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

Room temperature ferromagnetic semiconductor rutile Ti1-xCoxO2-\delta (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 room temperature in sputter-grown films for the first time. The magnetization value is nearly as large as 3\mu 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.