Preparation of homogeneous Mn-X-Bi (X=Cu, Ni) thin films by rf sputtering

The conditions (annealing temperature and chemical composition) for preparing Mn-X-Bi (X=Cu, Ni) thin films with good homogeneity have been investigated. The films were made by annealing two-layered films of Mn-Cu (or Mn-Ni) and Bi deposited by rf sputtering. The annealing temperature to crystallize the Mn-Cu-Bi(Mn-Ni-Bi) films was above 245 °C (∼195 °C). The optimum compositions for getting good homogeneity of the film were nominally determined as Mn6Cu4Bi4 and Mn5Ni2Bi4. At these compositions, the magneto-optic activity and coercive force of the film became highest: For Mn6Cu4Bi4(Mn5Ni2Bi4) film with a thickness of 60 nm (80 nm), Faraday rotation was about 1.3° (∼1.1°) at λ=633 nm and the coercive force was 1.9 kOe (0.2 kOe). It has been found that the inhomogeneity of the film is suppressed by adding Te.