Evolution of ferromagnetic circular dichroism coincident with magnetization and anomalous Hall effect in Co-doped rutile TiO2

Magnetic circular dichroism (MCD) of rutile ${\mathrm{Ti}}_{1-x}{\mathrm{Co}}_x{\mathrm{O}}_{2-\delta }$ is systematically examined with various $x$ and $\delta$ to reveal a phase diagram for the appearance of ferromagnetism at higher carrier concentration and Co content. The phase diagram exactly matches with that determined from anomalous Hall effect (AHE). The magnetic field dependence of MCD also shows good coincidence with those of the magnetization and AHE. The coincidence of these independent measurements strongly suggests single and intrinsic ferromagnetic origin.