Valence instability of europium in EuCo2Si2

Charge, lattice and magnetism across the valence crossover in EuIr2Si2 single crystals

“…The gray line represents (1) for Eex=(390±20) K, T sf =(101±7) K. room temperature are consistent with previous works [23], for EuIr 2 Si 2 the z parameter differs slightly from that reported in the literature [24] and the lattice parameters show strong temperature dependence. The refined parameter z for EuRh 2 Si 2 is published here for the first time.…”

Anomalous susceptibility in single crystals of EuCo2Si2 with trivalent Eu: Influence of excited J multiplets

“…Notice, however, that the low temperature susceptibilities in Fig. 3 are over fifty times smaller than that reported for polycrystals 11.…”

“…5. The resistivity is metallic and presents no clear evidence of a valence transition or magnetic order in the temperature range 2–300 K. A value of ρ 0 ∼ 0.74 µΩ cm is reached at the lowest temperatures, corresponding to a residual resistivity ratio ρ (300 K)/ ρ 0 = 72, roughly an order of magnitude higher than the value reported for polycrystalline samples 11. Below ∼30 K the resistivity is compatible with Fermi liquid behavior $\rho _{{\rm FL}} (T) = \rho _{0} + AT^{2} $ with A ∼ 0.00022 µΩ cm K −2 , indicating weak electron–electron correlations.…”

Electronic structure and photoemission properties of EuF3 and EuCo2X2 (X = Si, Ge) compounds by ab initio methods

“…In the EuF 3 compound, Eu exhibits the Eu 3+ (4f 6 ) state with possible surface valence transition to Eu 2+ state [3,4]. In polycrystalline EuT 2 X 2 , where T is the transition metal and X = Si or Ge, the valence of europium is unstable and depends on temperature, pressure and composition (Si ↔ Ge substitution) ( [5] and references cited therein). The valence of metallic Eu and in its compounds was the subject of the theoretical band structure investigations [1,2], but the EuF 3 and EuCo 2 X 2 compounds were * Corresponding author at: ul.…”

“…For the EuCo 2 X 2 compounds the ThCr 2 Si 2 -type crystal structure (space group: I4/mmm) was assumed and atomic positions were taken from our X-ray diffraction data analysis. The calculations for all compounds were performed using the experimental lattice parameters [5,6]. The band structure calculations were performed with the use of the WIEN2k code of Blaha et al [7] based on very accurate full potential linearized augmented plane waves (FP-LAPW) method.…”