Magnetic properties of evaporated CoCr films

Perpendicular magnetic CoCr films were prepared on glass substrates using electron beam evaporation. The magnetic properties depend strongly on the substrate temperature, T
s
. The anisotropy field,
H_{k}^{eff}
, and the perpendicular coercivity, H
c
(
\perp
) show maximum values at T
s
around 250°C. In this case, the alignment of c-axis is optimal and the grain size is smallest. The lattice spacing of the c-planes increases wlth T
s
until 300°C. When the films prepared below 200°C were annealed around 300°C in high vacuum, the saturation magnetization, M
s
, increased. The value of M
s
, however, decrease by annealing above 400°C. In spite of the decrease of M
s
due to the annealing above 400°C,
H_{k}^{eff}
and H
c
(
\perp
) increase by annealing above 400°C. If the films were bombarded by argon ions during film growth, M
s
decreased and the internal stress changed from tensile to compressive. For low substrate temperature (below 150°C),
H_{k}^{eff}
decreased due to ion bombardment.