Texture formation and magnetic properties of RF sputtered CoCrTa/Cr longitudinal thin films

CoCrTa films of different thicknesses were RF-sputtered on 1000-Å-thick Cr underlayers. The in-plane coercivity has a maximum of 1670 Oe for 200-Å-thick CoCrTa films and then decreases to 740 Oe for 9000-Å-thick films. The in-plane squareness also decreases monotonically from 0.80 to 0.25 when the thickness of CoCrTa films increases from 100 Å to 9000 Å. By using transmission electron diffraction, it was found that CoCrTa films thinner than 400 Å have a distribution of c-axes lying mostly in the film plane or tilted by an angle of about 28° with respect to the film plane. 9000-Å-thick CoCrTa films are dominated by perpendicularly oriented c-axes. Crystallographic texture change during the growth process of CoCrTa films could be responsible for the observed thickness dependence of the in-plane coercivity and squareness. TEM (transmission electron microscope) micrographs of these films show no physical voids in the grain boundaries