Abstract
The simultaneous presence of an Fe-related spin-density wave and the antiferromagnetic order of moments ranks among the most interesting parent compounds of iron-based pnictide superconductors. Here we explore the consequences of the dilution of magnetic lattice through on-site Ca substitution. By employing macro- and microscopic techniques, including electrical transport and magnetometry, as well as muon-spin spectroscopy, we study the evolution of Eu magnetic order in both the weak and strong dilution regimes, achieved for Ca concentration and 0.43, respectively. We demonstrate the localized character of the Eu antiferromagnetism mediated via RKKY interactions, in contrast with the largely itinerant nature of Fe magnetic interactions. Our results suggest a weak coupling between the Fe and Eu magnetic sublattices and a rapid decrease of the Eu magnetic interaction strength upon Ca substitution. The latter is confirmed both by the depression of the ordering temperature of the moments , and the decrease of magnetic volume fraction with increasing . We establish that, similarly to the parent compound, the investigated Ca-doped compounds have a twinned structure and undergo a permanent detwinning upon applying an external magnetic field.
8 More- Received 6 April 2018
- Revised 13 July 2018
DOI:https://doi.org/10.1103/PhysRevB.98.104412
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