The growth of the dental implant market increases the concern regarding the quality, efficiency, and lifetime of dental implants. Titanium and its alloys are dominant materials in this field thanks to their high biocompatibility and corrosion resistance, but they possess a very low wear resistance. Besides problems related to osteointegration and bacterial infections, tribocorrosion phenomena being the simultaneous action between corrosion and wear, are likely to occur during the lifetime of the implant. Therefore, tribocorrosion resistant surfaces are needed to guarantee the preservation of dental implants. This work focused on the incorporation of magnesium, together with calcium and phosphorous, in the structure of titanium oxide films produced by micro-arc oxidation (MAO). The characterization of morphology, chemical composition, and crystalline structure of the surfaces provided important insights leading to 1) a better understanding of the oxide film growth mechanisms during the MAO treatment; and 2) a better awareness on the degradation process during tribocorrosion tests. The addition of magnesium was shown to support the formation of rutile which improves the tribocorrosion properties of the surfaces.

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We studied experimentally and theoretically the perpendicular anisotropy and the stripe-domain structure in both Fe x Si 1Ϫx thin films and Fe x Si 1Ϫx /Si multilayers, the latter being in the low-modulation-length regime (0.4 nmϽϽ7 nm). The experimental study was made by means of the transversely biased initial susceptibility t␤ via the magneto-optic Kerr effect. The samples under study were prepared by dc triode sputtering at T S ϭ300 K. It is found that the appearance of stripe domains is more pronounced for decreasing as x remains constant and may be caused by both the increase in effective magnetic thickness and the reduction in effective magnetization as decreases. For multilayers with ϭ0.4 nm, the observed field dependence of t␤ Ϫ1 is similar to that found in homogeneous thin films when weak stripe-domain structures arise as a consequence of the existence of perpendicular anisotropy K N . We propose a quasistatic one-dimensional model to explain the behavior of t␤ Ϫ1 when stripe domains are present, and we analyze the critical occurrence of stripe domains. We calculated the so-called pseudo-uniaxial anisotropy field H Ks , associated with the stripes, in two extreme cases: exchange-driven susceptibility or magnetic free poles ͑nonzero divergence in the bulk͒. The latter case agrees better with experiment. We found that perpendicular anisotropy is not exclusive of a well-defined multilayer structure; i.e., K N arises even when there are no interfaces in the volume. By setting the experimental saturation field H s ͑obtained by hysteresis loops͒ into our model, we obtain both the perpendicular anisotropy constant K N ϭ10 4 -10 5 J/m 3 and the critical thickness t c for the occurrence of a stripe-domain structure. Some possible sources of perpendicular anisotropy are discussed, for example, the associated isotropic compressive stress , whose contribution is found to be ͉K N ͉ magnetoel Ϸ1.5-4.5ϫ10 4 J/m 3 .

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