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Journal ArticleDOI

Synthesis and physical properties of oxygen adsorbed YbFe 2 As 2

29 Aug 2017-Vol. 4, Iss: 8, pp 086101
About: The article was published on 2017-08-29. It has received 3 citations till now. The article focuses on the topics: Oxygen.
Citations
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TL;DR: In this paper, the presence of oxygen on the surfaces of flux grown BaFe2As2 single crystals which were kept in air ambience for several months was found by Energy Dispersive X-ray Analysis (EDAX).
Abstract: Presence of Oxygen (O2) has been found by Energy Dispersive X-ray Analysis (EDAX) on the surfaces of flux grown BaFe2As2 single crystals which were kept in air ambience for several months. Transport studies show that the O2 adsorbed crystals are more resistive and do not display any sharp slope change near 140 K which is the well known Spin Density Wave (SDW) transition temperature (TSDW) accompanying structural transition for as grown BaFe2As2. An anomalous slope change in resistivity is observed around 18 K at 0 and 5T. Magnetoresistance (MR) is noticed to increase as a function of applied field (H) quite differently than that for as grown crystals below TSDW which may be attributed to aging effec

5 citations

Journal ArticleDOI
TL;DR: In this article, a double-step solid-state reaction method was used to synthesize polycrystalline samples of YbFe2As2 by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive Xray analysis (EDAX), and Xray photoelectron spectroscopy (XPS).
Abstract: Polycrystalline samples of YbFe2As2 were synthesized by double step solid-state reaction method. Two different samples were grown at the temperatures of 900 and 1200 °C. The synthesized YbFe2As2 polycrystalline samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX) and X-ray photoelectron spectroscopy (XPS). SEM images revealed that the YbFe2As2 compound was formed as polycrystalline with typical sizes of granules ranging from 5 to 10 μm. The Rietveld refinement of the XRD data of YbFe2As2 crystals was performed to understand the structural phase. The oxygen adsorption in to the surface of YbFe2As2 crystals was studied by means of XPS analysis. A possible explanation was given for the synthesis temperature dependent oxygen adsorption in to the YbFe2As2 based on the results of XPS, EDAX and resistance versus temperature measurements.

4 citations

Journal ArticleDOI
01 Jan 2022
TL;DR: In this article , the scaling analysis of magnetoresistance has been carried out and the verification of Kohler's rule has been explored in YbFe 2 As 2 crystal is found that satisfies an unusual scaling relationship between applied magnetic field and temperature within limited temperature range.
Abstract: Study of normal-state behaviour of YbFe 2 As 2 single crystals has been reported through transport, specific heat and magnetotransport measurements. The YbFe 2 As 2 crystals have been synthesized by using melt growth aided method. It is found that Sommerfeld coefficient (γ = 213.16 mJ mol −1 K −1 ) is strongly enhanced suggesting existence of heavy quasiparticles. Analysis of resistivity data at low temperature yields Fermi-liquid co-efficient (A) value of 5.47 × 10 −5 Ω cm K −2 . Evaluation of Kadowaki-Woods ratio ( A/γ 2 = 1.204 × 10 −5 μΩ cm mole 2 mJ −2 ) indicates that the YbFe 2 As 2 crystal is a strongly correlated metal. The scaling analysis of magnetoresistance (MR) has been carried out. We have observed from MR results that YbFe 2 As 2 show quadratic behaviour on magnetic field up to 5 T and beyond that it shows linear nature. Additionally, the verification of Kohler's rule has been explored. The measurement of MR as a function of magnetic field (B) up to 8 T indicates that Kohler's rule is not satisfied in YbFe 2 As 2 . However, it is found that YbFe 2 As 2 satisfies an unusual scaling relationship between applied magnetic field and temperature within limited temperature range, which was reported in other iron-based superconductors recently. • YbFe 2 As 2 crystals were synthesized by high temperature melt growth. • The scaling analysis of magnetoresistance were carried out. • The verification of Kohler's rule has been explored. • Evaluation of Kadowaki-Woods ratio indicates that the YbFe 2 As 2 crystal is a strongly correlated metal.
References
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Journal ArticleDOI
TL;DR: A review of the metal-insulator transition can be found in this article, where a pedagogical introduction to the subject is given, as well as a comparison between experimental results and theoretical achievements.
Abstract: Metal-insulator transitions are accompanied by huge resistivity changes, even over tens of orders of magnitude, and are widely observed in condensed-matter systems. This article presents the observations and current understanding of the metal-insulator transition with a pedagogical introduction to the subject. Especially important are the transitions driven by correlation effects associated with the electron-electron interaction. The insulating phase caused by the correlation effects is categorized as the Mott Insulator. Near the transition point the metallic state shows fluctuations and orderings in the spin, charge, and orbital degrees of freedom. The properties of these metals are frequently quite different from those of ordinary metals, as measured by transport, optical, and magnetic probes. The review first describes theoretical approaches to the unusual metallic states and to the metal-insulator transition. The Fermi-liquid theory treats the correlations that can be adiabatically connected with the noninteracting picture. Strong-coupling models that do not require Fermi-liquid behavior have also been developed. Much work has also been done on the scaling theory of the transition. A central issue for this review is the evaluation of these approaches in simple theoretical systems such as the Hubbard model and $t\ensuremath{-}J$ models. Another key issue is strong competition among various orderings as in the interplay of spin and orbital fluctuations. Experimentally, the unusual properties of the metallic state near the insulating transition have been most extensively studied in $d$-electron systems. In particular, there is revived interest in transition-metal oxides, motivated by the epoch-making findings of high-temperature superconductivity in cuprates and colossal magnetoresistance in manganites. The article reviews the rich phenomena of anomalous metallicity, taking as examples Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Ru compounds. The diverse phenomena include strong spin and orbital fluctuations, mass renormalization effects, incoherence of charge dynamics, and phase transitions under control of key parameters such as band filling, bandwidth, and dimensionality. These parameters are experimentally varied by doping, pressure, chemical composition, and magnetic fields. Much of the observed behavior can be described by the current theory. Open questions and future problems are also extracted from comparison between experimental results and theoretical achievements.

