Defect Types And Room Temperature Ferromagnetism In Rutile TiO₂Single Crystals

Dilute magnetic semiconductors (DMSs) have attracted much interest due to their favorable magnetic and semiconducting properties for application of spin-dependent electronic devices. Although many diluted magnetic oxides have been found room temperature ferromagnetism (RTFM) by doping, there is still great debate on the origin of room temperature ferromagnetism. By researching Literature, it is found that d0magnetic oxides can be very good to solve the origin of room temperature ferromagnetism.This paper applies rutile TiO2single crystals as the research sample. The samples are dealing with heat treatment of high temperature and high vacuum and N ions doping. Then by using X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), positron annihilation lifetime spectroscopy (PALS), X-ray absorption near edge structure (XANES), slow positron beam and superconducting quantum interference device (SQUID), defect types and room temperature ferromagnetism were characterized. The test results were further analyzed and processed.According to the test results, a lot of oxygen vacancies (Vo) and especially Ti3+-Vo defect complexes are formed in high vacuum annealing samples. And two kinds of defects are the intrinsic defects. It can be demonstrated that room temperature ferromagnetism of annealed samples in high vacuum is closely associated with oxygen vacancies. The unpaired3d electrons in Ti3+ions provide vast spin magnetic moments which are decisively related to the observed ferromagnetism. In addition, when there is excess oxygen ions in rutile TiO2lattice, they also can produce Ti vacancies (VTi) which increase magnetization obviously. Many oxygen vacancies, titanium vacancies and VTi-No complexes are generated due to N ion irradiation. The room temperature ferromagnetism is attributed to oxygen vacancies and substitution of0with N (No) defects in the rutile structure. The production of titanium vacancies can enhance the RTFM, and substitution of O with N is the onset of ferromagnetism by inducing relatively strong ferromagnetic ordering.