Structural strain and competition between charge density wave and superconductivity in La(Fe,Mn)As(O0.89 F0.11) compounds

Selected members of the La(Fe,Mn)As(O0.89F0.11) system were analyzed using high-resolution synchrotron x-ray powder diffraction. The tetragonal to orthorhombic structural transition is progressively recovered in the optimally electron-doped LaFeAs(O0.89F0.11) phase by very light Mn substitution; at the same time, superconductivity is suppressed whereas magnetic ordering is restored. Distinct incommensurate satellite peaks develop within different thermal ranges and mark the occurrence of charge density waves characterized by distinct propagation wave vectors, as well as multiple incommensurate structural transitions; in particular, some of them arise in conjunction with the structural transformation process, disappearing after the completion of the dissymmetrization. The thermal evolution of satellite reflections observed at Q~1.93Å-1 indicates a strong competition between the charge density waves and the superconductive state. A phase diagram of the La(Fe,Mn)As(O0.89F0.11) system is drawn on the basis of the structural, magnetic, and electronic properties of the analyzed samples.