Method of making a magnetic oxide film with high coercive force

DETAILED DESCRIPTION Accordingly, one object of this invention is to provide a method of making a homogeneous, high coercive force magnetic medium with high efficiency and with ease.
Another object of this invention is to provide a method of making a high coercive force magnetic film which can be used for a magnetic disk and is highly adhesive to the substrate, excellent in surface roughness and in mechanical strength and has a thickness of less than 0.
3.
mu.
m.
In accordance with this invention, the abovesaid objects can be achieved by the steps of sputtering a target made of iron and aluminum in a certain atmosphere of argon and oxygen gas to form a non-magnetic iron oxide (.
alpha.
-Fe.
sub.
2 O.
sub.
3) having dissolved therein aluminum, and reducing the non-magnetic iron oxide to precipitate fine magnetic phases (Fe.
sub.
3 O.
sub.
4) having dissolved therein aluminum.
The manufacturing process according to this invention comprises a step of sputtering for the formation of a non-magnetic iron oxide (.
alpha.
-Fe.
sub.
2 O.
sub.
3) film and a step of reducing said film for the formation of a magnetic oxide (Fe.
sub.
3 O.
sub.
4).
The feature of this invention resides in the composition of the film which is made of not only iron but also aluminum.
The addition of aluminum provides high coercive force.