Structural, Physical, Theoretical and Spectroscopic Investigations of Mixed-Valent Eu2Ni8Si3 and Its Structural Anti-Type Sr2Pt3Al8

Author(s)

Stegemann, Frank ^[1] ; Block, Theresa ^[1] ; Klenner, Steffen ^[1] ; Zhang, Yuemei ^{[2, 3]} ; Fokwa, Boniface P. T. ^[2] ; Doerenkamp, Carsten ^[4] ; Eckert, Hellmut ^{[4, 5]} ; Janka, Oliver ^{[1, 6]}

Affiliation

^[1] Westfalische Wilhelms Univ Munster, Inst Anorgan & Analyt Chem Westfalische Wilhelms, Corrensstr 30, D-48149 Munster - Germany

^[2] Univ Calif Riverside, Dept Chem, 501 Box Springs Rd, Riverside, CA 92521 - USA

^[3] Warren Wilson Coll, Dept Chem & Phys, Asheville, NC 28815 - USA

^[4] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13566590 Sao Carlos, SP - Brazil

^[5] Westfalische Wilhelms Univ Munster, Inst Phys Chem, Corrensstr 28, D-48149 Munster - Germany

^[6] Saarland Univ, Inorgan Solid State Chem, Bldg C4 1, D-66123 Saarbrucken - Germany

• Document type: Journal article
• Source: European Journal of Inorganic Chemistry; v. 2021, n. 37 AUG 2021.
• Web of Science Citations: 0

Abstract

Eu2Ni8Si3 and its anti-type representative Sr2Pt3Al8 were synthesized from the elements. They crystallize in the tetragonal crystal system with space group P4(2)/nmc and with lattice parameters of a=997.9(1) and c=747.6(1) pm (Eu2Ni8Si3) as well as a=1082.9(2) and c=823.3(2) pm (Sr2Pt3Al8). Both compounds were investigated via single crystal X-ray diffraction, indicating slight Si/Ni mixing for the silicide. Sr2Pt3Al8 exhibits a temperature independent magnetic susceptibility, suggesting superimposed dia- and Pauli-paramagnetic contributions. The independent Al and Pt sites of the platinide were further characterized by Al-27 and Pt-195 solid-state NMR spectroscopy, which were assigned with the help of electronic structure calculations. ICOHP calculations and Bader charges were used to analyze the bonding situation. Eu2Ni8Si3 in contrast is paramagnetic with a ferromagnetic transition at T-C=46.9(2) K and exhibits an effective magnetic moment of mu(eff)=6.61(1) mu(B) per Eu atom. The latter is in line with an intermediate valence that was further proven by Eu-151 Mossbauer spectroscopic investigations. At 300 K, the refined Eu2+/Eu3+ ratios are 60 %/40 %, at 78 K 62 % and 38 % (Eu2+/Eu3+) are observed, being in line with the ratio deduced from the magnetic susceptibility. Finally, at 6 K a ratio of 68 % Eu2+ and 32 % Eu3+ was observed. Below the Curie temperature, the Eu2+ signal shows a full magnetic hyperfine splitting, with an internal magnetic field value of B-0=28.4 T. (AU)

• FAPESP's process: 13/07793-6 - CEPIV - Center for Teaching, Research and Innovation in Glass
• Grantee: Edgar Dutra Zanotto
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 17/06649-0 - New Optical Materials based on Rare-Earth Doped Oxyfluoride Glasses and Ceramics: Structural Studies by Electron Paramagnetic Resonance Methods
• Grantee: Carsten Doerenkamp
• Support Opportunities: Scholarships in Brazil - Post-Doctoral