In: Science, 2011, vol. 332, no. 6032, p. 937-940
The competition between collective quantum phases in materials with strongly correlated electrons depends sensitively on the dimensionality of the electron system, which is difficult to control by standard solid-state chemistry. We have fabricated superlattices of the paramagnetic metal lanthanum nickelate (LaNiO₃) and the wide-gap insulator lanthanum aluminate (LaAlO₃) with atomically...
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In: Physical Review B - Condensed Matter and Materials Physics, 2011, vol. 83, no. 17, p. 174407
Far-infrared spectra of magnetodielectric Dy₃Fe₅O₁₂ garnet were studied using a combination of transmittance, reflectivity, and rotating analyzer ellipsometry. In addition to purely dielectric and magnetic modes, we observed several hybrid modes with a mixed magnetic and electric dipole activity. Using 4×4 matrix formalism for materials with μ(ω)≠1, we modeled the experimental...
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In: Nature Materials, 2011, vol. 10, p. 39–44
Spintronics has shown a remarkable and rapid development, for example from the initial discovery of giant magnetoresistance in spin valves (Baibich, M. N. et al. Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. Phys. Rev. Lett. 61, 2472–2475, 1988) to their ubiquity in hard-disk read heads in a relatively short time. However, the ability to fully harness electron spin as...
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In: Physical Review Letters, 2011, vol. 106, no. 4, p. 047006
We show that a multilayer analysis of the infrared c-axis response of RBa₂Cu₃O7-δ (R=Y,Gd,Eu) provides important new information about the anomalous normal-state properties of underdoped cuprate high temperature superconductors. In addition to competing correlations which give rise to a pseudogap that depletes the low-energy electronic states below...
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In: Journal of Physics and Chemistry of Solids, 2011, p. -
We report the first observation of magnetic order above room temperature in zinc sulfide doped with Cu²⁺ made by a simple sintering process and detected by ferromagnetic resonance (FMR), SQUID magnetometry and the μSR experiments. FMR study shows nonzero absorption above room temperature indicating a high value of Curie temperature. Field-cooled and zero-field-cooled magnetization data...
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In: The European Physical Journal - Special Topics, 2010, vol. 188, no. 1, p. 73-88
With the technique of infrared ellipsometry we performed a detailed study of the temperature- and doping dependence of the c-axis response of a series of YBa₂Cu₃O7−δ single crystals. In particular, we explored the anomalous electronic properties at temperatures above the macroscopic superconducting transition temperature, T c, whose conflicting...
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In: Physical Review Letters, 2010, vol. 105, p. 037207
We report an inelastic-neutron-scattering and muon-spin-relaxation study of the effect of 2% spinless (Zn) impurities on the magnetic order and dynamics of YBa₂Cu₃O6.6, an underdoped high-temperature superconductor that exhibits a prominent spin pseudogap in its normal state. Zn substitution induces static magnetic order at low temperatures and triggers a large-scale...
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In: Physical Review Letters, 2010, vol. 105, no. 6, p. 067001
We measure the anisotropic midinfrared response of electrons and phonons in bulk YBa₂Cu₃O7-δ after femtosecond photoexcitation. A line shape analysis of specific lattice modes reveals their transient occupation and coupling to the superconducting condensate. The apex oxygen vibration is strongly excited within 150 fs, demonstrating that the lattice absorbs a major portion of the...
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In: Physical Review B, 2010, vol. 81, p. 214508
We performed combined infrared reflection and ellipsometry measurements of the in-plane optical response of single crystals of the pnictide high-temperature superconductor BaFe1.87Co0.13As₂ with Tc=24.5 K. Our experimental data provide evidence for multiple superconducting energy gaps and can be well described in terms of three isotropic gaps with...
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In: Physical Review Letters, 2010, vol. 104, p. 156807
With infrared ellipsometry and transport measurements we investigated the electrons at the interface between LaAlO₃ and SrTiO₃. We obtained a sheet carrier concentration of Ns≈5–9×10¹³ cm⁻², an effective mass of m*=3.2±0.4me, and a strongly frequency dependent mobility. The latter are similar as in bulk SrTi1-xNbxO₃ and...
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