Magnetic order and energetics of dipolar coupling in magnetic superconductors.
The exact (not just nearest-neighbor) dipolar coupling energy densities for the observed structures of the rare earth Chevrel compounds are calculated by the method of Luttinger and Tisza. The dipolar coupling energy density for the most probable spin configuration is comparable to the observed magnetic transition temperature, T(M), but the most probable ground state is not found experimentally. The discrepancy between the observed magnetic ground state and that predicted from dipole coupling may arise from conduction electron effects or possibly from some strong crystal field effect and should be included in any electronic theory of the superconductive state below T(M).
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Princeton University, Princeton, New Jersey 08544.
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