JP2003151116A - Magnetic recording medium and magnetic recorder using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium suitable for high density magnetic recording with high resolution, low noise and small thermal fluctuation, and a mass magnetic storage device realized in using the medium, etc. SOLUTION: In this magnetic recording medium having at least three or more magnetic layers on a non-magnetic substrate, when a magnetic layer which is farthest from the non-magnetic substrate is used as a magnetic layer for recording, a magnetic layer which is father from the non-magnetic substrate next to the layer for recording is used as a magnetic layer for stabilization, and the entire magnetic layers other than the magnetic layer for recording and the magnetic layer for stabilization are used as a group of lower magnetic layers, an AFC type thin film magnetic recording medium has a connection layer made of non-magnetic material or weak magnetic material having nature that makes the magnetization of a contact magnetic layer reverse between the magnetic layer for recording and the magnetic layer for stabilization, and uses a magnetic recording medium, wherein the rearrangement of the magnetic layer for stabilization and the group of lower magnetic layers generally ends within 10 millisecond after recording.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device used in electronic computers and information processing devices, a magnetic storage device for information home appliances such as digital VTRs, and a magnetic recording medium thereof, and more particularly to high density recording. The present invention relates to a magnetic recording medium suitable for implementation and a magnetic storage device using the same.

[0002]

2. Description of the Related Art A semiconductor memory, a magnetic memory, or the like is used for a storage (recording) device of information equipment. A semiconductor memory is used as an internal storage device from the viewpoint of high-speed accessibility, and a magnetic memory is used as an external recording device from the viewpoint of large capacity, low cost, and nonvolatility. The mainstream of magnetic memory is a magnetic disk device, a magnetic tape device, and a magnetic card device. In order to write magnetic information on a recording medium such as a magnetic disk, a magnetic tape or a magnetic card, a magnetic recording unit that generates a strong magnetic field is used. Further, in order to reproduce the magnetic information recorded at high density, a reproducing unit utilizing a magnetoresistive phenomenon or an electromagnetic induction phenomenon is used. Recently, the giant magnetoresistive effect and the tunnel type magnetoresistive effect have begun to be examined. These functional units are provided together with an input / output component called a magnetic head.

FIG. 10 shows the basic structure of a magnetic disk device. 9A is a plan view of the device, and FIG. 9B is a sectional view taken along the line AA ′ shown in FIG. The recording medium 101 is fixed to the rotary bearing 104 and is rotated by the motor 100. Although FIG. 10 shows three magnetic disks and four magnetic heads in an example in which five magnetic disks and ten magnetic heads are mounted, one magnetic disk or more and one magnetic head or more may be used. . The magnetic head 102 is
It moves on the surface of a recording medium that rotates. The magnetic head is supported by the rotary actuator 103 via the arm 105. The suspension 106 has a function of pressing the magnetic head 102 against the recording medium 101 with a predetermined load. A predetermined electric circuit is required for processing the reproduction signal and inputting / outputting information. Recently, EEPRML (Extended Extend
ed Partial Response Maximum Likelihood) or enhanced MEEPRML (Modified EEPRML), which is a signal processing circuit that actively utilizes waveform interference at the time of densification, which greatly contributes to densification. . These are attached to the case 108 or the like.

The information writing / reproducing function unit mounted on the magnetic head is constructed, for example, of the structure shown in FIG. The writing unit 111 is composed of a spiral coil 116 and magnetic poles 117 and 118 that are wrapped up and down and are magnetically coupled. Both the magnetic pole 117 and the magnetic pole 118 are composed of magnetic film patterns. The reproducing unit 112 is composed of the magnetoresistive effect element 113 and an electrode 119 for supplying a constant current to the same element and detecting a resistance change. A magnetic pole 118 which doubles as a magnetic shield layer is provided between the writing section and the reproducing section. A shield layer 115 is further provided below the magnetoresistive effect element 113. The reproduction resolution is the shield layer 115 and the magnetic pole.
The shorter the gap length with (also serving as the shield layer) 118, the larger the gap. The above-mentioned functional parts are the same as those of the magnetic head slider 1110.
Formed on.

In order to increase the capacity of the magnetic recording disk device, the density of the magnetization information recorded on the recording medium 101 of FIG. 10 should be increased. However, since the magnetic recording medium used in the past is composed of fine crystal grains, there is a problem that the number of grains per bit decreases and noise increases as the recording density increases. On the other hand, the noise has been reduced by reducing the diameter of the magnetic particles, promoting the segregation of non-magnetic components at the magnetic grain boundaries, and reducing the interaction between the magnetic particles. However, when the recording density is further increased with the recent annual efficiency of 50% or more and the areal recording density of about 15 Gb / in2 or more is attempted, the recording magnetization is attenuated due to thermal fluctuation as the volume of the magnetic particles becomes smaller. (Thermal demagnetization) has become a serious problem. This is a phenomenon in which the magnetization of particles forming the medium is reversed by heat, and becomes remarkable when the particle diameter is reduced to reduce noise. Therefore, in the perpendicular magnetic recording method proposed by Iwasaki et al.
It is expected that the effects of this thermal fluctuation will be mitigated. At the 2000 Intermag International Conference, Fujitsu and IBM proposed an in-plane medium in which the magnetic layer was antiferromagnetically coupled via Ru (called AFC medium) as a measure to suppress thermal demagnetization. It has been considered that this newly proposed medium has a high possibility of canceling the thermal demagnetization suppression merit because the write magnetic field becomes large. An antiferromagnetically coupled (AFC) medium, which is the base of the present invention, will be described with reference to FIG.

FIG. 3 conceptually shows the sectional structure of the medium. It comprises a stabilizing magnetic layer 12 formed on a non-magnetic substrate 15, and a recording magnetic layer 11 formed via a non-magnetic intermediate layer 13. When Ru is used as the non-magnetic intermediate layer 13, exchange interaction acts between the recording magnetic layer 11 and the stabilizing magnetic layer 12. Binding energy at this time
J makes an oscillatory change as shown in FIG. 4 with respect to the thickness of the Ru nonmagnetic intermediate layer 13. The magnetization direction of the recording magnetic layer 11 and the magnetization direction of the stabilizing magnetic layer 12 are exchange coupling energy J
Is a negative value, the exchange coupling energy
When J takes a positive value, the exchange interaction works such that they are arranged in parallel. Therefore, by setting the thickness of the Ru non-magnetic intermediate layer 13 to the thickness of the negative peak, the recording magnetic layer 11
And the magnetization of the stabilizing magnetic layer 12 can be antiferromagnetically (antiparallelly) coupled.

The product of the film thickness of the recording magnetic layer 11 and the residual magnetization is
It is assumed to be larger than the product of the film thickness of the stabilizing magnetic layer 12 and the residual magnetization. For the sake of simplicity, assuming that the saturation magnetization Ms and the magnetic anisotropy energy Ku of the recording magnetic layer 11 and the stabilizing magnetic layer 12 are the same, the particle volume of the recording magnetic layer 11 is v1, the particle volume of the stabilizing magnetic layer 12 is Is v2. When the antiferromagnetic interaction is sufficiently strong, Kβ (= Ku * v / (k * T), k: Boltzmann's constant, T: absolute temperature), which is an index to improve the thermal fluctuation, is the Ku v1 + v2) / (k * T), which is higher than Kβ of the stabilizing magnetic layer 12 as compared with (Ku * v1) / (k * T) of the recording magnetic layer 11 alone.
The value becomes larger ((Ku * v2) / (k * T)) and becomes thermally stable. However, the magnetization of the recording magnetic layer 11 and the stabilizing magnetic layer 1
Since the magnetization of 2 is anti-parallel, the overall saturation magnetization is effectively reduced to Ms (v1-v2) / v1, so the effective anisotropy of the system that determines the magnetic field that reverses the magnetization. Magnetic field (2 * Ku / Ms)
Is (2 * Ku / Ms) * (v1 + v2) / (v1-v2). Therefore, it is understood that the larger the v2 in order to obtain the thermal stability, the larger the reversal field of the magnetization. But,
At the 2001 Intermag International Conference, it was reported that the write magnetic field did not become large in the AFC medium where antiferromagnetic coupling was not so large. In this case, the effective Kβ value of the medium substantially matches the Kβ value of the recording magnetic layer. However, in this AFC medium in which the magnetic properties of the upper and lower layers are almost the same, the R / W characteristics have deteriorated, and the effect of improving the thermal demagnetization characteristics will not be improved if the overall film thickness is reduced to obtain the same R / W characteristics. It became extremely small, and it was difficult to achieve both thermal fluctuation characteristics and R / W characteristics. A model in which the magnetization of the recording magnetic layer 11 and the magnetization of the stabilizing magnetic layer 12 are parallel to each other during writing has been reported for an AFC medium in which antiferromagnetic coupling is not so large. In the AFC medium in which the antiferromagnetic coupling is not so large, we have made a large improvement in recording characteristics by making the magnetic anisotropy field of the stabilizing magnetic layer smaller than that of the recording magnetic layer. Proposes to be obtained.

[0008]

Problems to be solved by the invention will be described with reference to FIG. 12 for designing an AFC medium in which the antiferromagnetic coupling is not so large. FIG. 12 schematically shows a change in reproduction output immediately after recording on an AFC medium at a recording density of 50 kfci. Immediately after recording, since the magnetization of the recording magnetic layer and the magnetization of the stabilizing magnetic layer are parallel to each other, a large output is obtained. With the passage of time, the magnetization of the stabilizing magnetic layer reverses and becomes antiparallel to the magnetization of the recording magnetic layer (rearrangement process), so that the output sharply decreases. However, the magnetization of the recording magnetic layer during this period has not changed much. When a sufficient time (rearrangement completion time) elapses, the magnetization of most of the stabilizing magnetic layer is inverted and becomes antiparallel to the magnetization of the recording magnetic layer, so that the reduction of the reproduction output becomes extremely gentle. It is considered that the anti-ferromagnetic coupling magnetic field improved the heat resistance stability of the magnetization of the recording layer. In the figure, a dotted line indicates a period from immediately after recording to a certain time (rotation waiting time). The rotation waiting time mentioned here is the shortest waiting time when recording / reproducing is performed with the same head, and is required for one rotation of the disk until the medium portion on which the magnetic information is recorded moves again directly below the head for reproduction. It's a good time. Here, there are the following three problems with the reproduction characteristic during the rearrangement. 1) The error rate increases due to a sudden output change in the rearrangement process. 2) In the rearrangement process, a portion in which the magnetization of the recording magnetic layer and a magnetization in the stabilizing magnetic layer are parallel and a portion in which they are anti-parallel are mixed, so noise is generated at the boundary between the two and the error rate is increased. To increase. 3) Since the reproducing effective film thickness is large in the portion where the magnetization of the recording magnetic layer and the magnetization of the stabilizing magnetic layer are parallel to each other, the reproducing output at high recording density is reduced. Therefore, in the AFC medium, it is necessary to design the medium so that the rearrangement is completed after the recording and before the first reproduction. That is, the rearrangement completion time <rotation waiting time.

