NMR measurements of intrinsic spin susceptibility in LaFeAsO(0.9)F(0.1)

Abstract

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.

Invited paper to the Proceedings of the International Symposium on Iron-oxypnictide Superconductors (June 28-29, 2008, Tokyo). J. Phys. Soc. Jpn. Suppl. (in press)

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• To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report
• Spin susceptibility, phase diagram, and quantum criticality in the electron-doped high Tc Superconductor Ba[Fe(1-x)Co(x)]2As2
• 77Se NMR Investigation of the K(x)Fe(2-y)Se(2) High Tc Superconductor (Tc=33K)
• Antiferromagnetic fluctuations in the normal state of LiFeAs
• Theory of Multiband Superconductivity in Iron Pnictides
• Progressive slowing down of spin fluctuations in underdoped LaFeAsO${}_{1-x}$F${}_x$
• Systematic ^{75}As NMR study of the dependence of low-lying excitations on F doping in the iron oxypnictide LaFeAs(O_{1-x}F_{x})
• Novel Superconducting Characteristics and Unusual Normal-State Properties in Iron-based Pnictide Superconductors: 57Fe-NMR and 75As-NQR/NMR studies in REFeAsO_1-y (RE=La,Pr,Nd) and Ba0.6K0.4Fe2As2
• Observation of orbital ordering and origin of the nematic order in FeSe
• Nearly ferromagnetic metal state in the collapsed tetragonal phase of YFe${}_2$(Ge,Si)${}_2$