Effect of Thermal Annealing on the Stoichiometry and Magnetism of Mn–Ga Thin Films

Mn x Ga thin films (1.64 ≤ x ≤ 2) were grown at room temperature by molecular beam epitaxy on the native SiO2 layer of Si(100) commercial wafers. After growth, Mn x Ga films were thermally annealed at different temperatures (200, 300, and 400 °C). The X-ray diffraction results reveal D022-Mn2Ga as the main phase and an improvement of the crystalline quality as a function of the annealing temperature. The samples were also investigated using X-ray photoelectron spectroscopy, atomic force microscopy, and vibrating sample magnetometry techniques. The magnetization curves suggest that the magnetic behavior is strongly dependent on the annealing time and temperature and that the saturation magnetization decreases with an increase in the Mn concentration in the alloy. These magnetic properties are related to the morphology and crystallinity of the samples. The magnetic moment distributions of the films were calculated using density functional theory, bringing a better understanding of the origin of the observed magnetic anisotropy.