JPS61222104A - Vertical magnetic recording medium and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the characteristics of a vertically magnetized film by mainly using Fe and rare earth elements or these elements and Co and employing light rare earth elements mainly comprising Nd and Pr as rare earth elements. CONSTITUTION:Nd and Pr are used as 70% or more in rare earth elements R and one kind or more of Ce, Y, Yb, etc. as the remainder, and the range of R extends over 21-60at%. Co of less than 30% in the whole composition is substituted for residual Fe in R, the remainder is shaped by one kind or more of an element M, such as Ni, Zr, Sb, etc. of less than 10at% of the whole composition, and the thickness of a thin-film is brought to 0.3mum or more. Since the temperature of a substrate must be kept at a temperature up to the crystallizing temperature or lower of an alloy composition from 180 deg.C or higher in order to acquire a vertically magnetized film, elements capable of resisting said temperature are employed. Accordingly, the characteristics of the vertically magnetized film are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium used in a perpendicular magnetic recording system and a method for manufacturing the same.

[Prior art and problems to be solved by the invention] Conventionally, MnB1. Polycrystalline metal thin films such as MnCuB1゜CoCr, compound single crystal thin films typified by GIG, Gd-Co
, Gd-Fe, Tb-Fe, Dy-Fe, and other rare earth transition metal amorphous thin films are known.

Among these, the present invention particularly relates to rare earth transition metal amorphous alloy thin films. Amorphous films are advantageous as magneto-optical recording materials because they do not have crystal grain boundaries that cause noise, unlike polycrystalline thin films, and can be easily manufactured into wide films.

In order for a rare earth transition metal amorphous alloy to be used as a magneto-optical recording medium, it is required that the direction of easy magnetization is perpendicular to the film surface. Perpendicular magnetic anisotropy cannot be induced in any case, but rather the magnetic 5
In order to obtain a perpendicularly magnetized film that exhibits a tendency to be oriented in a direction parallel to the film surface due to the action of the demagnetizing field, it is necessary to provide anisotropic energy sufficient to overcome this demagnetizing field.

The degree of perpendicular magnetic anisotropy of the obtained thin film can be expressed by the magnitude of the -axis anisotropy constant Ku, and in order to become a perpendicularly magnetized film, there must be at least K between Ku and the saturation magnetization Ms.
In the present invention, "perpendicular magnetic anisotropy" refers to something that satisfies at least this condition.

Perpendicular magnetic recording media generally require high recording density.
In order to stably hold a minute magnetic domain, it is very important to obtain a large Ms and a sufficiently large Ku. In addition, magneto-optical disks use laser light as the writing power, but in order to make it usable, it is necessary to
It is required to have a sufficiently low Curie temperature Tc of about 200°C and a sufficiently higher crystallization temperature Tcry, with a temperature difference of at least 100°C or more.

The most well-known rare earth-transition metal combination for perpendicular magnetization films is a heavy rare earth element and iron. Typical examples include TbFe and GdFe.

There are DyFe, GdTbFe, TbDyFe, etc. For example, TbFe has a Curie temperature Tc = 140 to 250°C,
Kerr rotation angle θ, ~0.3°, saturation magnetization M! ! = 5
It has characteristics such as 0 to 100 e mu / CC and perpendicular magnetic anisotropy constant Ku-10' to 10' erg/cc.

However, the heavy rare earth elements such as Tb, Dy, and Gd used in these materials exist only in small amounts in the earth's crust and are rare resources, and require complicated separation processes and are very expensive.

Furthermore, since the atomic magnetic moments of heavy rare earth elements and iron are coupled in an antiparallel manner, it is difficult to produce many homogeneous products with large compositional stability in saturation magnetization Ms and Curie temperature Tc.

On the other hand, light rare earth elements such as Nd and Pr exist in far greater amounts than heavy rare earth elements in the earth's crust. Such a rare earth-iron perpendicular magnetization film is Nd.

If it could be manufactured using a light rare earth element such as Pr, resource problems would be eliminated.

Until now, studies on amorphous alloys of light rare earths and iron have been carried out by, for example, J.
J, Croat is Fe o, +so N do, +
A ribbon alloy was fabricated using a liquid quenching method with a composition near o, F e O, ao P r O, 40, and the possibility of using it as a permanent magnet was discussed because a high coercive force could be obtained (Appl, Phys. , Lett, 39 (4).

15, August, 1981), but the ribbons obtained by this method are not homogeneous throughout the alloy, and are only substantially isotropic.
Further, the thickness of the ribbon is 33 to 208 ILm, and it is not used as a recording medium.

Also, recently, K. Tsutsumi et al.
It has been reported that a sputtered thin film of s -N d 34-T i 4.5 has perpendicular magnetic anisotropy.

