We present a new low-temperature atomic layer deposition (ALD) process based on Mn2(CO)10 and ozone as precursors to fabricate crystalline α-Mn2O3 and Mn3O4 thin films; the phase composition is controlled by the deposition temperature such that the former phase forms in the range 60-100 °C and the latter in the range 120-160 °C. In both cases an appreciably high growth rate of ∼1.2 Å per cycle is achieved. The spinel-structured Mn3O4 thin films are shown to be ferrimagnetic with the transition temperature determined to be at ∼47 K.