Some aspects of the phase diagram of double-exchange systems

The phase diagram of doped manganate compounds ${\mathrm{La}}_{1-x}{A}_x{\mathrm{MnO}}_3$ (with divalent $A)$ with small $x$ is studied. We analyze an extension of the double-exchange model using the Schwinger boson formalism. Earlier work by de Gennes on the existence of a canted phase is reproduced, although this phase is shown to be unstable towards phase separation in a broad regime of physical interest. We numerically solve the mean-field equations for our model and exhibit its phase diagrams.