JPH0670924B2 - Perpendicular magnetic recording medium - Google Patents

Description

The present invention relates to a magnetic recording medium (particularly a magneto-optical recording medium) used in a perpendicular magnetic recording system.

[Prior Art and Problems to be Solved by the Invention] Conventionally, a polycrystalline metal thin film such as MnBi, MnCuBi, or CoCr as a ferromagnetic thin film having an easy axis of magnetization in a direction perpendicular to the thin film surface,
Compound single crystal thin film represented by GIG, Gd-Co, Gd-Fe, Tb-F
Rare earth transition metal amorphous thin films such as e and Dy-Fe are known.

The present invention relates to a rare-earth transition metal fine crystalline alloy thin film other than the above.

Generally, an amorphous film is advantageous as a magneto-optical recording material because it has features such as the absence of crystal grain boundaries that cause noise, unlike a polycrystalline thin film, and that a wide film can be easily manufactured. It has been.

In order to use the rare earth-transition metal amorphous alloy as a magneto-optical recording medium, it is required that the easy magnetization direction be perpendicular to the film surface. Perpendicular magnetic anisotropy cannot be induced in any case, but rather tends to be oriented in a direction parallel to the film surface due to the generation of a demagnetizing field of the magnetic thin film. In order to obtain a perpendicularly magnetized film, it is necessary to give anisotropic energy sufficient to overcome the energy of this demagnetizing field.

The degree of perpendicular magnetic anisotropy of the obtained thin film can be expressed by the magnitude of the uniaxial anisotropy constant Ku, and in order to form a perpendicular magnetization film, this Ku and demagnetizing field energy 2πMs ² (Ms is saturation magnetization) It is said that the relation of Ku> 2πMs ² must be satisfied during.

Perpendicular magnetic recording media generally require high recording density,
Ms is large in order to keep the small magnetic domains stable,
And it is very important to obtain a sufficiently large Ku. In addition, in the magneto-optical disk, laser light is used as the writing power.
It has a Curie temperature Tc that is sufficiently low and a crystallization temperature Tcry that is sufficiently higher than that, and at least this temperature difference is required to be 50 ° C., preferably 100 ° C. or higher.

The rare earth-transition metal combination best known as a perpendicular magnetization film is heavy rare earth element and iron. Representative
Examples include TbFe, GdFe, DyFe, GdTbFe, TbDyFe. For example
TbFe has a Curie temperature Tc of 140 to 250 ° C and a car rotation angle of about θ _K
It has characteristics such as 0.3 °, saturation magnetization Ms = 50 to 100 emu / cc, and perpendicular magnetic anisotropy constant Ku = 10 ⁵ to 10 ⁶ erg / cc.

However, the heavy rare earth elements such as Tb, Dy, and Gd used for these are rare resources because they are scarcely present in the crust, and require a complicated separation process, which is very expensive.

Further, since the atomic magnetic moments of heavy rare earth elements and iron are coupled antiparallel to each other, it is difficult to produce a large number of homogeneous products because the composition dependence of the saturation magnetization Ms and the Curie temperature Tc is large.

On the other hand, light rare earth elements such as Nb and Pr are much more abundant in the crust than heavy rare earth elements. Such rare earth-
If the iron perpendicular magnetization film can be formed using light rare earth elements such as Nb and Pr, the resource problem will be eliminated.

Until now, studies on amorphous alloys of light rare earths and iron have been conducted, for example, in JJ.
Croat made ribbon alloys with a composition near Fe _0.60 Nd _0.40 and Fe _0.60 Pr _0.40 by the liquid quenching method, and discussed the possibility as a permanent magnet because of the high coercive force (Ap
pl.Phys.Lett.39 (4) .15.August.1981). However, the ribbon obtained by such a method cannot obtain a homogeneous ribbon throughout the alloy, but only a substantially isotropic ribbon. The ribbon has a thickness of 33 to 208 μm and is not used as a recording medium.

Recently, K. Tsutsumi et al. Reported that a sputtered thin film of Fe _61.5 -Nd ₃₄ -Ti _4.5 has perpendicular magnetic anisotropy (Jpn.J.Appl.Phys.23 (1984), L169- L171). However, the characteristics were Ms = 430 emu / cc and Ku = 2 × 10 ⁶ erg / cc. Although the manufacturing conditions of the FeNd sputtered thin film containing no Ti are not clear, only those with in-plane anisotropy have been reported.

Amorphous thin films of light rare earth elements and iron have a high saturation magnetization, and therefore it has been almost impossible to impart perpendicular magnetic anisotropy energy to overcome the action due to the demagnetizing field of the thin film.

(Object) The basic object of the present invention is to provide a novel perpendicular magnetic recording medium (particularly a magneto-optical recording medium) centered on light rare earth and iron. Another object of the present invention is to provide a perpendicular magnetic recording medium having excellent characteristics as compared with the above conventional method.

