Localized and itinerant electronic states at the insulator-metal transition in Y1-xCaxVO3+delta: evidence from electric transport, magnetic properties and XAS spectroscopy

Electron transport and macroscopic magnetic properties of the perovskite mixed-valent system Y1-xCaxVO3+delta were investigated by means of resistivity and magnetic susceptibility measurements. As is shown by transport data, the system undergoes an insulator-metal transition on doping with Ca beyond the threshold concentration x approximate to 0.35. However, magnetic response data evidence a more complex scenario in which localized-electrons giving rise to magnetism coexist with itinerant electrons, well beyond the metal-insulator (M-I) transition. In the insulating compounds, susceptibility data suggest the occurrence of short-range order slightly above T approximate to 114 K, which is reminiscent of the temperature at which the parent compound YVO3 undergoes a transition to an antiferromagnetic long-range order. In the metallic samples, evidence of a possible electronic phase segregation are found.