Effects of hole doping on magnetic and lattice excitations in Sr2Ir1-xRuxO4 (x=0-0.2)

Raman scattering is employed to explore the effects of hole doping in single crystals of Sr2Ir1-xRuxO4 (x = 0, 0.01, 0.03, 0.05, 0.1, and 0.2). Introducing a few percentages of holes has a strong impact on magnetic excitations and lattice dynamics. With increasing x the well structured two-magnon continuum turns into diffusive magnetic scattering. Furthermore one-and two-phonon scatterings are rapidly suppressed. Remarkably, the two Ir(Ru)-O-Ir(Ru) bond angle modes with different Ir(Ru)O-6 octahedral rotations coexist and compete upon hole doping. This is ascribed to the difference of electronic properties between Ir4+ and Ru4+ ions. The doping and temperature dependence of the bond angle modes suggests that an electronically phase separated state develops upon Ru doping.