Unexpected large room-temperature ferromagnetism in porous Cu2O thin films

• Porous Cu2O films were deposited on porous anodic alumina (PAA) substrates.
• Significant room-temperature ferromagnetism has been observed in porous Cu2O films.
• Ferromagnetism of Cu2O films exhibited different magnetic signals with the field.
• The saturation magnetization is 94 emu/cm3 with an out-of-plane.

Porous Cu2O films have been fabricated on porous anodic alumina substrates using DC-reactive magnetron sputtering with pure Cu targets, and unexpectedly large room temperature ferromagnetism has been observed in the films. The maximum saturation magnetic moment along the out-of-plane direction was as high as 94 emu/cm3. Photoluminescence spectra show that the ferromagnetism originates with oxygen vacancies. The ferromagnetism could be adjusted by changing the concentration of oxygen vacancies through annealing in an oxygen atmosphere. These observations suggest that the origin of the ferromagnetism is due to coupling between oxygen vacancies with local magnetic moments in the porous Cu2O films, which can occur either directly through exchange interactions between oxygen vacancies, or through the mediation of conduction electrons. Such a ferromagnet without the presence of any ferromagnetic dopant may find applications in spintronic devices.