The filled skutterudite CeOs4As12: A hybridization gap semiconductor

Abstract

X-ray diffraction, electrical resistivity, magnetization, specific heat, and thermoelectric power measurements are presented for single crystals of the new filled skutterudite compound CeOs4As12, which reveal phenomena that are associated with f-electron-conduction electron hybridization. Valence fluctuations or Kondo behavior dominates the physics down to T ∼ 135 K. The correlated electron behavior is manifested at low temperatures as a hybridization gap-insulating state. The small energy gap Δ1/ kB ∼ 73 K, taken from fits to electrical resistivity data, correlates with the evolution of a weakly magnetic or nonmagnetic ground state, which is evident in the magnetization data below a coherence temperature T coh ∼ 45 K. Additionally, the low-temperature electronic specific heat coefficient is small, γ ∼ 19 mJ/mol K2. Some results for the nonmagnetic analogue compound LaOs4As12 are also presented for comparison purposes. © 2008 by The National Academy of Sciences of the USA.