Filmes de FePt para dispositivos da spintrônica

Abstract

The present study deals with magnetic and transport properties in the L10 FePt compound. The compound has tetragonal structure and strong magnetocrystalline anisotropy. Films were prepared by sputtering. For measuring Tunnel Anisotropic Magnetoresistance (TAMR), FePt/AlOx/Au trilayers were prepared. All prepared alloys exhibited significant coercivity. In some of them, coercive fields µ0Hc > 1, 6 T at 300 K were obtained. Magnetic Force Microscopy observations were analyzed considering the interplay existing between structural and magnetic properties. In FePt films, the resistance decrease observed as the strength of the applied field increased has been related to the reduction in electron-magnon scattering, due to the fact that the applied field induces additional magnetic order in the alloys. The magnetoresistance anisotropy (AMR) and the TAMR were found to reveal similar behavior qualitatively. This may be understood when one considers that the physical parameter, which determines these behaviors is the direction of the magnetization with respect to the current. The AMR signal calculated for the layer of in FePt is ∼ 10% at low temperature. However, due to the strong magnetocrystalline anisotropy of the FePt, only 2% was found. On the opposite, the TAMR signal is very weak, of only 1% at low temperature. It had been suggested that TAMR could offer one of the most promising perspective for the development of new objects in spintronics. Further studies are needed aiming at understanding which are the factors limiting TAMR values reached until today.