JPH09231543A - Magnetic recording medium and magnetic recording device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film magnetic recording medium which is suitable for high-density recording in which influences of thermal fluctuation are suppressed and the interaction among magnetic particles and the temp. coefft. of the coercive force are decreased, and to provide a magnetic recording device using this medium. SOLUTION: The magnetic layer 13 essentially composed of Co, Cu, a first rare earth element R and a second rare earth element M. The first rare earth element R is at least one element selected from Sm, Pr and Y and the second rare earth element is at least one element selected from Gd, Ho, Dy and Er. The density of Cu in the magnetic layer is 5-20at%, the density of the first rare earth element R is 11-22at%, and the density of the second rare earth element M is lower than the density of the first rare earth element R.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a magnetic recording medium and a magnetic storage device suitable for high density magnetic recording.

[0002]

2. Description of the Related Art As computers become smaller and faster,
There is an increasing demand for higher density of magnetic disk devices, which are external storage devices. Currently, magnetic recording media used in large-capacity magnetic disk devices include CoNiCr and CoC.
A Co alloy sputtered film such as rTa or CoCrPt is used, and a high recording density of several hundred megabits per square inch is realized. However, with the miniaturization of recording bits, the reduction in reproduction output and the increase in medium noise have become serious problems. The reduction in reproduction output can be solved by using a high-sensitivity magnetoresistive head as the reproduction head, but the problem of medium noise requires improvement of the characteristics of the medium itself.

As a method of reducing the medium noise, a method of making the magnetic particles fine, weakening the interaction between the particles, and reducing the magnetization reversal size has been studied. However, if the magnetization reversal size is made too small, the magnetization thermally fluctuates, and the recording becomes unstable. Therefore, it is necessary to use a material having large crystal magnetic anisotropy for the magnetic layer to reduce the influence of thermal fluctuation. Materials having large crystal magnetic anisotropy include RECo ₅ and RE ₂ C used in permanent magnets.
o ₁₇ etc. are known. Here, RE represents a light rare earth element.
The crystal magnetic anisotropy constants of these materials are about one digit larger than those of Co alloys, and the influence of thermal fluctuation can be reduced even if the magnetization reversal size is reduced.

As an attempt to apply such a permanent magnet material to a thin film magnetic recording medium, there is one in which an Sm-Co alloy is sputter-deposited on a non-magnetic underlayer, and a high coercive force of 3.6 kOe is realized. 〔IEEE Trans. Magn., 30 (19
94) 4038] etc. have been reported.

[0005]

However, although the Sm-Co thin film medium produced by the sputtering method has a high coercive force, the interaction between the magnetic particles is strong,
There is a problem that the medium noise is large. Current CoCr
In a Ta or CoCrPt thin film medium, the interaction between particles is weakened by segregating non-magnetic Cr in the grain boundaries of magnetic particles, but the Sm-Co thin film medium is composed of a very fine crystalline phase or amorphous phase. Therefore, strong interaction is exerted between the magnetic particles. In addition, Sm-Co
Since the coercive force of the thin film medium decreases significantly with increasing temperature, it is difficult to obtain high reliability in a magnetic memory device using the Sm-Co thin film medium.

The present invention has been made to solve the above problems. More specifically, it is an object of the present invention to provide a thin film magnetic recording medium that is less susceptible to thermal fluctuations and is suitable for high density recording with a small change in coercive force due to temperature, and a magnetic storage device using the same.

[0007]

In the magnetic recording medium of the present invention, as shown in FIG. 1, an underlayer 12, a magnetic layer 13 and a protective layer 14 are sequentially formed on a substrate 11 by a sputtering method. Here, the base layer 12 may be omitted. The magnetic layer is C
The main components are o, Cu, and the rare earth element R. Rare earth element R
Is at least one element selected from Sm, Pr, and Y, and the concentration of Cu in the magnetic layer is 5 to 20 at% and the concentration of the rare earth element R is 11 to 22 at% so that the interaction between the magnetic particles can be improved. It can be reduced. This is because the magnetic layer microscopically separates into two phases having different Co contents (a ferromagnetic phase having a large Co content and a nonmagnetic or weak magnetic phase having a small Co content). .

