Optical evidence for lattice polarons in lightly doped lanthanum manganites in paramagnetic state

摘要

The reflection and absorption spectra and the resistivity data for La _(0.93)Sr_(0.07)MnO_3, La_(0.9)Sr _(0.1)MnO_3, La_(0.85)Sr_(0.15)MnO _3, La_(0.92)Ca_(0.08)MnO_3 and La _(0.85)Ba_(0.15)MnO_3 single crystals have been collected and analyzed by using small lattice polaron theory. The activation energies of the polaron hop are determined. The lattice polarons are found to be dominated in the electronic transport and optical properties in the paramagnetic state in La_(0.93)Sr_(0.07)MnO_3, La _(0.92)Ca_(0.08)MnO_3 and La_(0.85)Ba _(0.15)MnO_3 crystals. It is shown that lattice polaron involves more than one Mn site.