Control of Oxygen Nonstoichiometry and Magnetic Property of MnCo₂O₄ Thin Films Grown by Atomic Layer Deposition

Spinel-structured (Mn,Co) 3 O 4 thin films were reproducibly fabricated by atomic layer deposition (ALD) using Mn(thd) 3, Co(thd) 2, and ozone as precursors. A full control of the cation ratio was achieved in the temperature interval 140−160 °C within which also the growth rate remained constant. Precise control of the oxygen content of as-deposited MnCo 2 O 4+δ films was achieved through postdeposition heat treatments at prefixed temperatures in air and N 2 atmospheres, as evidenced from the monotonous increases of both the unit cell volume and the Curie temperature ( T C ) with increasing annealing temperature/decreasing oxygen partial pressure. The T C value varied from 92 K for the as-deposited MnCo 2 O 4+δ films to 182 K for the films annealed at 700 °C in N 2 flow.