JP2003178416A - Magnetic recording medium and magnetic recording device - Google Patents

Abstract

(57) Abstract: In a magnetic recording medium, noise from a soft magnetic layer provided between a substrate and a magnetic recording layer is reduced, and a low-noise magnetic recording medium and the magnetic recording medium are used. Obtain a magnetic recording device. A magnetic recording medium having at least a soft magnetic layer and a magnetic recording layer formed on a substrate, wherein the soft magnetic layer has
A magnetic recording medium containing o, Zr and nitrogen, and a magnetic recording device using the magnetic recording medium.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention resides in a magnetic recording medium and a magnetic recording apparatus. Particularly, it is useful for providing a perpendicular magnetic recording medium and a perpendicular magnetic recording device with low noise.

[0002]

2. Description of the Related Art In recent years, the range of application of magnetic recording devices such as magnetic disk devices, floppy (registered trademark) disk devices, magnetic tape devices, etc. has been remarkably increased and the importance thereof is increasing. With respect to the magnetic recording media used, it has been attempted to cope with high recording density. For example, with the increase in recording density of magnetic recording media, use of MR heads and GMR heads as recording / reproducing heads and PRML (Partial Re) as digital signal error correction technology.
Since the introduction of the sponse most like hood technology, the increase in recording density has become more severe, and in recent years, it has continued to increase at a rate of 100% per year.

However, in the so-called "in-plane magnetic recording medium" in which the conventionally used magnetization is parallel to the substrate surface,
As the recording density increases, the repulsion between the adjacent recording magnetic domains occurs, so it is necessary to reduce the thickness of the magnetic recording layer. Due to this thinning and the decrease in recording magnetic domain length and width, the volume per recording magnetic domain in high density recording becomes extremely small. As a result, the thermal direction in the magnetization direction called "thermomagnetic relaxation phenomenon" is generated. Instability increases. Since the instability of magnetization rapidly increases as the recording density is increased, it is expected that the recording density will be limited in the longitudinal magnetic recording medium.

Many studies have been made to solve this problem, one of which is a perpendicular magnetic recording medium. The perpendicular magnetic recording medium is characterized in that the magnetization is oriented in the direction perpendicular to the substrate surface, and when high density recording is performed, adjacent magnetic domains do not repel each other, so higher density recording than in-plane magnetic recording media is possible. It is said to be suitable for.

[0005]

In the perpendicular magnetic recording medium, a soft magnetic layer is usually provided as a backing layer between the substrate and the magnetic recording layer. The purpose of this soft magnetic layer is to effectively concentrate the recording magnetic flux from the recording portion of the head in the recording layer direction during recording. Particularly in the case of a single-pole head, the soft magnetic layer plays the role of the opposing magnetic pole, and thus recording becomes difficult without the soft magnetic layer.

Here, the soft magnetic layer is a soft magnetic material generally defined in the field of magnetic materials, that is, a ferromagnetic material, a ferrimagnetic material, etc. (when an external magnetic field is applied, spontaneous magnetization is generated in the same direction as the external magnetic field). It has a coercive force of zero or relatively small among the magnetic materials it has, and is formed into a thin film. During reproduction, the magnetic flux generated from the magnetic recording medium is detected by a head similar to in-plane magnetic recording, for example, a GMR head.
When the soft magnetic layer is provided, the internal demagnetizing field is canceled out in a long recording magnetic domain, and there is an effect that the reproduced waveform becomes a good square shape.

FeNi, FeAlS are conventionally used for the soft magnetic layer.
i, CoZrTa, CoZrNb, and the like are used and required characteristics are high magnetic permeability, high magnetization, and low reproduction signal noise. However, in general, there is a problem that the noise when reproducing is increased in the soft magnetic layer having high magnetization. There are various causes of noise generation, such as roughening of the surface of the soft magnetic layer, and one of them is generation of perpendicular magnetic anisotropy in the soft magnetic layer. When the perpendicular magnetic anisotropy occurs, a so-called "striped magnetic domain" is formed in the soft magnetic layer, and the magnetization direction undulates to generate noise during reproduction. The perpendicular magnetic anisotropy in the soft magnetic layer tends to occur when the film thickness is large, but since the soft magnetic layer used for perpendicular magnetic recording is generally as thick as 200 nm or more, this perpendicular magnetic anisotropy is large. It's a problem.

