Demirdiş, S., C. J. van der Beek, Y. Fasano, N. R. Cejas Bolecek, H. Pastoriza, D. Colson, and F. Rullier-Albenque. "Strong pinning and vortex energy distributions in single-crystalline Ba(Fe{1−x}Co{x}){2}As{2}." Physical Review B 84, no. 9 (2011): 094517.
Abstract: The interrelation between heterogeneity and flux pinning is studied in Ba(Fe1−xCox )2As2 single crystals with widely varying Co content x.Magnetic Bitter decoration of the superconducting vortex ensemble in crystals with x = 0.075 and x = 0.1 reveals highly disordered vortex structures. The width of the Meissner belt bserved at the edges of the crystals, and above the surface steps formed by leaving, as well as the width of the intervortex distance distribution, indicate that the observed vortex ensemble is established at a temperature just below the critical temperature Tc. The vortex interaction energy and pinning force distributions extracted from the images strongly suggest that the vortex lattice disorder is attributable to strong pinning due to spatial fluctuations of Tc and of the superfluid density. Correlating the results with the critical current density ields a typical length scale of the relevant disorder of 40–60 nm.
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Gil, D. M., M. C. Navarro, M. C. Lagarrigue, J. Guimpel, R. E. Carbonio, and M. I. Gómez. "Crystal structure refinement, spectroscopic study and magnetic properties of yttrium hexacyanoferrate (III)." Journal of Molecular Structure 1003, no. 1-3 (2011): 129–133.
Abstract: Y[Fe(CN)6]·4H2O has been synthesized and characterized. The crystal structure was refined by Rietveld analysis using X-ray powder diffraction data. Y[Fe(CN)6]·4H2O crystallizes in the orthorhombic crystal system, space group Cmcm. Y3+ ion is eight-coordinated forming a bicapped distorted trigonal prism YN6O2. Fe3+ ion is six-coordinated in the form of an irregular octahedra FeC6 group and cyanide linkages between YN6O2 and FeC6 groups build an infinite polymeric array. The vibrational spectrum shows two bands corresponding to antisymmetric and symmetric stretching 12C14N in the CN stretching region. These bands are accompanied by four weak isotopic bands at lower frequency due to the presence of 13C and 15N in relative natural abundance. The HOH bending band split into three bands around 1600 cm−1 due to the presence of two kinds of water molecules in the structure. The thermal decomposition has been followed by thermogravimetric and differential thermal analysis, IR spectroscopy and powder XRD. The size and morphology of the complex and its thermal decomposition products were evaluated by scanning electron microscopy. The magnetic measurements confirm that Y[Fe(CN)6]·4H2O shows an antiferromagnetic order at low temperatures.
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Oh, Y. S., B. Jeon, S. Y. Haam, S. Park, V. F. Correa, A. H. Lacerda, S. - W. Cheong, G. S. Jeon, and K. H. Kim. "Strong magnetoelastic effect on the magnetoelectric phenomena of TbMn2O5." Physical Review B 83 (2011): 060405.
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Sereni, J. G. "Comparison of a Shastry-Sutherland lattice stability in Ce2Pd2Sn as a function of field and doping." In Journal of Physics: Conference Series, 012126. Vol. 273., 2011.
Abstract: A comparative study of the stability of a Shastry-Sutherland lattice (SSL) in Ce2Pd2Sn under different physical conditions is presented. Applied magnetic field suppresses the SSL of stoichiometric Ce2Pd2Sn in a magnetic critical point at Tcr(B) = 4.2K and Bcr = 0.13 T, whereas 25% of Ni does it at Tcr(Ni) = 3.4 K. Electronic concentration variation, driven by the increase of Pd (holes) concentration in Ce2Pd2+yIn1-y, decreases the magnetic transition down to TM = 2.8K in the limit of the alloy solubility, i.e. y = 0.4. The existence of a M(B) plateau in SSL predicted by theory and the crossing of those isotherms, previously observed in the model compound SrCu2(BO3)2 are analyzed.
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Sereni, J. G., M. Giovannini, M. G. Berisso, and A. Saccone. "Electron concentration effects on the Shastry-Sutherland phase stability in Ce2-xPd2+yIn1-z solid solutions." Physical Review B 83, no. 6 (2011): 064419.
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Seyfarth, G., D. Jaccard, P. Pedrazzini, A. Krzton-Maziopa, E. Pomjakushina, K. Conder, and Z. Shermadini. "Pressure cycle of superconducting Cs0.8Fe2Se2 : A transport study." Solid State Communications 151, no. 10 (2011): 747–750.
Abstract: We report measurements of the temperature and pressure dependence of the electrical resistivity (Ï) of single-crystalline iron-based chalcogenide Cs0.8Fe2Se2. In this material, superconductivity with a transition temperature Tc~30K source develops from a normal state with extremely large resistivity. At ambient pressure, a large “hump†in the resistivity is observed around 200 K. Under pressure, the resistivity decreases by two orders of magnitude, concomitant with a sudden Tc suppression around pc~30K. Even at 9 GPa a metallic resistivity state is not recovered, and the Ï(T) “hump†is still detected. A comparison of the data measured upon increasing and decreasing the external pressure leads us to suggest that the superconductivity is not related to this hump.
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Sirena, M., E. Kaul, M. B. Pedreros, C. A. Rodriguez, J. Guimpel, and L. B. Steren. "Structural, magnetic and electrical properties of ferromagnetic/ferroelectric multilayers." Journal of Applied Physics 109, no. 12 (2011): 123920.
Abstract: The La0.75Sr0.25MnO3 (LSMO)/Ba0.7Sr0.3TiO3 (BSTO) superlattices and bilayers, where LSMO is ferromagnetic and BSTO is ferroelectric, were grown by dc sputtering. X-ray diffraction indicates that the samples present a textured growth with the c axis perpendicular to the substrate. Magnetization measurements show a decrease of the sample’s magnetization for decreasing ferromagnetic thickness. This effect could be related to the presence of biaxial strain and a magnetic dead layer in the samples. Conductive atomic force microscopy indicates that the samples present a total covering of the ferromagnetic layer for a ferroelectric thickness higher than four unit cells. Transport tunneling of the carriers seems to be the preferred conduction mechanism through the ferroelectric layer. These are promising results for the development of multiferroic tunnel junctions.
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