Etude théorique des propriétés structurales de la structure électronique, du magnétisme et de l'effet Kerr dans les films ultraminces ferrimagnétiques

Abstract

By means of DFT, we investigate the structural, magnetic and magneto-optical properties of Cr ultrathin film on semi-infinite Ag substrate. The results show that Cr ultrathin film crystalizes in bct structure with lattice parameters (a=b= 2.88 Å, c/a=1.25) and it favor ferrimagnetic coupling between Cr planes. The anisotropy is shown to be perpendicular to the surface by polar-magneto-optical Kerr effect. The magnetic moment at free surface of Cr film reach the value of 3,78 µB. In Mn ultrathin film on Ag or Au in the direction of (001), the result shows that the applied strain of bct Mn film from lattice parameter a=2.89 Å to lattice value of 2.73 Å induces ferrimagnetic behavior between Mn layers. The magnetic easy axis of Mn film was demonstrated theoretically to switch from the in-plane to out-of-plane by magneto-optical Kerr effect investigation. By including spin-orbit coupling in full potential linearized augmented plane waves and linearized muffin-tin orbitals methods, manganese ultrathin film displays different magnetic behaviors and the spin-reorientation transition is shown to be correlated to these structural changes. The calculated magnetic moment of manganese planes are enhanced and reach a value of ~ 4.02 μB in the case of Ag substrate and reach a value of 4.30 μB in the case of Au substrate. The polar magneto-optical Kerr effect is calculated for a photon energy range extended to 10 eV. It shows a pronounced peak in visible light.