paper

Muon spin relaxation studies of magnetic order and superfluid density in antiferromagnetic NdOFeAs, BaFe2As2 and superconducting (Ba,K)Fe2As2

arXiv:0807.1044 · doi:10.1103/PhysRevB.78.214503

Abstract

Zero-field (ZF) muon spin relaxation ( $I^¼$ SR) measurements have revealed static commensurate magnetic order of Fe moments in NdOFeAs below $T_{N} \sim 135$ K, with the ordered moment size nearly equal to that in LaOFeAs, and confirmed similar behavior in BaFe $_{2}$ As $_{2}$ . In single crystals of superconducting (Ba $_{0.55}$ K $_{0.45}$ )Fe $_{2}$ As $_{2}$ , $I^¼$ SR spectra indicate static magnetism with incommensurate or short-ranged spin structure in $\sim$ 70 % of volume below $T_{N} \sim$ 80 K, coexisting with remaining volume which exhibits superfluid-response consistent with nodeless gap below $T_{c} \sim 30$ K.

4 pages 4 figures