JPH0337724B2 - - Google Patents

Description

[Detailed Description of the Invention] Recently, perpendicular magnetic recording and magneto-optical recording have been attracting attention and research as new magnetic recording methods capable of high-density recording. has magnetic anisotropy and
It is necessary to use a so-called perpendicular magnetization film that satisfies the conditions Ku⊥≧2xMs ² or Hc⊥>Hc, Br⊥>Br.

Conventionally, one of the most popular types of perpendicularly magnetized films is a Co--Cr thin film, which is produced by sputtering and vapor deposition. However, since the sputtering method has a low deposition rate, it is not suitable for media used in large quantities such as floppy disks and magnetic tapes.
There is a problem in terms of mass production. On the other hand, the vapor deposition method has a high deposition rate, but because the vapor pressures of Co and Cr are greatly different, it is difficult to control a stable Cr composition over a long period of time. However, there is a drawback that a perpendicularly magnetized film cannot be obtained with an unheated substrate.

Instead of this, the present invention provides an advantageous perpendicular magnetic recording body that has an excellent perpendicular magnetization film without heating a new substrate. Directly or through a soft magnetic thin film layer, the composition is expressed as (F _x Co _y Ni _z ) _100-n O _n , and x, y, z, and m are each at% and 0<x≦
5, 0<z≦40, x+y+z=100, 15≦m≦50
The crystal structure is a columnar grain structure with the C axis of the HCP structure oriented in the vertical direction, and the relationship between the vertical coercive force Hc⊥ and the parallel coercive force Hc is within the range of
Hc⊥＞Hc, and the residual magnetic flux density in the vertical direction
The relationship between Br⊥ and the residual magnetic flux density Br in the parallel direction is
It is formed by forming a perpendicular magnetization film where Br⊥＞Br,
The perpendicular magnetic recording body of the second invention has a composition of (Fe _x Co _y
Ni _z ) _100-n Om, x, y, z, m are each at%, 40≦x≦100, 0≦z≦25, x+y+
It is in the range of z=100, 15≦m≦50, and the crystal structure is
It has a columnar grain structure with the (100) direction of the BCC structure oriented perpendicularly, and the relationship between the coercive force Hc⊥ in the vertical direction and the coercive force Hc in the parallel direction is Hc⊥>Hc,
A perpendicular magnetization film is formed in which the relationship between the residual magnetic flux density Br⊥ in the vertical direction and the residual magnetic flux density Br in the parallel direction satisfies Br⊥>Br.

Each of the perpendicular magnetization films described above has a two-phase structure consisting of a ferromagnetic crystal grain phase grown into a columnar structure by Fe, Co, and Ni vapor deposition, and a non-ferromagnetic oxide phase surrounding the ferromagnetic crystal grain phase.

Next, examples of the present invention will be described.

The present inventor previously obtained Japanese Patent Application No. 58-36652 and
As proposed in No. 58-36653, Co-O and Co-
We have developed a perpendicular magnetic recording medium with a perpendicularly magnetized film made of Ni-O, but now we are conducting various studies on the case where O is introduced into the Fe-Co-Ni ternary component containing Fe, another ferromagnetic element. As a result, it was confirmed that an excellent partially oxidized ternary component perpendicularly magnetized film was obtained in the two areas A and B surrounded by diagonal lines, as shown in FIG.

The first region A is a region close to Fe and forms a BCC phase in a nearly ternary phase diagram. Another region B is a region close to Co that forms an HCP phase.

As is well known, to obtain a perpendicularly magnetized film, it is necessary that the perpendicular magnetic anisotropy energy K⊥ be larger than the energy of the demagnetizing field in the perpendicular direction of the thin film, 2πM ² s. In this case, the perpendicular magnetic anisotropy can be considered to be magnetocrystalline anisotropy or shape magnetic anisotropy.
It has a structure in which a ferromagnetic columnar particle phase of Co and Ni is isolated by a non-ferromagnetic oxide phase such as Fe, Co, and Ni, and the particle size of the ferromagnetic columnar particles is approximately 200 to 1000 Å along the short axis. It was confirmed that the material had an elongated shape with a long axis of 1000 Å to 1 μm. Therefore, large shape magnetic anisotropy occurs. Furthermore, as a result of X-ray diffraction, in the B region near Co, the C-axis direction of the HCP structure is oriented vertically, and even in the A region near Fe, the (100) direction of the BCC structure is oriented vertically. Both directions are easy magnetization directions of the respective crystals, and therefore, magnetocrystalline anisotropy also occurs in the perpendicularly magnetized film of the present invention.

The role of O ₂ introduction in the present invention is as described above.
Along with the role of isolating vertical columnar grains with non-ferromagnetic oxide, it reduces the saturation magnetization of the entire film, and K⊥≧
It has the role of satisfying the condition of 2πMs ² .

