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XPS study of RNiSb2 (R = Pr, Nd) compounds

Szytuła A., Penc B., Jezierski A.

Materials Science Poland

2008

Vol. 26, No. 3

759--765

The electronic structure of the ternary RNiSb2 (R = Pr, Nd) compounds, which crystallize in the tetragonal primitive ZrCuSi2-type structure, was studied by the X-ray photoemission spectroscopy. The R3d core-levels and the valence bands were investigated. The results for the PrNiSb2 valence band are compared with the previously calculated density of states. The obtained results indicate that the valence bands are mainly determined by the Ni3d band. The analysis of the XPS spectra of R3d5/2 and R3d3/2 based on the Gunnarsson–Schönhammer model gives the hybridization of the 4f orbitals with the conduction band. The experimental data concerning the valence band of these compounds are compared with the calculations based on the KKR-CPA method. The calculated data for the room temperature (paramagnetic region) give the peaks corresponding to the R4f states at the Fermi level EF = 0. A different distribution of the peaks corresponding to the Ni3d states is observed. For PrNiSb2 three peaks at 2.0, 2.3 and 3.5 eV are observed while for NdNiSb2 a broad maximum between 5.0 and 8.0 eV is visible. The experimental data for PrNiSb2 are in good agreement with the calculated ones while those for NdNiSb2 are not.

Electronic structures of RCuIn and R2CuIn3 (R = La, Ce, Pr)

Szytuła A, Kalychak Y M, Tyvanchuk Y, Penc B, Winiarski A

Materials Science Poland

2008

Vol. 26, No. 4

1061--1067

Electronic structures of ternary compounds RCuIn and R2CuIn3 (R = La, Ce, Pr) have been studied by the X-ray photoelectron spectroscopy. The valence bands and the XPS core levels were investigated. The two families of compounds crystallize in different hexagonal crystal structures: ZrNiAl-type for RCuIn and AlB2-type for R2CuIn3. Analysis of the XPS valence bands indicates that they are mainly determined by the Cu 3d band. The analysis of the Ce 3d spectra based on the Gunnarsson-Schönhammer model gives the hybridization of the 4f electrons with the conduction band equal to 45 meV for CeCuIn and to 140 meV for Ce2CuIn3. The appearance of the 3d94f0 component is a clear evidence of the intermediate valence behaviour for cerium. The 4f occupation number is 0.95 for CeCuIn and 0.92 for Ce2CuIn3. The analysis of the other core levels confirms a small influence of the atomic surrounding on the electronic structure.

Magnetic phase transitions from the point of view of macroscopic and microscopic methods

Szytuła A.

Materials Science Poland

2007

Vol. 25, No. 2

313--320

Magnetic phase transitions in some rare earth compounds are discussed from the point of view of different experimental methods. The discussion concentrates on the determination of phase transitions in magnetically ordered states. The data presented in this work suggest that the "classical" method, namely the specific heat method, does not yield information on phase transitions between commensurate and incommensurate magnetic structures.