Magnetic ordering in amorphous oxides

The magnetic structure of radio frequency sputtered amorphous oxides is investigated by magnetization and ferromagnetic resonance techniques. Samples of Bi₂O₃-Fe₂O₃ substituted with ABO₃ (AB=BaTi, PbTi, PbZr) and MeO (M=Cu,Ca,Zn)-type compounds are studied. As-deposited samples are paramagnetic, and samples annealed at high temperatures show a ferrimagnetic character possibly due to the formation of magnetically ordered clusters. Samples with nonmagnetic ABO₃ show a record room temperature magnetization. Films containing oxides of zinc, copper, or calcium are anisotropic amorphous magnets with a large uniaxial or planar anisotropy. The nature and composition of ordered clusters in some samples are inferred from magnetic characterization of the film. A similar ferrimagnetic character is observed in amorphous samples sputtered at high temperatures