[Means for Solving the Problems] (Outline) That is, the present invention provides a completely new magnetic recording medium mainly containing light rare earth and iron. The magnetic recording medium of the present invention is iron and rare earth elements, or these and Co, mainly, Nd as a rare earth element, using a light rare earth element mainly Pr, a few Å ~ several 100 Å fine crystalline phase in the thin film. It is a perpendicular magnetization thin film including.

A first aspect of the present invention provides a perpendicular magnetic recording medium as (claim 1) having the following features.

That is, 25 to 60 atomic% of a rare earth element R (provided that 70 atomic% or more of R is one or two of Nd and Rr, and the balance of R is Y, La, Ce, Sm, Gd, Tb, Dy. , Ho, Er, and Yb) and the balance Fe, and the thin film amorphous matrix contains at least a few Å to several hundred Å fine crystalline phase, and the perpendicular magnetic anisotropy constant Ku is demagnetizing field energy 2πMs. ² (Ms
Has a larger perpendicular magnetic anisotropy than the saturation magnetization), and the temperature difference Tcry between the crystallization temperature Tcry and the Curie temperature Tc.
-Tc is 100 ° C or higher.

As a second invention of the present application (claim 2), the Fe
A perpendicular recording medium is provided in which less than 30 atomic% (relative to the total composition) is replaced with Co (that is, Co is less than 30 atomic% in the total composition).

Further, as another invention of the present application (claim 3), when Co is not contained, other elements other than the predetermined amount M 10 atomic% or less (where M is Ni, V, Ta, Cr, Mo, W, Mn, Bi, Al, Si, Pb, Sn and Sb
Or more), and when Co is further included (claim 4), Zr can also be included as M.

The above is represented by the formula R (Fe, Co) M, where R25 to 60 atom%,
It has a composition of 0 to 10 atomic% M, less than 30 atomic% Co, and the balance Fe.

The perpendicular magnetic recording medium according to each invention of the present application, in the formation of a thin film on the substrate by the metal gas agglomeration method, the thin film having the perpendicular magnetic anisotropy having the above composition at a substrate temperature of 180 ℃ ~
While keeping the temperature below the crystallization temperature of the alloy,
It can be manufactured by forming a thin film having a perpendicular magnetic anisotropy of 0.3 to 3 μm.

(Summary of Actions and Effects) The present inventors have studied in detail the conditions for producing a fine crystalline thin film from the above-mentioned circumstances. As a result, resources are plentiful and inexpensive
Using light rare earth elements such as Nd and Pr and iron, the magnetic anisotropy constant Ku is larger than the magnetic field energy 2πMs ² , and a stable and sufficiently perpendicular magnetization film can be obtained. The value of the demagnetizing field energy changes depending on the state of the fine crystals generated by setting the manufacturing conditions. In an embodiment of the present invention, the Curie temperature Tc = 70-
250 ° C, saturation magnetization Ms about 450 emu / cc or more, and the value of the perpendicular magnetic anisotropy constant Ku is, for example, 1.5 × 10 ⁶ erg / cc depending on the condition setting.
More than 2.5 to 7 × 10 ⁶ erg / cc, car rotation angle θ _K
A perpendicular magnetization film having a characteristic of about 0.3 ° or more, that is, a characteristic equal to or higher than the above-mentioned heavy rare earth-iron amorphous thin film was obtained.

As described above, it is necessary that the relation of Ku> 2πMs ² is established in order to form the perpendicular magnetization film. However, it has been clarified by the present invention that the magnetic domains are divided into small regions, in which case the demagnetizing field is smaller than the apparent one, and a perpendicular magnetization film is obtained even if the above conditions are not always satisfied (generally, Ku ≧ 0.6. In the present invention, the value of × 2πMs ² ) is limited to a range where Ku> diamagnetic field energy 2πMs ^{2 and} a sufficiently stable perpendicular magnetization film is obtained.

Whether or not the film is a perpendicular magnetization film can be known by measuring the magnetization curves in the direction parallel to the film () and the direction perpendicular to the film (⊥) as shown in FIG.

In the present invention, the combination of Nd or Pr and iron is a heavy rare earth element when the magnetic moments of the respective atoms are combined in parallel.
The saturation magnetization higher than that of iron is obtained, and the reading accuracy of recording is improved. In the case of performing thermomagnetic writing, high saturation magnetization and leakage magnetic flux can be used, and the magnetic field that must be applied from the outside may be small. Further, substituting a part of Fe with Co raises the Curie temperature Tc and further increases the Kerr rotation angle θ _K , and θ _{K of} about 0.5 ° or more is obtained,
Improves corrosion resistance.

