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1.	Kunze, J., et al. (författare) Optical study of competition between ordering and metallicity in La(2-2x)Sr(1+2x)Mn(2)O(7) 2003 Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 67 Tidskriftsartikel (refereegranskat)abstract 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.

Kunze, J., et al. (författare)
Optical study of competition between ordering and metallicity in La(2-2x)Sr(1+2x)Mn(2)O(7)
2003
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 67
Tidskriftsartikel (refereegranskat)abstract
- 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.

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