The rearrangement completion time depends on the thickness of the stabilizing magnetic layer, and the anisotropic energy of the stabilizing magnetic layer is set to Ku.
2 (J / m ^ 3), the average particle diameter seen from the top is D, the film thickness is t2, and when the Boltzmann constant is k, the product of the square of Ku2 and D times t2 is divided by k (Ku2 × D × D × t2 / k) is the heat resistance coefficient of the stabilized magnetic layer, the heat resistance coefficient of the magnetic layer is 4000
The thickness t2 of the magnetic layer needs to be set so as to be as follows. Typically, for a CoCrPt alloy thin film with Ku2 = 160 kJ / m ^ 3 and D = 9 nm, 4.5 nm must be the upper limit (critical film thickness). Similarly, the signal-to-noise ratio S / N indicating the device performance
As shown in FIG. 1, together with the thickness t2 of the stabilizing magnetic layer,
It increases monotonically up to 4.5 nm. The thickness of the stabilizing magnetic layer is 4.
The sudden deterioration over 5 nm is due to the fact that the rearrangement of the stabilizing magnetic layer is not yet completed at the time of reproduction, so that the cancellation between the recording magnetic layer and the stabilizing magnetic layer is insufficient, and noise is generated. It is thought to be because there is.

It is an object of the present invention to accelerate rearrangement of a stabilizing magnetic layer in an AFC structure medium, which is suitable for high-resolution magnetic recording with high resolution, low noise and small thermal fluctuation, and this medium. Another object of the present invention is to provide a large-capacity magnetic storage device that is realized by using the above.

[0011]

Hereinafter, in an in-plane magnetic recording medium having three or more magnetic layers separated by a bonding layer made of a non-magnetic substance or a weak magnetic substance, the magnetic layer farthest from the non-magnetic substrate is The recording magnetic layer, the magnetic layer next to the recording magnetic layer and the magnetic layer farther from the non-magnetic substrate are called stabilizing magnetic layers, and all the magnetic layers other than the recording magnetic layer and the stabilizing magnetic layer are called lower magnetic layer groups. To In order to achieve the above-mentioned object, the present inventors have conducted intensive studies on the device structure technology such as the medium structure, material, process, and head, and use the lower magnetic layer group that promotes the inversion of the stabilizing magnetic layer as the underlayer of the stabilizing magnetic layer. It has been found to be effective. The lower magnetic layer group is set to be more susceptible to thermal fluctuations than the stabilizing magnetic layers, and this fluctuation promotes rearrangement of the stabilizing magnetic layers. It was also found that dividing the stabilizing magnetic layer with a bonding layer that induces weak ferromagnetic coupling is an extremely effective means for achieving the above object. Each magnetic layer, which is appropriately divided, is greatly affected by thermal fluctuations and has a faster rearrangement, but has little effect on the heat resistance of the recording magnetic layer.

In order to understand and improve the characteristics of the AFC medium, it is important to control the rearrangement process after writing. The stabilizing magnetic layer 12 was almost parallel to the magnetization of the recording magnetic layer 11 immediately after writing.
Is a process in which the magnetization of and is reversed by the influence of thermal fluctuations and becomes antiparallel. The reversal due to thermal fluctuation is a stochastic process, and it takes a finite time for most of the magnetic particles in the stabilizing magnetic layer to complete rearrangement and to form antiparallel magnetization pairs in the upper and lower layers.
When the rearrangement is not completed, the residual magnetization is too large, the reproduction resolution is deteriorated, and the thermal demagnetization is also large. To estimate the completion of rearrangement, it is effective to examine the magnetization curve.

FIG. 5 shows the magnetization curve and its derivative of a conventional two-layer (recording magnetic layer and stabilizing magnetic layer) AFC medium. In the process (MH loop) of applying a magnetic field in the track direction of the medium to magnetically saturate it, then decreasing the magnetic field and then applying a magnetic field in the opposite direction of this track to reach magnetic saturation (MH loop), It is observed that the magnetization of each of the layers reverses with different magnetic fields. FIG. 5 (a) shows an example of the MH loop of an AFC medium composed of two magnetic layers measured by reducing the magnetic field at a rate of 300 A / m per second. The horizontal axis of the figure is the magnetic field axis, and the track direction is positive. In the figure, the process of applying a magnetic field in the opposite direction to reach magnetic saturation, and then increasing the magnetic field to reach magnetic saturation again with a large magnetic field in the track direction is shown by a dotted line. It can be seen that during the change from the large positive magnetic field to the large negative magnetic field, it is divided into two large changes. The first change is caused by a small positive magnetic field, and the amount of change in magnetization is smaller than the amount of change in the other magnetization, and is considered to correspond to the magnetization reversal of the stabilizing magnetic layer. The change in magnetization in a large negative magnetic field corresponds to the magnetization reversal of the recording magnetic layer. FIG. 5B is a differentiation of the solid line MH loop of FIG. 5A by a magnetic field.
In FIG. 5B, peaks corresponding to the respective magnetization reversals are seen. In the example of FIG. 5, when the magnetic field is in the residual state of 0,
The change in magnetization due to the reversal of magnetization in the stabilizing magnetic layer has disappeared, and it is considered that the rearrangement is completed. 6 (a), (b)
5 shows an MH loop measured with the same AFC medium as in FIG. 5 at a magnitude of 30,000 A / m / sec and a magnetic field reduced, and its magnetic field derivative.

In FIG. 6, it can be seen that the magnetic field for reversing the magnetization of the stabilizing magnetic layer has moved to almost zero. It is considered that this is because the timing of the magnetization reversal of the stabilizing magnetic layer was delayed due to the large change in the magnetic field. On the other hand, the magnetic field for reversing the magnetization of the recording magnetic layer does not change so much. The cause of this is easy to understand if the magnetization reversal of the stabilizing magnetic layer occurs stochastically due to thermal fluctuation. In fact, even if the magnetic field was reduced by 300 A / m / sec, by lowering the measurement temperature by about 60 degrees, the same MH loop as in FIG. 6 was obtained. In FIG. 6, when the magnetic field is in the residual state of 0, the magnetization reversal of the stabilizing magnetic layer is only half completed. In this state, the remanent magnetization is large and further decreases with time. In the magnetic field change larger than that in the measurement of FIG. 6 or the measurement at a lower temperature, the magnetic field at which the magnetization reversal of the stabilizing magnetic layer shifts to a negative value. From the above,
1) The state of rearrangement can be grasped by examining the MH loop of the AFC medium or its magnetic field differential. 2) Even if the magnetic field sweep speed during MH loop measurement is constant, it is almost equivalent to the case where the magnetic field sweep speed is changed. The measurement temperature is present,
There was found.

In the magnetization curve of FIG. 6, the direction of the change of the magnetic field is reversed at the stage (magnetic field) at which the inversion of the stabilizing magnetic layer is completed, and the minor loop is formed in FIG. It can be seen that the stabilizing magnetic layer has hysteresis. This minor loop is shifted in the positive magnetic field direction, and the minor loop center magnetic field is usually the antiferromagnetic coupling field.
I call it Hex. The magnitude J of the antiferromagnetic exchange interaction between the recording magnetic layer and the stabilizing magnetic layer is estimated by Hex / (Ms2 * t2). However, Ms2 and t2 are the saturation magnetization and the film thickness of the stabilizing magnetic layer. The half value of the crossing of the minor loop in the magnetic field direction is considered to be the coercive force of the stabilizing magnetic layer. The half value across the major loop in the magnetic field direction is the coercive force of the recording magnetic layer. The stabilizing magnetic layer has a larger thermal fluctuation than the recording magnetic layer, and the coercive force greatly changes when the measurement temperature changes. FIG. 8 shows the temperature change of the coercive force of the recording magnetic layer and the stabilizing magnetic layer. These change in a substantially linear manner, and if the coercive forces at 200 Kelvin and 100 Kelvin are connected by a straight line, the absolute value becomes almost 0 degrees. In this measurement, the coercive force values at 200 Kelvin and 100 Kelvin change depending on the magnetic field sweep speed, but the estimated value at absolute 0 degrees does not change. This estimated value was about 40% with respect to the anisotropic magnetic field.

In the case of having three or more magnetic layers, there is a possibility that the differential value of the magnetization due to the magnetic field has at least three or more peaks. The magnetization variation in the above process corresponding to each peak is dM1, d in descending order from the largest value.
When referred to as M2 and dM3, dM1 corresponds to the magnetization of the recording magnetic layer, and the magnetic field that gives it is in the direction opposite to the direction magnetized first in the magnetization process. The amount of change in magnetization corresponding to each peak is shown in FIG.
It is given by the area of the shaded part surrounded by the geta part and the differential curve as shown in. The total amount of change in magnetization corresponding to each peak is approximately 60% to 75% with respect to twice the amount of magnetization when the measurement medium is sufficiently saturated. The change in magnetization below dM2 is the change in magnetization of the stabilizing magnetic layer and the lower magnetic layer group.
The completion of the rearrangement can be confirmed by the fact that in the magnetization process, all the peaks corresponding to the magnetization magnetization changes in the layers other than the recording magnetic layer are oriented in the direction in which they are magnetized first (there are peaks).

In the magnetic disk device, the time required for the disk to make one rotation immediately after writing and to start the reading operation is about
Assuming that the time is 10 milliseconds, the conditions under which the magnetization reversal of the stabilizing magnetic layer and the lower magnetic layer group is completed and the rearrangement is completed by this time were examined in various AFC media.
When changing the magnetic field with a magnitude of 00 A / m, MH loop measurement is performed at 135 Kelvin, and when the magnetic field differential is taken, the peak corresponding to the magnetization change of the lower magnetic layer group of the stabilizing magnetic layer is obtained. It was found that the applied magnetic field should be 0 or a positive value. When increasing the magnetic field sweep speed, it is sufficient to measure at a temperature about 30 degrees higher per digit.

