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Sonier JE Huang W Kaiser CV Cochrane C Pacradouni V Sabok-Sayr SA Lumsden MD Sales BC McGuire MA Sefat AS Mandrus D 《Physical review letters》2011,106(12):127002
It is shown that attempts to accurately deduce the magnetic penetration depth λ of overdoped BaFe(1.82)Co(0.18)As? single crystals by transverse-field muon spin rotation (TF μSR) are thwarted by field-induced magnetic order and strong vortex-lattice disorder. We explain how substantial deviations from the magnetic field distribution of a nearly perfect vortex lattice by one or both of these factors is also significant for other iron-arsenic superconductors, and this introduces considerable uncertainty in the values of λ obtained by TF μSR. 相似文献
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Geisheimer AR Huang W Pacradouni V Sabok-Sayr SA Sonier JE Leznoff DB 《Dalton transactions (Cambridge, England : 2003)》2011,40(29):7505-7516
A series of isomorphous M(H(2)O)(4)[Au(CN)(4)](2)·4H(2)O (M = Mn, Co, Ni, Zn; Cu is similar) coordination polymers was synthesized from the reaction of M(II) with KAu(CN)(4); they consist of octahedrally coordinated metal centres with four equatorial water molecules and trans-axial N-cyano ligands from [Au(CN)(4)](-) moieties, generating a linear 1-D chain of M(H(2)O)(4)[Au(CN)(4)]-units. An additional interstitial [Au(CN)(4)](-) unit forms AuN and hydrogen bonds with adjacent chains. The Cu(II) system readily loses water to yield Cu[Au(CN)(4)](2)(H(2)O)(4), which was not structurally characterized. The magnetic properties of these polymers were investigated by a combination of SQUID magnetometry and zero-field muon spin relaxation (ZF-μSR). Only weak antiferromagnetic interactions along the chains are mediated by the [Au(CN)(4)]-units, but the ZF-μSR data indicates that interchain interactions yield a phase transition to a magnetically ordered state for Cu[Au(CN)(4)](2)(H(2)O)(4) below 0.6 K, while for M(H(2)O)(4)[Au(CN)(4)](2)·4H(2)O (M = Co), depopulation of zero-field split Kramer's doublets to an effective "S = 1/2" ground state yields a transition to a spin-frozen magnetic state below 0.26 K. On the other hand, only a simple slowing-down of spins above 0.02 K is observed for the more weakly zero-field split M(H(2)O)(4)[Au(CN)(4)](2)·4H(2)O (M = Mn, Ni) complexes. 相似文献
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Sonier JE Ilton M Pacradouni V Kaiser CV Sabok-Sayr SA Ando Y Komiya S Hardy WN Bonn DA Liang R Atkinson WA 《Physical review letters》2008,101(11):117001
We report that in YBa2Cu3Oy and La2-xSrxCuO4 there is a spatially inhomogeneous response to the magnetic field for temperatures T extending well above the bulk-superconducting transition temperature Tc. An inhomogeneous magnetic response is observed above Tc even in ortho-II YBa2Cu3O6.50, which has highly ordered doping. The degree of the field inhomogeneity above Tc tracks the hole-doping dependences of both Tc and the density of the superconducting carriers below Tc, and therefore is apparently coupled to superconductivity. 相似文献
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Pacradouni V. Mandeville W.J. Cowan A.R. Young J.F. Johnson S.R. 《Optical and Quantum Electronics》2002,34(1-3):161-169
The influence of strong, two-dimensional (2D) periodic texture on the dispersion and lifetimes of resonant electromagnetic modes localized in the vicinity of thin (80 to 155 nm) GaAs membranes supported on thick (1 to 2 m) wet-oxidized AlAs cladding layers is reported. A method of extracting this information by fitting Fano-like features in broadband specular reflectivity spectra is described in detail, and applied to samples containing both triangular and square 2D lattices. A new and easier method of probing the properties of these modes is also demonstrated. It involves incorporating a superlattice of defects in the principal crystal lattice, and monitoring the defect diffraction spectrum, rather than the specular reflectivity. 相似文献
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