(Preferred Embodiment) As the rare earth element R used in the present invention, 70% or more of R is
Nd and Pr are used, and Nd is particularly desirable. The balance of R may be one containing other rare earth elements such as Ce, Y, Sm, Dy, Tb, Ho, Gd, La, Er and Yb due to availability.

When R is contained in an amount of 25 atomic% or more in the total composition, it becomes a perpendicularly magnetized film having a temperature difference of Tcry-Tc of about 100 ° C. or more (FIG. 2) and shows sufficient stability for writing by a laser. Also R2
At 5 atomic% or more, if the manufacturing conditions are taken into consideration, Ku easily becomes larger than the demagnetizing field energy of 2πMs ² and a sufficiently stable perpendicular magnetization film is formed.

When R is 31 atomic% (at%) or more of the total composition, the magnetic anisotropy constant Ku perpendicular to the thin film surface is 2.5 × 10 ⁶ erg / cc or more, which is a preferable range.

When R is 60 at% or more, the activity contains a large amount of rare earth elements and the stability after thin film formation is poor. Therefore, the range of R is 25 to 60 atomic% (preferably 31 to 60 atomic%). R is 33 to 55 at
% Is a more preferable range of Ku = 3 × 10 ⁶ erg / cc or more, and particularly preferably 35 to 45 at% (see FIG. 8).

Fig. 2 shows composition of saturation magnetization Ms and Curie temperature Tc (Nd amount)
It is a diagram showing the dependence, but the change rate of saturation magnetization Ms and Curie temperature Tc is small over a wide composition (Nd amount) range, and a product with much more stable quality can be easily produced compared to the case of heavy rare earth element iron. You can see how you can do it. Also, it can be seen that the crystallization temperature Tcry also changes monotonically.

The balance of R is mainly iron, but Fe is less than 30% of the total composition Co
Substitution with is effective in improving the saturation magnetization Ms, the Curie temperature Tc, the Kerr rotation angle, and the corrosion resistance of the thin film without impairing the characteristics of the magneto-optical recording medium or the perpendicular magnetization film. Replacing Co by 50% or more of Fe means crystallization temperature Tc
The difference between ry and the Curie temperature Tc becomes smaller, and the Kerr rotation angle also becomes smaller. Furthermore, since the target becomes brittle and manufacturing becomes difficult, the upper limit of Co is less than 30 atom% in the total composition. The amount of Co substitution with respect to total Fe is preferably about 8 to less than 30 atomic% (θ _K 0.45 ° or more), and most preferably about 12 to 27 atomic% (θ _K 0.5 ° or more).

Element M less than 10 at% of the total composition, that is, Ni, V, Ta, Cr, Mo,
Addition of W, Mn, Bi, Al, Pb, Sn, Sb, etc. does not impair the characteristics as a perpendicular magnetization film. When the predetermined amount of Co is contained, further addition of Zr does not impair the characteristics.

Further, the composition of the present invention has a Ti content of less than 10 at% of the total composition.
Can be included, and according to the method of the present invention, Ku3 × 1
0 ⁶ erg / cc can be obtained.

Further, since the thin film according to the present invention has a high saturation magnetization Ms, the perpendicular magnetic anisotropy constant is 1.5 × 10 ⁶ erg / cc under the conditions shown in the examples.
In some cases it may be larger (Figs. 6 and 7). Generally, the substrate material forming the substrate for forming the amorphous film is usually glass, Al, a polyimide resin material, a polyester resin material, etc., but in the case of the present invention, a perpendicular magnetization film containing a fine crystalline phase is used. In order to obtain it, the temperature of the substrate must be kept at 180 ° C. or higher and below the crystallization temperature of the alloy composition, so a material that can withstand this temperature is used. Ku at substrate temperature of 200-300 ℃
= 3 × 10 ⁶ erg / cc or more is a preferable range (FIG. 4).

Ku increases as the thickness of the thin film increases, and it is necessary to have 0.3 μm or more to obtain a perpendicular magnetization film.
If it exceeds, it is difficult to obtain a uniform layer, which is not preferable in production (Fig. 6).

The thin film according to the present invention is formed by a metal gas agglomeration method (so-called vapor phase deposition method), and is produced by any method such as vacuum vapor deposition method, physical deposition method (sputtering method, ion plating method, etc.) and CVD method. Although it is possible, in the case of the sputtering method, the pressure of argon is preferably around 2 × 10 ^-1 Torr (Fig. 7).

It is desirable that a magnetic field of several to several tens Oe is applied to the substrate in the direction perpendicular to the substrate during sputtering. This magnetic field can be easily obtained by winding a sheathing wire for heating attached under the substrate in a solenoid shape and using direct current as a heating current.

The state of the thin film according to the present invention is preferably a fine crystalline phase having a size of about several Å to about 100 Å (Figs. 5 and 17).

