EXAFS and EPR study of La 0.6Sr 0.2Ca 0.2MnO 3 and La 0.6Sr 0.2Ba 0.2MnO 3

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 La 0.6Sr 0.2Ca 0.2MnO 3 and La 0.6Sr 0.2Ba 0.2MnO 3 lanthanum manganites. The Mn–O bond distance (∼1.94 Å for both samples) and the Debye–Waller factors (0.36×10 −2 and 0.41×10 −2Å 2 for La 0.6Sr 0.2Ca 0.2MnO 3 and for La 0.6Sr 0.2Ba 0.2MnO 3, 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.