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As oxygen vacancies play an important role in ferromagnetism of rutile TiO2, a method of γ-ray irradiates rutile TiO2 single crystals was subtly proposed to study the effect of oxygen vacancies on magnetic properties. Remarkably, room temperature ferromagnetism was observed in γ-ray irradiated rutile TiO2 single crystals, and the saturation magnetization is the strongest when dose is 4 × 104 Gy which assigned to ESR results. Since the displacement threshold energy of Ti atom is much bigger than that of O atom, the defects produced by γ-irradiation are mainly oxygen vacancies. After irradiation, XPS, PL spectra indicate the presence of oxygen vacancies(VO), Ti3+, and VO-Ti3+ composite defects. [ABSTRACT FROM AUTHOR]

We have investigated the defect structure in pure Co-doped and (Co, Nb)-doped TiO2 (anatase) thin films grown by pulsed laser deposition on (001) single crystal LaAlO3. Although both films exhibit room temperature ferromagnetism, dilute Nb doping significantly improves the conductivity and microstructure of the TiO2 (anatase) thin film at the cost of a lower saturation magnetization. Z-contrast imaging and electron-energy-loss-spectroscopy study in the scanning transmission electron microscope show cluster-free microstructure in the (Co, Nb)-doped thin film although Co is enriched into the surface and forms a CoxTi1-x-yNbyO2-δ phase. In contrast, metallic Co, rutile TiO2, and cobalt oxide nanoparticles combined with some crystallographic shear defect structures are observed in the pure Co-doped thin film. The magnetic behavior in each film can be explained with the presence of these defect states or second phases. [ABSTRACT FROM AUTHOR]

Thin films of (0.5%, 1%) Nb:SrTiO3 dilutely doped with (2 at. %) magnetic transition elements (Cr, Co, Fe, Mn) are examined for ferromagnetism. X-ray diffraction, Rutherford backscattering ion channeling, scanning transmission electron microscopy Z-contrast imaging, and electron energy loss spectroscopy techniques establish high crystalline quality of the films with no impurity phase(s) and highly uniform dopant distribution. Although the film conductivity improves dramatically by Nb doping, no ferromagnetism is found in any of our samples over the temperature range of 365 down to 5 K. This is contrasted to the case of ferromagnetism reported in cobalt doped (La,Sr)TiO3. [ABSTRACT FROM AUTHOR]

It is shown that dilute niobium doping has a significant effect on the ferromagnetism and microstructure of dilutely cobalt-doped anatase TiO2 films. Epitaxial films of anatase TiO2 with 3% Co, without and with 1% niobium doping were grown by pulsed-laser deposition at 875°C at different oxygen pressures. For growth at 10-5 Torr niobium doping suppresses the ferromagnetism, while it enhances the same in films grown at 10-4 Torr. High-resolution Z-contrast scanning transmission electron microscopy and electron energy loss spectroscopy show uniform surface segregation of cobalt-rich Ti1-x-yCoxNbyO2-δ phase, but without cobalt metal clusters. [ABSTRACT FROM AUTHOR]

As oxygen vacancies play an important role in ferromagnetism of rutile TiO2, a method of γ-ray irradiates rutile TiO2 single crystals was subtly proposed to study the effect of oxygen vacancies on magnetic properties. Remarkably, room temperature ferromagnetism was observed in γ-ray irradiated rutile TiO2 single crystals, and the saturation magnetization is the strongest when dose is 4 × 104 Gy which assigned to ESR results. Since the displacement threshold energy of Ti atom is much bigger than that of O atom, the defects produced by γ-irradiation are mainly oxygen vacancies. After irradiation, XPS, PL spectra indicate the presence of oxygen vacancies(VO), Ti3+, and VO-Ti3+ composite defects. [ABSTRACT FROM AUTHOR]

Iridates represent a unique material system that possesses both strong spin-orbit coupling and electron correlation. The interplay between spin-orbit coupling and correlation could facilitate the emergence of novel electronic and magnetic states. In this work, we report on a systematic study of magnetism in the double perovskite iridate La2ZnIrO6 and its hole-doped compounds (La1-xSrx )2ZnIrO6 via dc magnetization measurement, heat capacity characterization, electron spin resonance spectroscopy, and simple modeling. Undoped La2ZnIrO6 undergoes two magnetic transitions, at T1∼7.3 K and T2∼8.5 K, respectively. While magnetic hysteresis loops with large remnant moments are observed below these two transition temperatures, the corresponding magnetic states are shown to be canted antiferromagnetic by the linear increase in magnetization in the high field region along with the observation of antiferromagnetic resonance. The nature of the canted antiferromagnetic states with large canting angles can be understood by a simple model that includes both the Heisenberg exchange interaction and the Dzyaloshinskii-Moriya interaction. With the introduction of Ir5+ by Sr2+ doping, the canted antiferromagnetic phases are suppressed, accompanied by an enhancement of electrical conductivity. [ABSTRACT FROM AUTHOR]