(Jpn, J. Appl, Phys, 23 (1984
), pages L189-L171) However, its characteristics are
S” 430 e m u / CC% K u m
It was 2 x 10'erg/cc. Furthermore, although the manufacturing conditions for FeNd sputtered thin films that do not contain Ti are not clear, only thin films that have in-plane anisotropy have been reported.

Although amorphous thin films of light rare earth elements and iron have high saturation magnetization, it has been considered almost impossible to impart perpendicular magnetic anisotropy energy to overcome the demagnetizing field effect of the thin film.

(Objective) The basic object of the present invention is to provide a novel perpendicular magnetic recording medium mainly made of light rare earth elements and iron, and a method for manufacturing the same. Another object of the present invention is to provide a perpendicular magnetic recording medium having the following characteristics and a method for manufacturing the same.

[Means to solve the problem]

(Summary) That is, the present invention provides a completely new magnetic recording medium mainly containing light rare earth elements and iron, and a method for manufacturing the same. This is a perpendicularly magnetized thin film using light rare earth elements mainly composed of Nd and Pr.

The perpendicular magnetic recording medium as the first aspect of the present invention has a rare earth element R of 31 to 60 atomic % (however, 70 atomic % or more of R is the sum of Nd + Pr, and the remainder of R is Y, La, Ce, S
, Gd, Tb, Dy.

It is characterized by having perpendicular magnetic anisotropy.

A second aspect of the present invention provides a perpendicular recording medium in which less than 30 at. % of the Fe is replaced with Go.

Furthermore, as another aspect of the present invention, other elements M other than the predetermined amount
IO atomic % or less (M is Ni, Zr.

Nb, V, Ta, Cr, Mo, W, Mn, Bi.

A! L, St 2 , Pb, Ge, Sn, and one or more of If).

The above is represented by the formula R(Fe, Co)M, and R31-6
0 atom%, M0 to lO atom%, and the balance Fe (however, Fe
Less than 30 atomic % of Co can be substituted with Co).

A method for manufacturing a perpendicular magnetic recording medium according to the present invention includes forming a thin film on a substrate by a metal gas agglomeration method.
It is characterized by forming a thin film having perpendicular magnetic anisotropy with a film thickness of 0.3 to 3 gm while maintaining the temperature at -0°C to below the crystallization temperature of the alloy.

(Summary of Effects) The present inventors have studied in detail the conditions for producing an amorphous thin film based on the above-mentioned circumstances. As a result, Nd is an abundant and inexpensive resource.
, using light rare earth elements such as Pr and iron, Curie temperature Tc = 70-250°C.

Saturation magnetization Ms approximately 450 em u/cc or more,
Perpendicular magnetic anisotropy constant Ku2.5~7X106e rg/
A perpendicularly magnetized film was obtained that had a property of cc or more and a Kerr rotation angle θ of 0.3°, that is, a perpendicularly magnetized film having properties equivalent to or better than the above-mentioned heavy rare earth-iron amorphous thin film.

In the present invention, in the combination of NdpPr and iron, when the magnetic moments of the respective atoms are coupled in parallel, higher saturation magnetization can be obtained than in the case of heavy rare earth elements/iron, and the reading accuracy of recording is improved. When performing thermomagnetic writing, high saturation magnetization makes it possible to utilize leakage magnetic flux, and the magnetic field that must be applied from the outside may be small.

(Preferred Embodiment) As the rare earth element R used in the present invention, at least 70% of R is Nd and Pr, and Nd is particularly desirable, and the remainder is Ce and Y due to availability reasons.

Sm, Dy, Tb, Ho, Gd, La, Er.

Materials containing other rare earth elements such as yb may also be used.

R is 31 atomic % (at%) or more of the total composition, and the magnetic anisotropy constant Ku perpendicular to the thin film surface is 2.5 × 1106 er/c
c or more, resulting in a sufficiently stable perpendicular magnetization film.

When R is 80 at % or more, the film contains a large amount of active rare earth elements, resulting in a lack of stability after forming a thin film. Therefore, the range of R is 31
~60at%. When R is 33 to 50 at%, Ku=3
The preferred range is X10'el rg/cC or more (see Figure 8).

Figure 2 shows the composition dependence of saturation magnetization Ms and Curie temperature Tc.
It can be seen that the rate of change in s and the Curie temperature Tc is small, and it is possible to easily produce a product with much more stable quality than in the case of heavy rare earth element iron.

The remainder of H is mainly iron, but substituting less than 30% of Fe with Co has the effect of increasing the saturation magnetization Ms, the Curie temperature Tc, and improving the corrosion resistance of the thin film without impairing the properties of the perpendicularly magnetized film. There is.

