2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/198177We study a classical double exchange magnet with direct antiferromagnetic superexchange coupling, J, between the localized spins. It is shown that the de-stabilization of the ferromagnetic ground state with increasing J leads to phase separation; the latter always preempts the spin-wave instability (softening of the magnon spectrum). It is also found that the boundaries separating the ferromagnetic and antiferromagnetic areas of the sample tend to be abrupt.3 pages, LaTeX-Revtex, 2 PostScript figures; misprints corrected, including those in the published versionStrongly Correlated ElectronsMaterials Sciencetext