Preparation of amorphous cobalt ferrite films with perpendicular anisotropy and their magnetooptical properties

Amorphous CoFe
2
O
4
films were made from CoFe
2
alloy and P
2
O
5
as the starting materials by the double source evaporation method. As the films were made in various levels of pressure of evaporated P
2
O
5
(P
p2
o
5
) in the bell jar, different crystal phases and perpendicular anisotropy constants (Ku) of the films were obtained. More precisely, when Pp
2
o
5
was higher than 5×10
^-3
torr, the amorphous films were produced and under Pp
2
o
5
of higher than 10
^-2
torr the maximum Ku of the films with the perpendicular anisotropy was 1.8×10
⁵
erg/cm
³
. The perpendicular anisotropy seemed to be induced by both shape anisotropy with the columnar structure and uniaxial magnetic anisotropy of Co
²⁺
and Fe
²⁺
. For amorphous CoFe
2
O
4
films, the dependence of the polar Kerr rotation angle on the wave length became complicated with the increase in Pp
2
o
5
. A curve showing the relation between polar Kerr rotation angle and the wave length had a broad, positive peak in the region from 300 nm to 500 nm which was characteristic of amorphous CoFe
2
O
4
films.