Extending the knowledge on the quaternary rare earth nickel aluminum germanides of the RENiAl4Ge2 series (RE=Y, Sm, Gd-Tm, Lu) - structural, magnetic and NMR-spectroscopic investigations

Author(s)

Witt, Melina ; Boennighausen, Judith ; Eustermann, Fabian ; Savourat, Aline ; Scheifers, Jan P. ; Fokwa, Boniface P. T. ; Doerenkamp, Carsten ; Eckert, Hellmut ; Janka, Oliver

• Document type: Journal article
• Source: ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES; v. 75, n. 1-2, p. 14-pg., 2020-02-01.

Abstract

The quaternary rare earth nickel aluminum germanide series RENiAl4Ge2 (RE=Y, Sm, Gd Tm, Lu) has been extended by several members. The compounds were synthesized from the elements by arc-melting, and single crystals of YNiAl4Ge2, GdNiAl4Ge2, and LuNiAl4Ge2 were grown from an aluminum flux. All members crystallize isostructurally in the rhombohedral SmNiAl4Ge2-type structure (R (3) over barm, Z=3). The compounds can be described as a stacking of RE delta+ and [NiAl4Ge2](delta-) slabs with an ABC stacking sequence, or alternatively as stacking of CsCl and CdI2 building blocks. The results of the magnetic measurements indicate that all rare earth atoms are in a trivalent oxidation state. Of the RENiAl4Ge2 series, the members with RE=Sm, Gd-Dy exhibit antiferromagnetic ordering with a maximum Neel temperature of T-N = 16.4(1) K observed for GdNiAl4Ge2. Al-27 NMR spectroscopic investigations yielded spectra with two distinct signals, in line with the crystal structure, however, significantly different resonance frequencies of delta(iso) (ms)(YNiAl4Ge2)=77(1) and 482(1) ppm as well as delta(iso) (ms)(LuNiAl4Ge2)=90(1) and 467(1) ppm were observed. These indicate significantly different s-electron densities at the two crystallographically different Al atoms, in line with the results from DFT calculations. The Bader charge analysis confirms that the present compounds must be considered as germanides, as expected from the relative electronegativities of the constituent elements, while the low charges on Al and Y indicate significant covalent bonding. (AU)

• 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