Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Cu1-x Fe x O: hopping transport and ferromagnetism.

ABSTRACT: Single phase, sol-gel prepared Cu1-x Fe x O (0???x???0.125) powders are characterized in terms of structural, electronic and magnetic properties. Using dielectric and magnetic studies we investigate the coupling of electron and spin. The electrical conductivities and activation energies are studied with increasing Fe content. Modelling of experimental conductivity data emphasizes a single hopping mechanism for all samples except x?=?0.125, which have two activation energies. Hole doping is confirmed by confirming a majority Fe3+ substitution of Cu2+ in CuO from X-ray photoelectron spectroscopy studies (XPS). Such a substitution results in stabilized ferromagnetism. Fe substitution introduces variation in coercivity as an intrinsic magnetic property in Fe-doped CuO, and not as a secondary impurity phase.

SUBMITTER: Nasir M

PROVIDER: S-EPMC5627081 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Cu1-x Fe x O: hopping transport and ferromagnetism.

Nasir Mohd M Islam Rakibul R Ahmed Md A MA Ayaz Saniya S Kumar Gautham G Kumar Sunil S Prajapat C L CL Roussel Frederick F Biring Sajal S Sen Somaditya S

Royal Society open science 20170913 9

Single phase, sol-gel prepared Cu1-x Fe x O (0 ≤ x ≤ 0.125) powders are characterized in terms of structural, electronic and magnetic properties. Using dielectric and magnetic studies we investigate the coupling of electron and spin. The electrical conductivities and activation energies are studied with increasing Fe content. Modelling of experimental conductivity data emphasizes a single hopping mechanism for all samples except x = 0.125, which ...[more]

PMID: 28989741

Similar Datasets

Strain-induced extrinsic high-temperature ferromagnetism in the Fe-doped hexagonal barium titanate.

Project description:Diluted magnetic semiconductors possessing intrinsic static magnetism at high temperatures represent a promising class of multifunctional materials with high application potential in spintronics and magneto-optics. In the hexagonal Fe-doped diluted magnetic oxide, 6H-BaTiO3-δ, room-temperature ferromagnetism has been previously reported. Ferromagnetism is broadly accepted as an intrinsic property of this material, despite its unusual dependence on doping concentration and processing conditions. However, the here reported combination of bulk magnetization and complementary in-depth local-probe electron spin resonance and muon spin relaxation measurements, challenges this conjecture. While a ferromagnetic transition occurs around 700 K, it does so only in additionally annealed samples and is accompanied by an extremely small average value of the ordered magnetic moment. Furthermore, several additional magnetic instabilities are detected at lower temperatures. These coincide with electronic instabilities of the Fe-doped 3C-BaTiO3-δ pseudocubic polymorph. Moreover, the distribution of iron dopants with frozen magnetic moments is found to be non-uniform. Our results demonstrate that the intricate static magnetism of the hexagonal phase is not intrinsic, but rather stems from sparse strain-induced pseudocubic regions. We point out the vital role of internal strain in establishing defect ferromagnetism in systems with competing structural phases.

| S-EPMC4287748 | biostudies-other

The dramatic enhancement of ferromagnetism and band gap in Fe-doped In2O3 nanodot arrays.

Project description:Ordered Fe-doped In2O3 nanodot arrays with diameters between 35?nm and 80?nm are fabricated using pulsed laser deposition with the aid of ultrathin porous anodized aluminumoxide templates. The 5?at.% Fe doped In2O3 nanodot arrays are shown to consist of the cubic bixbyite structure of In2O3. The nanodot arrays are demonstrated to be doped by Fe ions with mixed valences of?+2 and?+3, ruling out the presence of cluster and secondary phase related to Fe. The nanodot arrays exhibit the ferromagnetism at room temperature, where the magnetic moment increases as the dot size is reduced, rising to a maximum of about 230?emu/cm3 (equivalent to an average moment on the Fe ions of 15.30 µB/Fe). This indicates an effect due to the surface of the nanodot arrays. The optical band width is also increased to 4.55?eV for the smallest dot array, thus indicating that the surface states are responsible for the magnetism and also enhance the band gap due to Burstein-Moss effect. Our results will be benefit for understanding the physical properties of oxide semiconductor nanostructures in the application of nano-spintronics devices.

| S-EPMC5799379 | biostudies-other

Spin-Dependent Transport in Fe/GaAs(100)/Fe Vertical Spin-Valves.

