63 research outputs found
Role of charge carriers for ferromagnetism in cobalt-doped rutile TiO2
Electric and magnetic properties of a high temperature ferromagnetic oxide
semiconductor, cobalt-doped rutile TiO2, are summarized. The cobalt-doped
rutile TiO2 epitaxial thin films with different electron densities and cobalt
contents were grown on r-sapphire substrates with laser molecular beam epitaxy.
Results of magnetization, magnetic circular dichroism, and anomalous Hall
effect measurements were examined for samples with systematically varied
electron densities and cobalt contents. The samples with high electron
densities and cobalt contents show the high temperature ferromagnetism,
suggesting that charge carriers induce the ferromagnetism.Comment: 14 pages, 12 figure
Electronic Transport in the Oxygen Deficient Ferromagnetic Semiconducting TiO
TiO films were deposited on (100) Lanthanum aluminates
LaAlO substrates at a very low oxygen chamber pressure
mtorr employing a pulsed laser ablation deposition technique. In previous work,
it was established that the oxygen deficiency in these films induced
ferromagnetism. In this work it is demonstrated that this same oxygen
deficiency also gives rise to semiconductor titanium ion impurity donor energy
levels. Transport resistivity measurements in thin films of TiO
are presented as a function of temperature and magnetic field. Magneto- and
Hall- resistivity is explained in terms of electronic excitations from the
titanium ion donor levels into the conduction band.Comment: RevTeX4, Four pages, Four Figures in ^.eps forma
Magnetic oxide semiconductors
Magnetic oxide semiconductors, oxide semiconductors doped with transition
metal elements, are one of the candidates for a high Curie temperature
ferromagnetic semiconductor that is important to realize semiconductor
spintronics at room temperature. We review in this paper recent progress of
researches on various magnetic oxide semiconductors. The magnetization,
magneto-optical effect, and magneto-transport such as anomalous Hall effect are
examined from viewpoint of feasibility to evaluate the ferromagnetism. The
ferromagnetism of Co-doped TiO2 and transition metal-doped ZnO is discussed.Comment: 26 pages, 5 tables, 6 figure
Experimental studies on vacancy induced ferromagnetism in undoped TiO2
Room temperature ferromagnetism is observed in undoped TiO2 films deposited
on Si substrates using pulsed laser deposition (PLD). The ferromagnetic
properties of the samples depend on the oxygen partial pressure during the PLD
synthesis. The appearance of higher binding energy component (HBEC) in the
oxygen 1s core peak from x-ray photoelectron spectroscopy (XPS) suggests the
presence of oxygen vacancies in these samples. The amount of oxygen during the
synthesis determines the vacancy concentration in the samples which is directly
related to the magnetic behavior of the samples. The magnetic moment decreases
with oxygen vacancy concentration in the samples. Valence band measurements
were performed to study the electronic structure of both stoichometric and
reduced TiO2. The analyses show the presence of Ti 3d band near the Fermi level
in reduced TiO2 samples. These bands are otherwise empty in stoichiometric TiO2
and reside in the conduction band which makes them unobservable by XPS. The
existence of this Ti 3d band near the Fermi level can possibly lead to Stoner
splitting of the band.Comment: 20 pages, 9 figur
Optimization of Ti/Ta2O5âSnO2 electrodes and reaction parameters for electrocatalytic oxidation of methylene blue
Identification and Characterization of Novel Superantigens from Streptococcus pyogenes
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