐space Berry curvature picked up by conduction electron passing through the nontrivial spin texture. Compared to expensive neutron diffraction measurements, THE is often used as a cost‐effective tool to investigate nontrivial spin texture in the materials. In the present manuscript, THE in the (Mn1−xFex)3.25Ge (x = 0.4) alloy is studied using magneto‐transport measurements. Maximum THE is found in the system about 0.65 μΩ cm at 150 K, which is in contrast to the pristine Mn3Ge that has zero THE. The strong temperature variation of THE suggests that the noncoplanar spin structure due to competition among the magneto‐crystalline anisotropy, antiferromagnetic coupling, and ferromagnetic exchange interaction is the main source of THE in the present system. Herein, it is shown that chemical doping can be an effective way to induce THE in the material with vanishing THE in its parent phase.

Spin relaxation of conduction electrons in coupled quantum wells

Spin relaxation of conduction electrons in coupled quantum wells

Electron spin resonance study of mixed Bi[formula omitted]Se[formula omitted] topological insulator–magnetic insulator nanoparticles

We investigated Bi2Se3 topological insulator nanoparticles mixed with room-temperature ferromagnetic insulator nanoparticles by using electron spin resonance (ESR) of the surface conduction electrons in the Bi2Se3 nanoparticles. The ESR intensity and linewidth as a function of the molar ratio of the magnetic insulator could be well understood in terms of the magnetic proximity effect due to the short-range exchange field of the magnetic insulator nanoparticles along with the long-range magnetic dipole field effect and the surface-to-volume ratio effect.

Interplay between Kondo and magnetic interactions in Pr0.75Gd0.25ScGeH

Combined experimental and density functional theory (DFT) study of Pr0.75Gd0.25ScGe and its hydride (Pr0.75Gd0.25ScGeH) reveals intricacies of composition-structure-property relationships in those distinctly layered compounds. Hydrogenation of the intermetallic parent, crystalizing in a tetragonal CeScSi-type structure, leads to an anisotropic volume expansion, that is, a(=b) lattice parameter decreases while the lattice expands along the c direction, yielding a net increase of cell volume. DFT calculations predict an antiparallel coupling of localized Gd and Pr magnetic moments in both materials at the ground state. While experiments corroborate this for the parent compound, there is no conclusive experimental proof for the hydride, where Pr moments do not order down to 3 K. DFT results also reveal that rare-earth – hydrogen interactions reduce spin-polarization of the Pr and Gd 5d and Sc 3d states at the Fermi energy, disrupt indirect exchange interactions mediated by conduction electrons, dramatically reduce the magnetic ordering temperature, and open a pseudo-gap in the majority-spin channel. Both experiments and theory show evidence of Kondo-like behavior in the hydride in the absence of an applied magnetic field, whereas increasing the field promotes magnetic ordering and suppresses Kondo-like behavior.

Disorder induced cluster spin glass like state in MnFeSb

Hexagonal MnSb is a ferromagnet with Curie temperature and saturation magnetization values of 587 K and 110 emu/g, respectively. In this paper, the origin of the complex magnetic behavior of a single phase MnFe0.20Sb prepared using solid-state reaction method is examined. A thorough investigation of temperature dependent magnetization and magnetic relaxation measurements reveals the presence of a glassy like phase below 15 K. AC susceptibility measurements revealed the existence of a cluster glass-like state with a freezing temperature of 18 K. The presence of competing magnetic interactions and random occupation of Fe atoms at 2d site leads the system to exhibit a cluster glass state. Furthermore, resistivity measurements indicate that the material exhibits a Kondo-like behavior below 30 K and can be attributed to the interaction of conduction electrons with localized Mn moments.

Synthesis of doped metal sulfide nanoparticles and their graphene reinforced nanohybrid for Pb(II) detection

Abstract This paper explores different techniques to combine and improve the electrochemical sensing activities of the transition metal chalcogenide. The transition metal chalcogenide was doped with a suitable dopant to tune the band structure. Surface-assisted nanotechnology was used to enrich the superficial properties of the doped material. Lastly, the nanostructured doped materials were physically mixed with the graphene nanoplates (GNPs) to improve the flow of charges and the stability of the electrochemistry. The most electrically conductive and common metal sulfides in nature were chosen and prepared using a cheap and easy wet-route method. Crystal structure, chemical functionality, texture, composition, and thermal stability of undoped, doped, and composite materials were determined using physicochemical techniques such as X-ray diffraction, FTIR, SEM, EDX, and TGA. N2-adsorption-desorption, current-voltage, and impedance studies show that the composite sample’s surface area, electrical conductivity, and charge transport properties are superior to those of the undoped and doped samples. Regarding electrochemical applications, the composite material supported a glassy carbon electrode (Co–Cu2S/Gr@GCE) with excellent Pb(II) ion sensing activity. Moreover, the sensitivity, detection, and quantification limits of the modified electrode for Pb(II) detection were computed to be 88.68 μAμMcm−2, 0.091 μM, and 0.30 μM, respectively. The key features developed in the metal sulfide for its enhancement of electrochemical sensing activity are a high surface area, good conductivity, and fast electron transport by adopting nanotechnology, metal doping, and composite formation methodologies. Based on the results of the experiments, we can say that using multiple inputs to integrate the feature we want is an excellent way to make electrochemical systems for the next generation.