In order to prevent the occurrence of perpendicular magnetic anisotropy associated with the increase in film thickness, a method has also been proposed in which the soft magnetic layer is divided in the film thickness direction by a nonmagnetic layer or the like to reduce the thickness of each layer. However, this method has a drawback that the number of layers required is significantly increased and the process becomes complicated. For example, when a 400 nm soft magnetic layer is divided into 100 nm layers, four soft magnetic layers and three nonmagnetic layers sandwiched in between are required for a total of seven layers. In a normal mass-production film forming machine that forms one layer in one chamber, 7 chambers are required only for the soft magnetic layer,
It is very costly.

The cause of the perpendicular magnetic anisotropy in the thick soft magnetic layer has not been completely clarified, but the following is presumed. As the thickness of the soft magnetic layer becomes thicker, the domain wall therein shifts from the Neel domain wall to the Bloch domain wall as the demagnetizing field decreases. In the Bloch domain wall, the magnetization passes through a direction perpendicular to the film surface and rotates, so that a perpendicular component of the magnetization is generated. It is presumed that this perpendicular component affects the soft magnetic layer deposited on the perpendicular magnetic component to generate perpendicular magnetic anisotropy.

[0010]

The present invention suppresses the occurrence of magnetic anisotropy by containing nitrogen in the soft magnetic layer when forming a specific soft magnetic layer, and thus soft magnetic layer with low noise is obtained. It realizes the layers. That is, the gist of the present invention is a magnetic recording medium having at least a soft magnetic layer and a magnetic recording layer formed on a substrate, wherein the soft magnetic layer contains Co, Zr and nitrogen. And a magnetic recording device.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The reason why perpendicular magnetic anisotropy occurs and noise increases is that the domain wall shifts from the Neel domain wall to the Bloch domain wall as the film becomes thicker as described above. Conceivable. As a result of diligent studies, the present inventors have found that by incorporating nitrogen into the soft magnetic layer made of Co and Zr, the Neel domain wall can be maintained even in a thick soft magnetic layer and the occurrence of perpendicular magnetic anisotropy can be suppressed. It was

The reason for this is not completely clear, but it can be explained as follows. Whether the Neel domain wall or the Bloch domain wall is formed is determined by the balance between the demagnetizing field and the exchange coupling energy. The Bloch domain wall has a large demagnetizing field and a small exchange coupling energy. As the film thickness increases and the demagnetizing field decreases, the Bloch domain wall becomes dominant in a region thicker than a certain film thickness. On the other hand, the Neel domain wall becomes dominant in the region thinner than that. By introducing nitrogen into the soft magnetic layer, the exchange coupling force between particles in the soft magnetic layer decreases. Therefore, the Neel domain wall is stabilized and the film thickness transferred to the Bloch domain wall can be shifted to a thicker side.

The above-described method of dividing the soft magnetic layer is a method of increasing the film thickness of the soft magnetic layer by keeping the demagnetizing field large. However, in the present invention, the demagnetizing field is not increased, but
By making the exchange coupling energy small, the Bloch domain wall is prevented from being formed even in a region where the soft magnetic layer is thick. The soft magnetic layer used here is composed of Co, Zr and nitrogen, and is generally preferably amorphous. Further, the soft magnetic layer is preferably made of Co, Zr, M and nitrogen. Here, M is Nb, Ta,
One or more elements selected from Y, Ti, and Hf are preferable for achieving low noise. More preferably, M is one or more elements selected from Nb and Ta.