The present inventors investigated various additive elements in order to promote such phase separation, which is effective in reducing the interaction between particles, and experimentally found that the addition of Cu is very effective. Revealed. The reason why the phase separation is promoted by the addition of Cu is that Cu has the property of forming an intermetallic compound with both Co and the rare earth element R, and therefore has a minimum free energy in a composition having a different Co content,
Moreover, it is considered that the melting point is relatively low at 1083 ° C., which facilitates the movement of atoms. Regarding the Cu concentration,
20a because the saturation magnetization decreases with increasing addition amount
It is preferably t% or less.

The rare earth element R is an important element for enhancing the crystal magnetic anisotropy of the magnetic layer, and its concentration is 11 to 22 at.
%, The magnetic layer is separated into _two phases of RCo ₅ (Cu) phase and R ₂ Co ₇ (Cu) phase, or R ₂ Co ₁₇ (Cu) phase and R ₂ Co ₇ (Cu) phase. It can have a structure. The substrate temperature at the time of forming the magnetic layer is 200 ° C. or higher and 40 ° C. or higher in order to promote phase separation and suppress excessive growth of magnetic particles.
It is preferably below 0 ° C. After the film formation, it is also possible to perform a heat treatment using an infrared lamp or a laser to promote the phase separation.

When the main components of the magnetic layer are Co, the first rare earth element R and the second rare earth element M, the temperature coefficient of coercive force, which is another object of the present invention, can be reduced. Here, the concentration of the first rare earth element R in the magnetic layer is 11 to 22 at%. The second rare earth element M is G
At least one element selected from d, Ho, Dy, and Er is used, and the concentration thereof is lower than the concentration of the first rare earth element R.

The Sm-Co thin film medium has a low Curie point (for example, 724 ° C. for SmCo _{5 and} 647 for Sm ₂ Co _17).
Therefore, the change in coercive force with temperature is large. Therefore, the present inventors examined various additive elements in order to reduce the temperature coefficient of coercive force, and experimentally revealed that the addition of the second rare earth element M is very effective. Second rare earth element M
The reason why the temperature coefficient of coercive force is decreased by adding
It is considered that the effect of increasing the coercive force as the temperature approaches the compensation point as seen in a magneto-optical recording medium such as FeCo suppresses the decrease in the coercive force of the entire magnetic layer. Since the spin of the second rare earth element M is coupled antiparallel to the spin of Co and causes a decrease in saturation magnetization, the concentration of the second rare earth element M should be lower than the concentration of the first rare earth element R. preferable.

Further, the main components of the magnetic layer are Co and Cu, the first rare earth element R and the second rare earth element M, the Cu concentration in the magnetic layer is 5 to 20 at%, and the first rare earth element R is By setting the concentration to be 11 to 22 at% and the concentration of the second rare earth element M to be lower than the concentration of the first rare earth element R, two problems of reduction of interaction between particles and reduction of temperature coefficient of coercive force are simultaneously achieved. Can be resolved.

The underlayer is used to control the crystal orientation and the crystal grain size of the magnetic layer, and the material is made of Cr, Ti, V, Mo, Ta and Cr-- depending on the lattice constant of the magnetic layer.
It is preferable to select from Cr alloys such as Ti, Cr-V, Cr-Mo, Cr-Ta and the like. The thickness of the underlayer is preferably 100 nm or less so that the centerline average roughness Ra is 1 nm or less. As the substrate, a glass substrate, S
If an iO ₂ substrate, a SiC substrate, a carbon substrate, etc. are used,
It is preferable because the substrate does not deform during heating of the substrate and during heat treatment after film formation. However, the substrate heating is kept below 300 ° C,
When heat treatment after film formation is not performed, an Al-Mg alloy substrate having a Ni-P layer formed on its surface can be used.

In the magnetic recording medium of the present invention, the product (Br × t _mag ) of the thickness t _mag of the magnetic film and the residual magnetic flux density Br for the magnetic recording medium at the time of recording is set to 70 Gμm or less, and the relative magnetic head is used. If the coercive force measured by applying a magnetic field in various strike directions is 3 kOe or more, 200
It is possible to obtain a sufficient reproduction strength at a high linear recording density of kFCI or more. Further, a magnetic recording medium according to the present invention, a drive unit for driving the magnetic recording medium in the recording direction, a magnetic head having an electromagnetic induction type recording unit and a magnetoresistive effect reproducing unit, and a magnetic head for the magnetic recording medium. By configuring the magnetic storage device using the means for relative movement and the recording / reproducing signal processing means, it is possible to realize a recording density of 3 gigabits or more per square inch.

