Leslaw Smardz

V/Fe multilayers were prepared on naturally oxidized Si(100) substrates at room temperature (RT) by UHV magnetron sputtering. Mixing effects at the Fe–V interfaces were investigated in-situ, directly after deposition, by means of X-ray photoelectron spectroscopy (XPS). The results of systematic in-situ XPS studies of the integral intensity of the Fe-2p peak, as a function of the nominal thickness of the Fe sublayer deposited on vanadium, allowed us to estimate the thickness of the pure iron layer that forms the mixed layer at about 0.4 nm. Assuming the same thickness of the vanadium layer that forms the mixed layer, the estimated thickness of the mixed layer near the Fe–V interface was about 0.8 nm. In the analysis of magnetic hysteresis loops, in addition to the bilinear (J₁) and biquadratic (J₂) coupling constant, the contribution of the cubic exchange constant (J₃) was taken into account, which also contributed significantly to the total energy. Higher order interactions (J₂ and J₃) are particularly important for V spacer thicknesses greater than 7 atomic monolayers. Hydrogen absorption in V/Fe multilayers at RT and a pressure of about 1 bar causes an increase in the biquadratic coupling constant J₂, while the values of J₁ and J₃ are reduced. A comparison of the obtained experimental results and available theoretical models leads to the conclusion that the mechanism of “fluctuating thickness of the non-magnetic spacer” could be responsible for the biquadratic exchange coupling. On the other hand, the “loose spins” model can explain the cubic coupling in the V/Fe multilayers. The modification of the interlayer exchange coupling using hydrogen is fully reversible.

In this work, pure Ti was anodically oxidized using 1M H₃PO₄ + 2–10 pct HF electrolytes at 10 V vs open circuit potential (OCP). The structure of the anodized samples’ surfaces was investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The results show the presence of titanium dioxide (TiO₂) and titanium hydrogen phosphate (Ti(HPO₄)₂) in the surface layer. Due to the chemical composition and properties that the materials have, they do not pose a threat and support the osseointegration process. The rough and porous anodic oxide morphology shown by the AFM is useful for tissue growth, as well as for improving corrosion resistance. The XPS confirms that the short anodization results in thin anatase-type TiO₂, which is a candidate for hard tissue implant applications. The corrosion is improved after oxidation in 1M H₃PO₄ + 2 pct HF electrolyte for 15 minutes. The wetting analysis shows hydrophilic properties and suggests good bioadhesion of the anodically oxidized surface. The surface supports osteoblast cell proliferation, indicating that the material has a surface state appropriate for hard tissue implant applications.