In order for the soft magnetic layer to have a small magnetic anisotropy and become amorphous, it is preferable that the composition of Co, Zr and M in the soft magnetic layer have the relationship represented by the following formula. C
_{o (100-xy) Zr x} M y, (3 ≦ x ≦ 10,3 ≦ y ≦ 12) the nitrogen content of the soft magnetic layer is 0 for all compositions in the soft magnetic layer.
It is preferably 5 atomic% or more. More preferably, it is 1 atomic% or more. If the amount of nitrogen in the soft magnetic layer is too small, the effect of suppressing the perpendicular magnetic anisotropy of the soft magnetic layer may be reduced. The amount of nitrogen in the soft magnetic layer is preferably 6 atom% or less with respect to the total composition in the soft magnetic layer. More preferably, it is 5 atomic% or less. If the amount of nitrogen is too large, the magnetic properties of the soft magnetic layer may deteriorate.

In general, when nitrogen is contained in the crystalline soft magnetic layer, the magnetic characteristics of the soft magnetic layer may be deteriorated or varied due to changes in the crystal shape of the soft magnetic layer. However, alloys composed of Co and Zr are usually amorphous in many cases, and not only can exhibit very low noise characteristics when used for magnetic recording media, but also contain crystalline soft magnetic properties even when nitrogen is contained. Unlike the layer, it is characterized in that deterioration or variation in magnetic characteristics rarely occurs.

Further, the soft magnetic layer contains an element other than the above elements,
For example, B, Mn, Cu, Ag, Pt, Pd, etc. may be contained. As the method for producing the soft magnetic layer, a sputtering method, a vacuum deposition method, an electrolytic plating method, or the like can be used, but the sputtering method is preferable because the film quality is fine and good. Examples of the method of containing nitrogen in the soft magnetic layer include reactive sputtering in which an inert gas such as argon gas is mixed with nitrogen gas, or a method in which the sputtering target itself contains nitrogen in advance.
It is preferable to use reactive sputtering because the nitrogen amount is easily controlled and the nitrogen amount is stable over time.

The coercive force of the soft magnetic layer is ideally zero, but in reality it may exhibit some coercive force. However, in order to improve the response of the soft magnetic layer to an external magnetic field, it is preferably 10 Oe or less, more preferably 6 Oe or less. In order for the soft magnetic layer to sufficiently converge the recording magnetic field, it is preferable that the soft magnetic layer is thick to some extent. The thickness of the soft magnetic layer is preferably 50 nm or more. The thickness is more preferably 80 nm or more, and particularly preferably 100 nm or more. The thickness of the soft magnetic layer is preferably 600 nm or less, more preferably 500 nm or less. If the film thickness of the soft magnetic layer is too large, the surface of the soft magnetic layer may be roughened, which may cause a problem of the floating characteristics of the magnetic head, or the productivity during film formation of the soft magnetic layer may be deteriorated.

The larger the saturation magnetic flux density Bs of the soft magnetic layer, the higher the efficiency of the recording magnetic field.
(Tesla) or more, more preferably 1 T or more, and particularly preferably 1.2 T or more. Generally, the higher the magnetization (or the magnetic flux density), the higher the noise tends to be in the soft magnetic layer, which can be explained by the reason described above. Therefore, the noise reduction effect according to the present invention becomes remarkable by using the soft magnetic layer having higher magnetization. However, if Bs is too high, it may not be possible to reduce the noise. Therefore, Bs of the soft magnetic layer is preferably 2T or less. More preferably, it is 1.8 T or less.

The soft magnetic layer according to the present invention is preferably used as a backing layer of a perpendicular magnetic recording medium as described above. At this time, a magnetic recording layer having perpendicular magnetic anisotropy is used. For example, an alloy containing Co as a main component, such as CoCr to which Pt, B, Ta or the like is added, can be given. Or Pd or Pt and Co or F
A multilayer film in which e is stacked for about 10 to 50 cycles at a cycle of about 0.1 to 0.5 nm, or PtFe alloy, TbFeC
Examples thereof include alloys of rare earths such as o and transition metals. Also,
These different types of magnetic recording layers may be laminated.