Further, when thermomagnetic writing is performed as a magneto-optical disk based on the fact that it has a large saturation magnetization, a leakage magnetic flux from the surrounding portion can be used, so a magnetic field applied from the outside may be small.

[Examples] Hereinafter, examples will be described in detail. The thin film was formed on a glass substrate in an Ar atmosphere using the high frequency sputtering method.

Before introducing Ar gas, the inside of the sputtering container was evacuated to 5 × 10 ⁻⁷ Torr or more. The sputter rate was about 2 μm / hr. No bias voltage is applied to the substrate during sputtering production.

The heating of the substrate was performed by adjusting the electric current of the sheath wire wound around the outer periphery of the cylindrical copper bobbin attached below the substrate.

Since a direct current was used as the current, a magnetic field of about 10 Oe was generated on the substrate. For the magnetic properties of the sample, a torque magnetometer with a maximum magnetic field strength of 20 kOe and a vibrating sample magnetometer (VSM) were used.
The structural analysis of the thin film was performed by X-ray diffraction using Cu-Kα ray and a transmission electron microscope.

(Example 1) Fig. 1 shows the composition of Fe _100-X Nd _X , X = 18,30,35,38,40, the Ar pressure is 1 to 2 x 10 ^-1 Torr, the substrate temperature is 220 to 290 ° C, and the film is formed. Thickness 5000Å ~
The temperature dependence of the magnetization of the thin film formed under the condition of 1.2 μm is shown.

Here, the magnetization is easily saturated in the direction of the magnetization axis and then VSM
The measurement was carried out in a magnetic field of 10 kOe.

The Curie temperature Tc was obtained from the point where the extrapolation line of the M ² / T (M: magnetization, T: temperature) curve intersects the temperature axis.

In FIG. 1, Tcry represents the crystallization temperature.

Curie temperature is 350 ~ 400K (77 ~ 127 ℃) and DyFe (Tc about 70
℃) and TbFe (Tc about 140 ℃).

The difference between the Curie temperature (Tc) and the crystallization temperature (Tcry) is Nd.
It can be seen that thermomagnetic writing by laser light can be sufficiently performed because it is about 200 ° C. at ≧ 30 atomic%.

FIG. 2 compares the Curie temperature and crystallization temperature of FIG. 1 with the composition (Fe _100-x Nd _x ). It can be seen that the Curie temperature or Ms changes little over a wide composition range. The temperature difference (Tcry-Tc) is about 100 ° C or more when Nd ≧ 25at%, and the difference is ≧ 200 ° C when Nd ≧ 30at%.

Fig. 2 also shows the Fe-Nd composition dependence of the saturation magnetization at 77K and 300K.

(Example 2) With a composition of Fe ₆₅ Nd ₃₅ and Fe ₆₀ Nd ₄₀ and a substrate temperature of 240 to 290 ° C,
The magnetic properties of the sputtered thin film prepared under the conditions of Ar pressure of 1 to 2 × 10 ^-1 Torr were measured at 77K and 300K. The result is the third
Shown in the figure. From the measurements in the vertical (⊥) and horizontal () directions of the thin films, it can be seen that these films are perpendicular magnetic films at 77K and 30K.

When the Kerr rotation angle θ _K of these thin films was determined, θ _K =
0.3 ° was obtained. This was equal to or higher than that of the above-mentioned heavy rare earth element-iron amorphous perpendicular magnetization film.

Example 3 Composition of Fe ₆₅ Nd ₃₅ , Ar pressure 1-2 × 10 ⁻¹ Torr, Thickness 6000-12
A 650 Å thin film was prepared and the perpendicular magnetic anisotropy constant Ku was determined with a torque meter. The substrate temperature during sputtering was changed between 70 and 330 ° C. The results are shown in FIG.

The value of Ku indicates the maximum value when the substrate temperature is 260 to 290 ° C. In the figure, a black circle indicates that it is a perpendicular magnetization film, and a white circle indicates that it is not. Substrate temperature Ts is crystallization temperature Tcry (≈320 ° C)
If it is higher than that, it no longer exhibits the properties of a perpendicular magnetization film.
(Ku≈0) FIG. 5 shows the X-ray diffraction pattern of the sputtered thin film when the substrate temperature Ts was 212 ° C., 287 ° C., and 335 ° C. Ts = 335 ℃ and 2
At 87 ° C, a sharp peak that is considered to correspond to Nd ₂ Fe ₁₇ and Nd appears.

Observation by an electron microscope also revealed that fine crystal grains were present at Ts = 212 ° C and 287 ° C, and that crystallization was considerably advanced at Ts = 335 ° C. From these facts, it is understood that in order to have perpendicular magnetic anisotropy, it is preferable that the amorphous matrix contains a fine crystal phase having a crystal grain size of several Å to 100 Å.

