Spatial distribution and electronic state of Co in epitaxial anatase CoxTi1−xO2 thin films grown by reactive sputtering

The magnetic and phase properties of CoxTi1−xO2 anatase thin films grown epitaxially on (001) LaAlO3 by a reactive rf magnetron cosputter deposition have been examined. CoxTi1−xO2 (x=0.07) thin films exhibit room-temperature ferromagnetism, as evidenced by hysteresis in M–H loop. Chemical mapping indicates segregation of the Co dopant atoms in these films. However, x-ray photoelectron spectroscopy suggests that the segregated Co is not metallic, but in the Co+2 state. These results are consistent with a segregated Ti–Co–O phase being responsible for the ferromagnetic behavior.