Perpendicular magnetic recording medium

#The present invention relates to a perpendicular magnetic recording medium which is used in perpendicular magnetic recording.

#In a perpendicular magnetic recording method, a magnetic recording medium, such as a magnetic tape or magnetic disc, is used, and on the surface of the magnetic recording medium a magnetic medium layer (perpendicular magnetization film) for magnetic recording is fabricated. And the magnetic medium layer has a magnetic easy axis in the direction perpendicular to the run direction of the magnetic recording medium, i.e. in the direction of thickness of the magnetic recording medium, and the magnetic recording medium is magnetized in the direction of thickness using a perpendicular magnetic recording head adapted to cause a strong magnetization distribution in the direction of thickness of this magnetic recording medium, thereby trapping the magnetization of the magnetic medium layer in this direction. In this way, the presence of residual magnetization distribution in the direction of thickness of the magnetic recording medium will suppress the occurrence of self-demagnetization field, thereby enabling the high density recording with little loss of recording information (for example, refer to Japanese Patent Application Laid-open No. 134706/77).

#With regard to perpendicular magnetic recording media to be used for the perpendicular magnetic recording method as described above, two perpendicular magnetic recording media are known: one having a double layer structure such that a magnetic layer (perpendicular magnetization film) having a magnetic easy axis in the direction perpendicular to the medium surface is formed through a high permeability magnetic layer on a non-magnetic substrate, and the other having a single layer structure consisting of only a perpendicular magnetization film without a high permeability film. The former is known to have a higher characteristic than the latter (for example, refer to Japanese Patent Application Laid-open No. 78403/77).

#The above and other objects, features and advantages of the present invention will be apparent from the following detailed description in conjunction with the accompanying drawings, in which:

#FIG. 1 is a diagram showing the relations between the heat treatment temperatures of the Co-Cr thin film having various thicknesses and the perpendicular magnetic characteristics (each of which is represented by the variation ratio of half width of rocking curve corresponding to the (002) face of the hcp crystal);

#FIG. 2 is a diagram showing the relation between the content of Pt in the thin film of Co-Pt alloy and the coercive force;

#The present invention will now be described in detail hereinbelow with respect to preferred examples.

#As shown in FIG. 3, a Co.sub.80 Pt.sub.20 alloy film 2 having a thickness of 1.0 .mu.m was deposited by the sputtering method on an annular glass substrate 1 having a thickness of 5 mm and an outside diameter of 10 cm and an inside diameter of 2 cm, then a Co.sub.80 Mo.sub.9.5 Zr.sub.10.5 alloy film 3 having a thickness of 0.5 .mu.m was deposited on the alloy film 2 by the same sputtering method, thereafter a Co.sub.80 Cr.sub.20 alloy film 4 having a thickness of 0.2 .mu.m was deposited on the alloy film 3, thereby producing a recording medium 5.

#In the above process, before the Co.sub.80 Mo.sub.9.5 Zr.sub.10.5 alloy film 3 was produced of after it had been produced, radial magnetic fields that run toward the center of the recording medium 5 were applied to the recording medium 5 while rotating the recording medium 5 at 200 rpm using a magnet 10 having such a shape as shown in FIG. 4. The magnetic field strength applied was about 100 Oe on the average radius of the annular glass substrate. In FIG. 4, a reference numeral 5 is the recording medium; 10 is the magnet; 11 is a magnetic core having a fan-like portion; and 12 is a magnetization coil.