Element M of less than 1 Oat96 of the total composition, ie.

Ni, Zr, Nb, V, Ta', Cr, Mo, W.

Addition of Mn, Bi, All, Pb, Ge, Sn, Hf, etc. does not impair the properties of the perpendicularly magnetized film.

Furthermore, the addition of metalloids such as B, C, Sf 2 , P, etc. in an amount of 10 at % or less facilitates the formation of an amorphous state.

Furthermore, the compositions of the present invention can also contain less than 10 at% of Tf of the total composition, Ku3x106erg
/cc You can get prizes.

Further, since the thin film according to the present invention has a high saturation magnetization Ms, it is necessary that the perpendicular magnetic anisotropy constant is larger than 2.5×10′ erg/CC. In general, glass, AR, polyimide resin material, polyester resin material, etc. are used as the substrate material for forming the substrate for creating an amorphous film, but in the case of the present invention, the substrate material is Since the temperature must be kept at 180° C. or higher and lower than the crystallization temperature of the alloy composition, a material that can withstand this temperature is used.

When the substrate temperature is 200 to 300℃, Ku=3XlO'erg/
The preferred range is cc or more (Fig. 4).

As the thickness of the thin film increases, Ku increases, and in order to obtain a perpendicularly magnetized film, 0.3 gm or more is required, but 3
If it exceeds pm, it will be difficult to obtain a uniform layer, which is unfavorable in terms of production (Figure 6).

Shikin 88ζ Upper *Scale 1 Urine gas door focus
A value around -1 Torr is desirable (Fig. 7).

During sputtering, several to several + Oe are applied to the substrate in the direction perpendicular to the substrate.
It is desirable that a magnetic field of .

This magnetic field can be easily obtained by winding a heating sheath wire attached under the substrate in a solenoid shape and using direct current as the heating current.

The state of the thin film according to the present invention is an amorphous phase or a crystalline phase (fifth phase).
figure).

Furthermore, based on the large saturation magnetization, when performing thermomagnetic writing as a magneto-optical disk, leakage magnetic flux from the surrounding area can be used, so the magnetic field applied from the outside may be small.

〔Example〕

This will be explained in detail below using examples. The thin film was created on a glass substrate in an Ar atmosphere using a high frequency sputtering method.

Before introducing Ar gas, the inside of the sputtering chamber is 5×10-'
The vacuum was increased to more than T o r r. The sputtering speed was about 21 Lm/hr. No bias voltage was applied to the substrate during sputtering.

The substrate was heated by adjusting the current of a sheathed wire wound around the outer periphery of a cylindrical copper bobbin attached below the substrate.

Since direct current was used, a magnetic field of several tens of seconds was generated on the substrate. The magnetic properties of the sample have a maximum magnetic field strength of 20k.
An Oe torque magnetometer and a vibrating sample magnetometer (VSM) were used. The structure of the thin film was analyzed by X-ray diffraction using α-rays for Cu- and a transmission electron microscope.

(Example 1) Figure 1 shows Fe+. 6-! Nd! , X=18.30.

35.38.4057) Composition with Ar pressure of 1 to 2 x 10-
'Torr, substrate temperature 220N290℃, film thickness 500
The temperature dependence of magnetization of thin films created under conditions of 0 A to 1.2 gm is shown.

Here, magnetization is easy after saturated magnetization in the direction of the magnetization axis, and then VS
Measurements were carried out at M in a magnetic field of 10 kOe.

The Curie temperature Tc was determined from the point where the extrapolated line of the M2/T (M: magnetization, T: temperature) curve intersects the temperature axis.

In FIG. 1, Tcry indicates the crystallization temperature.

Curi temperature is 350-400K (77-127℃)
DyFe (Tc ~70℃), TbFe (Tc
What is N140℃? They were equivalent.

Also, Curie temperature (Tc) and crystallization temperature (Tcry)
The difference in temperature is approximately 200° C., which indicates that thermomagnetic writing using laser light can be performed satisfactorily.

Figure 2 shows the composition of the Curie temperature and crystallization temperature in Figure 1 (
Fe 160-! N dx ). It can be seen that the Curie temperature hardly changes over a wide composition range.

FIG. 2 also shows the compositional dependence of saturation magnetization at 77K and 300K.

(Example 2) Fe 6s N d 3g and Fe so N d
The magnetic properties of a sputtered thin film prepared with a composition of 4o under conditions of a substrate temperature of 240N, 290°C, and an Ar pressure of 1 to 2 x 106 Torr were measured at 77K and 300K. The results are shown in FIG. 3. From measurements of the thin films in the vertical direction (1) and horizontal direction (//), it can be seen that these thin films are perpendicularly magnetized films at 77 and 300K.

