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We examine dark matter production rates in supersymmetric axion modelstypified by the mass hierarchy m_gravitino << m_neutralino << m_axino. In suchmodels, one expects the dark matter to be composed of an axion/gravitinoadmixture. After presenting motivation for how such a mass hierarchy mightarise, we examine dark matter production in the SUSYKim-Shifman-Vainshtein-Zakharov (KSVZ) model, the SUSYDine-Fischler-Srednicki-Zhitnitsky (DFSZ) model and a hybrid model containingcontributions from both KSVZ and DFSZ. Gravitinos can be produced thermally andalso non-thermally from axino, saxion or neutralino decay. We obtain upperbounds on T_R due to overproduction of gravitinos including both the thermaland non-thermal processes. For T_R near the upper bound, then dark matter tendsto be gravitino dominated, but for T_R well below the upper bounds, then axiondomination is more typical although in many cases we find a comparable mixtureof both axions and gravitinos. In this class of models, we ultimately expectdetection of relic axions but no WIMP signal, although SUSY should ultimatelybe discovered at colliders.

Mixed axion/gravitino dark matter from SUSY models with heavy axinos