Observation of ferromagnetic behaviors in doped and undoped TiO$_{2}$ and ZnO

Transition-metal doping has been widely used to produce ferromagnetic oxides such as TiO$_{2}$ {\&} ZnO for use as a diluted magnetic semiconductor. Recently, however, undoped samples were also found to be ferromagnetic. We have studied the ferromagnetic behaviors of ZnO and TiO$_{2}$ single crystals and powders annealed both in vacuum and in flowing oxygen at various temperatures. In order to understand the observed ferromagnetism, we have used X-ray photoemission and electron spin resonance spectrometry to characterize the possible valance states or chemical bonding variation to study the roles that oxygen vacancies may have played in the occurrence of ferromagnetism. Comparisons on the doped and pure samples will be discussed.* Also with NSYSU .