Electronic and magnetic phase diagram of superconductors, SmFeAsO₁−xFx

A crystallographic and magnetic phase diagram of SmFeAsO 1− x F x is determined as a function of x in terms of temperature based on electrical transport and magnetization, synchrotron powder x-ray diffraction, 57 Fe Mössbauer spectra (MS), and 149 Sm nuclear resonant forward scattering (NRFS) measurements. MS revealed that the magnetic moments of Fe were aligned antiferromagnetically at ∼144 K ( T N (Fe)). The magnetic moment of Fe (M Fe ) is estimated to be 0.34 μ B /Fe at 4.2 K for undoped SmFeAsO; M Fe is quenched in superconducting F-doped SmFeAsO. 149 Sm NRFS spectra revealed that the magnetic moments of Sm start to order antiferromagnetically at 5.6 K (undoped) and 4.4 K ( T N (Sm)) ( x =0.069). Results clearly indicate that the antiferromagnetic (AF) Sm sublattice coexists with the superconducting phase in SmFeAsO 1− x F x below T N (Sm), while the AF Fe sublattice does not coexist with the superconducting phase.