Electron-phonon coupling assisted emission in single magnetic La0.67Ca0.33MnO3 domains of thin nanoplates.
A chemical method with small polymer templates is explored to obtain single magnetic domain La0.67Ca0.33MnO3 particles of thin nanoplates (25-35 nm thickness). The sample is light-emitting (480-800 nm) in multiple bands with two prominent bandgroups in the 570 nm green and 762 nm red emissions. The green emission consists of four bands 555.1, 565.7, 573.4, and 584.7 nm in the O2- -2p--> Mn3+ / Mn4+ -3d interband electronic transitions. Two excited-electronic levels G, (565.7 nm) and G2 (555.1 nm), which are exchange coupled via a phonon level v2* (678 cm(-1)), exhibit the four bands in the transitions to the ground state G0 and a phonon level v1 (575 cm(-1)). The bands v1 and v2 are well-resolved in the IR spectrum. A similar phonon assisted Mn3+ --> Mn4+ charge transfer transition results in the red emission. Both the green and red bandgroups appear in a common excitation over 350-450 nm from a xenon source. Evidently, as proposed with a model energy level diagram, the electron-phonon coupling governs a multiple light-emission in this example of the single domain particles. Otherwise, such specific ceramics of half-metallic ferromagnets hardly allows a light-emission at room temperature.
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Debasis
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Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302, W.B., India.
Ram
Shanker
S
Roy
Sanat K
SK
Banerjee
Alok
A