X-ray absorption spectroscopic analysis of CuIr2S4

X-ray-induced electronic structure change in CuIr2S4

“…The intensity ratio can be explained by the fact that there are more empty e g states than t 2g states (naively, 4 e g states and 0.5 t 2g states). This intensity ratio, in addition to the 2p core-hole broadening, is why the t 2g state has not been revealed in previous XAS studies [9,10] and in fact was not observed in our PFY-XAS. Only by utilizing the resonance enhancement of RXES can one see this state.…”

“…The high temperature metallic phase has a cubic spinel structure [8], but the system becomes insulating and diamagnetic with triclinic structure below the metal-insulator transition (MIT) temperature of T MI ∼ 230 K [9,10]. The "A"-site in the spinel structure is occupied by Cu, which is monovalent [11][12][13], and therefore inactive near the Fermi energy. The mixed-valent iridium ions (Ir 3.5+ ) occupy the B-sites, and form a pyrochlore lattice.…”

“…However, detailed investigation of electronic structure using core level x-ray spectroscopy has been limited. Although several Ir 4f photoemission experiments have reported that Ir 3+ /Ir 4+ charge disproportion does exist in the insulating phase, due to its surface sensitivity, the interpretation has not been straightforward [18][19][20].While x-ray absorption spectroscopy (XAS) at the S K-edge has been valuable in detecting redistribution of S 3p states across the MIT [12], the Ir L 3 -edge XAS has not been very useful due to broad spectral features arising from the short core-hole lifetime [12,13]. In this work, we report bulksensitive x-ray spectroscopic studies which allow us to obtain direct information regarding the Ir 5d electronic states across the MIT and also in the IILT phase.…”

Enhancement of the Peierls-like phase transition in the Cu 1− x Li x Ir 2 S 4 system

“…Introduction. -The sulphospinel CuIr 2 S 4 has attracted considerable attention due to the Peierls-like phase transition which rarely occurs in the threedimensional materials [1][2][3][4]. When the first-order phase transition takes place at T MI ∼ 230 K with temperature decreasing, the system changes from Normal State (NS) to Peierls-like State (PS) accompanied by the transformation of conductivity from metallic to insulating, the loss of localized magnetic moments, the lowering of the lattice symmetry from cubic to triclinic, etc.…”