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/sub in/ as large as 0.8*10/sup 5/ and 1.5*10/sup 5/ J/m/sup 3/ have been obtained for Tb/sub 28/Fe/sub 60/Co/sub 12/ and Tb/sub 19/Fe/sub 66/Co/sub 15/, respectively. Tb/sub 18/Fe/sub 82/ layers also exhibit a noticeable anisotropy (K/sub in/ approximately=4*10/sup 4/ J/m/sup 3/), demonstrating that Co is no prerequisite. K/sub in/ depends only slightly on the thickness of the TbFeCo layers. The deposition rate, nu /sub 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 nu /sub 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.<>