Influence of rotational disorder in C60 on electrical conductivity

The rotational order and disorder of C60 molecules in a lattice strongly modulates the density of states at the Fermi level and exerts a large influence on electrical transport. We report herein a study of this influence at high temperatures by employing microwave conductivity and static magnetic susceptibility as the observation probes, focusing on Na2CsC60. Microwave conductivity becomes 30% higher on going from a low-temperature (LT) orientationally ordered phase (space group: Pa-3) to a freely rotational high-temperature (HT) disordered phase (space group: Fm-3m). The density of states at the Fermi level, DEF, evaluated by static magnetic susceptibility measurements, increases from 15.1 states eV−1 C60−1 for the LT ordered phase to 17.4 states eV−1 C60−1 for the HT disordered phase. Both microwave conductivity and magnetic susceptibility show that Na2CsC60 maintains its macroscopic metallicity at least up to 673 K, although local probe NMR studies suggest electron localization in the disordered state at high temperatures. The rotational disorder greatly increases the scattering of conduction electrons. Different temperature evolutions of DEF(Na2CsC60) implied by NMR spectrometry and SQUID magnetometry are discussed.

Large Magnetoresistance of Isolated Domain Walls in La2/3 Sr1/3 MnO3 Nanowires.

Generation, manipulation, and sensing of magnetic domain walls are cornerstones in the design of efficient spintronic devices. Half-metals are amenable for this purpose as large low field magnetoresistance signals can be expected from spin accumulation at spin textures. Among half metals, La1- x Srx MnO3 (LSMO) manganites are considered as promising candidates for their robust half-metallic ground state, Curie temperature above room temperature (Tc = 360 K, for x = 1/3), and chemical stability. Yet domain wall magnetoresistance is poorly understood, with large discrepancies in the reported values and conflicting interpretation of experimental data due to the entanglement of various source of magnetoresistance, namely, spin accumulation, anisotropic magnetoresistance, and colossal magnetoresistance. In this work, the domain wall magnetoresistance is measured in LSMO cross-shape nanowires with single-domain walls nucleated across the current path. Magnetoresistance values above 10% are found to be originating at the spin accumulation caused by the mistracking effect of the spin texture of the domain wall by the conduction electrons. Fundamentally, this result shows the importance on non-adiabatic processes at spin textures despite the strong Hund coupling to the localized t2g electrons of the manganite. These large magnetoresistance values are high enough for encoding and reading magnetic bits in future oxide spintronic sensors.

Electrical properties and parameter analysis of all-solid-state LaZrO/InO electric double-layer transistors

All-solid-state electric double-layer (EDL) thin-film transistors (TFTs) consisting of solution-processed LaZrO gate insulators and sputtered InO channels with thicknesses of 10–200 nm were prepared, and their microstructures and electrical properties were investigated. In addition, mobility, carrier concentration, and their gate-voltage dependence in the InO layer were analyzed during a transistor operation to clarify the electron transport properties. It was confirmed that LaZrO was amorphous and that InO crystallized and had an In2O3 bixbyite structure. The transfer conductance increased with the InO thickness, and its normalized value was maximized (3.6 mS/V) at an InO thickness of 200 nm. The maximum capacitance of LaZrO was 31 μF/cm2, strongly suggesting the formation of an EDL. Solid EDL-TFTs operated stably without deterioration at gate voltages up to 5 V, which usually degrade liquid-electrolyte EDL transistors via electrolysis. Assuming the formation of a 1-nm-thick EDL, the concentration of carrier electrons induced during the transistor operation was estimated to be 1019–1021 cm−3. Moreover, the mobility increased with the InO thickness and reached a maximum value of 68 cm2/(V s) at an InO thickness of 120 nm. The conduction electrons were significantly affected by grain boundary scattering and surface scattering, in addition to scattering within the crystal grain. An increase in the InO thickness, which improved the crystallinity in the crystal grain, reduced the barrier height and the effect of grain boundary scattering.