The thickness of the magnetic recording layer is preferably 50 nm or less, more preferably 40 nm, further preferably 35 n.
m or less. If the thickness of the magnetic recording layer is too large, the magnetic coupling between the recording magnetic field and the soft magnetic layer may be insufficient, and the recording magnetic field may not be sufficiently converged on the soft magnetic layer. Also,
The thickness of the magnetic recording layer is preferably 10 nm or more, more preferably 12 nm or more, still more preferably 15 nm or more. If the film thickness of the magnetic recording layer is too thin, the signal may be reduced or the perpendicular magnetic anisotropy may be reduced.

An intermediate layer is preferably provided between the soft magnetic layer and the magnetic recording layer. The purpose of the intermediate layer depends on its type, but it improves perpendicular magnetic anisotropy of the magnetic recording layer by blocking exchange coupling between the soft magnetic layer and the magnetic recording layer, and crystal growth of the crystalline magnetic recording layer. And the crystal orientation of the magnetic recording layer.

When a CoCr alloy is used as the magnetic recording layer, by providing Ti as the intermediate layer, the C axis is oriented in the direction perpendicular to the substrate, and the growth is facilitated. In addition, non-magnetic Co is used as an intermediate layer.
Providing Cr is also preferable from the viewpoint of crystal growth. It is also possible to use CoRu, CoCrRu, or the like for the same purpose. For the purpose of reducing the crystal grain size, carbon, S
i, SiO ₂ or the like may be used. You may use the some intermediate | middle layer which combined these. If the thickness of the intermediate layer is too thin, the role as the intermediate layer described above may be insufficient, while if it is too thick, the distance between the recording portion of the head and the soft magnetic layer may be too large. Therefore, it is preferably 1 nm or more and 20 nm or less.

The distance between the head recording portion and the surface of the soft magnetic layer is preferably 80 nm or less, more preferably 60 nm or less. The substrate in the magnetic recording medium of the present invention is, for example, Al-Mg containing Al as a main component.
Any material such as an Al alloy substrate such as an alloy, a normal soda glass, an aluminosilicate glass, a crystallized glass, a substrate made of silicon, titanium, ceramics, or various resins can be used. Above all, it is preferable to use a glass substrate such as an Al alloy substrate or crystallized glass.

In the manufacturing process of the magnetic recording medium, a conventionally known method may be appropriately used. Generally, the substrate is usually washed and dried first, and from the viewpoint of ensuring the adhesiveness of each layer in the present invention, it is desirable that the substrate be washed and dried before its formation. In manufacturing the magnetic recording medium of the present invention, it may be preferable to form a metal coating layer such as NiP on the surface of the substrate. In the case of a substrate made of a conductive material, electrolytic plating can be used.

In the present invention, when the DC bias sputtering method is used for film formation, it cannot be used as it is for a non-conductive substrate such as a glass substrate. In this case, it is preferable to provide a conductive layer made of metal or the like on the substrate in advance and apply a bias voltage to the conductive layer. Examples of conductive layers include Ti, Ta, Cr, Ni
Examples thereof include Al. In this way, a glass substrate provided with a conductive layer may be regarded as a substrate.

Further, in order to improve the flying characteristics of the head, it is preferable that the substrate surface or the substrate surface on which the metal coating layer is formed is concentrically textured. In the present invention, the concentric circular texturing is, for example, mechanical texturing using free abrasive grains and a texture tape, texturing using a laser beam, or the like, or by using them in combination, by polishing in the circumferential direction. The state in which a large number of minute grooves are formed in the circumferential direction of the substrate is referred to.

