Influence of Pr substitution on the physical properties of the Ce1−xPrxCoGe3 system: Combined experimental and first-principles study

We present the results of our investigations of physical properties for the novel ${\mathrm{Ce}}_{1\ensuremath{-}x}{\mathrm{Pr}}_{x}\mathrm{Co}{\mathrm{Ge}}_{3}$ system performed with a number of experimental methods: magnetic susceptibility, specific heat, electrical resistivity, magnetoresistance, and thermoelectric power. Moreover, the electronic structure was studied by means of photoelectron spectroscopy measurements and first-principles calculations. All investigated compositions of the ${\mathrm{Ce}}_{1\ensuremath{-}x}{\mathrm{Pr}}_{x}\mathrm{Co}{\mathrm{Ge}}_{3}$ series crystallize in the tetragonal $\mathrm{Ba}\mathrm{Ni}{\mathrm{Sn}}_{3}$-type structure. The lattice parameters and unit cell volumes decrease with increasing Pr concentration. On the basis of the measurements taken, a preliminary magnetic phase diagram was created. Continuous suppression of the long-range magnetic ordering was observed with an increase of Pr concentration. The critical Pr concentration for magnetic moment ordering was determined from linear extrapolation of the ordering temperature versus $x$ to the lowest temperatures ($T=0$ K) and is equal to about 0.66. Based on the first-principles calculations, we show how the substitution of Pr for Ce affects the electronic structure and magnetic properties of the considered alloys. Within a single model, we take into account the magnetic ordering, fully relativistic effects, and Hubbard $U$ repulsion on Ce and Pr. The impact of Hubbard $U$ on the results of calculations is also discussed. We present the valence band analysis, Mulliken electronic population analysis, and calculated electronic specific heat coefficients. For $\mathrm{Ce}\mathrm{Co}{\mathrm{Ge}}_{3}$, it is found that the $++\ensuremath{-}\ensuremath{-}$ configuration of magnetic moments on Ce is slightly more stable than the $+\ensuremath{-}+\ensuremath{-}$ one, and also that the calculated value of total magnetic moment on Ce (including spin and orbital parts) is in good agreement with the measurements.