A study of the first-order valence transition in single crystals by magnetic susceptibility measurements

Abstract

The first-order valence transition in has been investigated for single crystalline samples with x = 0.32 and x = 0.35 as well as for polycrystalline samples with (x varied in steps of 0.01) through the measurements of magnetic susceptibility, . For the single crystal with x = 0.32, exhibits a strong anisotropic mixed-valence behaviour. On the other hand, of the crystal with x = 0.35 exhibits a sharp first-order valence transition at 50 K. In both crystals, the strong anisotropy, , is maintained as in the host compound CeNiSn. The arc-melted polycrystalline alloys with a narrow range of Co composition, x = 0.33-0.37, show a sharp drop in below 70 K and large hysteresis. This transition becomes sharper by annealing at . For the optimum concentration x = 0.35, the drop in at the transition becomes as high as 72% for the single crystal and 69% for the polycrystalline alloy for which a jump in ac heat capacity was observed at 55 K. Analysis of the above results reveals that the phase transition involves a large change in the Kondo temperature . The small volume discontinuity at the transition suggests that the phase transition is not due to a Kondo volume collapse. A possible mechanism responsible for the phase transition in the present alloys is proposed.

Successive phase transitions and energy-gap formation in CeRhAs

“…The broad feature might be due to the temperature cycle that is inevitable for the ac specificheat measurement. 20 It should be noted that the observed peak intensity for (ϩ1/3,k,0) is much weaker than that for (Ϫ1/3,k,0), where k is an integer. This asymmetry cannot be explained by taking account of solely the lattice modulation but suggests the modulation of charge density as found in CeP and CeSb, where the layers of Ce ions with two different 4 f -electron orbital states periodically stack along one crystallographic direction.…”

Bulk sensitive spectroscopy for the valence transition inYbInCu4-based compounds

“…The presence of the quasigap makes the Kondo temperature sensitive to the position of the Fermi level, showing the importance of the DOS dependence rather than the change in volume. In another related series of Ce-based mixed-valence transition compounds CeNi 1−x Co x Sn, Adroja et al 57 showed nonapplicability of the KVC model. We recently reported the PFY-XAS, RIXS, and resonant photoelectron spectroscopy for CeNi 1−x Co x Sn.…”

Cerium intermetallics with TiNiSi-type structure

“…Substitution of nickel by cobalt leads to a decrease of the VEC [266][267][268][269][270][271][272][273]. Samples were prepared up to a composition CeNi 1−x Co x Sn with x = 0.5 in polycrystalline as well as in single crystalline form (Czochralski technique along with inductive heating).…”