MAGNETIC-PROPERTIES AND GROWTH TEXTURE OF HIGH-COERCIVE ND-FE-B THIN-FILMS

We have investigated the growth texture and magnetic properties of spu ttered Nd-Fe-B thin films with thicknesses from 5 to 350 nm. Films dep osited directly onto a quartz substrate grow with a pronounced c-axis texture perpendicular to the film plane and have a coercivity of about 160 kA/m. If the films thickness is reduced below 150 nm, a significa nt part of the Nd is oxidized by substrate oxygen and the coercivity d ecreases to values below 20 kA/m. The deposition of a 80 nm Cr buffer layer between substrate and Nd-Fe-B film prevents oxidation of the fil m and decreases the growth texture of the films. This enables us to fa bricate Nd-Fe-B films as thin as 20 nm with good hard magnetic propert ies [H-cj = 800 kA/m, J(r) = 1.1 T, and a maximum energy product (BH)( max) = 190 kJ/m(3) perpendicular to film plane]. An inverse relationsh ip between growth texture and coercivity is found which can be underst ood in terms of domain wall motion. The deposition of a Cr buffer lead s to an island type of growth and a high surface roughness, while film s without Cr buffer are very smooth. By depositing a protective Cr lay er on top of the film, the corrosion resistance can be enhanced. (C) 1 998 American Institute of Physics.