Resumen: The magnetic domain structure is studied in epitaxial /MgO(0 0 1) films with 0 < x < 30 and thicknesses below 60 nm by magnetic force microscopy. For low gallium content, domains with the magnetization lying in the film plane and domain walls separating micrometric areas are observed. Above x ≈ 20, the magnetic contrast shows a fine corrugation, ranging from 300 to 900 nm, suggesting a ripple substructure with a periodic oscillation of the magnetization. We discuss the presence of a random magnetic anisotropy contribution, that superimposed to the cubic coherent anisotropy, is able to break the uniform orientation of the magnetization. The origin of that random anisotropy is attributed to several factors: coexistence of crystal phases in the films, inhomogeneous distribution of both internal strain and Ga–Ga next nearest neighbor pairs and interface magnetic anisotropy due to the Fe–O bond. Idioma: Inglés DOI: 10.1016/j.jmmm.2019.166135 Año: 2020 Publicado en: Journal of Magnetism and Magnetic Materials 498 (2020), 166135 [7 pp.] ISSN: 0304-8853 Factor impacto JCR: 2.993 (2020) Categ. JCR: PHYSICS, CONDENSED MATTER rank: 33 / 69 = 0.478 (2020) - Q2 - T2 Categ. JCR: MATERIALS SCIENCE, MULTIDISCIPLINARY rank: 188 / 333 = 0.565 (2020) - Q3 - T2 Factor impacto SCIMAGO: 0.665 - Electronic, Optical and Magnetic Materials (Q2) - Condensed Matter Physics (Q2)