Comparison between Ce and Yb heavy fermion compounds: versus

Temperature and pressure-induced valence transitions inYbNi2Ge2andYbPd2Yamaoka1, Jarrige2, Tsujii3 et al. 2010Phys. Rev. B486560View full textAdd to dashboardCite

“…One is the stronger localization of the 4f shell in Yb than in Ce and the other is the substantially stronger spin-orbit coupling of Yb than Ce. 48 Our present results are consistent with these observations, as they suggest that a slow crossover from Fermi liquid to magnetically ordered state occurs for both Yb compounds. The pressure dependence of the valence has not been reported yet for CeNi 2 Ge 2 and CePd 2 Si 2 , but we believe that the comparison with the Yb122 systems will be interesting because of the analogy with the relation between CeRh 2 Si 2 and YbRh 2 Si 2 .…”

“…For example, in CeRh 2 Si 2 the transition from AFM order to a paramagnetic ͑PM͒ state is believed to be first order with a volume discontinuity. 48 On the other hand, YbRh 2 Si 2 shows a continuous change from AFM to PM under pressure. 49 This difference in the pressure dependence between these systems has been explained by two kinds of scenarios.…”

Superconductivity in Ce- and U-Based “122” Heavy-Fermion Compounds

“…36,38,39 The superconducting T c reaches a maximum at p c with T c ≈ 0.42 K. 40 It should be noted that antiferromagnetism vanishes in a first order phase transition at p c as recently proven by clear volume discontinuities in thermal expansion measurements under pressure around p c . 41,42 Moreover, at the magnetic instability Fermi-liquid behavior is observed. For instance, the electrical resistivity displays Fermiliquid behavior even around p c with a ∆ρ = AT 2 temperature very large values of this ratio [3].…”

“…39 However, the A coefficient of the electrical resistivity shows a pronounced maximum at the critical pressure p c . 40,42 At the same time, the temperature-independent specific heat coefficient γ rises steeply from ambient pressure, where the mass enhancement is small (γ = 23 mJ/molK 2 ) up to p c where γ ≈ 80 J/molK 2 is found (cf. Fig.…”

Development of the Valence Fluctuation in the Nearly Divalent Compound YbCu2Ge2under High Pressure

“…However, the energy scales, e.g. characteristic pressures, temperatures, and magnetic fields, are quite different as discussed in the the case of YbRh 2 Si 2 and CeRh 2 Si 2 [5,6]. Recently, important differences between two systems have been pointed out: the hierarchy of the significant energy scales, the band width of the 4 f -electron and the strength of the spin-orbit splitting, resulting in the noticeable different variations of their valence in a real lattice , i.e.…”