Preparation, Characterization And Room Temperature Ferromagnetism Of Porous Cu₂O Films

Metal oxide semiconductors with room temperature ferromagnetic (RTFM)which are promising materials with numerous applications in spintronic devices,biosensors, catalysts,etc.There has been tremendous interest in understanding theorigin of room temperature unconventional ferromagnetism observing in a variety ofnonmagnetic materials and the weak RTFM can not meet the actual needs ofspintronic devices.Pure porous Cu2O films were prepared by DC-reactive magnetronsputtering on porous anodic alumina substrates.The structure and physical propertiesof the Cu2O films were characterized using SEM, EDX, UV-Vis,SPM, XRD, PPMS.The results are as follows.1. AAO templates were prepared in0.3M oxalic acid electrolyte, using asecondary anodic oxidation method. AAO prepared has nano-pore structure of orderly,neatly arranged and hexagonal close-packed.2. Porous Cu2O films were prepared by DC-reactive magnetron sputtering onporous anodic alumina substrates.The Cu2O films have porous structure consistentwith the AAO by SEM.Oxygen flow determines the phase composition as depositiontime and power decide the specific surface area and pore size of the film.3. The magnetic test results show that the porous Cu2O thin film having aobvious room temperature ferromagnetism and show a marked magnetic anisotropywhich the magnetic along the hole is easy magnetization direction.The saturationmagnetization of the film is associated with power,oxygen flow and depositiontime.The maximum saturation magnetization is about130emu/cm3.4. The saturation magnetization of the film were significantly weakened afterannealed in oxygen, photoluminescence spectra proved the presence of oxygenvacancies and the experimental results show that the oxygen vacancies are mainlyproduce ferromagnetism. Oxygen vacancies trapped electrons which make oxygenvacancies producing local magnetic moment. If magnetic oxygen vacancies are veryclose to each other, they follow Heisenberg direct exchange mechanism. When it is relatively far between oxygen vacancies, the conduction electrons can be magnetizedby the local magnetic moment of oxygen vacancies. The longer-range ferromagneticexchange between the oxygen vacancies can be mediated by carriers, which makesamples shown RTFM.The result of easy magnetization direction perpendicular to thefilm plane prove the reasonable of oxygen vacancies produced ferromagnetism byfree electrons as the media, which is a desired result for spin electronic device.