<Superscript>75</Superscript>As NMR local probe study of magnetism in (Eu<Subscript>1−x</Subscript>K<Subscript>x</Subscript>)Fe<Subscript>2</Subscript>As<Subscript>2</Subscript>

<Superscript>75</Superscript>As NMR measurements were performed as a function of temperature and doping in Eu<Subscript>1−x </Subscript>K<Subscript> x </Subscript>Fe<Subscript>2</Subscript>As<Subscript>2</Subscript> (x=0.5,0.7) samples. The large Eu<Superscript>2+</Superscript> moments and their fluctuations are found to dominate the <Superscript>75</Superscript>As NMR properties. The <Superscript>75</Superscript>As nuclei close to the Eu<Superscript>2+</Superscript> moments likely have a very short spin-spin relaxation time (T <Subscript>2</Subscript>) and are wiped out of our measurement window. The <Superscript>75</Superscript>As nuclei relatively far from Eu<Superscript>2+</Superscript> moments are probed in this study. Increasing the Eu content progressively decreases the signal intensity with no signal found for the full-Eu sample (x=0). The large <Superscript>75</Superscript>As NMR linewidth arises from an inhomogeneous magnetic environment around them. The spin lattice relaxation rate (1/T <Subscript>1</Subscript>) for x=0.5 and 0.7 samples is nearly independent of temperature above 100 K and results from a dipolar coupling to paramagnetic fluctuations of the Eu<Superscript>2+</Superscript> moments. The behavior of 1/T <Subscript>1</Subscript> at lower temperatures has contributions from the antiferromagnetic fluctuations of the Eu<Superscript>2+</Superscript> moments as also the fluctuations intrinsic to the FeAs planes and from superconductivity. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2013