JPH0527169B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a perpendicular magnetization recording medium having a thin film of a magnetic recording medium that has excellent wear resistance and magnetic recording characteristics and has magnetic anisotropy perpendicular to the film surface. In general, magnetic disks, floppy disks, audio magnetic tapes, VTR magnetic tapes, magnetic photographic disks, and computer magnetic tapes have perpendicular magnetic recording functions that enable high-density magnetic recording. known as the body. These perpendicular magnetization recording bodies are usually made by forming a film on the surface of a substrate such as a plastic film, metal sheet, metal disk, or glass disk using surface treatment techniques such as sputtering, vacuum evaporation, and chemical plating. Thin films of magnetic recording media made of Co-Cr alloys, Co-Ru alloys, and Co-based alloys such as Co-Cr-Ru, which have magnetic anisotropy perpendicular to the plane, are directly or highly transparent. It is manufactured by forming a thin film of magnetic Fe-Ni alloy or the like. However, although the perpendicular magnetization recording medium described above has excellent perpendicular magnetization characteristics, the thin film of the magnetic recording medium made of Co-based alloy is soft, so during magnetic recording, single crystal Mn-Zn-based ferrite cannot be used. If it comes into frictional contact with a magnetic head made of hard materials such as ferrite, high-density ferrite, sendust, or amorphous metal, it will cause significant wear and damage.
Alumina (Al ₂ O ₃
Currently, a hard non-magnetic thin film made of silica (SiO ₂ ) or the like is formed to suppress wear caused by the magnetic head. However, even in conventional perpendicular magnetization recording materials with excellent wear resistance, the top layer is
Since it is composed of a non-magnetic thin film such as Al ₂ O ₃ or SiO ₂ , during magnetic recording, the magnetic field is separated by the thickness of the uppermost layer, that is, in a state where there is a space loss, and the magnetic field is separated from the lower layer by the thickness of the uppermost layer. Since magnetic recording will be performed on the magnetic recording medium, the magnetic recording density will decrease accordingly. Therefore, from the above-mentioned viewpoint, the present inventors conducted research to develop a perpendicular magnetization recording material that has excellent wear resistance and does not reduce magnetic recording density. The compositional formula: CoxFe ₃ -xO is essentially deposited as a target on the top surface of a thin film of a magnetic recording medium made of a Co-based alloy with magnetic anisotropy perpendicular to the plane using a normal sputtering method. ₄ (however, x preferably has a value within the range of 0.01 to 1.0) and forms a thin film of this Fe-Co ferrite, the Fe-Co ferrite thin film has the following properties: Due to its excellent wear resistance and magnetic recording properties, perpendicularly magnetized recording bodies whose top layer is composed of a thin film of Fe-Co ferrite suffer almost no wear or damage from the magnetic head during magnetic recording. They discovered that it is possible to perform high-density magnetic recording even when there is no magnetic field. The present invention has been made based on the above findings, and is applied as a top layer on the top surface of a thin film of a magnetic recording medium made of a Co-based alloy having magnetic anisotropy perpendicular to the film surface. It is characterized by a perpendicular magnetization recording body formed of a thin film made of Fe--Co ferrite, which has excellent abrasion resistance and magnetic recording properties. Next, the perpendicular magnetization recording body of the present invention will be specifically explained using examples. Example A polyester film with a thickness of 50 μm was prepared as a substrate, and this substrate was mounted on a normal magnetron sputtering device, and while rotating, Fe-Ni alloy (containing 50% Ni) and Co-Cr Using targets of alloy (Cr: 18% content), alumina (Al ₂ O ₃ C), silica (SiO ₂ ), and various Fe-Co ferrites with the compositions shown in Table 1, (1) Ultimate vacuum: 2.0×10 ^-6 torr or less, (2) Ar gas pressure: 3.0×10 ^-3 torr, (3) Distance between substrate and target: 50 mm, (4) Discharge power and sputtering time, (a) For Co-Cr alloy and Fe-Ni alloy targets: 400 seconds at DC360W, (b) Fe-Co ferrite, Al ₂ O ₃ , and
In the case of SiO ₂ target: Sputtering was performed at RF 100W for 600 seconds under the following conditions, and thin films with the average layer thickness shown in Table 1 were sequentially deposited on the above substrate surface.

【table】

[Table] Perpendicular magnetization recording body 1 of the present invention by forming the following
- 6 and conventional perpendicular magnetization recording bodies 1 and 2 were manufactured, respectively. Next, the anisotropic magnetic field Hk and coercive force Hc of the various perpendicularly magnetized recording bodies obtained as a result were measured using a vibrating magnetic measuring device, and this was further formed into a floppy disk size and mounted on a ferrite head. In order to conduct a driving test using a disk drive device equipped with
Ratio of reproduction voltage (Vm) to initial reproduction voltage (Vi) after 1 million passes, i.e. γ = Vm/Vi
In order to measure (deterioration rate) and evaluate high-density magnetic recording characteristics, we performed recording and reproduction while varying the recording density, and measured the recording density (D ₅₀ ) at which the reproduction voltage was half of the reproduction voltage of 1KBPI. did. Furthermore, thin films of the various Fe-Co ferrites, Al ₂ O ₃ , and SiO ₂ were formed on the glass substrate under the same conditions except that the sputtering time was 2 hours.
The hardness of these formed thin films was measured using a Knoop hardness meter. These measurement results are also shown in Table 1. From the results shown in Table 1, the perpendicular magnetization recording bodies 1 to 6 of the present invention not only have superior wear resistance compared to the conventional perpendicular magnetization recording bodies 1 and 2, but also enable higher-density magnetic recording. One thing is clear. As mentioned above, the perpendicular magnetization recording body of the present invention has the following features:
By configuring the uppermost layer with a thin film consisting essentially of Fe--Co ferrite, excellent wear resistance is ensured and high-density magnetic recording is made possible.

Claims (1)

[Claims] 1. In a perpendicular magnetization recording medium composed of a Co-based alloy magnetic recording medium in which the surface thin film has magnetic anisotropy perpendicular to the film surface, abrasion resistance and magnetic recording properties are further added to the surface thin film. Excellent Fe
- A perpendicular magnetization recording body formed by forming a thin film of Co-based ferrite.