Example 4 A sputtered film having a composition of Fe ₆₅ Nd ₃₅ was formed at a substrate temperature of 210 to 290 ° C. and Ar.
Fig. 6 shows the results of magnetic anisotropy constant Ku obtained with a torque meter by changing the film thickness under the condition of pressure of 1 to 2 x 10 ^-1 Torr.

In FIG. 6, black circles indicate perpendicularly magnetized films, and white circles indicate anisotropy in the film plane of the thin film. The index number in FIG. 6 indicates the temperature of the substrate. Ku ≧ 1.5 × 10 ⁶ erg / cc when the film thickness D is 0.3 μm or more, and Ku ≧ 2.5 × 10 ⁶ erg when the film thickness D is 0.7 μm or more.
It becomes / cc.

(Example 5) Fe ₆₅ Nd ₃₅ at a substrate temperature 210 to 290 ° C., the Ar pressure dependence of the magnetic anisotropy constant Ku of the sputtered film produced by changing the Ar pressure under the conditions of the film thickness 6140~1265Å seventh Shown in the figure.

Ku shows a sharp peak at Ar pressure around 2 × 10 ^-1 Torr,
The Ar pressure dependence is not so remarkable as other factors, that is, the substrate temperature and the film thickness. Under this condition, the value of 2πMs ² is 1.5 × 10 ⁶ erg / cc, so Ku ≧ 1.5 × 10 ⁶
It can be seen that erg / cc results in a perpendicular magnetic film.

Example 6 In Fe _100-X Nd _X , the substrate temperature is 250 to 280 ° C., the Ar pressure is 1 to 3 × 10 ⁻¹ Torr, and the film thickness is 6000 in a wide composition range of X = 18 to 50.
Fig. 8 shows the result of obtaining a perpendicular magnetic anisotropy constant Ku by making a sputtered thin film of -13000Å. Although both are perpendicularly magnetized films, it can be seen that the value of Ku depends on the composition. The maximum value of Ku is obtained around 40 atomic% Nd, and is 1-2 x 10
^It shows a high value as high as ⁷ erg / cc.

When the amount of Nd is less than this, Ku drops sharply and becomes less than 2.5 × 10 ⁶ erg / cc when less than 31 atomic%, but when Nd ≧ 25at%, Ku> diamagnetic field energy 2πMs ²
And a sufficiently stable perpendicular magnetic film is obtained.

(Example 7) Hf, Bi, V, Nb, Ta, Cr, Mo, W, M as M in the composition of Fe ₆₀ Nd ₃₅ M ₅
n, Al, Sb, Ge, Sn, Si, Pb, Ni Ts = 220-290 ℃, Ar pressure 1-2
Magnetic properties are measured by making × 10 _-1 Torr and film thickness 6300 to 11000Å.

In each case, a perpendicular magnetization film with Ku ≧ 2.5 × 10 ⁶ erg / cc and a Kerr rotation angle of 0.3 ° or more can be obtained.

(Example 8) Fe ₄₀ Co ₂₅ Nd ₃₅ composition, Ts = 240 ° C., Ar pressure 2 × 10 ₋₁ Tor
r, film thickness 7400Å was prepared and the magnetic properties were measured.

In each case, a perpendicular magnetization film with a Ku ≧ 2.5 × 10 ⁶ erg / cc or more was obtained.

(Example 9) Fe ₆₀ Nd ₂₅ Pr ₁₅ composition Ts = 260 ° C. Ar pressure 1.5 to 2 × 10 ₋₁ Torr
r, sputtered thin film with a film thickness of 7900Å and Ku2.5 × 10 ⁶ erg / c
A perpendicular magnetization film of c or more was obtained.

(Example 10) Fe ₆₀ Nd ₃₂ Dy ₈ , Fe ₅₈ Nd ₃₂ Ce ₁₀ , Fe ₅₇ Nd ₃₀ Ce ₁₀ V ₃ , Ts = 240 to 290 ° C., Ar pressure 1 to 2 × 10 ⁻¹ Torr, film Thickness 7300
Create a sputtered thin film of ~ 11000Å, Ku2.5 × 10 ⁶ erg / cc
The above perpendicular magnetization film was obtained.

Example 11 With a composition of Fe ₆₅ Nd ₃₅ and Fe ₆₀ Nd ₄₀ , the substrate temperature Ts was 290 each.
℃, 250 ℃, Ar pressure 2 × 10 ^-1 Torr, film thickness 12650Å, 48 respectively
A 60 Å sputtered thin film was prepared. Fe ₆₀ Nd _{40 at} 4.2
Torque curves obtained at ~ 300K are shown in Fig. 9 (1) and (2).