5,781 citations

Journal ArticleDOI
TL;DR: A detailed review of the superconductivity of FePnictide and chalcogenide (FePn/Ch) superconductors can be found in this paper.
Abstract: Kamihara and coworkers' report of superconductivity at ${T}_{c}=26\text{ }\text{ }\mathrm{K}$ in fluorine-doped LaFeAsO inspired a worldwide effort to understand the nature of the superconductivity in this new class of compounds. These iron pnictide and chalcogenide (FePn/Ch) superconductors have Fe electrons at the Fermi surface, plus an unusual Fermiology that can change rapidly with doping, which lead to normal and superconducting state properties very different from those in standard electron-phonon coupled ``conventional'' superconductors. Clearly, superconductivity and magnetism or magnetic fluctuations are intimately related in the FePn/Ch, and even coexist in some. Open questions, including the superconducting nodal structure in a number of compounds, abound and are often dependent on improved sample quality for their solution. With ${T}_{c}$ values up to 56 K, the six distinct Fe-containing superconducting structures exhibit complex but often comparable behaviors. The search for correlations and explanations in this fascinating field of research would benefit from an organization of the large, seemingly disparate data set. This review provides an overview, using numerous references, with a focus on the materials and their superconductivity.

1,349 citations

Journal ArticleDOI
TL;DR: The surprising discovery of high-temperature superconductivity in a material containing a strong magnet (iron) has led to thousands of publications as discussed by the authors, and it becomes clear what we know and where we are headed.
Abstract: The surprising discovery of high-temperature superconductivity in a material containing a strong magnet—iron—has led to thousands of publications. By placing all the data in context, it becomes clear what we know and where we are headed.

1,224 citations

Journal ArticleDOI
TL;DR: This is the first example of superconductivity induced by electron doping in this family of materials, and in contrast with cuprates, the BaFe2As2 system appears to tolerate considerable disorder in the FeAs planes.
Abstract: Here we report bulk superconductivity in ${\mathrm{BaFe}}_{1.8}{\mathrm{Co}}_{0.2}{\mathrm{As}}_{2}$ single crystals below ${T}_{c}=22\text{ }\text{ }\mathrm{K}$, as demonstrated by resistivity, magnetic susceptibility, and specific heat data. Hall data indicate that the dominant carriers are electrons, as expected from simple chemical reasoning. This is the first example of superconductivity induced by electron doping in this family of materials. In contrast with cuprates, the ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$ system appears to tolerate considerable disorder in the FeAs planes. First principles calculations for ${\mathrm{BaFe}}_{1.8}{\mathrm{Co}}_{0.2}{\mathrm{As}}_{2}$ indicate the interband scattering due to Co is weak.

855 citations

Journal ArticleDOI
TL;DR: In this paper, simultaneous measurements of conductance and work function changes induced by gaseous ambient have been performed on α-Fe2O3 thick film polycrystalline samples.
Abstract: The simultaneous measurements of conductance and work function changes induced by gaseous ambient have been performed on α-Fe2O3 thick film polycrystalline samples kept at 280 °C and exposed to different gaseous atmospheres. The switching from n- to p-type conductivity on α-Fe2O3 is shown to have an electronic origin, which is due to the oxygen adsorption and formation of a surface inversion layer and, therefore, to the inversion of the surface conduction type. The modeling of the n–p switching is described in terms of conductance dependence on the band bending induced by gaseous ambient.

156 citations