The surface of the substrate has basically no effect on the effect of the present invention regardless of the surface roughness (Ra), but the head flying height is as small as possible to realize high density magnetic recording. Is effective, and since one of the characteristics of these substrates is excellent surface smoothness, Ra on the substrate surface is preferably 1 nm or less, more preferably 0.5 nm or less, and especially 0.3 nm or less. Preferably there is. However, here, Ra is assumed to be measured using a stylus type surface roughness meter. At this time, the tip of the measuring needle has a radius of about 0.2 μm.

Generally, an optional protective layer is formed on the magnetic recording layer, and then a lubricating layer is formed. As the protective layer, carbonaceous layers such as carbon (C), hydrogenated C, nitrogenated C, amorphous C and SiC, SiO ₂ , Zr ₂ O ₃ and TiN are used.
A commonly used protective layer material can be used.
Further, the protective layer may be composed of two or more layers. The layer thickness of the protective layer is 1 to 50 nm, particularly 1 to 10 nm, and it is preferable to set it as thin as possible within a range where durability can be secured. Examples of the lubricant used in the lubricating layer include a fluorine-based lubricant, a hydrocarbon-based lubricant and a mixture thereof, and the like, usually 0.1 to 5 nm, preferably 1
A lubricating layer is formed with a layer thickness of ˜3 nm.

The film forming method for forming the magnetic recording layer is arbitrary, but for example, direct current (magnetron) sputtering method, high frequency (magnetron) sputtering method, EC
Physical vapor deposition methods such as R (electron cyclotron resonance) sputtering method and vacuum vapor deposition method can be used. It is particularly preferable to use the sputtering method because the magnetic recording layer has high adhesion and strength and good head flying characteristics.

In the sputtering film formation, it is usually preferable that the ultimate vacuum is 2 × 10 ⁻⁵ Pa or less and the sputtering gas pressure is 0.1 to 2 Pa. When the magnetic recording layer is a CoCr alloy, when the magnetic recording layer is formed, the substrate is generally 100 to 400 ° C. in order to promote crystal growth of the magnetic recording layer and promote Cr segregation of the magnetic recording layer. It is preferable to heat to some extent.

The magnetic recording apparatus of the present invention includes at least the above-described magnetic recording medium, a drive unit for driving the magnetic recording medium in the recording direction, a magnetic head including a recording unit and a reproducing unit, and a magnetic head for the magnetic recording medium. And a recording signal processing means for inputting a recording signal of the magnetic head and outputting a reproduction signal from the magnetic head.

A magnetic recording device having a high recording density can be realized by forming the reproducing portion of the above magnetic head by an MR head. Further, the recording portion may be a ring head which has been used in the conventional longitudinal magnetic recording, or a single magnetic pole head (SPT head) having only a single magnetic pole, but it is sharp when combined with a soft magnetic layer. It is preferable to use an SPT head that can obtain a magnetic field distribution. This magnetic head is 0.01 μm or more, 0.03 μm
A high S / N ratio can be obtained by levitating the magnetic recording medium to less than about 100 μm, and a magnetic recording device having a large capacity and high reliability can be provided. In addition, PRML (Partial Response)
The recording density can be further improved by combining a signal processing circuit according to SE Most Likehood), for example, a track density of 90 kFTPI or more and a linear recording density of 7
S / N sufficient for recording / reproducing at a recording density of at least 00 kFTPI and at least 60 Gbits per square inch
The ratio and thermal stability of the recording are obtained.

[0033]

EXAMPLES The present invention will be described more concretely with reference to the following examples. However, as long as the present invention does not exceed its gist,
The present invention is not limited to the following examples. (Experimental Examples 1 to 12) A vacuum chamber in which an aluminum substrate for a hard disk was set was previously set to 1.0 × 10 ^−5.
It was evacuated to Pa or less. Aluminum substrate has N on the surface
An iP-plated product was used. The substrate is Ra
The diameter was about 0.5 nm, the outer diameter was 65 mm, and the inner diameter was 20 mm.

