Room Temperature Ferromagnetic Semiconductor Rutile Ti1-xCoxO2-δ Epitaxial Thin Films Grown by Sputtering Method

Room temperature (RT) ferromagnetic semiconductor rutile Ti_1-xCo_xO_2-δ(101) epitaxial thin films were grown on r-sapphire substrates by a dc sputtering method. Ferromagnetic magnetization, magnetic circular dichroism, and anomalous Hall effect were clearly observed at RT in sputter-grown films for the first time. The magnetization value is nearly as large as 3 µ_B/Co that is consistent with the high spin state Co²⁺ in this compound recently established by spectroscopic methods. Consequently, its originally large magneto-optical response is further enhanced.