Study Of Dilute Magnetic Properties Of Doped Titanium Dioxide Nano-materials

Diluted magnetic oxide semiconductors?DMOSs?have been extensively studied because of the combined transport properties and magnetic properties,which are desirable for spintronic applications,such as spin field-effect transistors and magnetoresistance random access memory.The investigations mainly focus on element doped TiO₂,such as Co,Mn,Ru,Mo,Fe.Researchers reported that,the origin of RTFM mainly comes from the Ti³⁺exists in samples;others researchers reported that the origin of RTFM mainly comes from the Vos exists in samples.To study the RTFM origin of TiO₂ doped samples,non-metal element?N?and the metal element?Ru,Ag,W?co-doped TiO₂ samples were investigated.The details are shown follows:?1?The room temperature ferromagnetism?RTFM?of the undoped,N doped,Ru doped,and Ru-N co-doped anatase TiO₂ nanotubes?TNTs?films are investigated combined with experiments and first principles approaches.All samples display anatase structures and ferromagnetism at room temperature.The values of the saturation magnetization?Ms?of undoped TiO₂,N doped TiO₂,Ru doped TiO₂,and Ru/N codoped TiO₂,respectively,are 0.065emu/g,0.015emu/g,0.155emu/g,and 0.073emu/g.The calculated net moment is in the order of Ru doped>Ru/N co-doped>un-doped>N doped.The oxygen vacancies play an important role in RTFM of TNTs.The experiments are highly consistent with the theory calculations.Moreover,the hybridization of Ru 4d,N 2p,and O 2p led to the spin-spilt of Ru 4d,N 2p,and O 2p which is devoted to the system magnetism.?2?We employ TiO₂ single-crystal films as a substrate and use photochemical deposition method to prepare Ag doped and Ag/N co-doped TiO₂ single-crystal films.We also investigate the optical and magnetic properties of the samples using various measurements.No diffraction peaks related to silver oxide appear in the X-ray diffraction?XRD?spectra,which implies the existence of Ag atoms in Ag-doped TiO₂ single-crystal films.X-ray photoelectron spectroscopy?XPS?spectra indicate the existence of Ti⁴⁺and Ag⁰ in Ag/N co-doped TiO₂ single crystal films.It is found that Ag is deposited on a TiO₂single-crystal film surface in the form of Ag particles.Meanwhile,Ag particles can slightly enhance ferromagnetism in Ag-doped TiO₂ single-crystal films compared with the TiO₂ single-crystal film sample.Oxygen vacancies and Ag particle synergy influence ferromagnetism in Ag/N co-doped TiO₂ single-crystal films.?3?In this work,undoped,N-doped,WO₃-loaded undoped,and WO₃-loaded with N-doped TiO₂ rutile single-crystal wafers were fabricated by direct current?DC?magnetron sputtering.N-doping into TiO₂ and WO₃ loading onto TiO₂ surface were used to increase and decrease oxygen vacancies.Various measurements were conducted to analyze the structural and magnetic properties of the samples.X-ray diffraction results showed that the N-doping and WO₃ loading did not change the phase of all samples.X-ray photoelectron spectroscopy results revealed that W element loaded onto rutile single-crystal wafers existed in the form of WO₃.UV-Vis spectrometer results showed that the absorption edge of WO₃-loaded undoped and WO₃-loaded with N-doped TiO₂ rutile single-crystal wafers had red shift,resulting in a slight decrease in the corresponding band gap.Photoluminescence spectra indicated that oxygen vacancies existed in all samples due to the post annealing atmosphere,and oxygen vacancies density increased with N-doping,while decreasing with WO₃ loading onto TiO₂ surface.The magnetic properties of the samples were investigated,and the saturation magnetization values were in the order N-doped>WO₃-loaded with N-doped>undoped>WO₃-loaded undoped rutile single-crystal wafers,which was the same order as the oxygen vacancy densities of these samples.N-doping improved the saturation magnetization values,while WO₃-loaded decreased the saturation magnetization values.This paper reveals that the magnetic properties of WO₃-loaded with N-doped rutile single-crystal wafers originate from oxygen vacancies.