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|Type:||Artigo de periódico|
|Title:||Phonon Raman Scattering In A2mn2o7 (a=tl,in,y)|
|Abstract:||Raman scattering of optical phonons in polycrystalline A2Mn2O7 (A=Y, In, and Tl) are reported as a function of temperature. For A=In and Tl a hardening of the two lowest energy modes is observed below Tc that we associate to a phonon modulation of the exchange interaction. These data suggest superexchange as the mechanism responsible for magnetic ordering in these systems. All but one of the Raman modes in the In- and Tl-based compounds appear at lower frequencies when compared with those in the Y-based one. This frequency shift may be due to the strong hybridization of the Tl(In) 6s(5s) orbital with O 2p and Mn 3d, claimed by recent band-structure calculations on these materials. ©1999 The American Physical Society.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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