Paramagnetic scattering from the valence-fluctuation compoundYbAl3

Localized Excitation in the Hybridization Gap inYbAl3

“…1 we plot the scattering at T = 6 K as a function of energy transfer at different momentum transfers. In agreement with the earlier results reported for polycrystals, 8,9 the scattering shows two features: a peak centered at E 2 = 33 meV, whose width is essentially equal to the instrumental resolution, and a broad feature centered near For each value of Q 1 = (2p/a 0 ) (h,k l) we measured the 10 K spectra at a second momentum transfer Q 2 = (2p/a 0 ) (h,k l+2) that is equivalent to Q 1 in the reduced zone scheme and has a similar structure factor, and then fit the data as the sum of a magnetic contribution M(E) that varies with Q as the 4f form factor, a phonon contribution Ph(E) that scales as Q 2 and a constant background, measured in energy gain.…”

“…3c, independent of (reduced) Q. This spectrum is very similar to that seen in polycrystals 8 at 100 K; the sharp feature at E 2 disappears above 40 K. The Q-independence suggests that the spin dynamics for T > T coh is that of incoherent Kondo scattering. We note, however, that the scattering at the (1/2,1/2,1/2) zone boundary point is considerably weaker.…”

“…It is believed that the minimum and the mid-IR peak arise from the (vertical) interband transitions across the hybridization gap, while the Drude resonance arises from intraband transitions across the Fermi level, which lies in a region of high density of states near the zone boundary. Inelastic neutron scattering (INS) experiments 8 in polycrystalline samples of YbAl 3 have shown that for T > 40 K the magnetic scattering is broad with a characteristic energy of order E 1 ≈ 50 meV, corresponding to the Kondo temperature, but 3 at low temperature an additional narrow peak occurs in the INS near E 2 = 33 meV. This is the same energy as the minimum in the optical conductivity, i.e it occurs on the same scale as the hybridization gap.…”

Reduced moment magnetic ordering in a Kondo lattice compound: Ce8Pd24Ga

“…no magnetic scattering) and a broad q-independent peak centred at 65 meV with a linewidth of 68 meV. 29,30 This is a typical response observed in valence-fluctuating systems, in which the strong hybridization between localised 4f electrons and conduction electrons is present. 31 The presence of well defined CF excitations in Ce 8 Pd 24 Ga indicates that the strength of hybridization has reduced considerably.…”

“…Figure 5a shows the magnetic inelastic response from Ce 8 Pd 24 Ga measured on HET at 17 K. The phonon scattering has been subtracted using a standard scaling method. 21,29 We observed two welldefined crystal field (CF) excitations at energies of 3.2 meV and 12.8 meV, corresponding to transitions from the ground state doublet to the two excited CF doublets. It is noteworthy that the inelastic response of CePd 3 does not show any sign of CF excitations, instead it exhibits a gap type response below 20 meV (i.e.…”