12044-16-5Relevant articles and documents
Superconductivity in CeO1-xFxFeAs with upper critical field of 94 T
Prakash,Singh,Patnaik,Ganguli
, p. 82 - 85 (2009)
We have successfully synthesized Ce based oxypnictide superconductors with fluorine doping (CeO1-xFxFeAs) by a two step solid state reaction method. Detailed XRD and EDX confirm the crystal structure and chemical compositions. We obs
Next-nearest neighbour contributions to the XPS binding energies and XANES absorption energies of P and As in transition-metal arsenide phosphides MAs 1-yPy having the MnP-type structure
Grosvenor, Andrew P.,Cavell, Ronald G.,Mar, Arthur
, p. 2549 - 2558 (2008)
X-ray photoeleetron spectroscopic (XPS) and X-ray absorption near-edge spectroscopic (XANES) measurements have been made for several series of metal arsenide phosphides MAs1-yPy, (M= Co, Fe, Cr) that adopt the MnP-type structure. The P and As XPS binding energies (BEs) and XANES absorption energies of the metal arsenide phosphides do not follow the trend observed for the simple binary phosphides or arsenides, a deviation that arises from the combination of nearest and nextnearest neighbour contributions acting on the P or As photoemission or absorption site. The P 2p3/2 BEs and K-edge absorption energies are lower in MAs1-yPy than in MP because the P atoms are more negatively charged and because the P photoemission or absorption site is screened to a greater extent by less positively charged nearest-neighbour M atoms and more negatively charged next-nearest neighbour P atoms. The As L3- and K-edge absorption energies are higher in MAs1-yPy than in MAs primarily because the As atoms are less negatively charged. The M charge has been evaluated from analysis of the M 2p XPS spectra and the M L- and K-edge XANES spectra.
The synthesis and characterization of LiFeAs and NaFeAs
Chu,Chen,Gooch,Guloy,Lorenz,Lv,Sasmal,Tang,Tapp,Xue
, p. 326 - 331 (2009)
The newest homologous series of superconducting Fe-pnictides, LiFeAs (Li111) and NaFeAs (Na111) have been synthesized and investigated. Both crystallize with the layered tetragonal anti-PbFCl-type structure in P4/nmm space group. Polycrystalline samples a
A safe low temperature route to nanocrystalline transition metal arsenides
Xie, Yi,Lu, Jun,Yan, Ping,Jiang, Xuchuan,Qian, Yitai
, p. 114 - 115 (2000)
Nanocrystalline FeAs, CoAs and NiAs were prepared by keeping the mixture of FeCl3, CoCl2 or NiCl2 with arsenic and KBH4 in ethylenediamine (en) at 100 °C for 4 h, respectively. X-Ray powder diffraction (XRD) patterns and transmission electron microscope (TEM) images show that the products are orthorhombic FeAs, CoAs and hexagonal NiAs, respectively, and all are well crystalline in nanometers.
Doping dependence of magnetic and transport properties in single crystalline Co-doped BaFe2As2
Nakajima, Yasuyuki,Taen, Toshihiro,Tamegai, Tsuyoshi
, p. S408-S410 (2010)
We report the doping dependence of transport and magnetic properties in Co-doped BaFe2As2. With increasing Co concentration x, structural and magnetic transitions are suppressed and superconductivity emerges in the range of 0.3c at low temperatures and low fields obtained from bulk magnetization is reasonably large and the doping dependence shows a maximum at x～0.07 similar to Tc. The values of Jc at low temperatures reach about 1×106A/cm2 around the optimally doped region, which is potentially attractive for technological applications.