When the magnetic field is measured at 216 Kelvin (dry ice temperature) by changing the magnetic field at a rate of 3000 A / m / s, the rearrangement of the stabilizing magnetic layer and the lower magnetic layer group shows that the magnetic field is zero. It was found that even under the condition that the process was completed at the point when the recording was completed, the magnetization reversal was completed in the stabilizing magnetic layer and the lower magnetic layer group by 10 ms after recording, and the condition that the rearrangement was completed was in agreement. This includes the magnetization change amounts dM1 and dM2
The differential peaks corresponding to are defined as peak 1 and peak 2, respectively, and the magnetization amount when the tangent line drawn on the magnetization curve crosses the zero magnetic field in the average magnetic field considering the signs of the magnetic fields of the peak 1 and the peak 2 is Mrte, where Mrta is the actual magnetization amount in the zero magnetic field of the magnetization curve, the ratio of the magnetization change amount dM2 of the peak 2 of the difference (Mrte-Mrta) between the two magnetization amounts ((M
rte-Mrta) / dM2) should be 0.05 or less (Fig. 7). Magnetization change amount dM2 of peak 2 in the magnetization curve
If the magnetic field when 95% of the change is Hx95, the above condition is given by Hx95> 0. Further, assuming that the magnetization amount in the magnetic field that gives the peak 2 is Mt2, the magnetic field Hx that gives the magnetization amount (Mt2 + 0.45 × dM2) on the magnetization curve.
Then, it may be examined whether or not the difference ΔH in the magnetic field that gives the magnetization amount (Mt2-0.45 × dM2) is 1.5 times or less the magnitude of the magnetic field that gives the peak 2 (FIG. 20). These are indicators of dispersion of the switching magnetic field of the stabilizing magnetic layer. If the dispersion is large, noise tends to increase from a film thickness smaller than the critical film thickness.

In the case of having three or more magnetic layers, it is preferable that the stabilizing magnetic layer and the lower magnetic layer group have the same peak in order to obtain good writing characteristics. At this time, it is considered that the position of the write bubble (boundary of the magnetization reversal region due to the head magnetic field) is the same in the stabilizing magnetic layer and the lower magnetic layer group. In this case, the anisotropic magnetic field of each magnetic layer needs to be smaller as it is closer to the substrate. However, as long as the distance between the recording head and the stabilizing magnetic layer and the distance between the recording head and the lower magnetic layer group are not significantly different, the anisotropic magnetic fields of the stabilizing magnetic layer and the lower magnetic layer group are the same. Even if it does, it does not cause a large deterioration of the writing performance.

Further, the write bubbles formed in the stabilizing magnetic layer and the lower magnetic layer group are 30 nm or more, preferably 40 nm to 90 nm with respect to the write bubbles formed in the recording magnetic layer.
It has been clarified from the results of micromagnetic simulation of the magnetization transition width that the better writing characteristics can be obtained by being outside the nm. When the improvement effect is large, the position of the magnetic transition formed in the stabilizing magnetic layer having a small magnetic anisotropy is formed behind the head of the transition position of the recording magnetic layer. It was found that the head magnetic field at the transition position of the recording magnetic layer was modulated and the magnetic field gradient dH / dx was sharpened by the magnetic field from. This effect disappears rapidly when the difference between the transition position of the recording magnetic layer and the transition position of the stabilizing magnetic layer approaches or exceeds the magnetization transition width. The value (Hco1Hco2) / (πa × dH / dx) obtained by dividing the difference between the estimated values of the coercive force at absolute zero between the recording magnetic layer and the stabilizing magnetic layer by the product of the magnetization transition width and the magnetic field gradient is 0.8.
When it is smaller, the magnetic field from the magnetization transition of the stabilizing magnetic layer acts in the opposite direction, and the magnetization transition width increases rapidly. If the value (Hco1Hco2) / (πa × dH / dx) is 0.9 or more and 1.5 or less, a sufficient head magnetic field magnetic field gradient can be obtained. When the value (Hco1Hco2) / (πa × dH / dx) exceeds 1.5, the difference between the transition position of the recording magnetic layer and the transition position of the stabilizing magnetic layer is too large, and the head magnetic field hardly changes.

In order to satisfy the above-mentioned relationship of the formation position of the write bubble formed in the stabilizing magnetic layer and the lower magnetic layer group, the ratio of the anisotropic magnetic field of the stabilizing magnetic layer to the anisotropic magnetic field of the recording magnetic layer is set. It is preferably 0.7 or less, more preferably 0.2 or more and 0.6 or less. When the magnetization transition width of the isolated transition is observed by a magnetic force microscope (MFM), the magnetic anisotropy field Hk2 of the stabilizing magnetic layer and the magnetic anisotropy field Hk1 of the recording magnetic layer of the AFC medium are observed.
It can be seen that the magnetization transition width changes according to the ratio Hk2 / Hk1 of In comparison with the single-layer in-plane medium, when the ratio Hk2 / Hk1 exceeds 0.7, the magnetization transition width is wider than in the single-layer in-plane medium having the same film thickness as the recording magnetic layer, which is not preferable. Furthermore, the ratio Hk2 / Hk
If 1 is 0.2 or more and 0.6 or less, a steep magnetization transition width comparable to that of a single-layer in-plane medium having an equivalent effective film thickness can be obtained. When the magnetization transition width of the isolated transition is observed by a magnetic force microscope (MFM), the ratio Hk2 / HkA of the magnetic anisotropy field Hk2 of the stabilizing magnetic layer of the AFC medium to the magnetic anisotropy field Hk1 of the recording magnetic layer is observed. The width of the magnetization transition changes in accordance with. Compared with single layer in-plane media, the ratio
When Hk2 / Hk1 exceeds 0.7, the magnetization transition width is wider than that of the single-layer in-plane medium having the same film thickness as the recording magnetic layer, which is not preferable. Further, when the ratio Hk2 / Hk1 is 0.2 or more and 0.6 or less, a steep magnetization transition width similar to that of a single-layer in-plane medium having an equivalent effective film thickness can be obtained.

For estimating the ratio of the anisotropic magnetic field, the recording magnetic layer and the stabilizing magnetic layer measured at an appropriate temperature separated by 100 Kelvin or more, for example, 216 Kelvin (dry ice) and 77 Kelvin (liquid nitrogen). The values of the magnetic field obtained by extrapolating the magnetic field that gives the differential peak of the layer to the absolute temperature zero are Hxo1 and Hxo2, respectively, and the ratio of Hxo2 to Hxo1 may be used. Also, different magnetic field changes, for example,
The magnetic field that gives the differential peak of the recording magnetic layer and the stabilizing magnetic layer measured at 300 A / m / s and 3000 A / m / s is the logarithmic axis to the amount of change in the magnetic field that changes by a magnetic field of a magnitude that gives a peak 1 in 1 nanosecond. When the values of the magnetic field extrapolated above are Hxr1 and Hxr2, Hxr2 for Hxr1
May be used as the estimated value of the anisotropy ratio. The ferromagnetic resonance method may be used to measure the magnetic anisotropy field of each magnetic layer. By applying a magnetic field perpendicular to the film surface, it is possible to measure the anisotropy magnetic field Hk of a medium having an in-plane magnetic anisotropy axis.
(J. Appl. Phys., Vol. 85, No. 8, 4720 (1999). Resonance frequency is f, gyromagnetic ratio is γ, saturation magnetic flux density of magnetic layer is B.
Letting s be, the resonance magnetic field Hr given by the equation (2πf / γ) ^ 2 = (Hr-Bs) (Hr-Bs-Hk) can be obtained corresponding to Hk of each magnetic layer. If the combination of the saturation magnetic flux density and the anisotropic magnetic field is different in each magnetic layer, it can be observed as another resonance magnetic field peak.

The rearrangement of the stabilizing magnetic layer is generally considered to be delayed with its thickness. As shown in FIG. 7, this is due to the effect of a decrease in the antiferromagnetic coupling magnetic field, which is inversely proportional to the thickness of the stabilizing magnetic layer, and the effect of the stabilizing magnetic layer having a hysteresis and causing a minor loop. . Regardless of the influence, when the magnetic field is set to zero in the above-mentioned magnetization process and the rearrangement is not completed, the stabilizing magnetic layer does not sufficiently cancel the recording underlayer. FIG. 13 shows an example of a plot of the amount of magnetization when the magnetic field is zero in the above-described magnetization process, plotted against the thickness of the stabilizing magnetic layer. In a conventional AFC medium composed of two layers, a recording magnetic layer and a stabilizing magnetic layer, the magnetization of the recording magnetic layer is canceled and the amount of magnetization of the entire medium decreases as the thickness of the stabilizing magnetic layer increases.
Bounds at 4.5nm (critical film thickness) and suddenly increases. It indicates that the rearrangement does not end beyond 4.5 nm. 2-layer AFC
The critical film thickness tc of the stabilizing magnetic layer in the medium changes somewhat depending on the size of the antiferromagnetic coupling, but generally, the anisotropic energy of the stabilizing magnetic layer is Ku2 (J / m ^ 3), from the top surface. When the average particle diameter is D and the Boltzmann constant is k, Ku2 and D
The product of the square of x and tc divided by k (Ku2 x D x D x tc / k) = 40
Determined by 00. When designing the medium in an actual device, the upper limit should be a value that is about 1.5 nm thinner than the critical film thickness, considering variations in magnetic properties. The critical film thickness obtained from the measurement of the magnetization curve at room temperature is about 1 to 2 nanometers larger than the film thickness at which noise abruptly increases.

FIG. 13 shows an example of the rearrangement promoting effect in the four-layer AFC medium of the present invention. As the effective stabilizing magnetic layer thickness, the sum of the products of the saturation magnetization and the film thickness of the stabilizing magnetic layer and the lower magnetic layer (group) divided by the saturation magnetization of the stabilizing magnetic layer was used. Saturation magnetization of each magnetic layer is 10 nm
The one obtained by measuring the magnetization of the formed film was used. From the figure, it can be seen that the critical film thickness increased to 6.5 nm. d
The ratio of dM2 to M1 could be increased from 0.41 when the critical film thickness was 4.5 nm to 0.59 when the critical film thickness was 6.5 nm.

In order to have the property that the magnetization of the magnetic layer in contact with the junction layer between the recording magnetic layer and the stabilizing magnetic layer is reversed, Ru or Ir, Rh, C
It is preferable to use at least one metal element selected from the group consisting of r, Cu, and Re. Rh and Cu are metals that are highly ductile and malleable, and the thicknesses that maximize the antiferromagnetic coupling field are also Ru and I.
Since it is about 0.8 nm, which is about twice as large as r and Re, variations in the antiferromagnetic coupling magnetic field due to pinholes and the like in the disk surface are small, and a high-quality medium with uniform magnetic characteristics can be obtained. Further, Ru, Ir, and Re are excellent in process control because the range of the film thickness at which the antiferromagnetic coupling magnetic field is obtained is wider than the average. When Cu or Cr is used for the non-magnetic intermediate layer, the lattice matching with the Co alloy magnetic film is good, so that the crystallinity and orientation of the recording magnetic layer are improved. When Cr is used, a large antiferromagnetic coupling magnetic field may be obtained if Fe is contained in the magnetic film in contact or the surface of the magnetic film.

