Influence of A-site substitution on ESR spectra of lanthanum manganite perovskites

Abstract We studied electron spin resonance (ESR) spectra of La0.7A′0.3MnO3 (A′=Sr, Ba, Pb, and Cd) perovskites in a large range of temperature, from their Curie temperature to ∼500 K. Asymmetrical EPR signals at temperatures T C T T min , due to FM correlations, became Lorentzian at T ⩾ T min , where Tmin is the temperature corresponding to the narrowest ESR linewidth. The ESR linewidth vs. temperature, ΔH(T), in the region T > T min well fits to the model of adiabatic hopping motion of small polarons Δ H ( T ) = Δ H 0 + ( a / T ) exp ( - E a / k B T ) , where Ea and kB are the activation energy and the Boltzmann factor, respectively; ΔH0 and a are constants. It is worth noticing that, in this temperature range, the Lande factor g for the samples is about 2.00, indicating spin–spin interaction among electrons of Mn3+ and Mn4+ ions playing an important role.