Enhancement of room temperature ferromagnetism of Fe-doped ZnO epitaxial thin films with Al co-doping

Epitaxial films of ZnO doped with magnetic ion Fe and, in some cases, with 1% Al show clear evidence of room temperature ferromagnetic ordering. The Al doped optimized samples with carrier concentration nc∼8.0×1020 cm−3 show about 3 times enhanced saturation magnetization (0.58 μB/Fe2+) than the one with nc∼3.0×1020 cm−3 (0.18 μB/Fe2+). A clear correlation between the magnetization per transition metal ion and the ratio of the number of carriers to the number of donors have been found as is expected for carrier-induced room temperature ferromagnetism. The transport mechanism of the electrons in all the DMS films at low temperature range has been identified with the Efros's variable range hopping due to the electron–electron Coulomb interaction.

Research highlights
► Epitaxial films of ZnO doped with magnetic ion Fe and, in some cases, with 1% Al show clear evidence of room temperature ferromagnetic ordering.
► The Al doped optimized samples with carrier concentration nc∼8.0×1020 cm−3 show about 3 times enhanced saturation magnetization (0.58 μB/Fe2+) than the one with nc∼3.0×1020 cm−3 (0.18 μB/Fe2+).
► A clear correlation between the magnetization per transition metal ion and the ratio of the number of carriers to the number of donors have been found as is expected for carrier-induced room temperature ferromagnetism.
► The transport mechanism of the electrons in all the DMS films at low temperature range has been identified with the Efros's variable range hopping due to the electron–electron Coulomb interaction.