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79 - L. Jiao , Z. F. Weng , J. Z. Liu 2014
We measure the magnetic penetration depth $Deltalambda(T)$ for NdO$_{1-x}$F$_{x}$BiS$_{2}$ ($x$ = 0.3 and 0.5) using the tunnel diode oscillator technique. The $Deltalambda(T)$ shows an upturn in the low-temperature limit which is attributed to the p aramagnetism of Nd ions. After subtracting the paramagnetic contributions, the penetration depth $Deltalambda(T)$ follows exponential-type temperature dependence at $Tll T_c$. Both $Deltalambda(T)$ and the corresponding superfluid density $rho_s(T)$ can be described by the BCS model with an energy gap of $Delta(0)$ $approx$ 2.0 $k_BT_c$ for both $x$ = 0.3 and 0.5, suggesting strong-coupling BCS superconductivity in the presence of localized moments for NdO$_{1-x}$F$_{x}$BiS$_{2}$.
61 - P. Gao , T. A. Tyson , Z. Liu 2008
Synchrotron infrared measurements were conducted over the range 100 to 8000 cm-1 on a self-doped LaxMnO3-d (x~~0.8) film. From these measurements we determined the conductivity, the effective number of free carriers, and the specific phonon modes as a function of frequency. While the metal-insulator transition temperature (TMI) and the magnetic ordering temperature (TC) approximately coincide, the free carrier density onset occurs at a significantly lower temperature (~~45 K below). This suggests that local distortions exist below TMI and TC which trap the eg conduction electrons. These regions with local distortions constitute an insulating phase which persists for temperatures significantly below TMI and TC. The initial large drop in resistivity is due to the enhanced magnetic ordering while further drops correspond to reductions in the insulating phase which increase the number of free carriers.
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