Estudo da transição de reorientação de spin em filmes de cobalto recobertos por grafeno e de ligas de FeCo

Abstract

In this thesis, we have studied the structural and magnetic propertiesof two systems with strong perpendicular magnetic anisotropy (PMA).First, PMA on cobalt thin films is induced after their intercalationunder graphene grown on different substrates: Ru(0001), Ir(111) ePt(111). The thickness and temperature driven spin reorientationtransition (SRT) on cobalt films is studied, mainly, by spin polarizedlow energy electron microscopy. Regardless of the substrate, we haveobserved a PMA enhancement due to the graphene/Co interface. Asmooth SRT is detected, where the spins continuously rotate froman out-of-plane magnetization to an in-plane state. Additionally, theevolution of magnetic domains and domain walls are studied. Onthat case, we have pointed out the presence of DzyaloshinskiiMoriyainteraction, responsible for symmetry breaking of the spin structureof domain walls. On the second system, we have investigated the surface structure andthe spin texture of FeCo thin films under a tetragonal distortion inducedby its epitaxial grown on Cu3Au(001) single crystal. Prior to theFeCo growth, we have fully characterized the (001) surface structure ofCu3Au by low energy electron diffraction. Due to the substrate structure,FeCo showed a perpendicular spin texture only when depositedby a repeated stack of 1 ML Fe and 1 ML Co, whereas co-depositedfilms prefer an in-plane magnetization.Keywords: Spin reorientation transition (SRT); perpendicular magneticanisotropy (PMA); DMI; SPLEEM; LEED; graphene; FeCo;Cu3Au.