Structure, magnetization reversal, and magnetic anisotropy of evaporated cobalt films with high coercivity

Grain structure, crystal structure, and magnetic properties relating to coercivity of cobalt thin films with high coercivity are described. Cobalt films evaporated under vacuum at a normal angle of incidence on thallium and titanium sublayers and at a high angle of incidence on a substrate have a coercivity higher than 400 Oe. Transmission electron microscopy shows that the grain structure of the film deposited on a thallium sublayer is like large islands and that the grain structure of the film deposited at a high angle of incidence is columnar. The grain structure of the film deposited on a titanium sublayer, when similarly examined, seems homogeneous. Magnetization reversal and the magnetic anisotropy mechanism under whose influence magnetization is reversed have been investigated using the rotational hysteresis measurement method. A noncoherent rotation process is operative in these films in spite of the differences in the grain and crystal structures and the coercivity. The magnetic anisotropy for the film on the titanium sublayer is probably the magnetocrystalline anistropy of cobalt. On the other hand, the columnar grain shape anistropy should be added to the magnetocrystalline anistropy of cobalt in the oblique incidence film.