Magneto-optical properties of ZnO-based diluted magnetic semiconductors

Magnetic circular dichroism (MCD) spectra of ${\mathrm{Zn}}_{\text{1−x}}{\mathrm{TM}}_x\mathrm{O}$ (TM=Sc, Ti, V, Cr, Mn, Co, Ni, and Cu) films were measured to clarify their magneto-optical properties. Noticeable magneto-optical effect was not observed for ${\mathrm{Zn}}_{\text{1−x}}{\mathrm{Sc}}_x\mathrm{O},$ ${\mathrm{Zn}}_{\text{1−x}}{\mathrm{Ti}}_x\mathrm{O},$ ${\mathrm{Zn}}_{\text{1−x}}{\mathrm{V}}_x\mathrm{O},$ and ${\mathrm{Zn}}_{\text{1−x}}{\mathrm{Cr}}_x\mathrm{O}.$ On the contrary, ${\mathrm{Zn}}_{\text{1−x}}{\mathrm{Mn}}_x\mathrm{O},$ ${\mathrm{Zn}}_{\text{1−x}}{\mathrm{Co}}_x\mathrm{O},$ ${\mathrm{Zn}}_{\text{1−x}}{\mathrm{Ni}}_x\mathrm{O},$ and ${\mathrm{Zn}}_{\text{1−x}}{\mathrm{Cu}}_x\mathrm{O}$ showed pronounced negative MCD peaks near 3.4 eV which correspond to the band gap of the host ZnO semiconductor. These results show that ZnO alloyed with Mn, Co, Ni, and Cu is a diluted magnetic semiconductor with strong exchange interaction between $\mathrm{sp}$ -band carriers and localized d electrons.