Ir 4f hard X-ray photoemission spectrum of CuIr2S4

We have measured Ir 4f core-level photoemission spectra using an excitation photon energy of 6 keV for single crystalline CuIr 2 S 4 at 250 and 200 K across the metal–insulator transition temperature of about 226 K . The Ir 4f spin–orbit doublet shifts by about 0.25 eV towards higher binding energy with decreasing temperature. Tails and satellites around 1 and 13 eV , respectively, higher in binding energy than the peaks of Ir 4f doublets are observed in the 250-K spectrum, but they almost disappear at 200 K . The peak analysis here done indicates that the Ir 4f spectrum at 200 K consists of two components 0.2 eV apart corresponding to the charge separation of Ir ions in CuIr 2 S 4 .