Amorphous TbFeCo with in-plane easy anisotropy for memory applications

TbFeCo layers with field-induced in-plane easy anisotropy axis have been realized by sputtering at zero bias field. In-plane anisotropy constants K_in as large as 0.8×10⁵ and 1.5×10⁵ J/m³ have been obtained for Tb ₂₈Fe₆₀Co₁₂ and Tb₁₉Fe₆₆ Co₁₅, respectively. Tb₁₈Fe₈₂ layers also exhibit a noticeable anisotropy (K_in≈4×10⁴ J/m³), demonstrating that Co is no prerequisite. K_in depends only slightly on the thickness of the TbFeCo layers. The deposition rate, ν_d, of the TbFeCo films has to exceed a composition-dependent threshold value in order to suppress the natural tendency to create an easy axis along the growth direction of the film and to enforce the in-plane orientation. Films simultaneously grown outside the field region exhibit a reduction by a factor of five in the vertical anisotropy constant with increasing ν_d. This tendency facilitates the in-plane orientation of the magnetization during the deposition of the layers, a prerequisite for the formation of the in-plane easy axis. The induction of the in-plane easy axis by field annealing after deposition is impractical, as the Curie temperatures are too low to provide an annealing temperature with sufficient mobility of the atoms