Project description:The integration of magnetic materials with semiconductors will lead to the development of the next spintronics devices such as spin field effect transistor (SFET), which is capable of both data storage and processing. While the fabrication and transport studies of lateral SFET have attracted greatly attentions, there are only few studies of vertical devices, which may offer the opportunity for the future three-dimensional integration. Here, we provide evidence of two-terminal electrical spin injection and detection in Fe/GaAs/Fe vertical spin-valves (SVs) with the GaAs layer of 50?nanometers thick and top and bottom Fe electrodes deposited by molecular beam epitaxy. The spin-valve effect, which corresponds to the individual switching of the top and bottom Fe layers, is bias dependent and observed up to 20?K. We propose that the strongly bias- and temperature-dependent MR is associated with spin transport at the interfacial Fe/GaAs Schottky contacts and in the GaAs membranes, where balance between the barrier profiles as well as the dwell time to spin lifetime ratio are crucial factors for determining the device operations. The demonstration of the fabrication and spin injection in the vertical SV with a semiconductor interlayer is expected to open a new avenue in exploring the SFET.

| S-EPMC4949422 | biostudies-literature

Microscopic Insights into Cation-Coupled Electron Hopping Transport in a Metal-Organic Framework.

Project description:Electron transport through metal-organic frameworks by a hopping mechanism between discrete redox active sites is coupled to diffusion-migration of charge-balancing counter cations. Experimentally determined apparent diffusion coefficients, Deapp, that characterize this form of charge transport thus contain contributions from both processes. While this is well established for MOFs, microscopic descriptions of this process are largely lacking. Herein, we systematically lay out different scenarios for cation-coupled electron transfer processes that are at the heart of charge diffusion through MOFs. Through systematic variations of solvents and electrolyte cations, it is shown that the Deapp for charge migration through a PIZOF-type MOF, Zr(dcphOH-NDI) that is composed of redox-active naphthalenediimide (NDI) linkers, spans over 2 orders of magnitude. More importantly, however, the microscopic mechanisms for cation-coupled electron propagation are contingent on differing factors depending on the size of the cation and its propensity to engage in ion pairs with reduced linkers, either non-specifically or in defined structural arrangements. Based on computations and in agreement with experimental results, we show that ion pairing generally has an adverse effect on cation transport, thereby slowing down charge transport. In Zr(dcphOH-NDI), however, specific cation-linker interactions can open pathways for concerted cation-coupled electron transfer processes that can outcompete limitations from reduced cation flux.

| S-EPMC8990995 | biostudies-literature

Extremely Non-Equilibrium Hopping Transport and Photogeneration Efficiency in Organic Semiconductors: An Analytic Approach.

Project description:An analytical model of highly nonequilibrium hopping transport of charge carriers in disordered organic semiconductors has been developed. In particular, the initial time interval is considered when transport is controlled by hops down in energy. The model is applied to the calculation of the separation probability of geminate pairs in a semiconductor with a Gaussian energy distribution of localized states. This probability determines the photogeneration efficiency. The temperature dependence of the separation probability is obtained and shown to be much weaker than predicted by the classical Onsager model, in agreement with experiment and Monte Carlo simulations. The field dependence is taken into account using a modified effective temperature method.

| S-EPMC11017315 | biostudies-literature

Nature of charge transport and p-electron ferromagnetism in nitrogen-doped ZrO2: an ab initio perspective.

Project description:Zirconium dioxide provides an exceptional prototype material for studying the redistribution of the polaron holes and its magnetic coupling with their nearby anions owning to the difference oxygen binding behavior in the monoclinic phase. Here, we perform a comprehensive study of the p-electron magnetism in the nitrogen doped 2 × 2 × 2 monoclinic ZrO2 based on spin-polarized density functional theory. Nitrogen substitutions make the system display half-metallic properties, and the origin of room temperature ferromagnetism ascribes to the p-p coupling interaction between N 2p and the host 2p states. The charge density difference and Mülliken population analyses provide evidences of charge redistributions. Our results reveal that the polaron transfer may alter the magnetic properties and it is greatly facilitated ferromagnetic coupling if the polaron holes are localized around a single anion dopant.

| S-EPMC4341218 | biostudies-literature

Unusual Electrical Transport Driven by the Competition between Antiferromagnetism and Ferromagnetism in Antiperovskite Mn₃Zn1-xCoxN.

