Suppression of ferromagnetic double exchange by vibronic phase segregation.
From Raman spectroscopy, magnetization, and thermal expansion on the system La(2/3)(Ca(1-x)Sr(x))(1/3)MnO3, we have been able to provide a quantitative basis for the heterogeneous electronic model for manganites exhibiting colossal magnetoresistance (CMR). We construct a mean-field model that accounts quantitatively for the measured deviation of T(C)(x) from the T(C) predicted by de Gennes double-exchange in the adiabatic approximation and predicts the occurrence of a first-order transition for a strong coupling regime, in accordance with the experiments. The existence of a temperature interval T(C) < T < T*, where CMR may be found, is discussed in connection with the occurrence of an idealized Griffiths phase.
Physical-Chemistry Department, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain.
F
F
Rivadulla
M
M
Otero-Leal
A
A
Espinosa
A
A
de Andrés
C
C
Ramos
J
J
Rivas
J B
JB
Goodenough