Application of Doniach Diagram on Valence Transition in EuCu₂(Si_xGe_1-x)₂

Europium mixed-valence, long-range magnetic order, and dynamic magnetic response in EuCu2(SixGe1−x)2Nemkovski1, Козленко2, Alekseev3 et al. 2016Phys. Rev. B301140View full textAdd to dashboardCite

“…This result, however, seems to contradict the overall "Eu 2+ -like" behavior observed in bulk properties (entropy, magnetization). This discrepancy was already noted in the paper by Fukuda et al, 32 but no explanation was proposed. It has been argued, in earlier x-ray absorption studies of other Eu intermetallics such as EuPd 2 P 2 (Ref.…”

“…23,32 However, quantitative determinations using different experimental techniques have remained controversial. Therefore, before discussing the dependence of the magnetic properties on the degree of valence mixing, one needs to consider possible problems in the interpretation of XANES and Mössbauer data.…”

“…Pure EuCu 2 Si 2 , on the other hand, can be described as an intermediate-valence Van-Vleck paramagnet. The suppression of magnetic order and the transition to a Fermi-liquid, HF regime takes place in a concentration range, near x c ∼ 0.65, where the Eu valence was reported 23,32 to deviates strongly from an integer value. In the Si-rich compounds (x = 0.9, 1.0), inelastic neutron scattering (INS) spectra 33 are characterized by a renormalized Eu 3+ -like intermultiplet (spinorbit) transition, together with an extra magnetic peak at lower energy, which has been interpreted as an excitonlike "resonance", related to the formation of a spin gap of 20-30 meV below T ∼ 100 K.…”

“…23 compare to those studied previously in Ce or Yb compounds. The key issue of a possible coexistence of long-range magnetic order with a MV state, as suggested in previous work, 23,32 is addressed by means of different microscopic probes (XANES, Mössbauer spectroscopy, neutron powder diffraction (NPD)). Evidence is reported for an unconventional coexistence of long-range magnetic order and a homogeneous MV state with spin fluctuations in EuCu 2 (Si x Ge 1−x ) 2 , occurring over a significant range of Si concentrations x below the critical value x c ≈ 0.65.…”

Pressure-Induced Valence Transition in Antiferromagnet EuRh2Si2

“…For ambient pressure, the -T curve, which generally shows a metallic behavior, exhibits a steep bend at T N and a linear temperature dependence above 100 K. The curve is similar to those of other Eu-based antiferromagnets with the ThCr 2 Si 2 -type structure. 12,13,[18][19][20] Below T N , the resistivity decreases more rapidly, which reflects the suppression of conduction-electron scattering by paramagnetic local moments of Eu 2þ . The application of a pressure of 0.51 GPa does not markedly change the shape of the curve but slightly shifts T N toward higher values, which is consistent with the present result of the susceptibility measurement.…”