An alloy containing Ru and at least one metal element selected from the group consisting of Mo, Re, W and Cr, or at least one elemental alloy selected from Rh, Pt and Pd In the case of an alloy containing and, other metal elements are well dissolved in Ru and Rh, which is useful for controlling and lowering the binding energy. The antiferromagnetic coupling field of AFC media is
It decreases in inverse proportion to the thickness of the effective stabilizing magnetic layer of the present invention. By providing a region of the recording magnetic layer or the stabilizing magnetic layer which is in contact with the junction layer and has a larger saturation magnetization than other regions in the same magnetic layer, the antiferromagnetic coupling between the recording magnetic layer and the stabilizing magnetic layer is strengthened. Such an enhanced structure (Japanese Patent Application 2000-10707
The combined use of 1) and the like can bring out the full advantage of the present invention. The stabilizing magnetic layer may be made of Co or an alloy containing 90% or more of Co. In addition, a large antiferromagnetic coupling magnetic field can be obtained by forming the bonding layer by the RF sputtering method. The antiferromagnetic coupling magnetic field obtained by the DC sputtering method is 1/3 that of the RF scattering method.
It is about the size, but twice as large as the MBE method. It is preferable to use a method that can obtain a necessary coupling magnetic field for forming the bonding layer. Also, when there are a plurality of bonding layers having the property of reversing the magnetization of the magnetic layers in contact with each other, the other bonding layers should be connected to each other. By including the elements that are not contained, the production process control becomes easy.

The stabilizing magnetic layer and the lower magnetic layer group are made of Co,
Fe, Ni or Co as the main component, Fe, Ni, Cr, Ta, Pt, P
It is preferable to use an alloy containing at least one element selected from d and Ru or an alloy containing B (boron) or O (oxygen) in addition. Co, Fe, Ni or an Fe or Ni alloy containing Co as a main component has a large saturation magnetization and has a function of enhancing effective antiferromagnetic coupling with the recording magnetic layer. If a small amount of oxygen is introduced at the time of forming the stabilizing magnetic layer, the stabilizing magnetic layer is subdivided and the rearrangement is promoted. Also, with Co as the main component, Cr,
When an alloy containing at least one element selected from Ta, Pt, Pd and Ru is used and the Co composition is 85 at% or more, the exchange interaction between the magnetic particles in the stabilized magnetic layer becomes large. , The width of the reversal magnetic field is reduced and the S / N ratio is improved. If the exchange interaction between the magnetic particles in the stabilizing magnetic layer is too large, the S / N ratio suddenly deteriorates because the magnetization transition region in the stabilizing magnetic layer is disturbed. Exchange interaction between magnetic particles in the stabilized magnetic layer becomes large. By setting the number of junction layers that induce antiferromagnetic coupling to be an odd number, it is possible to sufficiently cancel the magnetization in the lower magnetic layer group.

The thickness ti of each magnetic layer constituting the lower magnetic layer group is Kui (J / m ^ 3), which is the anisotropy energy of the i-th magnetic layer from the substrate, and is the average particle diameter seen from the upper surface. When D is the film thickness and ti is the Boltzmann constant, the product of the square of Ku and D and ti is divided by k (Kui x D x D x ti / k) to be the heat resistance coefficient of the magnetic layer. When the heat resistance coefficient of the magnetic layer is 40
By setting it to be 00 or less, the rearrangement of the lower magnetic layer group is 10 milliseconds or less. When promoting the magnetization reversal of the stabilizing magnetic layer, the heat resistance coefficient of the lower magnetic layer group is
Should be 3000 or less. In this case, by setting the heat resistance coefficient of the lower magnetic layer group to increase as the distance from the nonmagnetic substrate increases, the rearrangement can be promoted from the nonmagnetic substrate, and stable rearrangement can be expected. When Ku of the recording magnetic layer and the lower magnetic layer group is close, the condition for satisfying the heat resistance coefficient is that the thickness of each magnetic layer of the lower magnetic layer group is about 0.3 times or less than the thickness of the recording magnetic layer. Is. Similarly, the thickness of the magnetic layer increases with increasing distance from the non-magnetic substrate.
By increasing the thickness, rearrangement from the substrate side can be induced. Further, when making the thicknesses of the lower magnetic layer groups approximately equal, a value obtained by subtracting Nc from 80% of Np, and further subtracting 55% of Nb (0.7 × Np-Nc-0.55, is used by using the above Ku's estimation formula. × N
Since b) becomes smaller with increasing distance from the non-magnetic substrate, rearrangement from the substrate side can be induced.

To estimate the magnetic anisotropy energy Ku of each magnetic layer, a single layer (10 nm) having the composition of each magnetic layer was prepared, and the pulse time dependence of the residual coercive force was measured by VSM measurement or inverse DC demagnetization method. K calculated by fitting and fitting to Sharock's formula
It may be calculated from the β value and the value of Hk using the relational expressions Kβ = Ku * v / (kT) and Hk = 2 * Ku / Ms. In addition, when the magnetic layer is a CoCrPtB magnetic thin film, the atomic composition of Cr is set to the atomic composition of Nc and Pt.
The atomic composition of Np and B is Nb, and the formula Ku = (4.4-0.18 × Nc + 0.15
XNp-0.1xNb) x 100000 J / m ^ 3 may be simply calculated (Fig. 22).

It is also an effective means to accelerate the rearrangement that the heat resistance coefficient of these magnetic layers is lowered by dividing the stabilizing magnetic layer and the lower magnetic layer group by the joining layer which induces weak ferromagnetic coupling. . The weak ferromagnetic coupling magnitude is well decoupled when the exchange surface binding energy of the bonding layer is less than 5/10000 J / m ^ 2. Ru and Nb, Ti, Pd, Pt,
An alloy containing at least one metal element selected from the group consisting of Au, Cu, Pt, and Pd hardly forms a solid solution, so that the vibrational property is lost as shown in the binding energy of the RuTi alloy in FIG. Since only exponential decay is observed, it is suitable for a junction layer in which the magnetization directions of adjacent magnetic layers are substantially parallel. In particular, an alloy of Ru and Pt or Pd has a relatively gradual decrease in the thickness of the bonding layer and is easy to handle.

When the magnetic layer is used as the bonding layer, the exchange surface binding energy J is a value obtained by dividing twice the exchange stiffness constant A by tcr, where tcr is the thickness of the bonding layer. An alloy containing Co as a main component and at least one element selected from Fe, Ni, Cr, Ta, Pt, Pd, and Ru, or in addition B
An alloy containing (boron) or O (oxygen) changes the saturation magnetization and A depending on the composition, and is therefore suitable for a junction layer in which the magnetization directions of adjacent magnetic layers are substantially parallel. Further, when an alloy containing Co as a main component and containing at least one element selected from Cr, Ta, Pt, Pd, and Ru is used and the Co composition is 85 at% or more, The exchange interaction between the magnetic particles is increased, the width of the switching magnetic field is reduced, and the S / N ratio is improved. If the exchange interaction between the magnetic particles in the stabilizing magnetic layer is too large, the S / N ratio suddenly deteriorates because the magnetization transition region in the stabilizing magnetic layer is disturbed. As the bonding layer, Ru having a thickness of 0.1 nm to 0.4 nm or 1.0 nm to 1.6 nm, or at least one metal element selected from the group consisting of Ir, Rh, Cu, and Re, or Ru and Mo, An alloy containing at least one metal element selected from the group consisting of Re, W and Cr, or an alloy containing Rh and at least one elemental alloy selected from Pt and Pd, or a thickness However, even if Cr of 0.2 nm to 1.0 nm or 2.5 nm to 3.2 nm or an alloy containing Cr as a main component is used, the magnetization directions of the adjacent magnetic layers can be made substantially parallel.

Even when the stabilizing magnetic layer and the lower magnetic layer group are divided by the joining layer which induces weak ferromagnetic coupling, the anisotropic energy of the i-th magnetic layer from the substrate is Kui (J / m ^ 3). ,
When the average particle diameter viewed from the top is D, the film thickness is ti, and the Boltzmann constant is k, the product of the square of Ku and D and ti is divided by k (Kui × D × D × ti / k). When the heat resistance coefficient of the magnetic layer is set to be 4000 or less, the rearrangement of the stabilizing magnetic layer and the lower magnetic layer group is 10 milliseconds or less. Typically, the thickness of each magnetic layer may be set to 5 nanometers or less.

In a magnetic recording medium in which the stabilizing magnetic layer and the lower magnetic layer group are substantially parallel to each other, in order to make the rearrangement times of the stabilizing magnetic layer and the lower magnetic layer group approximately the same, exchange is performed. Considering the influence of the coupling magnetic field, it is necessary to make the heat resistance coefficient of the stabilizing magnetic layer slightly larger than that of the magnetic layer closest to the substrate in the lower magnetic layer group. When the stabilizing magnetic layer and the lower magnetic layer group are all made of the same material, the thickness of the stabilizing magnetic layer should be larger than the thickness of the magnetic layer closest to the substrate in the lower magnetic layer group. Thus, good recording characteristics and reproducing characteristics can be obtained.

The stabilizing magnetic layer is in contact with the recording magnetic layer via a bonding layer that induces antiferromagnetic coupling, and the thermal demagnetization of the recording magnetic layer greatly changes depending on the magnetization state of the stabilizing magnetic layer. When the magnetizations of the stabilizing magnetic layer and the recording magnetic layer are antiparallel, the thermal demagnetization of the recording magnetic layer is suppressed by the AFC effect. When the magnetizations of the stabilizing magnetic layer and the recording magnetic layer are parallel, conversely, thermal demagnetization of the recording magnetic layer is induced. Therefore, by quickly completing the rearrangement of the stabilizing magnetic layer prior to the rearrangement of the lower magnetic layer group, it becomes possible to suppress the thermal demagnetization of the recording magnetic layer during the rearrangement. This object is achieved by making the thickness of the stabilizing magnetic layer smaller than the thickness of the lower magnetic layer group in contact with the stabilizing magnetic layer. It is typically good to set it to 2 nanometers or less.

The recording magnetic layer is composed of Co, Fe and Ni, such as Co-Cr-Pt, Co-Cr-Pt-B, Co-Pt and Fe-Co-Ni alloys, which are usually used as magnetic recording media. At least one selected from the group
A crystalline magnetic body containing 50 at% or more of the seed metal element may be used. However, since it is necessary to make it thicker than the conventional single-layer magnetic layer medium, consideration must be given to suppressing the expansion of the grain size and not lowering the exchange interaction within the grain. Further, when a further high recording density medium is produced by using the present invention, it is expected that the thickness of the recording magnetic layer exceeds twice the magnetic particle size. At this time, if the magnetization does not rotate at the same time in the magnetic grains, the thermal fluctuation characteristics are significantly deteriorated. This object is achieved when the exchange stiffness constant in the recording magnetic layer is larger than 3 pico J / m, the saturation magnetization of the recording magnetic layer exceeds 0.85 Tesla, and the Co composition of the recording magnetic layer exceeds 83 at%. To be done.