On the substrate (Co86Zr8Nb6) _100-a N
_a (a is atomic% of nitrogen in the soft magnetic layer) or (Co86
Zr8Ta6) _100-a N _a soft magnetic layer (film thickness 200 n
m) was formed into a film by a reactive sputtering method using a mixed gas of argon gas and nitrogen gas. The argon gas pressure was set to about 7.0 × 10 ⁻¹ Pa, and the substrate temperature was room temperature. Several kinds of soft magnetic layers having different nitrogen contents (a) in the soft magnetic layer were prepared by changing the mixing ratio of argon gas and nitrogen gas. Amount of nitrogen in soft magnetic layer (a)
Was measured by Auger electron spectroscopy.

On the soft magnetic layer produced as described above, a carbon protective layer (film thickness 5 nm) was formed by a DC (direct current) sputtering method using argon gas. The argon gas partial pressure during film formation was set to about 7.0 × 10 ⁻¹ Pa and the substrate temperature was set to 350 ° C. A fluorine-based lubricant (Fomblin Z-Dol) is formed on the carbon protective layer.
2000: manufactured by Ausimont Co., Ltd.).

The coercive force of each soft magnetic layer was 5 Oe or less. The noise characteristics of the produced laminated body (those having a soft magnetic layer, a carbon protective layer and a lubricating layer formed on a substrate)
It evaluated as follows using the spin stand. A GMR head manufactured by Alps Electric Co., Ltd. was used as a head, and the laminated body was rotated at a rotation speed of 4,200 rpm to measure noise characteristics. The noise spectrum was taken from 1 to 100 MHz. Then, the integrated intensity of the noise spectrum was frequency averaged, and the rms value (root mean square value) was taken to obtain the noise. Tables 1 and 2 collectively show the composition, nitrogen content (a) and noise of the soft magnetic layer in each experimental example.

[0037]

[Table 1] Soft magnetic layer composition: (Co86Zr8Nb6) _100-a N _a

[0038]

[Table 2] Soft magnetic layer composition: (Co86Zr8Ta6) _100-a N _{a In} FIG. 1, the nitrogen content (a) in the soft magnetic layer is 0 atom% (Experimental Example 1) and 1.6 atom% (Experimental Example 4). The noise spectrum of 2 shows the relationship between the amount of nitrogen (a) in the soft magnetic layer and noise in Experimental Examples 1 to 12. It was prepared a laminate having a (Experimental Examples 13 and 14) the composition in the same manner as in Experimental Example 1 (Co86Zr8Nb6) soft magnetic layer made of _100-a N a (film thickness 400 nm).

Two kinds of nitrogen (a) in the soft magnetic layer were prepared, 0 atomic% (Experimental Example 13) and 1.6 atomic% (Experimental Example 14). M of VSM (vibrating magnetometer)
3 (Experimental Example 13) and FIG. 4 (Experimental Example 1) show the results of measurement of the −H loop (a loop showing the relationship between the external magnetic field H and the magnetization M of the laminated body when the external magnetic field H is applied to the laminated body).
4). When the nitrogen content (a) in the soft magnetic layer is 0 atom% (Experimental Example 13), a loop having a typical striped domain structure originating from perpendicular magnetic anisotropy is shown. The nitrogen content (a) of 1.6 atomic% (Experimental Example 14) shows an MH loop that does not exhibit perpendicular magnetic anisotropy. (Example 1 and Comparative Example 1) By the same method as in Experimental Example 1, _a soft magnetic layer (film thickness 200 nm) composed of (Co84Zr8Nb6) _100- aNa was formed. Two types were prepared in which the nitrogen content (a) in the soft magnetic layer was 0 atom% (Comparative Example 1) and 1.6 atom% (Example 1).

On the soft magnetic layer, a first intermediate layer made of Ti (film thickness 10 nm), a second intermediate layer made of Co63Cr37 (film thickness 5 nm), a magnetic recording layer made of Co66Cr19Pt12B3 (film thickness 20 nm), carbon protection. Layer (film thickness 5n
m) were sequentially laminated using a DC (direct current) sputtering method. The argon gas pressure at this time is about 7.0 × 10 ^-1 P
a, the substrate temperature was 350 ° C.

