Study On The Structure And Magnetic Properties Of K-doped Sno₂ And V-doped Zno Diluted Magnetic Semiconductor Powders

Diluted magnetic semiconductors ( DMSs ) is a new type of functional materials, which can be obtained by using a small amount of magnetic transition metal elements or rare earth elements to replace the cations in the non-magnetic semiconductor materials ( usually AB type ). Currently, people have discovered many new physical phenomena in the DMSs materials, such as giant Faraday effect, giant Zeeman splitting, anomalous Hall effect, giant negative magnetoresistance, magnetic mnsulator-metal transition and so on. Some new functional devices can be prepared when using these effects and will provide a new way to technology development. So now it is attracting people's more and more attention.In this thesis, a series of K-SnO₂ and V-ZnO diluted magnetic semiconductor nanoparticles had been synthesized by sol-gel method. Structural and magnetic measurements were carried out by X-ray diffraction( XRD ), Transmission electron microscopy( TEM ), X-ray photoelectron spectroscopy( XPS ), and Vibrating sample magnetometer( VSM ), respectively.In the K-SnO₂ DMSs, We found that all nanopowders peaks can be identified with those of pure rutile SnO₂ nanopowders. The size of the nanoparticles is about a few nanometers. K ions have a valence of +1. Magnetization measurements revealed that the samples with K doping exhibited room temperature ferromagnetism, and the saturation magnetization was enhanced as the concentration of K-doped increased. Ferromagnetism still existed in Sn_0.96K_0.04O₂ when annealed in O₂ at 400℃for 1h, so we can conclude that oxygen vacancies are not the main origin of the ferromagnetism. When a K ion replaces a Sn ion, three anion holes will appear because of the difference between the valence of K ions and Sn ions. Exchange interactions will be occurred between cations and holes and finally lead to ferromagnetism. The specific mechanism of magnetic can be explained by RKKY model.In the V-ZnO DMSs, we found that the samples peaks with the V ions concentration less than 5% can be identified with typical wurtzite structure of ZnO, and the size of the nanoparticles is about a few nanometers. V ions have a valence of +5. According to magnetic measurement, all the samples with V doping exhibited room temperature ferromagnetism, and the saturation magnetization of the sample was enhanced as the concentration of V-doped increased. When Zn_0.97V_0.03O was annealed at different temperatures (500℃, 600℃, 700℃) in the air for 1h, the saturation magnetization was also enhanced with the increasing temperatures. We can conclude that oxygen vacancies and the concentration of defects are the main origin of the ferromagnetic in V-ZnO DMSs, and the specific mechanism of magnetic can be explained by BMPs model.