  The samples LaCoO3 with dilute substitutions on cobalt sites have been
studied using the resistivity, thermopower and magnetic susceptibility
measurements over the temperature range up to ~900 K. The Co-site substitution
does not affect the magnetic transition at ~100 K and the onset of massive
population of hole carriers at ~500 K, characteristic for undoped LaCoO3. On
the other hand, the low-temperature transport and magnetism is markedly
distinct for samples with extra charge on cobalt ions introduced by the
heterovalent dopants (Mg2+, Ti4+) compared to samples with minor
non-stoichiometry (LaCoO3, Ga3+ doped sample). Magnetic properties suggest that
these extra charges create thermally stable magnetic polarons of total S ~ 2-3.
Common features of Co-site doped and La-site doped samples (La1-xSrxCoO3) are
discussed
