  The Andreev transport through a quantum dot coupled to two external
ferromagnetic leads and one superconducting lead is studied theoretically by
means of the real-time diagrammatic technique in the sequential and cotunneling
regimes. We show that the tunnel magnetoresistance (TMR) of the Andreev current
displays a nontrivial dependence on the bias voltage and the level detuning,
and can be described by analytical formulas in the zero temperature limit. The
cotunneling processes lead to a strong modification of the TMR, which is most
visible in the Coulomb blockade regime. We find a zero-bias anomaly of the
Andreev differential conductance in the parallel configuration, which is
associated with a nonequilibrium spin accumulation in the dot triggered by
Andreev processes.
