75As NMR local probe study of magnetism in (Eu1−xKx)Fe2As2

• Published in: The European physical journal. B, Condensed matter physics Condensed matter physics, 2013-11, Vol.86 (11), Article 458
• Main Authors: Dey, Tusharkanti, Khuntia, Panchanana, Mahajan, Avinash V., Anupam, Hossain, Zakir
• Format: Article
• Language: English
• Subjects: Complex Systems; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Fluid- and Aerodynamics; Magnetic properties; Physics; Physics and Astronomy; Properties of type I and type II superconductors; Regular Article; Solid State Physics; Superconductivity
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1140/epjb/e2013-40483-6

75 As NMR measurements were performed as a function of temperature and doping in Eu 1− x K x Fe 2 As 2 ( x = 0.5,0.7) samples. The large Eu 2+ moments and their fluctuations are found to dominate the 75 As NMR properties. The 75 As nuclei close to the Eu 2+ moments likely have a very short spin-spin relaxation time ( T 2 ) and are wiped out of our measurement window. The 75 As nuclei relatively far from Eu 2+ 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 75 As NMR linewidth arises from an inhomogeneous magnetic environment around them. The spin lattice relaxation rate (1/ T 1 ) 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 2+ moments. The behavior of 1/ T 1 at lower temperatures has contributions from the antiferromagnetic fluctuations of the Eu 2+ moments as also the fluctuations intrinsic to the FeAs planes and from superconductivity.