Dielectric Properties and Room-Temperature Ferromagnetism of Ordered Porous ZnO/EA Nanofilms for Spintronic Applications
Aiqi Zhang, Lingna Jia, Tianen Liu, Panzhe Hou, Yuanyuan Qiao, Qiaoyan Xing, Peipei Lu, Lihu Liu, Junmeng Zhang, Huiyuan SunAbstract
Ordered porous undoped ZnO nanofilms with high specific surface area were successfully fabricated on an etched aluminum (EA) substrate using direct-current magnetron sputtering. The nanofilms exhibit significant room-temperature ferromagnetism (RTFM) with a maximum saturation magnetization of 16.63 emu/cm3. A strong correlation is established between the ferromagnetic response and oxygen vacancy concentration, as evidenced by photoluminescence (PL) spectroscopy and controlled annealing experiments. Theoretical calculations have confirmed that the Curie temperature of this nanofilm is higher than room temperature (TC = 343 K), which is consistent with the experimental results. Using the hydrogen-like impurity state model, the effective Bohr radius of an oxygen vacancy capturing a single electron (VO+) in the porous ZnO nanofilm was calculated to be approximately 5.81 nm, which is much larger than the lattice constant of ZnO, providing a theoretical basis for the direct Heisenberg exchange coupling between adjacent VO+ sites. This work demonstrates that defect engineering through controlled preparation conditions can achieve significant room-temperature ferromagnetism in undoped oxide systems, providing a promising strategy for developing spintronic devices, defect-based sensors, and multifunctional memory applications.