Europhys. Lett.
Volume 76, Number 5, December 2006
Page(s) 933 - 937
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 November 2006
Europhys. Lett., 76 (5), pp. 933-937 (2006)
DOI: 10.1209/epl/i2006-10345-8

Optical indication of metallic clusters in the layered manganites $\chem{La_{2 - 2{\it x}}Sr_{1 + 2{\it x}}Mn_{2}O_{7}}$ above $\mth{T_\ab{C}}$

N. N. Loshkareva, E. V. Mostovshchikova, N. I. Solin, Yu. P. Sukhorukov, S. N. Tugushev and S. V. Naumov

The Institute of Metal Physics of UD of the Russian Academy of Sciences 620041, Ekaterinburg, S. Kovalevskoy str. 18, Russia

received 26 July 2006; accepted in final form 3 October 2006
published online 1 November 2006

Optical absorption in the bi-layered manganites $\chem{La_{2 - 2{\it x}}Sr_{1 + 2{\it x}}Mn_{2}O_{7}}$ (x=0.3 and 0.4) was studied and metallic clusters were revealed in the temperature range $T_\ab{C}<T<270\un{K}$ in the composition with x=0.4. The existence of metal clusters is considered as the principal cause of magnetoresistance, the tails of magnetization and ferromagnetic correlations, which are observed in this manganite up to temperatures several times exceeding the temperature $T_\ab{C}$ of 3D magnetic ordering.

75.47.Lx - Manganites.
78.20.-e - Optical properties of bulk materials and thin films.

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