UNSPECIFIED (2005) Low-energy excitations in La1.2Sr1.8Mn2O7 investigated by ellipsometry. PHYSICAL REVIEW B, 72 (21). -. doi:10.1103/PhysRevB.72.214437 ISSN 1098-0121.

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Abstract

The low-energy excitations of the bilayered manganite La1.2Sr1.8Mn2O7 have been explored by spectral ellipsometry from two faces of a single crystal over the range from 0.006 to 0.6 eV. This compound is a paramagnetic insulator at ambient temperature, with a transition to a ferromagnetic metal below a Curie temperature (T-c) of 125 K. Both the ab-plane and c-axis temperature-dependent conductivities have been determined. Essentially no temperature-dependent behavior is observed above T-c although below T-c both the phonon and electronic contributions are strongly temperature sensitive. The highest-frequency phonons, especially those involving Mn-O bond stretching, split and show frequency changes consistent with structural results in the literature, and furthermore there is clear evidence of an increase in electron-phonon coupling at and below T-c. We interpret the temperature-dependent electronic spectral contribution in the light of recent calculations that indicate that a mixed phase exists in the doped manganites below T-c, with coexisting regions of an itinerant large-polaron phase and a localized small-polaron phase.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Journal or Publication Title:	PHYSICAL REVIEW B
Publisher:	AMERICAN PHYSICAL SOC
ISSN:	1098-0121
Official Date:	December 2005
Dates:	Date Event December 2005 UNSPECIFIED
Volume:	72
Number:	21
Number of Pages:	5
Page Range:	-
DOI:	10.1103/PhysRevB.72.214437
Publication Status:	Published

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