Workshop "NMR, µSR, Mössbauer spectroscopies in the study of Fe-based and other unconventional high-Tc superconductors"


Identical spin fluctuations in Cu- and Co-doped BaFe2As2 independent of doped electrons

Hans-Joachim Grafe, IFW Dresden, Germany


In this talk, 75As Nuclear Magnetic Resonance measurements on single crystals of BaFe2As2, BaFe1.8Co0.2As2, and BaFe1.82Cu0.18As2 will be presented. While only Co doping induces superconductivity, the spin fluctuations probed by the nuclear spin lattice relaxation rate (T1T)-1 are identical for both dopings down to Tc. Below this temperature, (T1T)-1 of the Cu doped sample continues to rise, proving that (a) there is a quantum critical point below the superconducting dome, and (b) adding electrons does not affect the spin fluctuations. Consequently, we analyze the Knight shift data in terms of a two-component scenario, with one hyperfine coupling to an itinerant degree of freedom and the other to Fe-moments.


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