Mossbauer study of Eu0.57Ca0.43Fe2As2 and Eu0.73Ca0.27(Fe0.87Co0.13)2As2: A comparison to '122' iron-based superconductors parent compounds EuFe2As2 and CaFe2As2

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:457

Article

Komedera, K.¹  Blachowski, A.¹  Ruebenbauer, K.¹  Zukrowski, J.²  Dubiel, S. M.³  Tran, L. M.⁴  Babij, M.⁴  Bukowski, Z.⁴ 

[1] Pedag Univ, Inst Phys, Mossbauer Spect Lab, Ul Podchorazych 2, PL-30084 Krakow, Poland

[2] AGH Univ Sci & Technol, Acad Ctr Mat & Nanotechnol, Av A Mickiewicza 30, PL-30059 Krakow, Poland

[3] AGH Univ Sci & Technol, Fac Phys & Appl Comp Sci, Av A Mickiewicza 30, PL-30059 Krakow, Poland

[4] Polish Acad Sci, Inst Low Temp & Struct Res, Ul Okolna 2, PL-50422 Wroclaw, Poland

关键词: Fe-57 Mossbauer spectroscopy;    Eu-151 spectroscopy;    SDW;    Superconductivity;   

DOI  :  10.1016/j.jmmm.2018.02.079

来源: Elsevier

【 摘 要 】

Fe-57 and Eu-151 Mossbauer spectra were obtained versus temperature for Eu0.57Ca0.43Fe2As2 compound with 3d and 4f magnetic order and Eu0.73Ca0.27(Fe0.87Co0.13)(2)As-2 re-entrant superconductor, where the finite resistivity reappears while approaching the ground state. They were compared with previously obtained spectra for parent compounds EuFe2As2 and CaFe2As2. It was found that substitution beyond the Fe-As layers does not lead to the rotation (canting) of the Eu2+ magnetic moments and does not generate Eu3+ states. On the other hand, re-entrant superconductor exhibits rotation (canting) of the Eu2+ moments on the c-axis of the unit cell leading to the transferred hyperfine magnetic field on iron nuclei. Divalent europium orders magnetically within the bulk of the re-entrant superconducting phase. The re-entrant superconductor remains in the inhomogeneous state close to the ground state with about 27% of the volume being free of 3d magnetism, while the remainder exhibits weak spin density wave. Those two regions slightly differ by the electric field gradient and electron density on iron nuclei. (C) 2018 Elsevier B.V. All rights reserved.

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