To Fernanda Mendes, I want to express my gratitude for never giving up on me and be by my side all over these years through this journey.Anita, my dear 'little sis', many thanks for all the help, support, patience, and incentive, and without you, it would have been much harder to get through this journey. Janana, we don't need words, my twin, thanks for all the support since the cradle. Ivone, my dear "big sis" thanks for your beautiful friendship over all the years, your kindness and support.Dear Becas and Claúdio, I want to thank you for your sweet friendship and to for being by my side all these years, you are like family to me. My dear Su, thanks for so many smiles and tears shared with a tight hug, and your support even at distance. Debby gata, many thanks for welcoming me so well when I arrived at the home and for all the support.Many thanks to my dear friends, Hugo, Mini e Dee, Marco e Xana, Suzie, Joana (Wally), Rui e Susana, Zé Manel, who, over the years, have been by my side and shared so many significant moments. I would like to thank my family support. Quero agradecer à minha família, titó Regina, tia São e tio Adelino, tio Helder, e às primas Ana Raquel, Luisinha e Tininha.Last but not least, I would like to thank my loved ones. Uma palavra especial de agradecimento aos meus queridos pais, Maria Isabel e José, à minha irmã Rute, à minha sobrinha Constança, ao meu sobrinho Salvador e ao meu 'irmão' José, pelo vosso apoio incondicional e sempre presente, sem qual seria impossível chegar até aqui. Vocês são a minha inspiração, a minha força. ResumenPalabras clave: dinámica de magnetización ultrarrápida; multicapas de películas ultrafinas; espectroscopia de pulsos de pocos ciclos.