Project description:The magnetic, electrical transport and thermal expansion properties of Mn₃Zn1-xCoxN (x = 0.2, 0.4, 0.5, 0.7, 0.9) have been systematically investigated. Co-doping in Mn₃ZnN complicates the magnetic interactions, leading to a competition between antiferromagnetism and ferromagnetism. Abrupt resistivity jump phenomenon and negative thermal expansion behavior, both associated with the complex magnetic transition, are revealed in all studied cases. Furthermore, semiconductor-like transport behavior is found in sample x = 0.7, distinct from the metallic behavior in other samples. Below 50 K, resistivity minimum is observed in samples x = 0.4, 0.7, and 0.9, mainly caused by e-e scattering mechanism. We finally discussed the strong correlation among unusual electrical transport, negative thermal expansion and magnetic transition in Mn₃Zn1-xCoxN, which allows us to conclude that the observed unusual electrical transport properties are attributed to the shift of the Fermi energy surface entailed by the abrupt lattice contraction.

| S-EPMC5848983 | biostudies-literature

Comparing data driven and physics inspired models for hopping transport in organic field effect transistors.

Project description:The past few decades have seen an uptick in the scope and range of device applications of organic semiconductors, such as organic field-effect transistors, organic photovoltaics and light-emitting diodes. Several researchers have studied electrical transport in these materials and proposed physical models to describe charge transport with different material parameters, with most disordered semiconductors exhibiting hopping transport. However, there exists a lack of a consensus among the different models to describe hopping transport accurately and uniformly. In this work, we first evaluate the efficacy of using a purely data-driven approach, i.e., symbolic regression, in unravelling the relationship between the measured field-effect mobility and the controllable inputs of temperature and gate voltage. While the regressor is able to capture the scaled mobility well with mean absolute error (MAE) ~ O(10-2), better than the traditionally used hopping transport model, it is unable to derive physically interpretable input-output relationships. We then examine a physics-inspired renormalization approach to describe the scaled mobility with respect to a scale-invariant reference temperature. We observe that the renormalization approach offers more generality and interpretability with a MAE of the ~ O(10-1), still better than the traditionally used hopping model, but less accurate as compared to the symbolic regression approach. Our work shows that physics-based approaches are powerful compared to purely data-driven modelling, providing an intuitive understanding of data with extrapolative ability.

| S-EPMC8654921 | biostudies-literature

Globe-hopping.

Project description:We consider versions of the grasshopper problem (Goulko & Kent 2017 Proc. R. Soc. A 473, 20170494) on the circle and the sphere, which are relevant to Bell inequalities. For a circle of circumference 2π, we show that for unconstrained lawns of any length and arbitrary jump lengths, the supremum of the probability for the grasshopper's jump to stay on the lawn is one. For antipodal lawns, which by definition contain precisely one of each pair of opposite points and have length π, we show this is true except when the jump length ϕ is of the form π(p/q) with p, q coprime and p odd. For these jump lengths, we show the optimal probability is 1 - 1/q and construct optimal lawns. For a pair of antipodal lawns, we show that the optimal probability of jumping from one onto the other is 1 - 1/q for p, q coprime, p odd and q even, and one in all other cases. For an antipodal lawn on the sphere, it is known (Kent & Pitalúa-García 2014 Phys. Rev. A 90, 062124) that if ϕ = π/q, where q∈N , then the optimal retention probability of 1 - 1/q for the grasshopper's jump is provided by a hemispherical lawn. We show that in all other cases where 0 < ϕ < π/2, hemispherical lawns are not optimal, disproving the hemispherical colouring maximality hypotheses (Kent & Pitalúa-García 2014 Phys. Rev. A 90, 062124). We discuss the implications for Bell experiments and related cryptographic tests.

| S-EPMC7428041 | biostudies-literature

Magnetic critical behavior of the van der Waals Fe5GeTe2 crystal with near room temperature ferromagnetism.

Project description:The van der Waals ferromagnet Fe5GeTe2 has a Curie temperature TC of about 270 K, which is tunable through controlling the Fe deficiency content and can even reach above room temperature. To achieve insights into its ferromagnetic exchange that gives the high TC, the critical behavior has been investigated by measuring the magnetization in Fe5GeTe2 crystal around the ferromagnetic ordering temperature. The analysis of the measured magnetization by using various techniques harmonically reached to a set of reliable critical exponents with TC = 273.7 K, β = 0.3457 ± 0.001, γ = 1.40617 ± 0.003, and δ = 5.021 ± 0.001. By comparing these critical exponents with those predicted by various models, it seems that the magnetic properties of Fe5GeTe2 could be interpreted by a three-dimensional magnetic exchange with the exchange distance decaying as J(r) ≈ r-4.916, close to that of a three-dimensional Heisenberg model with long-range magnetic coupling.

| S-EPMC7501290 | biostudies-literature