XPS spectra, electronic structure, and magnetic properties of RFe₅Al₇ intermetallics

The results of X-ray photoelectron spectroscopy measurements (core levels and valence bands) of RFe₅Al₇ (R = Lu, Tm, Er, Ho, Dy, Tb, Gd) single crystals are presented in comparison with the results of bulk magnetization studies and electronic structure calculations. It is shown that the increase of the Curie temperature in RFe₅Al₇ from Tm to Gd is associated with an increase of the indirect R 4f - Fe 3d exchange interaction at the expense of the multiplicity 2S + 1 (statistical weight) in the ground state ^{2S + 1}L_J of R³⁺ ions. The nonmonotonic behavior of the ferrimagnetic compensation temperature, Tcomp, as well as the values of the spontaneous magnetic moment, Ms, and formation energy, E_form, of the 4fⁿ levels in R metals in a series from ErFe₅Al₇ to GdFe₅Al₇ are explained by the difference in the quantum numbers L, J and S of the ground state of R³⁺ ions, leading to a maximum value of T_comp, M_s and E_form for the Dycontaining compound. The electronic structure of Gd/LuFe₅Alsub>7 is calculated using the GGA+U approach, on the basis of which the physical mechanism and relative strength of the interatomic R-Fe and Al-Fe interactions are considered, and also the difference in the magnetic moments of iron atoms in different structural positions is explained.