57Fe and 151Eu Mössbauer studies of 3d-4f spin interplay in EuFe2−xNixAs2

• Published in: Scientific reports Vol. 11; no. 1; p. 11484
• Main Authors: Komędera, K, Gatlik, J, Błachowski, A, Żukrowski, J, Rybicki, D, Delekta, A, Babij, M, Bukowski, Z
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 01.06.2021; Nature Publishing Group UK; Nature Portfolio
• Subjects: Magnetic fields; Magnetism; Mossbauer spectroscopy
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-90657-x

Abstract The EuFe 2−x Ni x As 2 (with 0 ≤ x ≤ 0.4) compounds exhibiting 3 d and/or 4 f magnetic order were investigated by means of 57 Fe and 151 Eu Mössbauer spectroscopy. Additionally, results for EuNi 2 As 2 are reported for comparison. It was found that spin-density-wave order of the Fe itinerant moments is monotonically suppressed by Ni-substitution. However, the 3 d magnetic order survives at the lowest temperature up to at least x = 0.12 and it is certainly completely suppressed for x = 0.20. The Eu localized moments order regardless of the Ni concentration, but undergo a spin reorientation with increasing x from alignment parallel to the a -axis in the parent compound, toward c -axis alignment for x > 0.07. Change of the 4 f spins ordering from antiferromagnetic to ferromagnetic takes place simultaneously with a disappearance of the 3 d spins order what is the evidence of a strong coupling between magnetism of Eu 2+ ions and the conduction electrons of [Fe 2−x Ni x As 2 ] 2- layers. The Fe nuclei experience the transferred hyperfine magnetic field due to the Eu 2+ ordering for Ni-substituted samples with x > 0.04, while the transferred field is undetectable in EuFe 2 As 2 and for compound with a low Ni-substitution level. It seems that the 4 f ferromagnetic component arising from a tilt of the Eu 2+ moments to the crystallographic c -axis leads to the transferred magnetic field at the Fe atoms. Superconductivity is not observed down to 1.8 K, although a comparison with 57 Fe and 151 Eu Mössbauer data for EuFe 2 As 2 -based superconductors indicates a similar magnetic structure.