Oxygen vacancies modulated coexistence of antiferromagnetism and ferromagnetism in ZnxCo1−xO single crystal epitaxial films

Abstract Recently antiferromagnetic materials become very attractive due to their new applications in spintronic devices. High-quality single crystal epitaxial ZnxCo1−xO (1 1 1) thin films were grown by co-evaporating Zn and Co and simultaneously oxidizing in oxygen plasma. It is found that the exchange bias fields of Co/as-prepared ZnxCo1−xO bilayers decrease with increasing Zn composition. When as-prepared ZnxCo1−xO layer was annealed in oxygen plasma to remove oxygen vacancies, the exchange bias field of Co/oxygen-plasma-annealed ZnxCo1−xO bilayers can be further enhanced. Moreover, a weak ferromagnetism was observed at 300 K in the as-prepared antiferromagnetic ZnxCo1−xO film with oxygen vacancies, but it did not exist in oxygen-plasma-annealed ZnxCo1−xO film. This indicates that oxygen vacancies can simultaneously weaken the antiferromagnetism but enhance the ferromagnetism of ZnxCo1−xO layer. Therefore, we offer a method of manipulating the antiferromagnetism of ZnxCo1−xO films by changing Zn composition and oxygen vacancies, which is useful for designing antiferromagnetic spintronic devices.