[0015]

Embodiments of the present invention will be described below in detail. [Embodiment 1] A Cr underlayer having a thickness of 50 nm and a C having a thickness of 25 nm are formed on an Al-Mg substrate having an outer diameter of 65 mm, an inner diameter of 20 mm and a thickness of 0.4 mm and having NiP formed on the surface.
A _83-X Cu _X Sm ₁₇ magnetic layer and a 10 nm carbon protective layer were continuously formed by a DC magnetron sputtering method. The film formation condition is that the partial pressure of argon gas is 25 mTo.
rr, input power was 1 kW, and substrate temperature was 300 ° C.
The Cu concentration X in the magnetic layer was changed from 1 at% to 25 at%. For comparison, Cu is not included (X
= 0) was also formed. The magnetostatic characteristics of the obtained magnetic recording medium were evaluated by a sample vibrating magnetometer VSM.

FIG. 2 shows the relationship between the Cu composition X, the coercive force Hc and the saturation magnetization Ms measured by applying a magnetic field in the direction of travel of the magnetic head relative to the medium during recording. As compared with the case where Cu is not contained, the effect that the coercive force Hc increases when Cu is contained even slightly is recognized. Coercive force H
In order to set c to 3 kOe or more, the Cu concentration needs to be 5 at% or more. Moreover, the value of the saturation magnetization Ms monotonously decreases with the addition of Cu. As a result of evaluating the recording / reproducing characteristics, when the Cu concentration was 5 at% or more and 20 at% or less, the S / N ratio was high and particularly good characteristics were obtained. When a magnetic recording medium having a magnetic layer composition of Co ₆₈ Cu ₁₅ Sm ₁₇ was used for recording / reproducing with a magnetoresistive head under the condition of 3 gigabits per square inch, the medium S / N was 5.2. .

The Cu concentration is less than 5 at%, or 20
In a magnetic recording medium having a content higher than at%, the coercive force Hc is 3 k.
3 per 1 square inch because the reproduction output is decreased due to the decrease of less than Oe or the saturation magnetization Ms.
The medium S / N when recording and reproducing using a magnetoresistive head under a gigabit condition was a low value of 3 or less.

[Embodiment 2] Outer diameter 65 mm, inner diameter 20
mm, Al with NiP of 0.4mm thickness formed on the surface
-A 50 nm thick Cr underlayer on a Mg substrate, thickness 2
A 5 nm Co ₈₃ Sm ₉ Gd ₈ magnetic layer and a 10 nm thick carbon protective layer were successively formed by a DC magnetron sputtering method. The film forming conditions are the same as those in the first embodiment.

FIG. 3 shows the coercive force Hc from 25 ° C. to 200 ° C.
The results measured in the temperature range of are shown. As Comparative Example 1, G
The measurement results of the Co ₈₃ Sm ₁₇ magnetic layer to which d is not added are also shown. It can be seen that the Co ₈₃ Sm ₉ Gd ₈ magnetic layer has a smaller decrease in coercive force with the measurement temperature than the Co ₈₃ Sm ₁₇ magnetic layer. Further, the composition of the magnetic layer is set to Co ₈₁ Sm ₉ Gd ₁₀
As a result, the values of the saturation magnetization and the coercive force at 25 ° C. greatly decreased, and it was found that the magnetic recording medium was not suitable. Similar results were obtained even when Gd was replaced with Ho, Dy, and Er.

[Embodiment 3] Outer diameter 65 mm, inner diameter 20
mm, Al with NiP of 0.4mm thickness formed on the surface
-A 50 nm thick Cr underlayer on a Mg substrate, thickness 2
5 nm Co ₆₈ Cu ₁₅ Sm ₉ Gd ₈ magnetic layer, thickness 10 nm
The carbon protective layer of 1 was continuously formed by the DC magnetron sputtering method. The film forming conditions are the same as those in the first embodiment.