As the amount of O ₂ gas introduced increases while keeping the evaporation amount of Fe, Co, and Ni constant, the O ₂ concentration in the film increases, and at the same time, the refinement and isolation of columnar particles progresses. The saturation magnetization decreases and the perpendicular anisotropy field increases. As a result of various experiments, a perpendicular magnetization film was obtained in the region A with an O composition of 25 at% or more, in the region B with an O composition of 15 at% or more, and in the region A, an O composition of 15 to 50 at% was obtained. Valid ranges are from 35 to
45 at% is most preferable, and in the region B, 15 to
A range of 50 at% was effective, and the most favorable results were obtained with a range of 25 to 45 at%. That is, when the O composition exceeds 50 at%, the entire material becomes a non-magnetic oxide and there is no saturation magnetization. This is considered to be because the oxides are FeO, CoO, NiO, or a mixed crystal thereof, and the atomic ratio is 1:1. In region A, a perpendicularly magnetized film is obtained with a larger O composition than in region B, but this is because the Fe side region has a large saturation magnetization value and a small magnetocrystalline anisotropy. It is.

The above two areas A and B and the above specific range O
Perpendicular coercive force of perpendicularly magnetized film obtained by composition
The value of Hc⊥ is about 400 to 1000 Oe, which is the best value for a perpendicular magnetic recording medium.

Moreover, when manufacturing the perpendicular magnetic recording body of the present invention, this value can be obtained in the manufacturing method described later, whether or not the substrate is heated, or even when it is actively cooled with a water cooling can. It's advantageous. Therefore,
This eliminates the inconvenience of conventionally only being able to use expensive base materials such as particularly heat-resistant polyimide films as base materials for magnetic tapes, floppy disks, etc. Advantageously, any material such as a film can be used as the substrate.

Thus, in the present invention, the reason why good perpendicular magnetic properties are obtained even on an unheated room temperature substrate is thought to be related to the fact that O atoms can easily diffuse on the film surface even without heating. .

In the conventional Co-Cr-based perpendicular magnetization film, Cr atoms are
This is achieved by a structure that segregates near the grain boundaries of columnar grains to form a non-ferromagnetic phase to isolate the columnar grains, but for this purpose, it is necessary for Cr atoms to diffuse on the film surface. This objective can be achieved by increasing the substrate temperature, but if the substrate temperature is low or unheated at room temperature, the diffusion of Cr atoms is poor and a perpendicularly magnetized film cannot be obtained.

On the other hand, in the present invention, since O ₂ is introduced,
It is thought that O atoms can easily diffuse on the surface of the film, and that a perpendicularly magnetized film can be obtained satisfactorily even on an unheated room temperature substrate. Furthermore, when trying to create a conventional Co-Cr-based perpendicularly magnetized film by vapor deposition, it is difficult to control the Cr composition and it is extremely difficult to obtain a perpendicularly magnetized film that is uniform over a long period of time. When manufacturing the perpendicular magnetization film of the present invention, it is sufficient to keep the evaporation rate of Co and the amount of O ₂ gas introduced constant, and with the current technology, it is extremely easy to produce a perpendicular magnetization film that is uniform over a long period of time. can be manufactured.

Furthermore, according to the present invention, even if a perpendicularly magnetized film is formed on a PET substrate, it hardly curls, which is extremely advantageous for application to floppy disks and magnetic tapes compared to Co-Cr perpendicularly magnetized films that curl more severely. be.

In the Fe--Co--Ni composition, the reason why a perpendicularly magnetized film is obtained only in the regions indicated by A and B and not in other regions is not sufficiently clear at present. However, considering that the regions other than A and B are all FCC phases, it is thought that there is probably a change in the columnar grain structure.
Note that the perpendicular magnetization film of the present invention includes Fe, Co, Ni, and O.
Cr, V, Mo, W,
There is no problem even if trace amounts of elements such as Rh, Ti, and Re are mixed in.

Next, the perpendicular magnetic recording body of the present invention will be explained along with manufacturing examples thereof.

FIG. 2 shows a vacuum evaporation apparatus used for producing the perpendicular magnetic recording medium of the present invention, in which a rotary cooling can 2 and a rotary cooling can 2 directly below the container 1 are connected on one side to a vacuum pump (not shown). An electron beam evaporation source 3 is provided on the top of the evaporation source 3, and an unwinding roller 4 and a take-up roller 5 are arranged on both sides of the upper part of the evaporation source 3. c was made to rotate along the circumferential surface of the cooling can 2 and be wound around the roller 5. Furthermore, the container 1 is provided with a supply pipe 6 for introducing oxygen.

In the illustrated example, this is a long one that opens near the c-plane of the running tape. 7 shows an adhesion prevention plate that is placed horizontally leaving the bottom surface of the cooling can 2 facing directly above the evaporation source, so that the evaporated Fe atoms, Co atoms, and Ni atoms from the evaporation source d are transferred to the tape base material c.
The incident deposition was performed substantially perpendicularly to the surface.

