The phase diagram and low temperature properties of the doped manganites
A1-xBxMnO3 are discussed for the concentrations x < 0.4. The transition from
insulating antiferromagnetic to metallic ferromagnetic state at x_cr = 0.16 is
treated by means of percolation theory. The unifying description of insulating
and metallic states is presented. The undoped manganite is a band insulator
consisting of ferromagnetic layers, which are coupled antiferromagnetically
along the c direction with a low Neel temperature. The metallic phase can be
described by the two-band Fermi liquid picture. The behavior of conductivity,
spin wave excitations, etc. is analyzed and the comparison with experimental
data is carried out.Comment: To appear in EPJ, 35 pages, 5 figure