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The impact of in-plane alternating currents on the exchange bias, resistance, and magnetoresistance of a Co 85 Fe 15 / Ni 0.85 Co 0.15 O / Co 85 Fe 15 / Cu/ Co 85 Fe 15 spin valve is studied. With increasing current, the resistance is increased while the maximum magnetoresistance ratio decreases. Noticeably, the reversal field of the pinned layer is systematically suppressed in both field sweeping directions. Since Ni 0.85 Co 0.15 O is a good insulator, it is expected that the ac flows only in the Co 85 Fe 15 / Cu/ Co 85 Fe 15 top layers, thus ruling out any presence of spin-transfer torque acting on the spins in the antiferromagnetic layer. Instead, our measurements show clear evidence of the influence of Joule heating caused by the current. Moreover, results from temperature-dependent measurements very much resemble those of the current dependence, which indicates that the effect of Joule heating plays a major role in the current-in-plane spin-valve configurations. The results also suggest that spin-transfer torques between ferromagnetic layers might still exist and compete with the exchange bias at sufficiently high currents.

Two groups of TiO 2 thin films were deposited onto Corning glass substrates by the RF magnetron sputtering in reactive argon gas containing 20% oxygen and by the sol-gel technique combined with dip coating. The films prepared by RF sputtering were annealed for 15 min at 650 • C with different rates of increase of temperature with the aim to search for the TiO 2 anatase phase formation. Besides, with the same aim, a set of the TiO 2 films prepared by sol-gel technique was doped with Co in the concentration range from 0 to 8% by weight. Influence of the rate of increase of temperature and Co doping on the anatase phase formation have been observed and estimated by x-ray diffraction and Raman scattering. Structure deformation induced by rapid heating and Co doping is considered as the main reason affecting the anatase phase formation in TiO 2 thin films.

Titanium oxide (TiO2) nanopowders can be reproducibly formed by hydroxylation of titanium organic complexes. The crystallisation to anatase and rutile can be controlled by systematic calcination and a complex range of properties optimized for specific applications. Characterisation of the powders has been undertaken using advanced physical techniques. The morphology of the TiO2 powders is determined by solution concentration and precipitation phenomena, particularly temperature and stirring regime. However the fine powders have limitations in terms of processing flexibility particularly when nanostructured and organised features are desired, due to their fine particle structure and inability to be sintered without undergoing complete phase change. Anodising titanium metal can overcome these difficulties and under appropriate conditions semi-ordered nanotubes of TiO2 have been prepared. These can be heat treated to develop the phase of choice, anatase or rutile. A mechanism for the formation of the nanotubes has been proposed which is based on the linkage of pores developed in the anodized oxidation product. The pores are driven to into alignment by the applied potential and link up to form the tubular structures. A degree of control of the tube size and wall thickness is shown possible by control of applied voltage. The nanotubes have been investigated using SEM, TEM, XRD and Raman spectroscopy to elucidate the structure and postulate the formation mechanism.

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