In the recording medium of the present invention, since the total thickness of the stabilizing magnetic layer for canceling the magnetization of the recording magnetic layer and the lower magnetic layer group is large with respect to the thickness of the recording magnetic layer, an effective film for recording and reproduction is provided. The thickness can be reduced, and the ratio of the minimum magnetic transition width formed on the recording medium to the total value of all magnetic layers is 1.5.
It is possible to make it smaller.

For the non-magnetic substrate, glass, NiP plated Al,
3.5, 2.5 made of ceramics, Si, plastic, etc.
It has a disk shape such as 1.8, 1 diameter, or the shape of a tape or card, and further has Cr, Mo, W, Ta, V, Nb, Ta, Ti, and
Cr, Mo, W, CrMo, CrTi, CrCo, NiCr, T containing at least one element selected from the group consisting of Ge, Si, Co and Ni
a, CoCr, Ta, TiCr, C, Ge, TiNb, non-magnetic CoCr / CrTi laminated underlayer, non-magnetic CoCrTa / CrTi / Cr laminated underlayer, etc. And lattice matching can be controlled. The multilayer structure of the non-magnetic layer on the surface increases the degree of freedom in control, and is more preferable from the viewpoint of reducing thermal fluctuation.

To reproduce the recorded information, a giant magnetoresistive effect element or a tunnel junction film exhibiting a magnetoresistive effect is used in combination with a magnetic head having a reproducing element having an effective track width of 0.5 μm or less. By reproducing the magnetic information, with the help of the signal processing method, a device S / N of 20 dB or more necessary for device operation can be obtained, and EEPRML and MEEPRML,
Areal recording density of 50 when combined with trellis code, ECC, etc.
It is possible to record and reproduce at Gb / in2 or higher. It is preferable to use a head using a magnetic pole having a saturation magnetic flux density of 1.8 T or more in the recording portion because a recording magnetic layer material having greater magnetic anisotropy can be used. Here, the giant magnetoresistive effect element (GMR) and the tunnel type magnetic head are disclosed in JP-A-61-097906 and JP-A-02-61.
572, JP 04-358310 A, JP 07-33 A
3015, and Japanese Patent Laid-Open Nos. 02-148643 and 02-21.
The technology described in each publication of 8904, KrF
An effective track width of 0.5 μm or less was achieved by making full use of lithography with a stepper, FIB processing technology, and the like.

By using the present invention, a medium for reducing the magnetic anisotropy field of the above-mentioned stabilizing magnetic layer which defines the optimum value of the magnetic anisotropy as compared with the magnetic anisotropy field of the recording magnetic layer (special characteristics Applicant 2001-? (Chuken) 31010410) The merit of effective stabilizing magnetic layer thickness (the sum of the product of the saturation magnetization and the film thickness of the stabilizing magnetic layer and the lower magnetic layer group is divided by the saturation magnetization of the stabilizing magnetic layer). ) Can be fully pulled out to a thick area. This is because when the magnetic anisotropy energy is reduced to promote rearrangement, sufficient heat-resistant demagnetization characteristics of the recording layer cannot be obtained.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION The contents of the present invention will be described in detail below with reference to Examples and Comparative Examples. (Embodiment 1) A first embodiment of the present invention will be described with reference to FIG. The figure is a conceptual diagram of a magnetic disk embodying the present invention. FIG. 2 shows the three-layer AFC medium having the structure shown in FIG. 14 formed on both sides of the non-magnetic substrate 15. In this embodiment, as a comparison, a conventional two-layer AFC medium as shown in FIG. 3 and a four-layer AFC medium having the configurations shown in FIGS. 13 and 15 will be described together. 15 is made of glass, NiP plated Al, ceramics, Si, plastic, etc., and is 3.5, 2.5,
The disk-shaped or tape-shaped non-magnetic substrate having a diameter of 1.8, 1 or the like, the card-shaped non-magnetic substrate, and the recording magnetic layer 11 are usually used as a magnetic recording medium. CoCrPtB, CoCrPt, CoCrPtO, CoCrTa, CoNiPt, Co
Pt-SiO2, FeNiCo, CoFeTa, NiTa, CoW, CoNb, GdFeCo,
50at of at least one metal element selected from the group consisting of Co, Fe, and Ni such as GdTbFeCo, Fe-N, Co-CoO, and Co-Pt alloy.
% Of the crystalline magnetic material, the stabilizing magnetic layer 12 and the lower magnetic layer group 21 are mainly composed of Co, Fe, Ni or Co, and Fe,
At least 1 selected from Ni, Cr, Ta, Pt, Pd, Ru
Alloys containing certain elements, or in addition B (boron) or O
An alloy layer containing (oxygen).

B is added to the stabilizing magnetic layer 12 and the lower magnetic layer group 21.
When (boron) or O (oxygen) is contained, the magnetic particle size becomes small and the noise reduction effect becomes remarkable. In addition, the stabilizing magnetic layer 12 and the lower magnetic layer group 21 contain Co as a main component and at least one selected from Cr, Ta, Pt, Pd, and Ru.
When using an alloy containing seed elements, if the Co composition is 85 at% or more, the exchange interaction between the magnetic particles in the stabilized magnetic layer becomes large and the width of the reversal magnetic field becomes small, improving the S / N ratio. To do. The non-magnetic underlayer 14 is made of Cr, Mo, W, Ta, V, Nb,
Cr, Mo, W, CrMo, CrTi, CrC containing at least one element selected from the group consisting of Ta, Ti, Ge, Si, Co and Ni
o, NiCr, Ta, CoCr, Ta, TiCr, C, Ge, TiNb, non-magnetic Co
It is a non-magnetic layer such as Cr / CrTi laminated base or non-magnetic CoCrTa / CrTi / Cr laminated base. By making the non-magnetic underlayer 14 multi-layered, the crystal grain size, orientation and lattice matching of the magnetic layer can be easily controlled. 16 is a protective film of N-added C, H-added C, BN, ZrNbN, etc., 17 is a perfluoroalkyl polyether having an adsorptive or reactive end group such as OH and NH2,
Lubricants such as metal fatty acids.

Ru is used for the bonding layer 13 that induces antiferromagnetic coupling.
Was used, but at least one metal element selected from the group consisting of Ir, Rh, Cr, Cu, and Re, or Ru and Mo, Re,
An alloy containing at least one metal element selected from the group consisting of W and Cr, or an alloy containing Rh and at least one elemental alloy selected from Pt and Pd may be used. Co-40at% is used for the bonding layer 22 that induces weak ferromagnetic coupling.
Cr was used, but an alloy containing Ru and at least one metal element selected from the group consisting of Nb, Ti, Pd, Pt, Au, Cu, Pt, and Pd, or Co as a main component, and Fe , Ni, Cr, Ta, P
A magnetic substance which is an alloy containing at least one element selected from t, Pd, and Ru, or an alloy containing B (boron) or O (oxygen) in addition, and whose saturation magnetization is smaller than that of the adjacent magnetic layer. Similar results were obtained with. The bonding layer 22 that induces weak ferromagnetic coupling has a thickness of 0.1 nm to 0.4 nm.
Or Ru of 1.0 nm to 1.6 nm, or at least one metal element selected from the group consisting of Ir, Rh, Cu and Re, or selected from the group consisting of Ru and Mo, Re, W and Cr. Alloy containing at least one metal element, or Rh and Pt, Pd
An alloy containing at least one or more elemental alloys selected from, or having a thickness of 0.2 nm to 1.0 nm or 2.5 nm
3.2 nm of Cr or an alloy containing Cr as a main component may be used. When a material having a low Pt composition is used between the recording magnetic layer 11 and the non-magnetic intermediate layer, antiferromagnetic coupling is stabilized, and when a material having a large saturation magnetization as shown in FIG. 16 is used, antiferromagnetic coupling is strengthened. .

Here, the non-magnetic underlayer 14, the magnetic layer, and the bonding layer are all formed on the substrate 15 by DC sputtering in a low-pressure Ar gas or Ar-O gas atmosphere containing several% oxygen. did. In this facility, the parameters can be changed independently for each layer. At this time, in this equipment, Ar pressure was 1-10 mTorr, substrate temperature was 100-300 ° C, and film formation rate was 0.1-10.
nm / s. The protective layer is 10 nm. The Cr content of the Co alloy type magnetic layer of the recording magnetic layer was 19 to 23 atomic percent, the Pt content was 4 to 20 atomic percent, and the V and Ta contents were 2 to 5 atomic percent. The thickness, saturation magnetization, and anisotropic magnetic field of the recording magnetic layer were changed at 12-22 nm, 0.3-0.7T, and 500-1200 kA / m, respectively. The thickness, saturation magnetization, and anisotropic magnetic field of the stabilizing magnetic layer and the lower magnetic layer group are 1-8 nm, 0.3-1.5T, and 100-120, respectively.
It was changed at 0 kA / m. Since the antiferromagnetic coupling magnetic field is sensitive to the interface state between the magnetic material and the nonmagnetic intermediate layer, it is also greatly affected by the film forming conditions. In particular, a large antiferromagnetic coupling magnetic field can be obtained by the RF sputtering method. The antiferromagnetic coupling field obtained by the DC sputtering method is about 1/3 that of the RF sputtering method, but it is twice as large as that of the MBE method. It is preferable to use a method capable of obtaining a necessary coupling magnetic field for forming the bonding layer. In the case of the medium structure shown in FIG. 15 in which there are three bonding layers that induce antiferromagnetic coupling, if elements that are not included in the other bonding layers are selected from Mo, Re, W, and Cr and used as an alloy with Ru. , The production process management becomes easy. According to X-ray diffraction measurement, the magnetic film had the same orientation as that of a typical in-plane recording medium in which the c-axis of hexagonal crystal was randomly distributed in the plane.

FIG. 17 shows the dependence of the residual magnetization on the thickness of the stabilizing magnetic layer when a 16 nm CoCrPtB recording magnetic layer is fixed. The remanent magnetization is measured by applying a magnetic field in the track direction to saturate it and then removing the magnetic field. The medium of the present invention has a four-layer structure shown in FIG.
2nm thickness under the stabilizing magnetic layer of the conventional two-layer AFC medium
A pair of CoCrPt lower magnetic layers are attached. The critical thickness of the conventional medium is about 4.5 nm, whereas the medium of the present invention has a thickness of up to 6.5 nm, which indicates that rearrangement is promoted.

