Tuning ferromagnetism in MgxZn1−xO thin films by band gap and defect engineering

We investigate the room temperature ferromagnetism in band gap tunable MgxZn1−xO (x≤0.22) alloy thin films and find that ferromagnetism is significantly enhanced in p-type MgxZn1−xO (x≥0.17) compared with the n-type counterparts (x≤0.15). Temperature-dependent photoluminescence measurements reveal the correlation between the p-type behavior, enhanced ferromagnetism, and zinc vacancies. First-principle calculations demonstrate that the formation energy of zinc vacancies decreases with the increasing Mg content and the zinc vacancies in MgxZn1−xO alloys stabilize the ferromagnetic coupling. Our results suggest a viable route to tune the magnetic properties of oxides through band gap and defect engineering.