Spin dynamics investigated by EPR in the paramagnetic regime of La2/3Ca1/3Mn1− x Me x O3 (Me = Al, In) manganites.

We report an electron paramagnetic resonance (EPR) investigation of the spin dynamics in the paramagnetic regime of the colossal magnetoresistive manganites La_2/3Ca_1/3Mn_{1− x} Me _x O₃ (Me=Al, In; x≤0.05). The temperature dependences of the EPR linewidth and integral intensity have been analyzed in terms of the bottleneck spin relaxation and small-polaron hopping models. The exchange coupling integral between Mn³⁺ and Mn⁴⁺ ions and the polaron activation energy decrease with increasing doping level. A discussion is given concerning the factors which could explain the observed changes. [ABSTRACT FROM AUTHOR]