JPH0624054B2 - Perpendicular magnetic recording medium and magnetic recording / reproducing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perpendicular magnetic recording medium excellent in high density recording characteristics and a magnetic recording / reproducing method using the same.

2. Description of the Related Art A perpendicular magnetic recording method is known as a magnetic recording method having excellent short wavelength recording characteristics. This system requires a magnetic layer having perpendicular magnetic anisotropy. When a signal is recorded on such a magnetic layer, the residual magnetization is oriented substantially perpendicular to the film surface. Therefore, the shorter the wavelength of the signal, the smaller the demagnetizing field in the medium and the larger the reproduction output. A perpendicular magnetic recording medium is one in which a perpendicular magnetic anisotropic film of a Co-based alloy such as Co-Cr, Co-V, or Co-Cr-Rh is formed as a magnetic layer on a substrate by a sputtering method in general. is there. However, the sputtering method has a low film deposition rate and poor mass productivity.

In contrast to the sputtering method, according to the vacuum vapor deposition method (including the method of ionizing a part of the vapor deposition atoms like the ion plating method), the film deposition rate is 1 μm / two times higher than that of the sputtering method. More than a second is possible,
Excellent mass productivity. The present inventors have found that the vacuum deposition method
It has been found that a Co-Cr perpendicular magnetic anisotropy film can be obtained.

Problems to be Solved by the Invention As described above, the present inventors have clarified that the vacuum deposition method can provide a perpendicular magnetic anisotropic film with extremely excellent mass productivity. Has not been found to have excellent recording and reproducing characteristics. Regarding the film produced by the sputtering method, it is desirable that M _r ⊥ / M _r be 1 or more as the perpendicular magnetic anisotropic film, and in particular, the perpendicular magnetic anisotropic film was formed directly on the non-magnetic substrate, For a so-called single-layer film medium, it was considered that the requirement that M _r ⊥ / M _r be 1 or more was a necessary condition. However, the film forming conditions for satisfying this condition are strict, and the mass productivity and the yield are low, so that a condition with a wider margin has been demanded.

Means for Solving Problems The hysteresis curve in the direction perpendicular to the film surface of the perpendicular magnetic anisotropy film in a perpendicular magnetic recording medium measured by a vibrating sample magnetometer has a slope equal to the slope at the intersection with the horizontal axis. and a line passing the origin, the magnetic field H _o at the intersection of the straight line composed magnetization M = saturation magnetization M _s, the value divided by the saturation magnetization M _s H _o / M _s is less than or equal 3.5Pai, and the hysteresis curve the ratio M _r ⊥ / M _r of the residual magnetization M _r of the residual magnetization M _r and the film plane in the direction perpendicular to the film plane is in the range of 0.2 to 0.98 in.

Action By making the magnetostatic characteristics of the perpendicular magnetic anisotropic film satisfy the conditions of the present invention, a perpendicular magnetic recording medium having excellent recording and reproducing characteristics can be obtained.

Embodiment An embodiment of the present invention will be described with reference to FIG. First
The figure shows an example of the first and second quadrants of the hysteresis curve of a perpendicular magnetic anisotropic film measured by a vibrating sample magnetometer, and curves 1 and 2 are the direction perpendicular to the film surface and the film surface, respectively. It is inside. The horizontal axis of FIG. 1 represents the applied magnetic field and the vertical axis represents the magnetization. The straight line 3 has a slope equal to the slope of the portion where the hysteresis curve 1 in the direction perpendicular to the film surface intersects the horizontal axis, and passes through the origin. 4 is a straight line of magnetization M = saturation magnetization M _s . The H _o in the figure is the value of the horizontal axis at the intersection of the straight line 3 and the line 4. M _r and M _r are remanent magnetization in the direction perpendicular to the film surface and remanent magnetization in the film surface, respectively.

Different Co-Cr of said H _o was divided by the saturation magnetization M _s value H _o / M _s
The characteristics when the perpendicular magnetic anisotropy film is formed on the non-magnetic substrate by the vacuum deposition method and the recording / reproducing is performed by the ring head made of Mn-Zn ferrite will be described below. Co-C
The film thickness of the r perpendicular magnetic anisotropy film was 0.25 μm, the gap length of the head was 0.2 μm, and the low frequency reproduction output and D ₅₀ were measured. The second FIG shows the relative value of the output in 1KFRPI as low frequency reproduction output, reproduction output value from the D ₅₀ 1KFR
It is the recording density that is half the output at PI. Here, 1KFRPI is a recording state of a digital signal having magnetization reversal 1000 times per inch. Curve 5 in Figure 2
And 6, respectively showing the H _o / M _s dependence of the low-frequency reproduction output and D _50. It can be seen from FIG. 2 that when H _o / M _s exceeds 3.5π, both the low-frequency reproduction output and D ₅₀ sharply decrease.
Therefore, H _o / M _s needs to be 3.5π or less. The reason why the recording / reproducing characteristics depend on H _o / M _s is not clear yet, but it is considered that the microscopic structure of the perpendicular magnetic anisotropy film is involved.

