Evidence of Homogeneous Intermediate Valence Coexisting with the Long-Range Magnetic Order in EuCu2(Si, Ge)2

Uncommon Magnetism in Rare-Earth Intermetallic Compounds with Strong Electronic Correlations

“…The dependence of T N on pressure according to the results of all the above experiments is shown in Figure 9. The dependence of T N on pressure obtained in [22] qualitatively and quantitatively (by the value of T N ) reproduces the dependence of T N on the concentration of Si shown in the inset in Figure 9. The monotonic increase in the ordering temperature with pressure turns into a sharp decrease; there is no magnetic ordering at P > 9.5 GPa, similar to Si concentrations above x = 0.65.…”

“…The study of EuCu 2 (Si,Ge) 2 -type systems seems to be very important in terms of the coexistence of intermediate valence and LRMO. For this series of compounds [17][18][19][20][21][22], as well as for similar 1-2-2-type Eu systems [23,[25][26][27][28][29], extensive regions of the phase diagram have been obtained, corresponding to both the ground state with LRMO AFMtype and the intermediate-valence state of europium. An important feature of all these compounds is that one of the initial Eu configurations involved in the formation of the intermediate-valence state is formally non-magnetic (Eu 3+ , J = 0), similar to Ce-and Yb-based systems, which do not exhibit LRMO [14,32].…”

“…The direct relationship, established in [22], between the effects of "chemical" [18,20] and hydrostatic [68] pressure allows the generalisation of the results obtained from a series of neutron experiments and their correspondence to the magnetic phase diagram of EuCu 2 (Si,Ge) 2 . Lots of important data obtained from measurements of neutron spectra in relation to the magnetic phase diagram of EuCu 2 (Si,Ge) 2 [17][18][19] are shown in Figure 10.…”

“…In this situation, it was extremely important to make a direct comparison of the effects of hydrostatic and "chemical" pressure on the initial compound EuCu 2 Ge 2 . The phase diagram of the intermediate-valence system EuCu 2 Ge 2 has been studied by measuring the temperature dependence of the heat capacity and electrical resistance as a function of pressure up to 15 GPa in [22]. The dependence of T N on pressure according to the results of all the above experiments is shown in Figure 9.…”

“…In Sm's intermediate-valence compounds, magnetism has not been reliably detected. On the contrary, wide regions of the pressure (substitution)-temperature phase diagram, which correspond both to the ground state with the long-range magnetic order (LRMO) of AFM-type (typical T N ∼10-30 K) and intermediate-valence state of europium, were obtained for Eubased 1-2-2 compounds (EuCu 2 (Si,Ge) 2 [17][18][19][20][21][22], EuPd 2 Si 2 [23], EuPt 2 Si 2 [24] EuNi 2 P 2 [25], EuNi 2 Ge 2 [26,27], and EuRh 2 Si 2 [28,29]).…”