Optical study of competition between ordering and metallicity in La(2-2x)Sr(1+2x)Mn(2)O(7)

Times Cited: 3
We study by spectroscopic ellipsometry the optical in-plane anisotropies in La(2-2x)Sr(1+2x)Mn(2)O(7) with 0.32less than or equal toxless than or equal to0.40 above and below the metal to insulator (MI) transition. Spectral-weight changes in the optical conductivity occur at a cross-over temperature T(’)=280 K for all dopings. Local ordering of orbital and charge degrees of freedom sets in doping dependently at temperatures of 145 Kless than or equal toT(*)less than or equal to310 K. Below the MI transition we observe for all dopings except x=0.36 a vanishing of the charge ordering and an isotropic and metallic state at low frequencies, whereas the local orbital ordering persists. For x=0.36 we observe two different characteristic developments of the ordering processes, one being compatible with the parabolic doping dependence on T(*) established by the other doping levels and the second showing ordering at a temperature slightly above the MI transition. We argue that our observations are compatible with a phase separation scenario.

Av författaren/redakt...: Kunze, J.; Naler, S.; Bäckström, Joaki ...; Rubhausen, M.; Mitchell, J. F.

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