FIG. 18 shows another dependence of residual magnetization on the thickness of the stabilizing magnetic layer when a 16 nm CoCrPtB recording magnetic layer is fixed. The medium has a coupling layer that induces weak ferromagnetic coupling, and has a three-layer structure (divided into two) shown in FIG.
4 layer structure (3 divisions) shown in FIG.
A comparison of C medium structures was made. The stabilizing magnetic layer and the lower magnetic layer group are CoCrPt having the same composition. The effective stabilizing magnetic film thickness was defined as the total value of the thicknesses of the stabilizing magnetic layer and the magnetic layers of the lower magnetic layer group. The critical film thickness of the conventional medium is about 4.5 nm, whereas the two-division medium of the present invention is as thick as 6.0 nm and the three-division medium of the present invention is as thick as 8.5 nm, which facilitates rearrangement by division. It indicates that

AFC with three or more layers shown in FIGS. 17 and 18
The medium did not measure more than two differential peaks as shown in FIG. If the exchange coupling is weak, more than two peaks appear to be measured. Assuming that the magnetization change corresponding to the recording magnetic layer is dM1 and the magnetization change corresponding to the stabilizing magnetic layer and the lower magnetic layer is dM2, the ratio dM2 / dM1 is 0.3 at the maximum in the conventional medium, whereas 2 split media is 0.
5, 0.7 for three-division media, 0.6 for four-layer media in FIG.
It turns out that it can be increased to a certain degree.

FIG. 21 is a circuit diagram of the circuit shown in FIG. 14 and FIG.
3 shows the critical film thickness with respect to the thickness of the bonding layer that induces the weak ferromagnetic layer made of CoCr16 in the divided medium and the three-divided medium. In both structures, when the CoCr16 bonding layer is thin, the critical film thickness is 4.5 nm, which shows that the stabilizing magnetic film and the lower magnetic film group are integrated. CoCr
It is considered that when the thickness of the 20-junction layer exceeds 2 nm, the magnetic layers are separated. The exchange stiffness constant of the CoCr20 single crystal was 0.5 pJ / m as measured by Brillouin scattering. Therefore, the surface exchange coupling energy at which each magnetic layer is scattered and the rearrangement promoting effect is obtained is 2A / t = 2 × (0.5 / 10 ^ 12) /
The value of (2/10 ^ 9) = 5 / 10000J / m ^ 2 was obtained.

The above medium was replaced with 45Ni-55F having a saturation magnetic flux density of 1.5T.
e is a magnetic pole material having a track width of 0.4 μm and a recording gap length of 0.15 μm (gap material: Al2O3) by FIB (Focused Ion Beam) processing technology, NiFe / Co (4 nm),
Cu (2.5 nm), fixed layer CoFe (3 nm), CrMnPt (20n
m) are sequentially laminated and formed into a rectangular pattern, and then Co80-Cr15-Pt5 (10 nm) / Cr (10 nm) permanent magnet and Ta
A structure in which an electrode film (100 nm) is arranged and a giant magnetoresistive element with a track width of 0.3 μm specified by the KrF stepper lithography technology is sandwiched between 2 μm Ni80-Fe20 shield films (shield interval: 0.07 μm, gap) Material: Al2O
The magnetic head element having the reproducing portion of 3) was formed on an Al2O3-TiC-sized slider of 1.0 × 0.8 × 0.2 mm 3 and mounted on the magnetic disk device of the present invention shown in FIG. Evaluated. The slider is a negative pressure type in which three minute protrusions are provided, and a CH protective film is provided on the air bearing surface. Further, FIG. 10 (a) is a plan view of the device and FIG. 10 (b) is a sectional view. The same predetermined electric circuit as in the prior art is necessary for processing the reproduction signal and inputting / outputting information. Here, EEPR
ML (Extended Extended Partial Response Maximum Like)
lihood) and enhanced ECC function MEEPRML (Mo
We introduced a signal processing circuit called "dified PRML" that positively utilizes waveform interference during high density.

FIG. 1 shows the dependence of the signal noise ratio (Smf / N) at 450 kFCI on the stabilized magnetic film thickness as the gain from the value obtained by the recording magnetic layer alone. The comparison was made for the media used in FIGS. 17 and 18. The Smf / N gain increases as the stabilizing magnetic film thickness increases, but it is 3.5 nm in the conventional medium, 5.0 nm in the two-division medium of the present invention (FIG. 14), and 6.5 nm in the four-layer medium of the present invention (FIG. 13). When the value exceeds nm, the Smf / N gain component sharply decreases. When the film thickness of Hex95 = 0 of each medium is examined, it is 3.4 nm in the conventional medium, 5.1 nm in the two-divided medium of the present invention, and 6.3 nm in the four-layer medium of the present invention, and the Smf / N gain component changes rapidly. It matched the film thickness. In each configuration of the medium used in FIG. 1,
When recording / reproducing was performed at a higher recording density with a stabilized magnetic film thickness that gives the maximum Smf / N gain, it was 60 with the conventional medium.
Good characteristics were obtained up to 0 kFCI, up to 800 kFCI in the two-division medium of the present invention, and up to 850 kFCI in the four-layer medium of the present invention.
According to the present invention, the ratio of the minimum magnetization transition width formed in the recording medium to the total value of all magnetic layers of the recording medium can be made smaller than 1.5.

FIG. 19 shows the dependence of overwriting on the stabilizing magnetic film thickness in the two-division medium shown in FIG. 14 as a gain amount from a value obtained by the recording magnetic layer alone. The thicker the stabilizing magnetic layer, the larger the overwrite gain. However, when the anisotropic magnetic field Hk2 of the stabilizing magnetic layer and the anisotropic magnetic field Hk3 of the lower magnetic layer are different, sufficient gain is not obtained.

The resolution, which is the ratio of the reproduction output at 450 kFCI to the output of the isolated transition, is the ratio Hk of the anisotropic magnetic field Hk2 of the stabilizing magnetic layer to the anisotropic magnetic field Hk1 of the recording magnetic layer.
The relationship as shown in FIG. 9 was obtained for 2 / Hk1. Ratio Hk2 / Hk1
When the value exceeds 0.7, the resolution becomes worse than that of the medium composed of the magnetic layer of the recording magnetic layer alone. When the ratio Hk2 / Hk1 is 0.2 or more and 0.6 or less, a resolution equivalent to that of a single layer medium having the same residual magnetization can be obtained.

The heads having the recording poles of 1T (80Ni-20Fe composition), 1.3T (FeTaC) and 1.7T (FeNiN) as the recording magnetic poles were also evaluated. Sufficiently sharp recording could not be performed, noise was extremely large and it could not be used practically, and good recording was confirmed only at 1.5T and 1.7T. From the above, it was found that 1.5T or more is necessary. Further, when the characteristics were evaluated by a tunnel type magnetic head having a reproducing track width of 0.4 μm, which was prototyped by the techniques disclosed in JP-A-02-148643 and 02-218904, the same result was obtained. With the conventional MR head having the same track width, sufficient reproduction sensitivity was not obtained, and the evaluation could not be endured.

The embodiments described above are representative of similar inventions disclosed in the present invention, and even examples which can be easily inferred by those skilled in the art from the present invention fall within the scope of the present invention. For example, the same effect can be obtained by the RF magnetron sputtering method, the ECR sputtering method, the helicon sputtering method, or the like. Further, according to the magnetic recording medium disclosed in the present invention, 15 Gb
Recording / reproducing at a recording density of / in2 or more becomes possible for the first time.
Therefore, a magnetic recording / reproducing apparatus using a magnetic tape, a magnetic card, a magneto-optical disk, etc., which is possible with the magnetic recording medium of the present invention, is also within the scope of the present invention. As described above, by using the magnetic recording medium and the magnetic recording / reproducing apparatus of the present invention, high-speed and large-capacity recording / reproducing becomes possible for the first time. As a result, it is possible to realize a magnetic recording / reproducing device having extremely strong product competitiveness. (Example 2) The magnetic recording medium of Example 2 is characterized in that in a longitudinal magnetic recording medium having at least three magnetic layers formed on a non-magnetic substrate, the magnetic layer farthest from the non-magnetic substrate is recorded. When the magnetic layer next to the magnetic layer and the recording magnetic layer is the stabilizing magnetic layer, and the magnetic layers other than the recording magnetic layer and the stabilizing magnetic layer are the lower magnetic layer groups, The magnetic layers are separated by a bonding layer made of a non-magnetic material or a weak magnetic material, and a magnetic field is applied in the track direction to cause magnetic saturation, and then the magnetic field is reduced, and then a magnetic field is applied in the opposite direction. In the magnetization process to reach saturation, the differential value of the magnetic field of the magnetization has at least two peaks, and the magnetization change amount in the process corresponding to each peak is dM1, d in descending order from the largest value.
When called as M2, the sum of dM1 and dM2 is 90% or more, which is twice the saturation magnetization, and the ratio of dM2 to dM1 is 0.45.
Above, further, between the recording magnetic layer and the stabilizing magnetic layer, a junction layer made of a non-magnetic substance or a weak magnetic substance having a property of reversing the magnetization of the contacting magnetic layer is provided. is there.

The joining layer made of a non-magnetic substance or a weak magnetic substance having a property of reversing the magnetization of the magnetic layer in contact is selected from the group consisting of Ru, Ir, Rh, Cr, Cu and Re. At least one metal element or Ru
An alloy containing at least one metal element selected from the group consisting of Mo, Re, W and Cr, or an alloy containing Rh and at least one elemental alloy selected from Pt and Pd. Is preferred.

Also, at 135 Kelvin, a magnetic field of 3 per second
The differential peaks corresponding to the magnetization change amounts dM1 and dM2 obtained by the magnetization process obtained by changing the magnetic field with a magnitude of 000 A / m are defined as peak 1 and peak 2, respectively. It is preferable that the magnetic field is in the magnetically saturated direction, and the magnetic field of the peak 1 is the magnetic field in the next magnetically saturated direction.

Further, the differential peaks corresponding to the above-mentioned magnetization change amounts dM1 and dM2 are referred to as peak 1 and peak 2, respectively,
Let Hxo1 and Hxo2 be the values of the magnetic fields obtained by extrapolating the magnetic fields that give the peaks 1 and 2 measured at 216 Kelvin and 77 Kelvin to absolute temperature zero, respectively.
The ratio of Hxo2 to o1 is preferably 0.7 or less.

Furthermore, the above-mentioned magnetic field ratio Hxo2 / Hxo1 is 0.
It is preferably 2 or more and 0.6 or less.

The differential peaks corresponding to the amounts of change in magnetization dM1 and dM2 are defined as peak 1 and peak 2, respectively, and the magnetic field is 300 A / m / s and 300 / s in the magnetization process.
The magnetic field of the peak obtained by changing the magnetic field at a magnitude of 0 A / m is extrapolated on the logarithmic axis to the magnetic field change amount that changes by a magnetic field of a magnitude giving peak 1 in 1 nanosecond. When the values are Hxr1 and Hxr2 respectively, for Hxr1
The ratio of Hxr2 is preferably 0.7 or less.

Furthermore, the magnetic field ratio Hxr2 / Hxr1 is 0.2 or more.
It is preferably 0.6 or less.