Further, FIG. 10 shows a temperature change at a low temperature of the rotation hysteresis loss W in a magnetic field of 15 kOe.

Example 12 (Fe _1-y Co _y ) ₆₀ Nd ₄₀ , y = 0, 0.075, 0.15, 0.25, Ar pressure 1-2 × 10 ⁻¹ Torr Substrate temperature 230-290 ° C.,
Fig. 11 shows changes in the crystallization temperature Tcry, the Curie temperature Tc, the temperature T _{1 at} which the perpendicular magnetic anisotropy constant Ku takes the maximum value, and the coercive force Hc of the thin film formed under the condition of the film thickness of 7700Å to 1.1 μm. .

Increasing Co results in increasing Tc, Hc, and T ₁ without changing Tcry.

(Example 13) Nd ₃₅ Fe ₆₅ obtained in Example 1 and obtained in Example 12 (F
e _1-y Co _y ) ₆₀ Nd ₄₀ thin film linearly polarized light with an incident angle of 80 ° (mercury lamp light source, wavelength λ = 230 to 830 nm, half mirror was not used, and measurement was performed from the thin film surface side. The apparatus used was a “Magnetic-Optical Measuring Device J-250” manufactured by JASCO Corporation, and the wavelength λ dependence of the Kerr rotation angle θ _K was determined (No. 12
Figure). In the figure, Co5, Co10, and Co15 are y = 5/60 (= 0.083) and 1 respectively.
It corresponds to 0/60 (= 0.17) and 15/60 (= 0.25).

The rotation angle is positive on the low wavelength side, θ _K is almost 0 near λ = 340 nm, and | θ _K | increases sharply in the wavelength range above λ = 340 nm.
Almost constant at> 500 nm, but λ for all compositions
It takes the maximum value at 400 to 500 nm. λ = 500 and 633 nm
FIG. 13 shows the composition dependence of | θ _K | in. | Θ _K | increases with an increase in Co composition y, and almost shows a peak near y = 0.25. The value at λ = 500 and 633 nm is y = 0.25
At 0.55 ° and 0.45 °. These values are conventional Gd-Fe-
It is much larger than that of the Co system.

Example 14 Saturation magnetization at 300K in the same sample used in Example 13
FIG. 14 shows the results of determining Ms and the perpendicular magnetic anisotropy energy constant Ku. The saturation magnetization Ms and the magnetic anisotropy energy constant Ku are gradually lowered as the amount of substitution of Co for a part of Fe is increased.

(Example 15) The coercive force Hc was determined from the Kerr rotation angle θ _K of a thin film of the composition Fe _100-X Nd _X prepared under the same conditions as in Example 1, and the results are shown in FIG.

It was found that the Kerr rotation angle of Nd35 and 50at% films (thickness of about 100-300Å immediately after film formation and surface oxidized) increased as shown by the arrow in Fig. 15. For example, in the case of Nd50at%, θ _K is from 0.3 ° to about 0.6 ° (λ = 633 nm), which is an almost double increase. This is because by oxidizing the surface, the contribution of both Kerr and Faraday effect is obtained by the multiple interference method, and the effective Kerr rotation angle is increased. This method can increase the rotation angle by oxidizing the surface of the magnetic film as it is, which is different from the conventional method of coating the surface of a heavy rare earth-iron group perpendicular magnetization film with SiO or the like to increase the rotation angle. Is the way. This is a characteristic of this perpendicular magnetization film.

After the sputtering, the oxide film on the thin film surface can be directly
It is obtained by holding at 0 to 150 ° C for about 30 minutes to 1 hour.

A SiO coating was also applied to the surface of a similar sample with x = 35 atomic%. The result is shown in FIG. The SiO coating also increases the Kerr rotation angle. Further SiO on the oxide film
By applying the coating, θ _K and the protective effect can be further increased.

(Example 16) Using the same sample as in Example 15, the temperature dependence of the perpendicular magnetic anisotropy constant Ku was determined. (Fig. 16) Ku increases at low temperature and reaches a maximum value at T ₁ to some extent,
It further decreases.

(Example 17) Writing experiment by laser light Nd ₃₈ Fe ₆₂ having a thickness of about 4000 Å obtained by the same method as in Example 1
A writing experiment using a laser beam was performed on the film.

Laser: Semiconductor laser (power 20 mW) Bias magnetic field ~ 1000e Line writing method As a result, it was confirmed by a polarization microscope using the Kerr effect that bits with a width of about 2 to 10 µm could be written.

(Example 18) FIG. 17 shows that the present invention makes Fe ₆₀ Nd having a thickness of 150Å made at 220 ° C.
₄₀ A transmission electron micrograph of the fine crystal structure of the perpendicular magnetization film is shown together with the diffraction pattern in the area indicated by the arrow. Spacing
0.2 nm, cluster diameter 2-10 nm, average 3-5 nm are shown.