FIG. 3 shows the coercive force Hc from 25 ° C. to 200 ° C.
The results measured in the temperature range of are shown. C without Gd
The measurement results of the o ₆₈ Cu ₁₅ Sm ₁₇ magnetic layer (Embodiment 1) are also shown. Co ₆₈ Cu ₁₅ Sm ₉ Gd _{8 In the} magnetic layer, Co ₆₈
It can be seen that the amount of decrease in coercive force with the measurement temperature is smaller than that of the Cu ₁₅ Sm ₁₇ magnetic layer. Note that Gd is Ho, D
Similar results were obtained by substituting with y and Er.

[Embodiment 4] FIGS. 4A and 4 are a schematic plan view and a schematic vertical sectional view of a magnetic memory device according to the present invention.
(B). This apparatus comprises a magnetic recording medium 41, a drive unit 42 for rotationally driving the magnetic recording medium 41, a magnetic head 43 and a driving means 44 for the magnetic head, and a recording / reproducing signal processing means 4 for the magnetic head.
5 is a magnetic storage device having a well-known structure.

A schematic view of the structure of the magnetic head used in this magnetic storage device is shown in FIG. This magnetic head has a base 57
This is a recording / reproducing separation type head in which an electromagnetic induction type magnetic head for recording and a magnetoresistive head for reproduction formed on the above are combined. The magnetoresistive sensor 51 is attached to the lower shield layer 52.
The portion sandwiched between the upper shield recording magnetic pole / layer 53 and the upper shield recording magnetic pole layer 53 functions as a reproducing head, and the upper shield recording / magnetic layer 53 and the upper recording magnetic pole 55 sandwiching the coil 54 function as a recording head. The output signal from the magnetoresistive sensor 51 is the electrode pattern 5
Take out to the outside via 6.

FIG. 6 shows a vertical sectional structure of the magnetoresistive sensor. This magnetoresistive sensor uses a thin film magnetoresistive conductive layer 63 of a ferromagnetic material formed on the gap layer 61 between the shield layer and the magnetoresistive sensor, and the thin film magnetoresistive conductive layer 63 as a single magnetic domain. An antiferromagnetic domain control layer 62 of
The nonmagnetic layer 65 for cutting off the exchange interaction between the thin film magnetoresistive conductive layer 63 and the antiferromagnetic domain control layer 62 in the magnetic sensitive portion 64 of the thin film magnetoresistive conductive layer 63, and the magnetic sensitive portion 6
4 for adjusting the current shunt ratio between the soft magnetic layer or the permanent magnet film bias layer 67 and the soft magnetic layer or the permanent magnet film bias layer 67 and the thin film magnetoresistive conductive layer 63 as a means capable of generating a bias magnetic field. A high resistance layer 66 is included.

As the magnetic recording medium, the medium having the coercive force Hc of 3.2 kOe and the residual magnetic flux density / magnetic layer thickness product (Br × t _mag ) of 70 Gμm described in the first embodiment was used.
Using this magnetic storage device, the head flying height is 30 nm, the shield layer spacing is 0.35 μm or less, and the linear recording density is 230 kFC.
When the recording and reproducing characteristics were evaluated under the conditions of I and track density of 13 kTPI, a device S / N of 4.5 was obtained. Also,
By subjecting the input signal to the magnetic head to the 8-9 code modulation processing, recording / reproduction could be performed at a recording density of 3 gigabits per square inch. Moreover, the number of bit errors after 50,000 head seek tests from the inner circumference to the outer circumference is 10
Bits / plane or less, MTBF achieved 150,000 hours.

[Fifth Embodiment] In a magnetic memory device having the same structure as that of the fourth embodiment, the coercive force Hc described in the third embodiment as a magnetic recording medium is 3.2 kOe, the residual magnetic flux density and the magnetic layer film. A medium having a thickness product (Br × t _mag ) of 70 Gμm was used.

Using this magnetic storage device, the head flying height is 3
When the recording / reproducing characteristics were evaluated under the conditions of 0 nm, a shield layer spacing of 0.35 μm or less, a linear recording density of 230 kFCI, and a track density of 13 kTPI, a device S / N of 4.6 was obtained. Further, by subjecting the input signal to the magnetic head to 8-9 code modulation, recording and reproduction could be performed at a recording density of 3 gigabits per square inch in a temperature range of 10 ° C. to 50 ° C. Moreover, the number of bit errors after 50,000 head seek tests from the inner circumference to the outer circumference was 10 bits / plane or less, and 150,000 hours could be achieved with MTBF.

