Phase Diagram of Electronic Models for Transition Metal Oxides in One Dimension

The zero temperature phase diagram of the ferromagnetic Kondo model in one dimension is studied using numerical techniques, especially at large Hund coupling. A robust region of fully saturated ferromagnetism (FM) is identified at all densities. Phase separation between hole-rich and hole-poor regions and a paramagnetic regime with quasilocalized holes were also observed. It is argued that these phases will also appear in two and three dimensions. Our results apply both to manganites and one-dimensional compounds such as Y_2-xCa_xBaNiO₅. As the transition metal ion spin grows, the hole mobility rapidly decreases, explaining the differences between Cu oxides and Mn oxides.