Epitaxial thin films for a cubic manganate (La,Sr)MnO 3 and for a layer-structured (La,Sr) 3 Mn 2 O 7 have been grown by sputtering on SrTiO 3 (100) for the use as electrodes in polarized-spin injection experiments to the (La,Sr) 2 CuO 4 high T c superconductor. (La,Sr)MnO 3 thin films show a sufficiently smooth surface with optimal electric and magnetic properties. A decrease in the superconducting transition temperature T c has been obtained when the injected spin-current is increased, which suggests the occurrence of non-equilibrium effects. In contrast to (La,Sr)MnO 3 , the growth of c-axis (La,Sr) 3 Mn 2 O 7 layered manganate thin films has been found to occur under limited conditions characterized by a very low deposition rate of approximately 0.8nm/min at 760°C. It is found that annealing improves the magnetic properties while it deteriorates the flat film surfaces by giving rise to many precipitates, supposedly due to the existence of intergrowths. The control of intergrowth content is essential in order to use these layered materials as spin-polarizers.