Imprinted Magnetic Anisotropy and Zigzag Domain Structure of Amorphous TbCo Films

We investigate the magnetic anisotropy and domain structure of amorphous Tb (x) Co(1-x) films grown in external in-plane magnetic field by high-frequency ion sputtering. Films with different thicknesses 100 and 500 nm and rare-earth element concentrations x = 12 % and x = 34 % present strong imprinted in-plane uniaxial anisotropy. Measurements of magnetic properties and domain structure imaging were performed by means of longitudinal and polar magneto-optical Kerr effect (MOKE). The coercivity fields increase by an order of magnitude for the higher Tb concentration and increase with film thickness (H (c) along the hard axis are 495, and 580 Oe, for 100 and 500 nm, with x = 34 % and 65, and 95 Oe for 100 and 500 nm with x = 12 %, respectively). Polar MOKE measurements revealed the existence of an out-of-plane magnetization component for the films with a Tb concentration of 34 % in lower fields. Large-scale domain structure of TbCo films with imprinted anisotropy was also studied as a function of applied field. Kerr imaging shows a zigzag domain structure of Tb12Co88 films, while no domains were found in Tb34Co66 samples. We also demonstrate that the zigzag angle depends on the film thickness. We suggest that domain structure in these films is determined by the interplay of imprinted and local magnetic anisotropies as well as exchange interaction.