The recovery of a magnetically dead layer on the surface of an anatase (Ti,Co)O₂ thin film via an ultrathin TiO₂ capping layer

The effect of an ultrathin TiO₂ capping layer on an anatase Ti_0.95Co_0.05O_2-δ (001) epitaxial thin film on magnetism at 300 K was investigated. Films with a capping layer showed increased magnetization mainly caused by enhanced out-of-plane magnetization. In addition, the ultrathin capping layer was useful in prolonging the magnetization lifetime by more than two years. The thickness dependence of the magnetic domain structure at room temperature indicated the preservation of magnetic domain structure even for a 13 nm thick film covered with a capping layer. Taking into account nearly unchanged electric conductivity irrespective of the capping layer’s thickness, the main role of the capping layer is to prevent surface oxidation, which reduces electron carriers on the surface.