Next, for a perpendicular magnetic anisotropy film satisfying H _o / M _s 3.5 π, the ratio of the residual magnetization M _r in the direction perpendicular to the film surface and the residual magnetization M _r in the film surface M _r ⊥ / M _r and recording / reproduction The relationship with the characteristics will be described. The measurement was performed in the same manner as above by forming a Co-Cr perpendicular magnetic anisotropy film with a thickness of 0.25 μm on a non-magnetic substrate by a vacuum deposition method and using a ring head made of Mn-Zn ferrite with a gap length of 0.2 μm. I did. The results are shown in FIG. Curves 7 and 8 in FIG. 3 show the M _r ⊥ / M _r dependence of the low frequency reproduction output and D ₅₀ , respectively. From FIG. 3, it can be seen that the low frequency reproduction output sharply decreases when M _r ⊥ / M _r exceeds 0.98, and D ₅₀ sharply decreases when M _r ⊥ / M _r becomes less than 0.2. Therefore, Co-Cr with excellent low range reproduction output and D ₅₀
The perpendicular magnetic anisotropic film is obtained when M _r ⊥ / M _r is 0.2 or more and 0.98 or less.
The same result as above was obtained even when a ring head made of a metal such as amorphous or sendust was used as the ring head instead of Mn-Zn ferrite.

Above such as the results of showing the recording and reproducing characteristics with excellent perpendicular magnetic anisotropy film satisfying 0.2M _r ⊥ / M _r 0.98 under conditions of H _o / M _s 3.5π is perpendicular This is obtained by overcoming the conventional technical common knowledge that it is desirable that M _r ⊥ / M _r be 1 or more as an anisotropic film. In addition, than the perpendicular magnetic anisotropy film that satisfies the _{M r ⊥ / M r> 1} , 0.2M r ⊥ / M is the deposition conditions towards the perpendicular magnetic anisotropy film that satisfies the r 0.98 is loosely High productivity and yield can be achieved. In particular, when the perpendicular magnetic anisotropic film containing Co and Cr as the main components is formed by the vacuum evaporation method, the film forming conditions for satisfying M _r ⊥ / M _r > 1 are severe. Is very effective.

Specific examples will be described below.

A long polyamide film having a film thickness of 10 μm was used as a substrate, and a Co—Cr perpendicular magnetic anisotropic film having a film thickness of 0.2 μm was formed thereon by a continuous vapor deposition method. Here, the continuous vapor deposition method is, as is well known, a method of continuously vapor depositing a film while running a long film along the circumferential surface of a cylindrical can. The deposition conditions for forming the Co-Cr perpendicular magnetic anisotropy film are as follows: vacuum degree 3 × 10 ^-5 Torr, film deposition rate 0.8 μm /
Sec., Surface temperature of cylindrical can 250 ℃, film composition Co ₈₂ wt%,
Cr ₁₈ wt%. The Co / Cr perpendicular magnetic anisotropy film deposited under the above conditions had a H _o / M _s of 3.1π and a M _r ⊥ / M _r of 0.4. Gap length 0.25
μm, Gap width 30μm, Mn with 16 turns
When recording and reproducing with a ring head made of -Zn ferrite, a low frequency reproduction output of 190 μV / turn · mm · m / sec and a D _{50 of} 125 KFRPI were obtained. Note that 190 μV / turn · mm · m / sec means that the coil output is 1 turn, the gap width is 1 mm, and the head output per 1 m / sec of the relative speed between the medium and the head is 190 μV.

In the specific examples described above, examples of Co-Cr perpendicular magnetic anisotropy films have been described, but the perpendicular magnetic properties of Co-based alloys such as Co-Cr-Ni, Co-O, and Co-Ni-O films have been explained. The same applies to an anisotropic film.

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a perpendicular magnetic recording medium having excellent recording and reproducing characteristics with high mass productivity and yield.

[Brief description of drawings]

FIG. 1 is a diagram showing a hysteresis curve of a perpendicular magnetic anisotropy film measured by a vibrating sample magnetometer, and FIG. 2 is a low frequency reproduction output in a perpendicular magnetic recording medium and D ₅₀ and H _o / M _s . FIG. 3 is a diagram showing the relation, and FIG. 3 is a diagram showing the relation between the low frequency reproduction output and D ₅₀ and M _r ⊥ / M _{r in the} perpendicular magnetic recording medium. 1 ... Hysteresis curve in the direction perpendicular to the film surface, 2 ... Hysteresis curve in the film surface.

Claims (3)

[Claims] 1. A hysteresis curve measured by a vibrating sample magnetometer in a perpendicular magnetic recording medium in a perpendicular magnetic recording medium has a slope equal to a slope at a portion where a hysteresis curve in a direction perpendicular to a film surface intersects with the horizontal axis, and has an origin. a straight line passing through the magnetic field H _o at the intersection of the straight line composed magnetization M = saturation magnetization M _s, the saturation magnetization M
_The value H _o / M _s divided by _s is 3.5π or less, and the ratio M _r ⊥ / M _r of the residual magnetization M _r in the direction perpendicular to the film surface in the hysteresis curve and the residual magnetization M _r in the film surface is A perpendicular magnetic recording medium characterized by being in the range of 0.2 to 0.98. 2. The perpendicular magnetic recording medium according to claim 1, wherein the magnetic film is a single-layer film having only a perpendicular magnetic anisotropic film. 3. A vertical axis of a perpendicular magnetic recording medium in a perpendicular magnetic recording medium measured by a vibrating sample magnetometer has a slope equal to a slope at a portion where a hysteresis curve perpendicular to the film surface intersects with the horizontal axis, and has an origin. a straight line passing through the magnetic field H _o at the intersection of the straight line composed magnetization M = saturation magnetization M _s, the saturation magnetization M
_The value H _o / M _s divided by _s is 3.5π or less, and the ratio M _r ⊥ / M _r of the residual magnetization M _r in the direction perpendicular to the film surface in the hysteresis curve and the residual magnetization M _r in the film surface is A magnetic recording / reproducing method characterized by performing recording / reproducing using a ring head with respect to a perpendicular magnetic recording medium in the range of 0.2 to 0.98.