D~0 Ferromagnetism Of Nonmagnetic Materials

d0 ferromagnetism which describes a latest discovered physical phenomenon that a nonmagnetic oxide semiconductor doped with priori nonmagnetic impurities behaves ferromagnetic has attracted a lot of interest recently. It overturns a traditional impression that ferromagnetism only occurs in materials with partially filled shells. The investigation of d0 ferromagnetic materials is significant and essential not only from the point of view of fundamental physics but also for their practical applications. In this thesis, we present detailed fabrication and characterization of new d0 ferromagnetic materials. These include their physical origin of d0 ferromagnetism. The details are shown below:1:Arrays of Cu2+ doped ZnO nanowires have been successfully prepared by a combination of an electrodeposition of Cu2+ ion into anodic aluminum oxide templates (AAO) and post-oxidation annealing in air atmosphere. The influence of the doped Cu2+ concentration and the conditions of post-oxidation thermal treatments on the d0 ferromagnetic behaviors of the samples has been studied. Whist, Al3+ doped ZnO nanoparticles have been prepared by a sol-gel method, and the influence of the Al3+ concentrations on their d0 ferromagnetic behaviors investigated. The experimental measurements show that a small amount of Zn atoms in the ZnO lattice were substituted by Cu2+ and Al3+ respectively, and both Cu2+ and Al3+ doped samples showed clear ferromagnetic behaviors at room temperature. The strengths of their ferromagnetism can be tuned by changing the ion doping concentration or the conditions of post-oxidation annealing. A bound magnetic polaron model is suggested to explain the physical origins of ferromagnetism of both Cu2+ and Al3+ doped samples.2:Pure ZnO and ZnO2 nanoparticles have been fabricated by a co-precipitation and hydro-thermal method individually, their structure and magnetic properties investigated at the nanoscale. Both samples behave ferromagnetic at room temperature. The oxygen vacancies at the surface/interface of both nanoparticles were deduced to be the reason causing the ferromagnetic behaviors of ZnO and ZnO2 nanoparticles at room temperature. It is also found that the ferromagnetic properties of both samples can be tuned by changing the post-annealing and hydro-thermal conditions.3:CaO nanopowders have been fabricated by above sol-gel method, and their magnetic properties were measured to be ferromagnetic at room temperature. The measurements of positron annihilation lifetime spectra and the Ms variation revealed that there are Ca defects existed in the samples either before or after annealed in oxygen atmosphere or vacuum. The strength of CaO ferromagnetism is found to increase with the increase of Ca defect concentrations among samples. The experimental results are well fitted by the simulations using a first-principle calculation.4:Sphalerite ZnS nanoparticles fabricated using the hydrothermal method in ethanol alcohol were measured to be ferromagnetic as well. Their ferromagnetism can be tuned by the sulfur deficiencies inside individual ZnS nanoparticles, which were realized by adjusting the synthesis temperatures and the hydrogen concentrations used in annealing process during the sample preparation. The structure and magnetic properties of ZnS nanoparticles fabricated using water as solvent rather than ethanol alcohol have been also investigated.