Charge ordering driven metal-insulator transition in the layered cobaltite HoBaCo2O5.5

In this Brief Report we report high-resolution synchrotron x-ray diffraction and x-ray pair-distribution-function analysis as a function of temperature on the HoBaCo2 O5.5 cobaltite. These investigations provided a direct evidence of a structural phase transition from an orthorhombic to a monoclinic phase in the HoBaCo2 O5.5 layered cobaltite which occurs concomitantly with the metal to insulator transition. The structural data suggest a possible charge ordered state in the monoclinic phase which may be responsible for the insulating character at low temperature