Magnetic and Electrical Properties of Al³⁺ Implanted Co–ZnO

Co-doped ZnO ceramic samples sintered at four different temperatures were prepared by solid-state reaction method and implanted by Al ions subsequently. The microstructural, defect, magnetic and electrical properties of the samples were systematically investigated by x-ray diffraction, micro-Raman spectroscope, vibrating sample magnetometer and Hall measurement, respectively. The results show that all the samples exhibit room-temperature ferromagnetism with a saturation magnetization of 0.02–0.03 emu g⁻¹, the value of which is affected by the sintering temperature. The origin of room-temperature ferromagnetism is considered as the formation of Co²⁺– V_O–Co²⁺ bound magnetic polarons. Even though the implantation of Al³⁺ slightly reduces the saturation magnetization because of the lattice damage, less V_O and larger lattice spacing, however, an appropriate amount of Al³⁺ implantation and a proper sintering temperature can remarkably improve the electrical properties with the mobility of 200 ∼300 cm² Vs⁻¹ and the resistivity of 20 ∼40 Ω cm. In general, samples sintered at 1200^∘C present more excellent comprehensive performances.