IMPROVED CRYSTAL TEXTURE CONTROL FOR RARE-EARTH TRANSITION-METAL MAGNETIC-FILMS SPUTTERED IN AR-XE GAS-MIXTURES

The influence of energetic neutral sputtered atoms impinging during the growth of crystalline textured rare earth transition metal films has been experimentally studied and modeled. The main system studied has been Sm2(Co,Fe,Cu,Zr)17 films that have been directly crystallized by sputtering onto heated sapphire and polycrystalline Al2O3 substrates. By varying the sputtering pressures and gas compositions, the composition of the films sputtered from the same targets could be shifted so that either a disordered hexagonal TbCu7-type structure was formed or, for richer samarium concentrations, a hexagonal 1-5-type structure was formed. Films exhibiting the TbCu7-type structure were the principal interest for these studies. The magnetic anistropy field of these films was sufficiently high that the magnetic properties were a very sensitive indicator of the presence of crystallites that had c axes skewed out of the film plane. It has been possible to sputter such films, with thicknesses from 1 to more that 50-mu-m, with in-plane energy products of about 20 MG Oe in Ar-Xe sputtering gas mixtures such that no crystallites that have c axes skewed out of the film plane can be detected. A principal result of the modeling which uses a distribution of sputtered neutral atom energies, is that the fraction of non-thermal atoms striking the crystallizing films can be appreciably lowered by using Ar-Xe mixtures at much lower total pressures than it argon alone were used as the sputtering gas.