Magnetic Impurities in the Pnictide Superconductor Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$

Abstract

NMR measurements have been performed on single crystals of Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ (x = 0, 0.45) and CaFe${}_2$As${}_2$ grown from Sn flux. The Ba-based pnictide crystals contain significant amounts of Sn in their structure, $\sim 1$%, giving rise to magnetic impurity effects evident in the NMR spectrum and in the magnetization. Our experiments show that the large impurity magnetization is broadly distributed on a microscopic scale, generating substantial magnetic field gradients. There is a concomitant 20% reduction in the transition temperature which is most likely due to magnetic electron scattering. We suggest that the relative robustness of superconductivity ($x=0.45$) in the presence of severe magnetic inhomogeneity might be accounted for by strong spatial correlations between impurities on the coherence length scale.

14 pages, 6 figures (submitted to New Journal of Physics)

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Cited by in corpus (13)

• Homogeneous vs. inhomogeneous coexistence of magnetic order and superconductivity probed by NMR in Co and K doped iron pnictides
• Magnetoelastic Coupling in the Phase Diagram of Ba1-xKxFe2As2
• Interplane resistivity of underdoped single crystals (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$, $0\le x<0.34$
• As-vacancies, local moments, and Pauli limiting in LaO_0.9F_0.1FeAs_(1-delta) superconductors
• ${}^{75}$As NMR of Ba(Fe${}_{0.93}$Co${}_{0.07}$)${}_2$As${}_2$ in High Magnetic Field
• Anticollinear magnetic order induced by impurities in the frustrated Heisenberg model of pnictides
• Effect of proton irradiation on the normal state low-energy excitations of Ba(Fe${}_{1-x}$Rh${}_x$)${}_2$As${}_2$ superconductors
• NMR investigation of vortex dynamics in Ba(Fe0.93Rh0.07)2As2 superconductor
• Persistence of slow fluctuations in the overdoped regime of Ba(Fe1-xRhx)2As2 superconductors
• Revealing the degree of magnetic frustration by non-magnetic impurities
• Absence of large nanoscale electronic inhomogeneities in the Ba(Fe1-xCox)2As2 pnictide
• Magnetic field dependence of spin-lattice relaxation in the s$\pm$ state of Ba${}_{0.67}$K${}_{0.33}$Fe${}_2$As${}_2$
• Emergence of novel magnetic order at finite temperature in overdoped pnictides