Magnetic characterization of undoped and 15%F-doped LaFeAsO and SmFeAsO compounds
Cimberle,Canepa,Ferretti,Martinelli,Palenzona,Siri,Tarantini,Tropeano,Ferdeghini
, p. 3024 - 3030 (2009)
In this paper, the magnetic behavior of undoped and 15%F-doped SmFeAsO (Sm-1111) and LaFeAsO (La-1111) samples is presented and discussed. Magnetization measurements are not a simple tool to use for the characterization of the new family of Fe-based super
Effects of simultaneous carrier doping in the charge reservoir and conducting layers of superconducting CeO0.9F0.1Fe 1-xCoxAs
Singh,Prakash,Patnaik,Ganguli
, p. 1928 - 1932 (2010)
Electron-doping of the semimetal (CeOFeAs) by either fluorine (max T c ～ 43 K) or cobalt (max Tc ～ 11 K) leads to superconductivity. Here we show the effect of transition metal (Co) substitution at the iron site on the superconducting properties of CeO0.9F 0.1FeAs (Tc ～ 38 K) to understand the interplay of charge carriers in both the rare earth-oxygen and Fe-As layers. Simultaneous doping of equivalent number of charge carriers in both layers leads to a T c of 9.8 K which is lower than the Tc obtained when either the conducting layer (FeAs) or charge reservoir layer (CeO) is individually doped. This suggests a clear interplay between the two layers to control the superconductivity. Resistivity upturn and negative magnetoresistance are observed with Co doping that is interpreted in the gamut of Kondo effect. Hall coefficient and thermoelectric power indicate increased carrier concentration with cobalt doping in CeO0.9F0.1FeAs. The rf penetration depth both for CeO0.9F0.1Fe0.95Co 0.05As and CeO0.9F0.1FeAs show an exponential temperature dependence with gap values of ～1.6 and 1.9 meV respectively.
Compositionally controlled semimetal to superconducting transition in NaF doped LaOFeAs: Enhancement in Tc due to Na-doping
Prakash,Singh,Ahmed,Patnaik,Ganguli
, p. 300 - 304 (2009)
We report the synthesis of LaOFeAs based oxypnictide superconductors (La1-xNaxO1-xFxFeAs) using sodium fluoride as a fluorinating agent. NaF doping leads to a systematic decrease in both the a and c lattice para
Synthesis of Nanocrystalline Iron Monoarsenide via a Reductive Recombination Pathway
Zhang,Wang,Qian,Xie,Qian
, p. 237 - 239 (1999)
Nanocrystalline FeAs was prepared with FeCl3and AsCl3as the reactants and Zn as reductant via a reductive recombination pathway in the temperature range of 150-180°C. The XRD pattern indicated the products were the single phase of iron monoarsenide. A TEM image showed the average size of the FeAs was about 20 nm. XPS gave the ratio of Fe to As 50.9:49.1. The influence of reactions and the possible reaction route of the formation of iron monoarsenide are discussed.
The superconductivity at 18 K in LiFeAs system
Wang,Liu,Lv,Gao,Yang,Yu,Li,Jin
, p. 538 - 540 (2008)
The recent discovery of superconductivity in iron arsenide compounds RFeAsO (R=rare?earth) or AFe2As2 (A=alkaline?earth) has attracted great attention due to the unexpected high Tc in the system containing ferromagnetic elements like Fe. Similar to high Tc cuprates, the superconductivity in iron arsenide is related to a layered structure. Searching for new superconductors with [FeAs] layer, but of simpler structure will be of scientific significance either to build up new multilayered superconductors that may reach higher Tc or to study the mysterious underlined superconducting mechanism in iron arsenide compounds. Here we report that a new superconducting iron arsenide system LiFeAs was found. The compound crystallizes into a structure containing [FeAs] conducting layer that is interlaced with Li charge reservoir. Superconductivity was observed with Tc up to 18 K in the compounds.