At 216 Kelvin, the magnetic field is 3
The differential peaks corresponding to the magnetization change amounts dM1 and dM2 obtained by the magnetization process obtained by changing the magnetic field with a magnitude of 000 A / m are defined as peak 1 and peak 2, respectively. When the tangent line drawn in the magnetization curve in the average magnetic field considering the sign of the magnetic field crosses the zero magnetic field, the magnetization amount is Mrte, and the magnetization amount in the zero magnetic field of the magnetization curve is Mrta, the difference between the two magnetization amounts ( Mrte-Mrta)
Ratio of the amount of change in magnetization dM2 of peak 2 of ((Mrte-Mrta) / dM2)
Is preferably 0.05 or less.

At 216 Kelvin, the magnetic field is 3
The differential peaks corresponding to the magnetization change amounts dM1 and dM2 obtained by the magnetization process obtained by changing the magnetic field with a magnitude of 000 A / m are defined as peak 1 and peak 2, respectively. A magnetic field in a magnetically saturated direction, and assuming that the amount of magnetization in the magnetic field that gives the peak 2 is Mt2, the amount of magnetization (Mt2 + 0.45 × dM2) on the magnetization curve
It is desirable that the difference ΔH between the magnetic field that gives the magnetic field and the magnetic field that gives the amount of magnetization (Mt2-0.45 × dM2) is 1.5 times or less the magnitude of the magnetic field of the peak 2.

The stabilizing magnetic layer and the lower magnetic layer group contain Co, Fe, Ni or Co as a main component, and Fe, Ni,
An alloy containing at least one element selected from Cr, Ta, Pt, Pd and Ru, or additionally B (boron) or O (oxygen)
It is preferable that the alloy contains. (Embodiment 3) The feature of the invention described in Embodiment 3 is that in a magnetic recording medium having at least three magnetic layers formed on a non-magnetic substrate, the magnetic layer farthest from the non-magnetic substrate is the recording magnetic layer. When the magnetic layer next to the non-magnetic substrate next to the recording magnetic layer is a stabilizing magnetic layer and all the other magnetic layers except the recording magnetic layer and the stabilizing magnetic layer are lower magnetic layer groups, The layers are separated by a non-magnetic layer or a bonding layer made of a non-magnetic substance, the magnetization of the recording magnetic layer and the magnetization of the stabilizing magnetic layer are antiparallel to each other, and the magnetization of an adjacent magnetic layer is The number of bonding layers whose directions are anti-parallel is odd, and the anisotropy energy of the i-th magnetic layer from the substrate is Kui (J / m ^ 3), the average particle diameter seen from the top is D, and the film thickness is When ti is the Boltzmann constant and k is the value of the product of the square of Ku and D and ti divided by k (Kui × D XD × ti / k) is the heat resistance coefficient of the magnetic layer, the thickness ti of each magnetic layer constituting the lower magnetic layer group is the heat resistance coefficient of the magnetic layer.
The magnetic recording medium is characterized by being set to 4000 or less. Here, the film thickness of the magnetic layer is preferably set such that the heat resistance coefficient of the magnetic layer increases as the distance from the non-magnetic substrate increases. (Embodiment 4) The feature of the invention described in Embodiment 4 is that in a magnetic recording medium having at least three magnetic layers formed on a non-magnetic substrate, the magnetic layer farthest from the non-magnetic substrate is the recording magnetic layer. When the magnetic layer next to the non-magnetic substrate next to the recording magnetic layer is a stabilizing magnetic layer and all the other magnetic layers except the recording magnetic layer and the stabilizing magnetic layer are lower magnetic layer groups, The layers are separated by a non-magnetic layer or a bonding layer made of a non-magnetic substance, the magnetization of the recording magnetic layer and the magnetization of the stabilizing magnetic layer are antiparallel to each other, and the magnetization of an adjacent magnetic layer is The number of the bonding layers whose directions are antiparallel is odd, and the thickness of each magnetic layer forming the lower magnetic layer group is 0.3 times or less the thickness of the recording magnetic layer. It is called a magnetic recording medium.

Further, it is preferable that the film thickness of the magnetic layer be made thicker as the distance from the non-magnetic substrate increases. Further, the composition of the magnetic layer described above is such that the atomic composition of Cr is Nc and the atomic composition of Pt is Nc.
When the atomic composition of p and B is Nb, the value obtained by subtracting Nc from 80% of Np, and further subtracting 55% of Nb (0.7 × Np-Nc-0.55
It is preferable that xNb) becomes smaller as the distance from the nonmagnetic substrate increases.

Furthermore, it is preferable that the above-mentioned junction layers in which the magnetization directions of the adjacent magnetic layers are antiparallel to each other include elements that are not included in the other junction layers.

Further, in the non-magnetic layer or the joining layer made of a non-magnetic substance that separates the magnetic layers constituting the stabilizing magnetic layer and the lower magnetic layer group, the joining layers in which the magnetization directions of the adjacent magnetic layers are substantially parallel to each other. It is desirable to include at least one pair. Here, the exchange surface binding energy of the junction layer in which the magnetization directions of the adjacent magnetic layers are substantially parallel is 5/10000 J / m ^ 2.
It is preferably smaller.

The above-mentioned junction layers in which the magnetization directions of the adjacent magnetic layers are substantially parallel are Ru, Nb, Ti, Pd, Pt, Au, Cu and P.
An alloy containing at least one metal element selected from the group consisting of t and Pd, or Co as a main component and Fe, Ni, and C
Alloy containing at least one element selected from r, Ta, Pt, Pd and Ru, or in addition B (boron) or O (oxygen)
A magnetic substance having a saturation magnetization smaller than that of the adjacent magnetic layer, or having a thickness of 0.1 nm to 0.4 nm or 1.0 n
Ru from m to 1.6 nm or at least one metal element selected from the group consisting of Ir, Rh, Cu and Re, or Ru and M
o, Re, W, an alloy containing at least one metal element selected from the group consisting of Cr, or an alloy containing Rh and at least one elemental alloy selected from Pt and Pd, or Cr with a thickness of 0.2 nm to 1.0 nm or 2.5 nm to 3.2 nm,
Alternatively, an alloy containing Cr as a main component is preferable.

The thickness of the magnetic layers constituting the stabilizing magnetic layer and the lower magnetic layer group is the anisotropic energy Kui (J / m ^ 3) of the i-th magnetic layer from the substrate, viewed from the top. When the average particle diameter is D, the film thickness is ti, and the Boltzmann constant is k,
The value of the product of square and ti of Kui and D divided by k (Kui × D × D × ti /
Using the heat resistance coefficient of the magnetic layer defined in k), the film thickness of each magnetic layer may be set so that the heat resistance coefficient of the magnetic layer is 4000 or less. desirable.

The thickness of the stabilizing magnetic layer and the magnetic layers constituting the lower magnetic layer group is preferably less than 5 nanometers. Moreover, it is preferable that the magnetic anisotropy fields of the magnetic layers constituting the stabilizing magnetic layer and the lower magnetic layer group are substantially the same.

Further, it is preferable that at least one of the magnetic layers in contact with the bonding layer has a region having a saturation magnetization larger than that of other regions in the magnetic layer within a region of 1 nm in contact with the bonding layer. .

The ratio HkB / HkA of the average magnetic anisotropy field HkB of the stabilizing magnetic layer and the magnetic layers constituting the lower magnetic layer group to the magnetic anisotropy field HkA of the recording magnetic layer is 0.7 or less. Is preferable. In this case, HkB /
More preferably, HkA is 0.2 or more and 0.6 or less.

The thickness of the stabilizing magnetic layer is preferably larger than the thickness of the magnetic layer closest to the substrate in the lower magnetic layer group. It is also preferable that the thickness of the stabilizing magnetic layer is smaller than the thickness of the lower magnetic layer group in contact with the stabilizing magnetic layer.

The layer thickness of the stabilizing magnetic layer is preferably 2 nanometers or less. The exchange stiffness constant in the recording magnetic layer is preferably larger than 3 pico J / m.

The saturation magnetization of the magnetic layer preferably exceeds 0.85 tesla. Further, as a material composition of the magnetic layer, it is preferable that the Co concentration exceeds 83 at%.

The ratio of the average particle diameter D of the magnetic particles forming the magnetic layer as seen from the upper surface side of the recording film to the thickness t1 of the recording magnetic layer.
It is preferable that (D / t1) is smaller than 0.5.

As the material of the stabilizing magnetic layer and the lower magnetic layer group, an alloy containing Co as a main component and containing at least one element selected from Cr, Ta, and Pt, or O (oxygen) in addition to It is preferable that the alloy contains. In addition, Ru is preferably used as the material of the above-mentioned non-magnetic intermediate layer.

The material of the recording magnetic layer is an alloy containing Co as a main component and containing at least one element selected from Cr, Ta, and Pt, or an alloy containing B (boron) in addition. Is preferred. Further, the lower magnetic layer group is preferably formed on a non-magnetic underlayer, and as the material of the non-magnetic underlayer, Cr, Mo, W, Ta, V, Nb, Ta, Ti, Ge, Si, C
It is preferably a non-magnetic material containing at least one element selected from the group consisting of o and Ni.

The junction layer in which the magnetization directions of the adjacent magnetic layers are substantially parallel to each other is Ru and at least one metal element selected from the group consisting of Nb, Ti, Pd, Pt, Au, Cu, Pt, and Pd. Alloy containing Co or Co as the main component, Fe, Ni, Cr, Ta, Pt, P
d, an alloy containing at least one element selected from Ru, or an alloy containing O (oxygen) in addition to the magnetic substance having a saturation magnetization smaller than that of the adjacent magnetic layer, or having a thickness
Ru from 0.1 nm to 0.4 nm or 1.0 nm to 1.6 nm or I
From an alloy containing at least one metal element selected from the group consisting of r, Rh, Cu, and Re, or Ru and at least one metal element selected from the group consisting of Mo, Re, W, and Cr It is preferable that (Fifth Embodiment) The characteristics of the invention described in the fifth embodiment are the same as those of the fourth embodiment.
The point is a method of manufacturing a magnetic recording medium, which is characterized in that the bonding layer described in 1) is formed by the RF sputtering method. (Embodiment 6) A feature of the invention described in Embodiment 6 is that a magnetic head having a reproducing element having an effective track width of 0.5 .mu.m or less is combined with the magnetic recording medium described in Embodiments 1 to 5 to perform magnetic recording. It is a magnetic storage device characterized by reproducing information. For the recording head, it is particularly preferable that the saturation magnetic flux density of the recording magnetic pole is 1.8 T or more. Further, it is preferable that the ratio of the minimum magnetization transition width formed on the recording medium to the total value of all magnetic layers of the recording medium is smaller than 1.5.

[0078]

EFFECTS OF THE INVENTION It is possible to achieve both heat fluctuation resistance and a high S / N ratio.

[Brief description of drawings]

FIG. 1 is a main view showing an effect of the present invention.

FIG. 2 is a conceptual diagram of a main part of a magnetic recording medium of the present invention.

FIG. 3 is a conceptual diagram of an AFC medium.

FIG. 4 is a conceptual diagram of exchange coupling.

