Microscopic phase diagram of Eu (Fe1−x Nix) As2 (x = 0,0.04) under pressure

• Published in: Physical review. B 2021-05, Vol.103 (19), p.1
• Main Authors: Bi, Wenli, Nix, Zachary, Dutta, Utpal, Zhao, Jiyong, Alp, Esen E, Zhang, Dongzhou, Chow, Paul, Xiao, Yuming, Liu, Ya-Bin, Cao, Guang-Han, Vohra, Yogesh K
• Format: Article
• Language: English
• Subjects: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Critical pressure; Group 5A compounds; High Pressure, Phase Diagram, Magnetism; Iron; Iron 57; Lattice parameters; magnetic order; magnetic phase transitions; Magnetism; Mossbauer spectroscopy; Nickel; Phase diagrams; pnictides; pressure effects; superconductivity; Synchrotrons; transition temperature; x-ray diffraction
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.103.195135

To establish the microscopic P-T phase diagram of recent 112-type iron-pnictides Eu (Fe1−x Nix) As2 (x = 0, 0.04), high-pressure synchrotron Mössbauer spectroscopy experiments in 151Eu and 57Fe have been performed. In EuFeAs2 application of pressure completely suppresses the itinerant electron magnetism from the Fe sublattice and the local-moment magnetism in Eu ions at ~ 10 and ~ 11.6 GPa, respectively. High-pressure x-ray diffraction experiments in EuFeAs2 reveal an anomalous change in the lattice parameters and a discontinuity in volume around 10 GPa, suggesting an isostructural transition at this pressure. With Ni-doping (x = 0.04), a collapse of local magnetic order occurs at ~ 8 GPa, a lower critical pressure compared with the parent compound. In both systems, the suppression of local-moment magnetism is associated with a significant increase of mean valence in Eu ions.