Moessbauer study of iron-arsenic compounds
Yuzuri, Motoyoshi,Tahara, Ryoichi,Nakamura, Yoji
, p. 1937 - 1941 (1980)
The magnetic properties of the iron-arsenic compounds Fe2As, FeAs and FeAs2 have been studied with the Moessbauer effect of 57Fe. Fe2As has a Neel temperature of 353K and its magnetic moments align perpendicularly to the c-axis. These results are in agreement with the neutron diffraction measurements. The temperature variations of both the quadrupole interaction and the isomer shift suggest the onset of a second-order magnetic transition at the Neel temperature. FaAs 2 shows a doublet associated with quadrupole interactions at 5 K, leading to no magnetic ordering even at low temperatures. The broad absorption spectrum of FeAs at 5K indicates a magnetic ordering at low temperatures.
Superconductivity in PT doped BaFe2As2
Guo, Yanfeng,Wang, Xi,Li, Ju,Zhang, Shouba,Yamaura, Kazunar,Takayama-Muromachi, Eiji
, (2012)
A high-pressure method was used to systematically dope an antiferromagnetically metallic compound, BaFe2As2, with Pt, and the doped compounds were studied using X-ray diffraction, energy dispersive X-ray spectroscopy, and by measuring the electrical resistivity, magnetic susceptibility, and specific heat. This method significantly increased the Pt doping level for BaFe2As2, resulting in a revision of the phase diagram proposed for BaFe2-xMxAs2. The Pt doped system showed a dome-like superconductivity region in the thermal phase diagram (0:022-xMxAs2 (M = Co, Ni, Rh, or Pd), was confirmed for the 5d doped system, BaFe2-xM xAs2, which suggested that the electron-phonon coupling was insignificant at the superconducting state.
Study of the Structure and the Stability Conditions of a New Iron Arsenide: Fe12As5.
Maaref,Madar
, p. 473 - 480 (1983)
The crystal structure determination of the new phase Fe//1//2As//5 carried on the isostructural phase (RuFe)//1//2As//5 gives a rhombohedral cell with the space group R3. The metallic atoms are, on the one hand, inserted in square pyramidal and triangular bipyramidal sites and, on the other hand, gathered in a metallic bipyramidal cluster. This description makes clear the relation to the structures of M//2X and M//3X phases. This new structural type appears as an intermediate case resulting from an increase in metallic interactions, leading to the formation of metallic clusters.
Yttrium doped La1-xYxO0.9F0.1FeAs superconductors: Hall and thermopower studies
Singh,Prakash,Patnaik,Ganguli
, p. 511 - 515 (2010)
The effect of yttrium substitution at the lanthanum site on the superconducting properties of La1-xYxO0.9F0.1FeAs ('x' = 0, 0.10, 0.20, 0.30, 0.50 and 0.60) oxypnictides has been studied. Powder X-ray diffractio
Rare earth (RE - Ce, Gd) modified Nd1-xRExFeAsO0.7F0.3 superconductor with enhanced magneto-transport properties
Aswathy,Anooja,Varghese, Neson,Chandrakanth,Devendra Kumar,Sundaresan,Syamaprasad
, p. 41484 - 41492 (2015/05/27)
The influence of rare earth (RE - Ce, Gd) doping at the Nd site in the NdFeAsO0.7F0.3 superconductor wherein Ce and Gd have ionic radii in the order Ce > Nd > Gd is investigated. The structural and superconductivity characterization of the pure and doped samples show that Ce doping enhances the TC of Nd1-xRExFeAsO0.7F0.3 to a maximum of 53.6 K at x = 0.1 while Gd doping attains a TC of 55.1 K at x = 0.15. Interestingly, both Ce and Gd doping create neither secondary phases nor precipitates within the detection limit of XRD. However, the lattice defects due to Ce and Gd doping modifies NdFeAsO0.7F0.3 and assists in pinning the flux lines on these defects thereby exhibiting an enhanced JC(H) performance especially at high fields. It is also observed that the relatively small ionic size of Gd is more effective in TC enhancement, while the lattice defects due to larger ionic size of Ce favor the remarkable enhancement of JC(H).
