Enhancement of low-frequency fluctuations and superconductivity breakdown in Mn-doped La${}_{1-y}$Y${}_y$FeAsO${}_{0.89}$F${}_{0.11}$ superconductors

F. Hammerath, M. Moroni, L. Bossoni +9

${}^{19}$F NMR measurements in optimally electron-doped La${}_{1-y}$Y${}_y$Fe${}_{1-x}$Mn${}_x$AsO${}_{0.89}$F${}_{0.11}$ superconductors are presented. In these materials the effect of Mn d…