EXAFS and EPR study of La0.6Sr0.2Ca0.2MnO3 and La0.6Sr0.2Ba0.2MnO3

Abstract

Extended X-ray absorption fine structure (EXAFS) analysis and electron-paramagnetic resonance (EPR) have been used to examine the local structure and the internal dynamics of La0.6Sr0.2Ca0.2MnO3 and La0.6Sr0.2Ba0.2MnO3 lanthanum manganites. The Mn-O bond distance (similar to 1.94Angstrom for both samples) and the Debye-Waller factors (0.36 x 10(-2) and 0.41 X 10(-2) Angstrom(2) for La0.6Sr0.2Ca0.2MnO3 and for La0.6Sr0.2Ba0.2MnO3, respectively) were obtained from the EXAFS analysis. The dependence of the EPR line width on dopant kind (Ca or Ba) showed a decrease of the spin-lattice interaction with an increase of the Curie temperature. For both compositions, the EPR line intensity followed the exponential law I(T) = I-0 exp(E-a/k(B) T), deduced on the basis of the adiabatic polaron hopping model. (C) 2002 Elsevier Science B.V. All rights reserved.