Structure, room-temperature ferromagnetism and its mechanism in zirconia nanotubes prepared by anodization

Abstract

Defect-induced room-temperature ferromagnetism has important potential applications in data storage, sensors and spintronic devices. The anode ZrO2 nanotube film has the characteristics of simple preparation and abundant surface defects. In this work, highly ordered and independent of each other ZrO2 nanotubes with pore sizes of 31 ∼ 49 nm were successfully prepared by anodization. Interestingly, obvious room temperature ferromagnetism and magnetic anisotropy were observed in these prepared ZrO2 nanotube films, magnetism with out-of-plane direction significantly greater than that with in-plane direction. Among them, the ZrO2 nanotube film with a pore size of 40.23 nm was prepared the anodization voltage of 30 V, exhibiting an out-of-plane saturation magnetization of approximately 0.635 emu/cm3 and a coercivity of 11 Oe. It is found that the room temperature ferromagnetism is related to the special independent tubular structure and oxygen vacancy defects. From the perspective of hydrogen-like impurities and localized state, the coupling mechanism of oxygen vacancies trapped electrons is explained in this work, and these phenomena of room temperature ferromagnetism, magnetic anisotropy and higher Curie temperature are well interpreted. Our work not only improves the understanding of magnetic properties in tubular-structure materials but also expands the application in spintronic devices.