Fluorine-based lubricant (F
mblin Z-Dol 2000: manufactured by Ausimont Co., Ltd.) was formed as a lubricant layer to prepare a magnetic recording medium. At this time, the coercive force of the magnetic recording medium was 3300 Oe and the squareness ratio was 0.78, and no difference was observed depending on the amount of nitrogen (a) in the soft magnetic layer. The S / N ratio of the manufactured magnetic recording medium was measured by using a spin stand and a GMR head, rotating the magnetic recording medium at a rotation speed of 4200 rpm, and the head position at a radial position of 22.55 mm of the magnetic recording medium by the following method. It was measured.

Recording frequency 83.83 MHz, recording current 4
The noise voltage was obtained by frequency averaging the integrated intensity of 1 to 100 MHz of the noise spectrum obtained when the signal was recorded at 0 mA. The rms value (root mean square value) of this noise voltage was used as the noise output. Next recording frequency 15.72M
The signal was recorded at Hz and a recording current of 40 mA. The recording signal was obtained by converting the voltage at the recording frequency (15.72 MHz) of the reproduced signal obtained at this time into power.

The S / N ratio was obtained by dividing the recording signal output obtained as described above by the noise output. As a result, the S / N ratio of the magnetic recording medium (Comparative Example 1) in which the amount of nitrogen (a) in the soft magnetic layer was 0 atom% was 17.2 dB, and the amount of nitrogen (a) in the soft magnetic layer was 1.6. The S / N ratio of the magnetic recording medium of atomic% (Example 1) was 19.8 dB.

[0044]

As is clear from the above results, by using a soft magnetic layer containing Co, Zr and nitrogen as the soft magnetic layer, a low noise magnetic recording medium can be obtained and a high S / N ratio can be obtained.
It is possible to achieve a ratio. Therefore, the magnetic recording apparatus using the magnetic recording medium of the present invention can perform excellent recording / reproduction with low noise and high S / N ratio.

[Brief description of drawings]

FIG. 1 is a diagram showing a noise spectrum in Experimental Examples 1 and 2.

FIG. 2 is a diagram showing the relationship between the amount of nitrogen in the soft magnetic layer and noise in Experimental Examples 1 to 12.

FIG. 3 is a diagram showing an MH loop of a soft magnetic layer in Experimental Example 13.

FIG. 4 is a diagram showing an MH loop of a soft magnetic layer in Experimental Example 14.

Claims (7)

[Claims] 1. A magnetic recording medium in which at least a soft magnetic layer and a magnetic recording layer are formed on a substrate, wherein the soft magnetic layer contains Co, Zr and nitrogen. 2. The soft magnetic layer comprises Co, Zr, M (M is Nb, T
The magnetic recording medium according to claim 1, which contains one or more elements selected from a) and nitrogen. Wherein the soft magnetic layer is _{Co (100-xy) Zr x} M y (3 ≦
The magnetic recording medium according to claim 2, wherein the magnetic recording medium has a composition represented by x ≦ 10, 3 ≦ y ≦ 12) and contains nitrogen. 4. The magnetic recording medium according to claim 1, wherein the soft magnetic layer has a coercive force of 10 Oe or less. 5. The amount of nitrogen in the soft magnetic layer is 0.5 atomic% or more,
The magnetic recording medium according to claim 1, which is 6 atomic% or less. 6. The magnetic recording medium according to claim 1, wherein the magnetic recording layer is a perpendicular magnetization film. 7. A magnetic recording medium according to claim 1, a drive section for driving the magnetic recording medium in the recording direction, a magnetic head comprising a recording section and a reproducing section, and a magnetic recording for the magnetic head. A magnetic recording apparatus comprising: a means for relatively moving the medium, and a recording signal processing means for inputting a recording signal of a magnetic head and outputting a reproduction signal from the magnetic head.