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We will probe the intrinsic behavior of spin susceptibility chi_(spin) in the LaFeAsO(1-x)F(x) superconductor (x ~ 0.1, Tc ~ 27K) using 19-F and 75-As NMR techniques. Our new results firmly establish the pseudo-gap behavior with Delta_(PG)/kB ~ 140K. The estimated magnitude of chi_(spin) at 290K, ~1.8x10^(-4) [emu/mol-Fe], is approximately twice larger than that in high Tc cuprates. We also show that chi_(spin) levels off below ~50K down to Tc.
Magneto-optical imaging was used to study the local magnetization in polycrystalline NdFeAsO$_{0.9}$F$_{0.1}$ (NFAOF). Individual crystallites up to $sim200times100times30$ $mu m^{3}$ in size could be mapped at various temperatures. The in-grain, per
We have performed 75As Nuclear Magnetic Resonance (NMR) measurements on aligned powders of the new LaO0.9F0.1FeAs superconductor. In the normal state, we find a strong temperature dependence of the spin shift and Korringa behavior of the spin lattice
We report 19-F NMR investigation of the new high temperature superconductor LaFeAsO(0.89)F(0.11) (Tc ~ 28K). We demonstrate that low frequency spin fluctuations exhibit pseudo gap behavior above Tc. We also deduce the London penetration depth lambda from NMR line broadening below Tc.
Unveiling the driving force for a phase transition is normally difficult when multiple degrees of freedom are strongly coupled. One example is the nematic phase transition in iron-based superconductors. Its mechanism remains controversial due to a co
Temperature and magnetic field dependent measurements of the microwave surface impedance of superconducting LaFeAsO$_{0.9}$F$_{0.1}$ (Tc $approx$ 26K) reveal a very large upper critical field ($B_{rm c2} approx 56$T) and a large value of the depinnin