In: Physical Review Letters, 2010, vol. 105, no. 5, p. 057001
We report muon spin rotation (μSR) and infrared spectroscopy experiments on underdoped BaFe1.89Co0.11As₂ which show that bulk magnetism and superconductivity (SC) coexist and compete on the nanometer length scale. Our combined data reveal a bulk magnetic order, likely due to an incommensurate spin density wave (SDW), which develops below Tmag≈32 K and...
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In: Superconductor Science and Technology, 2010, vol. 23, no. 4, p. 045005
Carbon (C) and rare earth oxide (REO) co-doped bulk polycrystalline MgB₂ samples with nominal compositions Mg1 − y(REO)y(B0.95C0.05)₂ (where y = 0.00, 0.01, 0.03, 0.05 and REO = Eu₂O₃ or Pr₆O₁₁) have been synthesized via a solid state reaction route. The XRD results reveal the presence of impurity phases EuB₆ in...
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In: Physical Review Letters, 2010, vol. 104, no. 3, p. 036401
We report spectroscopic ellipsometry measurements of the anisotropy of the interband transitions parallel and perpendicular to the planes of (LaTiO₃)n(LaAlO₃)5 multilayers with n=1–3. These provide direct information about the electronic structure of the two-dimensional (2D) 3d¹ state of the Ti ions. In combination with local density approximation, including a Hubbard U calculation, we...
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In: Physica C: Superconductivity, 2010, p. -
The low-temperature spectra of the c-axis infrared conductivity of bilayer high-Tc cuprate superconductors (HTCS) exhibit two superconductivity-induced modes [Li Yu et al., Phys. Rev. Lett. 100 (2008) 177004; and references therein]. Both can be understood in terms of a microscopic theory developed recently [J. Chaloupka, C. Bernhard, D. Munzar, Phys. Rev. B 79 (2009) 184513]. Here we summarize...
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In: Superconductor Science and Technology, 2009, vol. 22, no. 12, p. 125014
In this paper we report the effect of carbon doping on the structural and superconducting properties of MgB₂ using citric and oxalic acids as carbon sources. The bulk polycrystalline samples have been synthesized via a standard solid state reaction route with composition MgB₂+x wt% of citric and oxalic acids (x = 0, 5 and 10). The x-ray diffraction results reveal the formation...
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In: Physica Status Solidi (a), 2009///doi-10.1002/pssa.200925180
In this paper we report the effect of Pr6O11 doping on the structural and superconducting properties of MgB2. The bulk samples of Pr6O11-doped MgB2 have been prepared with nominal compositions Mg1-x(Pr6O11)x/6B2 (where x = 0.0, 0.01, 0.02, 0.03, 0.04, and 0.05) via a standard solid-state reaction route by sintering in a reducing atmosphere of Ar/H2. The superconducting transition temperature Tc...
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In: Physica C: Superconductivity, 2009, vol. 469, no. 14, p. 846-851
Bulk polycrystalline samples of Eu₂O₃-doped MgB₂ have been synthesized by a standard solid state reaction route and their structural and superconducting properties have been investigated. As a function of Eu₂O₃ content we have found a significant increase in the critical current density (Jc) and the irreversibility field (Hirr) in the magnetic field...
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In: Nature Materials, 2009, vol. 8, p. 310 - 314
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In: Nature Materials, 2009, vol. 8, p. 315-319
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In: New Journal of Physics, 2009, vol. 11, p. 055050
We present a muon spin rotation (μSR) study of the magnetic and superconducting properties of single crystals of electron-doped BaFe2−xCoxAs₂ with x = 0.08, 0.20 and 0.25 (Tc = 9, 25 and 20 K) and of polycrystalline hole-doped Pr1−xSrxFeAsO with x = 0 and 0.2 (Tc = 15...
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