Influence of the Nd 4f states on the magnetic behavior and the electric field gradient of the oxypnictides superconductors NdFeAsO1−xFx
P. Jeglič, J.-W. G. Bos, A. Zorko, M. Brunelli, K. Koch, H. Rosner, S. Margadonna, D. Arčon
DOI 10.1103/PhysRevB.79.094515 · Physical Review B
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Abstract
The structural, electronic, and magnetic properties of the superconducting NdFeAsO1−xFx phases (TC=43 K for x=0.15) have been investigated experimentally by high-resolution synchrotron x-ray powder diffraction, magnetization and A75s NMR measurements. Density-functional calculations were performed to calculate and analyze the electric field gradient and the density of states. Compared to LaFeAsO family, the NdFeAsO family shows a contraction of the lattice parameters with shorter rare-earth (RE)-As bond distances, an increased thickness of the As-Fe2-As layer, and less distorted Fe-As4 tetrahedra. The A75s quadrupole frequencies are enhanced with respect to the La analogs. This is due to a more prolate As 4p electron distribution mainly caused by the reduced lattice parameters and not by the presence of Nd 4f electrons. A non-negligible hyperfine coupling between the A75s nuclei and the Nd 4f states indicates a weak coupling between the REO and FeAs layer and possibly opens the channel for a Ruderman-Kittel-Kasuya-Yosida (RKKY)-type interaction between localized Nd 4f moments mediated by itinerant Fe 3d and/or Nd 5d states.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| NdFeAsO1-xFx Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 43 | Pressure not reported | onset |
| NdFeAsO0.85F0.15 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 43 | Pressure not reported | onset |
| LaFeAsO Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 26 | Pressure not reported | unknown |
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