Conductive filaments controlled ferromagnetism in Co-doped ZnO resistive switching memory device

Both the bipolar resistive switching (RS) behavior and the ferromagnetism (FM) of a Co-doped ZnO device were investigated in this study. The magnetic hysteresis curves of the device with RS behavior in the high-resistance state (HRS) and low-resistance state (LRS) were analyzed, both of which showed ferromagnetic behavior. Interestingly, the intensity of the saturation magnetization in the device in HRS and LRS were observed to be the smallest and largest, respectively. X-ray photoelectron spectra demonstrated the existence of oxygen vacancies in the device, the concentration of which in LRS was larger than that in HRS. Especially, depth-profiling X-ray photoelectron spectra showed that a change in the conductive filaments was consistent with the resistance states and FM. The results clearly demonstrate that the RS effect and FM could be attributable to film defects. (C) 2019 The Japan Society of Applied Physics