Abstract 57Fe and 151Eu Mossbauer spectra were obtained versus temperature for Eu0.57Ca0.43Fe2As2 compound with 3d and 4f magnetic order and Eu0.73Ca0.27(Fe0.87Co0.13)2As2 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.

中文翻译：

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Eu 0.57 Ca 0.43 Fe 2 As 2 和Eu 0.73 Ca 0.27 (Fe 0.87 Co 0.13 ) 2 As 2 的穆斯堡尔研究：与“122”铁基超导体母体化合物EuFe 2 As 2 和CaFe 2 As 2 的比较

摘要 获得了具有 3d 和 4f 磁序的 Eu0.57Ca0.43Fe2As2 化合物和 Eu0.73Ca0.27(Fe0.87Co0.13)2As2 重入超导体的 57Fe 和 151Eu 穆斯堡尔谱随温度的变化，其中有限电阻率在接近基态。它们与先前获得的母体化合物 EuFe2As2 和 CaFe2As2 的光谱进行了比较。发现 Fe-As 层以外的置换不会导致 Eu2+ 磁矩的旋转（倾斜），也不会产生 Eu3+ 状态。另一方面，重入超导体表现出 Eu2+ 矩在晶胞 c 轴上的旋转（倾斜），导致铁核上转移的超精细磁场。二价铕在重入超导相的主体内磁性排列。重入超导体保持在接近基态的非均匀状态，其中大约 27% 的体积没有 3d 磁性，而其余的则表现出弱自旋密度波。这两个区域在铁核上的电场梯度和电子密度略有不同。