Browsing by Author "Duarte, A. C."
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- Argon assisted chemical vapor deposition of CrO2: An efficient process leading to high quality epitaxial filmsPublication . Duarte, A. C.; Franco, N.; Viana, A. S.; Polushkin, N. I.; Silvestre, António Jorge; Conde, O.A comparative study of the structural, microstructural and magnetic properties of CrO2 thin films grown onto (110) and (100) TiO2 rutile single crystal substrates by chemical vapor deposition (CVD), using CrO3 as chromium precursor and either oxygen or argon as carrier gas is presented. Our results show that growth under argon carrier gas leads to high quality CrO2 epilayers with structural and magnetic properties similar to those obtained using the more standard oxygen carrier gas. Furthermore, we interpret the larger magnetic coercivity observed for the (110) oriented films in terms of their microstructure, in particular of the highest strain and edge roughness of the building structures of the CrO2 epilayers, which are settled by the substrate crystallographic orientation.
- Laser-induced diffusion decomposition in Fe-V thin-film alloysPublication . Polushkin, N. I.; Duarte, A. C.; Conde, O.; Alves, E.; Barradas, N. P.; García-García, A.; Kakazei, G. N.; Ventura, J. O.; Araújo, J. P.; Oliveira, Vitor; Vilar, R.We investigate the origin of ferromagnetism induced in thin-film (similar to 20 nm) Fe-V alloys by their irradiation with subpicosecond laser pulses. We find with Rutherford backscattering that the magnetic modifications follow a thermally stimulated process of diffusion decomposition, with formation of a-few-nm-thick Fe enriched layer inside the film. Surprisingly, similar transformations in the samples were also found after their long-time (similar to 10(3) s) thermal annealing. However, the laser action provides much higher diffusion coefficients (similar to 4 orders of magnitude) than those obtained under standard heat treatments. We get a hint that this ultrafast diffusion decomposition occurs in the metallic glassy state achievable in laser-quenched samples. This vitrification is thought to be a prerequisite for the laser-induced onset of ferromagnetism that we observe. 2014 Elsevier B.V. All rights reserved.