(Example 19) Zr, Hf, V, Nb, Ta, Cr, M as M in the composition of Fe ₄₅ Co ₁₅ Nd ₃₅ M ₁₅
A film having o, Al, and Ti of Ts = 210 to 285 ° C., an Ar pressure of 1 to 2 × 10 ⁻¹ Torr and a film thickness of 5300 to 1200Å was prepared, and the magnetic characteristics were measured.

In each case, Ku is 2.5 × 10 ⁶ erg / cc or more, and car rotation angle θ _K is 0.
A perpendicular magnetization film of 4 ° or more was obtained.

(Example 20) Fe ₆₅ Nd ₃₅ obtained in the same manner as in Examples 1, 7, 12, and 18,
Fe ₆₀ Nd ₃₅ M ₅ , (M = Hf, V, Nb, Ta, Cr, Mo, Al, Bi, Mn, Sb, Ge,
Sn, Ni, Si), Fe ₄₅ Co ₁₅ Nd ₄₀ , Fe ₄₅ Co ₁₅ Nd ₃₅ M ₅ (M = Zr, H
Each thin film of f, V, Nb, Ta, Cr, Mo, Al, Ti, Ni, Si) is soaked in 1N saline for 20 minutes and then aged at 85 ℃ 85% RH (relative humidity) for 2 hours. The pitting corrosion was observed using an optical microscope. FeCoNdM has the best corrosion resistance against pitting corrosion, followed by FeCoNd and FeNdM (M = Hf, V, Nb, Ta, Cr, Mo, Al, N
i, Si) is good, and FeNd and FeNdM (M = Bi, Mn, Sb, Ge, Sn)
Pitting was the most advanced in comparison.

Example 21 A thin film having a composition of Fe _100-x Pr _x (x = 20, 30, 40, 50 atom%) was prepared under the following conditions. Ar pressure 2 × 10 ^-1 Torr, Ts is 290 each
℃ and 270 ℃, D is 8200Å (0.82μm) and 9400Å (0.9
4 μm).

With respect to these two kinds of thin films, the Kerr rotation angle θ _K when the wavelength λ of the incident light beam was changed was examined by the same method as in Example 12.
The results are shown in FIG. In Fe ₇₀ Pr ₃₀ , the Kerr rotation angle θ _K shows a maximum value of 0.35 ° near λ = 500 nm.

Further, FIG. 19 shows the result of measuring the relationship of the Kerr rotation angle with respect to the Pr concentration x (atomic%) with the incident light ray λ = 500, 633 nm. The Kerr rotation angle θ _K has a maximum value near Pr30 atomic%.

[Brief description of drawings]

FIG. 1 is a graph showing the magnetization temperature characteristics of an Fe _100-X Nd _X sputtered thin film according to an embodiment of the present invention, and FIG. 2 is a Curie temperature Tc and crystallization temperature of the Fe _100-X Nd _X thin film.
Graphs showing Tcry and saturation magnetization Ms (77K and 300K), and FIGS. 3 (a) and 3 (b) are magnetizations at 77K and 300K of Fe _100-X Nd _X (X = 35,40) sputtered thin film. A graph showing the curve, Fig. 4 is a graph showing the relationship between the substrate temperature of the Fe ₆₅ Nd ₃₅ sputtered thin film and the perpendicular magnetic anisotropy constant Ku, and Fig. 5 is X-ray diffraction at each substrate temperature of the Fe ₆₅ Nd ₃₅ sputtered thin film. Fig. 6 is a graph showing the pattern, Fig. 6 is a graph showing the relationship between the thickness of the Fe ₆₅ Nd ₃₅ sputtered thin film and Ku, Fig. 7 is a graph showing the relationship between the Ar pressure of the Fe ₆₅ Nd ₃₅ sputtered thin film and Ku, Fig. 8 Is a graph showing the results of an example under a predetermined substrate temperature, gas pressure, and film thickness conditions, in which the relationship between the Nd amount and Ku of the Fe _100-X Nd _X sputtered thin film was investigated, 9 (1), (2) The figure shows that Fe ₆₀ Nd ₄₀ is 4.2 to 300K
10 is a graph showing the temperature change of hysteresis loss W of the Fe _100-x Nd _x (x = 35,40) sputtered thin film, and FIG. 11 is a graph showing the torque curve obtained in (Fe _1-y For Co _y ) ₆₀ Nd ₄₀ , the temperature at which the Co concentration y, the crystallization temperature Tcry, and the Curie temperatures Tc, Ku have the maximum values.
A graph showing the relationship between T ₁ and coercive force Hc (Example 12), and FIG. 12 shows the wavelength λ (nm) of the incident light beam at each Co concentration y for (Fe _1-y Co _y ) ₆₀ Nd _40. FIG. 13 is a graph showing the relationship between the rotation angles θ _K (degrees) (Example 12), and FIG. 13 is a Kerr rotation angle | θ _{K at} λ = 500 and 633 nm.
A graph showing the relationship between | and Co amount (y) (Example 1)
3), FIG. 14 is a graph showing the relationship between the Co concentration y of Example 13, the saturation magnetization Ms and the perpendicular magnetic anisotropy constant Ku (Example 14), and FIG. 15 is Fe _100-x Nd _x. About x and Kerr rotation angle | θ _K
A graph showing the relationship between | (degree) and holding force Hc (Example 1
5), FIG. 16 is a graph showing the temperature dependence of Ku for the same sample as Example 15 (Example 16), and FIG. 17 is a transmission electron micrograph showing the crystal structure of one example of the present invention, FIG. 18 is a graph showing the relationship between the incident ray λ and the Kerr rotation angle θ _K (degrees) for each x (20, 30, 40, 50 atomic%) of Fe _100-x Pr _x (Example 21), FIG. 19 and FIG. 19 are graphs showing the relationship between Pr concentration x and Kerr rotation angle θ _K for the same system as FIG. 18, respectively.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G11C 13/06 A 6866-5L H01F 10/16 41/14 (56) Reference JP-A-58- 165306 (JP, A) JP 59-103314 (JP, A) JP 59-108304 (JP, A) JP 60-128606 (JP, A) JP 60-173810 (JP, A) JP-A-60-187008 (JP, A) JP-A-60-193125 (JP, A) JP-A-60-117436 (JP, A)

