科研之友
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摘要
We probe the real-space electronic response to a local magnetic impurity in isovalent and heterovalent doped BaFe2As2 (122) using nuclear magnetic resonance (NMR). The local moments carried by Mn impurities doped into Ba(Fe1-xCox)(2)As-2 (Co-122) and BaFe2(As1-xPx)(2) (P-122) at optimal doping induce a spin polarization in the vicinity of the impurity. The amplitude, shape, and extension of this polarization is given by the real part of the susceptibility chi'(r) of FeAs layers and is consequently related to the nature and strength of the electronic correlations present in the system. We study this polarization using As-75 NMR in Co-122 and both As-75 and P-31 NMR in P-122. The NMR spectra of Mn-doped materials are made of two essential features. First, there is a satellite line associated with nuclei located as nearest neighbors of Mn impurities. The analysis of the temperature dependence of the shift of this satellite line shows that Mn local moments behave as isolated Curie moments. The second feature is a temperature dependent broadening of the central line. We show that the broadening of the central line follows the susceptibility of Mn local moments, as expected from typical Ruderman-Kittel-Kasuya-Yosida (RKKY)-like interactions. This demonstrates that the susceptibility chi'(r) of FeAs layers does not make significant contribution to the temperature dependent broadening of the central line. chi'(r) is consequently only weakly temperature dependent in optimally doped Co-122 and P-122. This behavior is in contrast with that of strongly correlated materials such as underdoped cuprate high-T-c superconductors where the central line broadens faster than the impurity susceptibility grows, because of the development of strong magnetic correlations when T is lowered. Moreover, the FeAs layer susceptibility is found quantitatively similar in both heterovalent doped and isolvalent doped BaFe2As2.
- 出版日期2014-1-10
- 单位中国地震局