Next, using this device, first, the inside of the container 1 is evacuated to below 1×10 ^-5 Torr, and then the evaporated material d, that is,
While evaporating the Fe-Co-Ni alloy at a constant rate, the amount of O ₂ gas introduced is varied to achieve various partial pressures, and vertically deposited films of various compositions are formed on the c-plane of the tape substrate. Got the tape. In this manufacturing example, magnetic tapes having vertically deposited films of various compositions were manufactured using various composition ratios of the evaporation material a. In addition, by changing the running speed of the base material c, various types of films with different film thicknesses in the range of 1000 to 10000 Å were manufactured. The magnetic properties and alloy composition of these various products were measured using a vibrating magnetometer and fluorescent X-rays.

As a result, Fe with a constant O composition of 15 at%,
The values of Hc⊥/Hc and Br⊥/Br were measured when the Co and Ni compositions were changed. The results are shown in FIGS. 3 and 4. As is clear from this, in the composition of region B, Hc⊥/Hc and
Both Br⊥/Br exceed the value of 1, a perpendicular magnetization film is obtained, and in the composition of the region A,
The value of Hc⊥/Hc is 1 or more, but Br⊥/
It can be seen that the value of Br is small and the film is not perpendicularly magnetized. Furthermore, in the FCC phase regions other than the A and B regions, both values are less than 1, indicating that a perpendicular magnetization film cannot be obtained. Similarly, in Figures 5 and 6, O
The results are shown when the composition is 25at%. It can be seen that a perpendicular magnetization film can be obtained with both compositions in the AB region.

FIGS. 7 and 8 show the case where the O composition is 40 at %, and both show that even better perpendicular magnetization films can be obtained.

Although not shown in the figure, when the O composition is less than 15 at%, the amount of oxygen is insufficient and a vertical oxide film cannot be obtained in any composition, and conversely, when it exceeds 50 at%, all non-magnetic oxide is formed. It was confirmed that the saturation magnetization disappeared.

In the perpendicular magnetic recording method, permalloy, Fe, Co,
If a thin film of a magnetic material exhibiting relatively soft magnetism and high saturation magnetization, such as a Co-Zr amorphous film, is interposed, the recording current can be reduced and the reproduction output can be increased. After forming the soft magnetic thin film layer, a predetermined perpendicular magnetization film of the present invention is formed on the upper surface of the thin film layer, for example, according to the above manufacturing example, thereby forming a perpendicular magnetization film of the present invention in which the soft magnetic thin film layer is interposed. Magnetic recording bodies can be manufactured.

As described above, according to the present invention, a perpendicularly magnetized film can be obtained under the specific composition conditions described in the claims, and in its manufacture, the predetermined perpendicularly magnetized film can be easily formed by introducing O ₂ . A durable magnetic recording medium can be obtained, and in this case, an excellent product can be obtained without heating the base material, inexpensive materials can be used for the base material, and magnetic tapes, disks, floppy disks, etc. can be prevented from curling or warping. This has the effect of providing a good perpendicular magnetic recording medium without any problems.

[Brief explanation of the drawing]

FIG. 1 is a diagram specifying the metal component composition of a perpendicularly magnetized film in the present invention, FIG. 2 is a cutaway side view of an example of an apparatus used for manufacturing the perpendicular magnetic recording body of the present invention, and FIGS. FIG. 8 is a diagram showing the relationship between various component compositions and magnetic properties. A, B... Metal composition region of the present invention, 1... Container, c... Base material, 3... Evaporation source, d... Evaporation material, 4, 5... Roller, 6... Oxygen gas supply pipe, 7... Anti-adhesion plate.

Claims (1)

[Claims] 1. Directly or via a soft magnetic thin film layer on the surface of a non-magnetic base material, the composition is expressed as (F _x Co _y Ni _z ) _100-n O _n ,
x, y, z, m are each at% 0<x≦5, 0
<z≦40, x+y+z=100, 15≦m≦50, the crystal structure is a columnar grain structure with the C axis of the HCP structure oriented in the vertical direction, and the coercive force in the vertical direction
The relationship between Hc⊥ and coercive force Hc in the parallel direction is Hc⊥＞
Hc, and the relationship between the residual magnetic flux density Br⊥ in the vertical direction and the residual magnetic flux density Br in the parallel direction is Br⊥＞
A perpendicular magnetic recording medium formed by forming a perpendicularly magnetized film of Br. 2 Directly or via a soft magnetic thin film layer on the nonmagnetic substrate surface, the composition is expressed as (F _x Co _y Ni _z ) _100-n Om,
x, y, z, m are each at% 40≦x≦100,
It is in the range of 0≦z≦25, x+y+z=100, 15≦m≦50, and the crystal structure is a columnar grain structure with the (100) direction of the BCC structure oriented perpendicularly, and parallel to the perpendicular coercive force Hc⊥ The relationship between the coercive force Hc in the direction is
Hc⊥＞Hc, and the residual magnetic flux density in the vertical direction
The relationship between Br⊥ and the residual magnetic flux density Br in the parallel direction is
A perpendicular magnetic recording medium formed by forming a perpendicularly magnetized film where Br⊥>Br.