Short-Range Ordered Phase of the Double-Exchange Model in Infinite Dimensions
Abstract
Using dynamical mean-field theory, we have evaluated the magnetic instabilities and T=0 phase diagram of the double-exchange model on a Bethe lattice in infinite dimensions. In addition to ferromagnetic (FM) and antiferromagnetic (AF) phases, we also study a class of disordered phases with magnetic short-range order (SRO). In the weak-coupling limit, a SRO phase has a higher transition temperature than the AF phase for all fillings p below 1 and can even have a higher transition temperature than the FM phase. At T=0 and for small Hund's coupling JH, a SRO state has lower energy than either the FM or AF phases for 0.26 p < 1. Phase separation is absent in the JH --> 0 limit but appears for any non-zero value of JH.
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