On the Theory of Magnets with Competing Double Exchange and Superexchange Interactions

Abstract

In the CMR materials, ferromagnetic double exchange (DE) presumably coexists with a direct nearest-neighbour antiferromagnetic interaction. We construct a single-site mean field theory that explicitly takes into account the different nature of carrier-mediated ferromagnetism vs. Heisenberg-like superexchange. We find, in contrast to previous results in the literature, that the competition between these two exchange interactions leads to ferro- or antiferromagnetic order with incomplete saturation of the magnetization (or sublattice magnetization), rather than spin canting. The associated experimental implications are discussed.

This is a long version of an earlier paper, cond-mat/9712094. 10 pages, Latex-Revtex, 8 PostScript figures. Minor revisions, references added

References in corpus (3)

• Phase Separation in Electronic Models for Manganites
• Evolution of the low-frequency spin dynamics in ferromagnetic manganites
• Static and Dynamical Properties of the Ferromagnetic Kondo Model with Direct Antiferromagnetic Coupling Between the localized $t_{2g}$ Electrons

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