Electronic density of state in valence fluctuating kondo lattice systems studied by point-contact spectroscopy (Review article)

This article reviews our recent point-contact spectroscopy (PCS) investigation in valence fluctuating Kondo lattice systems, EuNi2P2 and Ge-substituted EuNi2(P0.8Ge0.2)2, and YbPd. A heavy fermion (HF) compound EuNi2P2 exhibits a significant valence fluctuation owing to the intermediate Eu valence of 2.5 + at low temperatures, leading to a strong hybridization between the conduction and f electrons (c–f hybridization). The electronic density of state measurements on EuNi2P2 by using PCS technique reveal that the HF behavior arises from the formation of the indirect hybridization gap with a double-peak structure near the Fermi level due to c–f hybridization. In EuNi2(P0.8Ge0.2)2, the valence fluctuation is suppressed by the Ge substitution, and the separation of the double-peak structure decreases. These suggest that the HF behavior is induced by the valence fluctuation. In YbPd, where two-dimensional (2D) layers of Yb3+ and Yb2.6+ are alternately aligned, a HF-like behavior with a large Sommerfeld coefficient appears at low temperatures in the specific heat. The PCS spectra represent a zero-bias dip structure with an asymmetric background, reproduced by the summation of two Fano curves with two different characteristic temperatures, meaning the formation of two Kondo resonance states for each Yb3+ and Yb2.6+ site. These suggest that a local coherence causes the large Sommerfeld coefficient in the 2D layers of Yb3+, which are screened by the conduction electrons provided by the valence fluctuating Yb2.6+ sites. The observed results indicate that PCS is a powerful technique for examining the variation of electronic DOS in valence fluctuating Kondo lattice systems.

PetaVolts per meter Plasmonics: introducing extreme nanoscience as a route towards scientific frontiers

A new class of plasmons has opened access to unprecedented PetaVolts per meter electromagnetic fields which can transform the paradigm of scientific and technological advances. This includes non-collider searches in fundamental physics in addition to making next generation colliders feasible. PetaVolts per meter plasmonics relies on this new class of plasmons uncovered by our work in the large amplitude limit of collective oscillations of quantum electron gas. This Fermi gas constituted by “free” conduction band electrons is inherent in conductive media endowed with a suitable combination of constituent atoms and ionic lattice structure. As this quantum gas of electrons can be as dense as 1024 cm-3, the coherence limit of plasmonic electromagnetic fields is extended in our model from the classical to the quantum domain, 0.1 √(n 0(1024 cm-3)) PVm-1. Appropriately engineered, structured materials that allow highly tunable material properties also make it possible to overcome disruptive instabilities that dominate the interactions in bulk media. The ultra-high density of conduction electrons and the existence of electronic energy bands engendered by the ionic lattice is only possible due to quantum mechanical effects. Based on this framework, it is critical to address various challenges that underlie PetaVolts per meter plasmonics including stable excitation of plasmons while accounting for their effects on the ionic lattice and the electronic energy band structure over femtosecond timescales. We summarize the challenges and ongoing efforts that set the strategy for the future. Extreme plasmonic fields can shape the future by not only opening the possibility of tens of TeV to multi-PeV center-of-mass-energies but also enabling novel pathways in non-collider HEP. In view of this promise, our efforts are dedicated to realization of the immense potential of PV/m plasmonics and its applications.

Synthesis and spectroscopic investigations of Au(III) seleno-organic complexes

ABSTRACT. Heterocyclic pyridazine continues to attract great interest, mainly arising from a large variety of interesting pharmacological activities, herbicides, insecticides, and fungicides. On the other hand, the current interest in selenium-containing heterocycles is a result of their chemical properties and biological activities. In addition to the many recent publications dealing with the pharmacological potential of a selenium compound, new active formulations are an attractive target for chemical research. 2-((3-cyano-4,6-dimethylpyridin-2-yl)selanyl) acetic acid (pyd-Se), 2-((4-cyano-5,6-diphenylpyridazin-3-yl)selanyl)acetic acid (pydz-Se) and 2-((4,6-dimethyl quinolin-2-yl)selanyl)acetic acid (quin-Se) reacts with gold(III) chloride to produce metal ion complexes of specific composition. These synthesized complexes were characterized by elemental analyses, molar conductivity, FTIR, 1H NMR and transmission electron microscopy (TEM) investigations. The complexes were found to have the formulas [Au(pyd-Se)2]Cl, [Au(pydz-Se)2]Cl and Au(quin-Se)2]Cl, respectively.
 