In the above embodiment, an example in which Sm is used as the rare earth element R has been described, but even if Pr or Y is used as the rare earth element R, the same effect as in the case of Sm is recognized. In addition, the composition of the magnetic layer should include Cr, Ti, B, and T.
Similar effects were observed when a trace amount of elements such as a and Pt were added.

[0029]

According to the present invention, since the medium S / N can be increased, by using a high-sensitivity magnetoresistive head, a high S / N is obtained at a recording density of 3 gigabits per square inch or more. It is possible to provide a small-sized and large-capacity magnetic storage device which can obtain an error rate and can realize an average failure interval of 150,000 hours or more.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional structural view of an example of a magnetic recording medium according to the present invention.

FIG. 2 is a diagram showing a relationship between Cu concentration in a magnetic layer and coercive force and saturation magnetization.

FIG. 3 is a diagram showing the relationship between measured temperature and coercive force.

FIG. 4A is a schematic plan view of a magnetic storage device, and FIG. 4B is a vertical sectional view taken along line AA ′.

FIG. 5 is a three-dimensional schematic diagram showing a cross-sectional structure of a magnetic head.

FIG. 6 is a schematic diagram of a vertical sectional structure of a magnetoresistive sensor portion of a magnetic head.

[Explanation of symbols]

 11 ... Substrate 12 ... Underlayer 13 ... Magnetic layer 14 ... Protective layer 41 ... Magnetic recording medium 42 ... Magnetic recording medium drive section 43 ... Magnetic head 44 ... Magnetic head drive section 45 ... Recording / reproducing signal processing system 51 ... Magnetoresistive sensor 52 ... lower shield layer 53 ... upper shield recording magnetic pole combined layer 54 ... coil 55 ... upper recording magnetic pole 56 ... conductor layer 57 ... substrate 61 ... gap layer between shield layer and magnetoresistive sensor 62 ... antiferromagnetic domain control layer 63 ... thin film Magnetoresistive conductive layer 64 ... Magnetic sensitive portion of thin film magnetoresistive conductive layer 65 ... Nonmagnetic layer 66 ... High resistance layer 67 ... Soft magnetic layer or permanent magnet film bias layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Inaba 1-280 Higashi Koigakubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (4)

[Claims] 1. A magnetic recording medium having a magnetic layer formed on a substrate directly or via an underlayer, wherein the magnetic layer contains Co, Cu, and a rare earth element R as main components, and the rare earth element R is Sm, The magnetic layer is composed of at least one element selected from Pr and Y, and the concentration of Cu in the magnetic layer is 5 to 2
0 at%, the concentration of the rare earth element R is 11 to 22 at%
A magnetic recording medium characterized by the following. 2. A magnetic recording medium having a magnetic layer formed directly on a substrate or via an underlayer, wherein the magnetic layer comprises Co, a first rare earth element R, and a second rare earth element M.
And the first rare earth element R is Sm, Pr,
The second rare earth element M is made of at least one element selected from Y, the second rare earth element M is made of at least one element selected from Gd, Ho, Dy, and Er, and the concentration of the first rare earth element R in the magnetic layer is Is 11 to 22 at%,
The magnetic recording medium, wherein the concentration of the second rare earth element M is lower than the concentration of the first rare earth element R. 3. A magnetic recording medium having a magnetic layer formed on a substrate directly or via an underlayer, wherein the magnetic layer is mainly composed of Co, Cu, a first rare earth element R and a second rare earth element M. As a component, the first rare earth element R is Sm,
Consisting of at least one element selected from Pr and Y,
The second rare earth element M is composed of at least one element selected from Gd, Ho, Dy and Er, the concentration of Cu in the magnetic layer is 5 to 20 at%, and the concentration of the first rare earth element R is 11 The magnetic recording medium is characterized in that the concentration of the second rare earth element M is lower than the concentration of the first rare earth element R. 4. A magnetic recording medium, a drive unit for driving the magnetic recording medium in the recording direction, a magnetic head having a recording unit and a reproducing unit,
In a magnetic storage device having a means for moving the magnetic head relative to the magnetic recording medium and a recording / reproducing signal processing means, the reproducing portion of the magnetic head is composed of a magnetoresistive sensor, and the magnetic recording The medium is claim 1.
3. A magnetic storage device comprising the magnetic recording medium according to any one of items 1 to 3.