Magneto-electronic interactions in La0.8Ca0.2MnO3 perovskite

By means of extended magnetic after-effect (MAE) and electric resistivity m easurements (4 K < T < 300 K), polycrystalline La0.8Ca0.2MnO3 has been iden tified below the Curie temperature (T-C similar or equal to 190 K), as a fe rromagnetic, metal-like band-conductor and above T-C as a paramagnetic semi conductor, displaying a huge, magnetic order-related resistivity peak near 200 K. Weakly structured MAEs, occurring in the temperature range 4 K < T < 190 K with logarithmic time dependence, are attributed to continuously sup erimposed Debye processes with activation enthalpy spectra in the range 0.0 08 < Q < 0.5 eV and pre-exponential factors, tau(0), of 10(-12) to 10(-11) s. These enthalpy spectra are related re electrons which, due to localizati on at Jahn-Teller stabilized Mn3+-ions, are able to contribute to MAEs only after thermal activation. According to our analysis, charge transport in t he semiconducting phase, above T-C, is supported by hopping of small polaro ns with activation enthalpies, Q, of about 0.15 eV.