Metal to insulator transition in Sr2Ru1−xIrxO4

Abstract

X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and X-ray diffraction (XRD) techniques along with calculations of tight-binding linear muffin tin orbitals within the atomic sphere approximation (TB-LMTO-ASA) have been used for studying the metal to insulator transition (MIT) in the series Sr2Ru1−xIrxO4. Rietveld analysis of the XRD data indicated that the samples of x=0 to 0.4 are of I4/mmm space group and x=0.6 and 1.0 are of I41/acd space group. A drastic increase of Ru (Ir)–O1 bond length is observed between x=0.4 and 0.6. UPS data showed finite density of states (DOS) at EF for the samples of x=0.0 to 0.4, whereas no DOS at EF was observed for x=0.6 and 1.0 samples, indicating an MIT between x=0.4 and 0.6. On the contrary, linear muffin tin orbitals (LMTO) calculations show a finite DOS at EF for Sr2IrO4 (x=1.0) with a gap of 1.2eV in the DOS which starts 0.3 above EF. A large spectral weight transfer is seen in UPS conduction bands. These results indicate that the MIT observed in the Sr2Ru1−xIrxO4 series is a combined effect of structure and electron correlation effects.