Infrared study on the electronic structure of alkaline-earth-filled skutterudites AT4Sb12 (A = Sr, Ba; M = Fe, Ru, Os)

Abstract

The optical conductivity [$\sigma (\omega )$] spectra of alkaline-earth-filled skutterudites with the chemical formula $A^{2+}{M}_4$Sb${}_{12}$ ($A$ = Sr, Ba, $M$ = Fe, Ru, Os) and a reference material La${}^{3+}$Fe${}_4$Sb${}_{12}$ were obtained and compared with the corresponding band structure calculations and with calculated $\sigma (\omega )$ spectra to investigate their electronic structures. At high temperatures, the energy of the plasma edge decreased with the increasing valence of the guest atoms $A$ in the Fe${}_4$Sb${}_{12}$ cage indicating hole-type conduction. A narrow peak with a pseudogap of 25 meV was observed in SrFe${}_4$Sb${}_{12}$, while the corresponding peak were located at 200 and 100 meV in the Ru- and Os-counterparts, respectively. The order of the peak energy in these compounds is consistent with the thermodynamical properties in which the Os-compound is located between the Fe- and Ru-compounds. This indicated that the electronic structure observed in the infrared $\sigma (\omega )$ spectra directly affects the thermodynamical properties. The band structure calculation implies the different electronic structure among these compounds originates from the different $d$ states of the $M$ ions.

7 pages, 6 figures

References in corpus (3)

• Self-consistent self-energy analysis of photoemission data
• Bare electron dispersion from photoemission experiments
• Iron-Based Heavy Quasiparticles in SrFe${}_4$Sb${}_{12}$: An Infrared Spectroscopic Study