The possibility of ferromagnetic instability in a system with hopping
between manganese cations and oxygen anions has been investigated on t
he basis of the concept of strong electron-electron interaction in one
unit cell. A phase diagram for ferromagnetic ordering as a function o
f the filling factors of the 2p(6)-shell of oxygen (n(p)) and 3t(g)(6)
-shell of manganese(n(t)) has been constructed. (C) 1998 American Inst
itute of Physics. [S1063-7761(98)02703-6].