Magnetic and electronic properties of RCoxGe2 (R = Pr, Nd) compounds

Magnetization, magnetic susceptibility, neutron diffraction and X-ray photoemission spectroscopy measurements were performed on polycrystalline samples: PrCo0.85Ge2 and NdCo0.82Ge2, crystallizing in an orthorhombic structure of the CeNiSi2-type. The magnetometric data indicate that both compounds are antiferromagnetic at low temperatures, PrCo0.85Ge2 below 5 K and NdCo0.82Ge2 below 2.1 K. The neutron diffraction data indicate an antiferromagnetic structure in PrCo0.85Ge2 at 1.5 K and give no evidence of any magnetic ordering in NdCo0.82Ge2. The X-ray photoemission data indicate that the valence bands are formed predominantly by R 4f5d6s and Co 3d bands. The spin-orbit splitting values determined from the Pr and Nd, 3d5/2 and 3d3/2 XPS spectra are equal to 20.9 eV for the Pr compound and 23.0 eV for the Nd compound. The analysis of these spectra performed on the basis of the Gunnarsson-Schonhammer model revealed a small hybridization between 4f-electrons of the rare earths with the conduction band which implies rather good stability of the f shell in these compounds.