FIG. 5 is a diagram showing a magnetization curve of the magnetic recording medium of the present invention.

FIG. 6 is a diagram showing another magnetization curve of the magnetic recording medium of the present invention.

FIG. 7 is a diagram defining magnetic characteristics of the magnetic recording medium of the present invention.

FIG. 8 is a diagram showing a temperature change of coercive force of each magnetic layer in the magnetic recording medium of the present invention.

FIG. 9 is a main view showing another effect of the present invention.

FIG. 10 is a conceptual diagram of a conventional magnetic disk device.

FIG. 11 is a conceptual diagram of a conventional magnetic head.

FIG. 12 is a conceptual diagram of rearrangement in an AFC medium.

FIG. 13 is a diagram showing a configuration of a magnetic recording medium of the present invention.

FIG. 14 is a diagram showing another configuration of the magnetic recording medium of the present invention.

FIG. 15 is a diagram showing another configuration of the magnetic recording medium of the present invention.

FIG. 16 is a diagram showing another configuration of the magnetic recording medium of the present invention.

FIG. 17 is a diagram showing another effect of the present invention.

FIG. 18 is another diagram showing another effect of the present invention.

FIG. 19 is a diagram showing another effect of the present invention.

FIG. 20 is a diagram defining another magnetic characteristic of the magnetic recording medium of the present invention.

FIG. 21 is a diagram showing another effect of the present invention.

[Explanation of symbols]

11 ... Recording magnetic layer, 12 ... Stabilizing magnetic layer, 13 ... Antiferromagnetic induction junction layer, 14 ... Nonmagnetic underlayer, 15 ... Nonmagnetic substrate, 16 ... Protective film , 17 ... Lubrication layer, 21 ...
Lower magnetic layer group, 22 ... Weak ferromagnetic induction junction layer, 23 ...
Saturation magnetization increasing region, 41 ... Maximum antiferromagnetic coupling energy J1, 42 ... Peak film thickness tpeak, 43 ... Antiferromagnetic coupling antivalue width dt, 51 ... For magnetization reversal of stabilizing magnetic layer Amount of magnetization change accompanying, 52 ... Amount of magnetization change accompanying reversal of magnetization of the recording magnetic layer, 71 ... Coercive force of the recording magnetic layer, 72 ... Minor loop width of the stabilizing magnetic layer, 73 ... Ferromagnetic coupling field,
81 ... Temperature change of coercive force of recording magnetic layer, 83 ... Temperature change of coercive force of stabilizing magnetic layer, 101 ... Recording medium, 102
... Magnetic head, 103 ... Rotary actuator, 104 ... Rotation bearing, 105 ... Arm, 106 ...
・ Suspension, 108 ... Housing, 111 ... Writing section, 112 ... Reproducing section, 113 ... Magnetoresistive element, 1110.
..Non-magnetic substrate, 115 ... Shield layer, 116 ... Spiral coil, 117 ... Magnetic pole, 118 ... Magnetic pole (also serves as shield layer), 119 ... Electrode

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[Procedure amendment]

[Submission date] February 8, 2002 (2002.2.8)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

In the case of having three or more magnetic layers, there is a possibility that the differential value of the magnetization due to the magnetic field has at least three or more peaks. The magnetization variation in the above process corresponding to each peak is dM1, d in descending order from the largest value.
When referred to as M2 and dM3, dM1 corresponds to the magnetization of the recording magnetic layer, and the magnetic field that gives it is in the direction opposite to the direction magnetized first in the magnetization process. Variation of magnetization corresponding to each peak, FIG 20 (b)
It is given by the area of the shaded part surrounded by the geta part (baseline) and the differential curve as shown in FIG. The total amount of change in magnetization corresponding to each peak is approximately 60% to 75% with respect to twice the amount of magnetization when the measurement medium is sufficiently saturated. The change in magnetization below dM2 is the change in magnetization of the stabilizing magnetic layer and the lower magnetic layer group. The completion of the rearrangement can be confirmed by the fact that in the magnetization process, all the peaks corresponding to the magnetization magnetization changes in the layers other than the recording magnetic layer are oriented in the direction in which they are magnetized first (there are peaks).

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

An alloy containing Ru and at least one metal element selected from the group consisting of Mo, Re, W and Cr, or at least one elemental alloy selected from Rh, Pt and Pd In the case of an alloy containing and, other metal elements are well dissolved in Ru and Rh, which is useful for controlling and lowering the binding energy. The antiferromagnetic coupling field of AFC media is
It decreases in inverse proportion to the thickness of the effective stabilizing magnetic layer of the present invention. By providing a region of the recording magnetic layer or the stabilizing magnetic layer which is in contact with the junction layer and has a larger saturation magnetization than other regions in the same magnetic layer, the antiferromagnetic coupling between the recording magnetic layer and the stabilizing magnetic layer is strengthened. Such an enhanced structure ( Japanese Patent Laid-Open No. 2001-56921
The merits of the present invention can be sufficiently brought out by the combined use of ( publication ) and the like. 90% Co or Co for stabilizing magnetic layer
An alloy containing the above may be used. In addition, a large antiferromagnetic coupling magnetic field can be obtained by forming the bonding layer by the RF sputtering method. The antiferromagnetic coupling field obtained by the DC spreader method is 1 / of the RF spreader method.
It is about 3, but twice as large as the MBE method. It is preferable to use a method that can obtain a necessary coupling magnetic field for forming the bonding layer. Also, when there are a plurality of bonding layers having the property of reversing the magnetization of the magnetic layers in contact with each other, the other bonding layers should be connected to each other. By including the elements that are not contained, the production process control becomes easy.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

To estimate the magnetic anisotropy energy Ku of each magnetic layer, a single layer (10 nm) having the composition of each magnetic layer was prepared, and the pulse time dependence of the residual coercive force was measured by VSM measurement or inverse DC demagnetization method. K calculated by fitting and fitting to Sharock's formula
It may be calculated from the β value and the value of Hk using the relational expressions Kβ = Ku * v / (kT) and Hk = 2 * Ku / Ms. In addition, when the magnetic layer is a CoCrPtB magnetic thin film, the atomic composition of Cr is set to the atomic composition of Nc and Pt.
The atomic composition of Np and B is Nb, and the formula Ku = (4.4-0.18 × Nc + 0.15
× Np-0.1 × Nb) × 100000J / m ^ 3 may be simply calculated.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction content]

By using the present invention, the merit of the medium in which the magnetic anisotropy magnetic field of the above-mentioned stabilizing magnetic layer which defines the optimum value of the magnetic anisotropy is made smaller than the magnetic anisotropy magnetic field of the recording magnetic layer. Can be sufficiently drawn to a region where the effective stabilizing magnetic layer thickness (the sum of the product of the saturation magnetization and the film thickness of the stabilizing magnetic layer and the lower magnetic layer group divided by the saturation magnetization of the stabilizing magnetic layer) is large. . This is because when the magnetic anisotropy energy is reduced to promote rearrangement, sufficient heat-resistant demagnetization characteristics of the recording layer cannot be obtained.

Continued front page    (72) Inventor Yoshiyuki Hirayama             1-280, Higashi Koikekubo, Kokubunji, Tokyo             Central Research Laboratory, Hitachi, Ltd. (72) Inventor Tomoo Yamamoto             1-280, Higashi Koikekubo, Kokubunji, Tokyo             Central Research Laboratory, Hitachi, Ltd. (72) Inventor Daishi Toyama             1-280, Higashi Koikekubo, Kokubunji, Tokyo             Central Research Laboratory, Hitachi, Ltd. (72) Inventor Joe Hosoe             1-280, Higashi Koikekubo, Kokubunji, Tokyo             Central Research Laboratory, Hitachi, Ltd. F term (reference) 5D006 BB02 BB05 BB07 BB08

Claims (4)

[Claims] 1. A non-magnetic substance or a weak magnetic substance provided between at least three magnetic layers formed directly or via an underlayer on a disk-shaped substrate and between the three magnetic layers. In a magnetic recording medium having a bonding layer made of, the differential curve of the magnetization due to the magnetic field has at least two peaks in the magnetization curve obtained by applying a magnetic field in the circumferential direction of the substrate, When the amount of change in magnetization corresponding to the peak is set to dM1 or dM2 from the largest change amount,
The sum of dM1 and dM2 is 90% or more, which is twice the saturation magnetization.
A magnetic recording medium having a ratio of dM2 to dM1 of dM2 / dM1 of 0.45 or more. 2. The magnetic recording medium according to claim 1,
The differential peaks corresponding to the magnetization change amounts dM1 and dM2 in the magnetization curve obtained by changing the magnetic field at a rate of 3000 A / m per second are defined as peak 1 and peak 2, respectively. It is a magnetic field in a magnetically saturated direction, and the amount of magnetization in the magnetic field that gives the peak 2 is Mt.
2, the magnetization amount (Mt2 + 0.45
A magnetic recording medium characterized in that a difference ΔH between a magnetic field giving a magnetic field (× dM2) and a magnetic field giving a magnetization amount (Mt2-0.45 × dM2) is not more than 1.5 times the magnitude of the magnetic field of the peak 2. 3. A bond composed of at least three magnetic layers formed directly or through an underlayer on a substrate and a non-magnetic substance or a weak magnetic substance provided between the magnetic layers of three or more layers. A magnetic layer farthest from the non-magnetic substrate is a recording magnetic layer, a magnetic layer next to the recording magnetic layer is a stabilizing magnetic layer, and the recording magnetic layer and the stabilizing magnetic layer are When all other magnetic layers except for the lower magnetic layer group, the magnetization of the recording magnetic layer and the magnetization of the stabilizing magnetic layer are antiparallel to each other, and the anisotropic i-th magnetic layer from the substrate side. The product of the square and ti of Kui and D is k in terms of the kinetic energy Kui (J / m ^ 3), the average particle diameter D of the I-th magnetic layer seen from the top surface, the film thickness ti of the magnetic layer, and the Boltzmann constant k. A magnetic recording medium characterized in that a heat resistance coefficient (√Kui × √D × ti) / k of a magnetic layer defined as a value obtained by dividing is 4000 or less. 4. A bond comprising at least three or more magnetic layers formed on a substrate directly or via an underlayer, and a non-magnetic substance or a weak magnetic substance provided between the three or more magnetic layers. A magnetic layer farthest from the non-magnetic substrate is a recording magnetic layer, a magnetic layer next to the recording magnetic layer is a stabilizing magnetic layer, and the recording magnetic layer and the stabilizing magnetic layer are When all other magnetic layers except for the lower magnetic layer group, the magnetization of the recording magnetic layer and the magnetization of the stabilizing magnetic layer are antiparallel to each other, and the magnetic layers constituting the lower magnetic layer group. The magnetic recording medium is characterized in that the thickness is less than 0.3 times the thickness of the recording magnetic layer.