We have performed zero-field $^{ 75}$As nuclear magnetic resonance study of SmFeAsO$_{ 1-x}$F$_x$ (x=0, 0.07) polycrystals in a wide frequency range at various temperatures. $^{ 75}$As resonance line was found at around 265 MHz revealing the formation of the intermetallic FeAs clusters in the new layered superconductors. We have also demonstrated that NMR is a sensitive tool for probing the quality of these materials.
Categories: cond-mat.supr-con cond-mat.mtrl-sci