Claims (4)

[Claims] 1. A rare earth element R of 25 to 60 atomic% (provided that 70 atomic% or more of R is one or two of Nd and Pr, and the balance of R is Y, La, Ce, Sm, Gd, One or more of Tb, Dy, Ho, Er and Yb) and the balance Fe, and the thin film amorphous matrix contains at least a few Å to several hundred Å fine crystalline phase. Magnetic field energy 2πMs ² (Ms
Has a larger perpendicular magnetic anisotropy than the saturation magnetization), and the temperature difference Tcry between the crystallization temperature Tcry and the Curie temperature Tc.
-Tc is 100 ° C or more, a perpendicular magnetic recording medium. 2. A rare earth element R of 25 to 60 atomic% (provided that 70 atomic% or more of R is one or two of Nd and Pr, and the balance of R is Y, La, Ce, Sm, Gd, One or more of Tb, Dy, Ho, Er and Yb), less than 30 atomic% of Co and the balance Fe, and the thin film amorphous matrix contains at least a few Å to several hundred Å fine crystalline phase, perpendicular magnetic field The anisotropy constant Ku is the demagnetizing energy 2πMs ² (Ms
Has a larger perpendicular magnetic anisotropy than the saturation magnetization), and the temperature difference Tcry between the crystallization temperature Tcry and the Curie temperature Tc.
-Tc is 100 ° C or more, a perpendicular magnetic recording medium. 3. A rare earth element R of 25 to 60 atomic% (provided that 70 atomic% or more of R is one or two of Nd and Pr, and the balance of R is Y, La, Ce, Sm, Gd, One or more of Tb, Dy, Ho, Er and Yb), Ni, V, Ta, Cr, Mo, W, Mn within 10 atomic%
At least one of Bi, Al, Si, Pb, Sn and Sb, balance
It consists of Fe and is a few Å to a few in the amorphous matrix of the thin film.
At least a 100Å fine crystalline phase is included, and the perpendicular magnetic anisotropy constant Ku has a diamagnetic field energy of 2πMs ² (Ms
Has a larger perpendicular magnetic anisotropy than the saturation magnetization), and the temperature difference Tcry between the crystallization temperature Tcry and the Curie temperature Tc.
-Tc is 100 ° C or more, a perpendicular magnetic recording medium. 4. A rare earth element R of 25 to 60 atomic% (provided that 70 atomic% or more of R is one or two of Nd and Pr, and the balance of R is Y, La, Ce, Sm, Gd, One or more of Tb, Dy, Ho, Er and Yb), Ni, Zr, V, Ta, Cr, Mo, W within 10 atomic%
Mn, Bi, Al, Si, Pb, at least one or more of Sn and Sb,
The amorphous matrix of the thin film contains less than 30 atomic% of Co and the balance Fe, and contains at least a fine crystalline phase of several Å to several hundred Å, and the perpendicular magnetic anisotropy constant Ku has a demagnetizing field energy of 2πMs ² (Ms
Has a larger perpendicular magnetic anisotropy than the saturation magnetization), and the temperature difference Tcry between the crystallization temperature Tcry and the Curie temperature Tc.
-Tc is 100 ° C or more, a perpendicular magnetic recording medium.