 KEY WORDS: Au(III), Organoselenium, Complexation, FTIR, 1H NMR, TEM
 Bull. Chem. Soc. Ethiop. 2023, 37(5), 1141-1150. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i5.7

Orbital hybridisation effects in B2 phase Cr doped Co2MnAl

We investigate here the magnetic, transport, local structural and electronic properties of Co2MnCr x Al (x = 0, 0.05, 0.1 and 0.2). Our results show that all the compounds stabilise in B2 phase and are ferromagnets. The results reveal disorder at the structural and magnetic levels. X-ray absorption near edge structure (XANES) analysis reveal signature of antisite disorder between Mn and Al atoms with equal ratio. The electronic structure calculations suggest enhancement in the half metallicity, localisation of electrons at the Fermi level and an increment in density of states with doping. The combined results of electronic structure calculations and XANES studies suggest transfer of electrons to the Co site. The results of high temperature resistivity measurements suggest the conduction electrons are undergoing transition from delocalisation to weak localisation to activated behaviour with Cr doping. The extended x-ray absorption spectroscopic analysis shows that the local structure around Mn atom is different from the global structure as obtained from the x-ray diffraction results. The behaviour of the edge region is in line with the trend as obtained from the compositional analysis. We observe link between the hybridisation of 3d like states at the Mn, Cr sites with that at the Co site and the transport properties. This could help in understanding the unusual decrement in the lattice parameter with doping. These results reveal the role of local structure in understanding the physical properties of such systems.

Investigation of Tungsten‐Based Seleno‐Chevrel Compounds with Different Compositions for Efficient Water Splitting

AbstractThis study investigates the photocatalytic water splitting performance for Chevrel phases with the chemical formula MxMo6Ch8, where M is a metal and Ch is a chalcogen, with x being 0, 1, 2, 3, or 4. Density Functional Theory (DFT) is used to study the Chevrel phases, which includes earth‐abundant elements for this specific study as an essential consideration for photocatalytic water splitting. The electronic properties are calculated for the NiW6Se8 and Ni2W6Se8 compounds with thermodynamical, mechanical, and dynamic stabilities. For photocatalytic water splitting, the band gaps below 1.23 eV are excluded, and the conduction and valence band levels are determined to examine the reduction and oxidation potentials for efficient photocatalytic water‐splitting materials. An examination of the selected band gaps, along with the conduction and valence band levels, reveals that NiW6Se8 is suitable for both reduction and oxidation reactions; whereas, Ni2W6Se8 is a convenient material only for the reduction reaction. This is the first attempt, as far as the literature reveals, to study Chevrel phases in detail and to identify a suitable compound for photocatalytic water splitting.

Evidence of weak itinerant ferromagnetism and Griffiths like phase in MnFeGe

Realizing the itinerant type of magnetic exchange in Mn-based alloys is quite unusual because of the weak hybridization between Mn-moments and conduction electrons. However, in the current study, we found MnFeGe to exhibit weak itinerant type magnetic character possibly arising due to the hybridization between Mn, Fe atoms with Ge atoms. Here, we present a comprehensive structural and magnetic study on polycrystalline MnFeGe. Rietveld refinement of the XRD pattern confirms that Mn and Fe atoms randomly (atomic disorder) occupy the 2a and 2d sites in MnFeGe. From the magnetic measurements, Curie temperature and saturation moment values are found to be 162 K and 1.58 at 2 K, respectively. The relative low values of Curie temperature, saturation magnetic moment, and a large value of Rhodes–Wohlfarth ratio (∼3.4) indicate the weak itinerant ferromagnetic character of the system. The Takahashi spin fluctuation theory analysis further supports the weak itinerant ferromagnetism in MnFeGe. Besides, we also observed Griffiths phase (GP) like behavior above the Curie temperature, which is attributed to the presence of atomic disorder in the system. The presence of GP is further confirmed by the zero spontaneous magnetization. Our findings demonstrate that MnFeGe is one of the very few Mn-based systems with weak itinerant magnetic behavior.

Управление динамикой спиновой поляризации электронов проводимости электрическим и механическим воздействием

A quantum model for the interaction of a collectivized conduction electron with a crystal field in a homogeneous and isotropic deformed polycrystalline sample, taking into account the spin-orbit interaction, is proposed. A dynamic equation of motion of the conduction electron spin in a stress-strained metal is obtained. It is shown that under conditions of inhomogeneous torsion in the stationary case, the average spin of conduction electrons is oriented predominantly along the current density vector. The maximum value of the spin-orbit interaction is observed when the torsion axis is orthogonal to the current density vector.