Magnetic Properties and Antiferromagnetic Coupling in Inhomogeneous Zn_1-xFe_xO Magnetic Semiconductor

Zn_1-xFe_xO inhomogeneous oxide magnetic semiconductor films with high Fe concentration are prepared by sputtering, and fast annealing is carried out at different temperatures. It is found that magnetic properties are greatly modulated by controlling the composition inhomogeneity and subsequently fast annealing. Both ferromagnetic and paramagnetic components are found to coexist in the as-deposited Zn_1-xFe_xO magnetic semiconductor. In particular, the antiferromagnetic coupling between the neighbouring local ferromagnetic regions is found in the as-deposited Zn_0.23Fe_0.77O film, and the antiferromagnetic coupling strength increases with increasing temperature from 110K to 300K. We believe that this unusual antiferromagnetic coupling is mediated by thermally activated hopping carriers.