Underdoped manganites: canted antiferromagnetic ordering or two-phase ferro-antiferromagnetic state?

We calculate the energy of charge-carrier-induced canted ordering in conduc ting layered antiferromagnetic systems with double exchange. The quantum ap proach to the d-spins is used. In the jellium model the energy of the cante d state is lower than the energies of both collinear ferro- and antiferroma gnetic states over a certain range of charge carrier densities, beginning w ith arbitrarily small densities. Nevertheless, the canted state cannot be r ealized, because it is unstable against charge-carrier density fluctuations . The two-phase ferro-antiferromagnetic state can play the role of an alter native to canting. The case of an intermediate electronic-impurity phase se paration is investigated. (C) 1998 American Institute of Physics. [S1063-77 61(98)02612-2].