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

(Example 3) Fe 6s N d 3g (7) Composition with Ar pressure of 1~
2 X 10-'Torr, thickness 6000-12650
A (7) thin film was prepared, and the perpendicular magnetic anisotropy constant Ku was determined using a torque meter. The substrate temperature during sputtering is 70-33
The temperature was varied between 0°C. The results are shown in FIG.

The value of Ku has a maximum value when the substrate temperature is 260 to 290°C. In the figure, black circles indicate that the film is perpendicularly magnetized, and white circles indicate that it is not. The substrate temperature Ts is the crystallization temperature Tcr.
If the temperature is higher than y (I-, 320° C.), it no longer exhibits the properties of a perpendicularly magnetized film.

Figure 5 shows the X-ray diffraction patterns of the sputtered thin film when the substrate temperature Ts is 212°C, 287°C, and 335°C.
= 335°C and 287°C, Nd2 Fe+7
A sharp peak appears that is thought to correspond to Nd and Nd.

Observation with an electron microscope also revealed that regions of fine crystals existed when Ts = 212°C and 287°C, and that crystallization had progressed considerably when Ts = 335°C. From these facts, it can be seen that in order to have perpendicular magnetic anisotropy, an amorphous phase or a fine crystalline phase of about several A to about 10 OA is preferable.

(Example 4) A sputtered film having a composition of F e 6s N d 3s was sputtered at a substrate temperature of 210 to 290°C and an Ar pressure of 1 to 2XlO-ITo.
Figure 6 shows the results of the magnetic anisotropy constant Ku obtained using a torque meter after the film was prepared by changing the film thickness under the conditions of rr.

The black circles in FIG. 6 indicate perpendicular magnetization films, and the white circles indicate cases where the thin film has in-plane anisotropy. The subscript in FIG. 6 indicates the temperature of the substrate, and the above-mentioned conditions Ku≧2, 5 x 10'
It can be seen that in order to satisfy e r g /CC, a film thickness of approximately 0.71 Lm or more is required.

(Example 5) FegNdg was deposited at a substrate temperature of 210 to 290°C and a film thickness of 614°C.
The Ar pressure dependence of the magnetic anisotropy constant Ku of the sputtered film produced under the conditions of 0 to 12650 A is shown in 7th rI4.

When the Ar pressure is around 2xlO-'Torr, Ku shows a dull peak, but relatively the Ar pressure compatibility is not as significant as other factors, such as substrate temperature and film thickness.

(Example 6) Fe 100-! Nd! In X=18~50
substrate temperature of 250 to 280°C over a wide composition range.

Ar pressure 1~3X10-ITorr, film thickness 6000~13
A sputtered thin film of 000A was prepared and the perpendicular magnetic anisotropy constant Ku was determined. The results are shown in FIG.

The maximum value of Ku is obtained around 40 atomic % of Nd.

It shows a high value reaching 1-2XIO'erg/cc.

When the amount of Nd decreases below this, Ku decreases rapidly,
2.5X106e r g/6 for less than 31 atomic%
Only bonds worth less than c can be obtained.

(Example 7) F e @a N d 3s M s M with 173 composition
As Zr.

Hf, Di, V, Nb, Ta, Cr, Mo, W.

Mn, AIL, Sb, Ge, Sn, Ts=220
~290℃, Ar pressure 1~2XIO' Torr, film thickness 6
300 to 1100 OA were prepared and their magnetic properties were measured.

In both cases, perpendicularly magnetized films were obtained.

(Example 8) F 646 CoHN d n (1) composition, Ts-
240℃, Ar pressure 2xlO-'T6rr, film thickness 7400
A was prepared and its magnetic properties were measured.

In all cases, perpendicular magnetization films with a Ku of 2.5×10′ erg/cc or more were obtained.

(Example 9) T with the composition F e @ 6 N d 2 @ P r Hm
s=260℃, Ar pressure 1.5~2XlO""'Torr
, a sputtered thin film with a thickness of 7900A was created and Ku2.5X
A perpendicular magnetization film of 10'erg/cc or more was obtained.

(Example 10) F e go N d n D ”j s, F
e 5IIN d HCe He.

F e 5v N d 311 Ce +o V s
(7) Composition: Ts=240-290℃, Ar pressure 1-2x
To-1 Torr, a sputtered thin film with a film thickness of 7300 to L100OA was created, and Ku2.5X10' erg/cc
The above perpendicular magnetization film was obtained.

(Example 11) T: m −N j −〒 z −/? 11ゑ1tk -911〒 a = 9 &% 11
"t'+Ar pressure 2XIO-'Torr, film thickness 940
A sputtered film of 0A was created, and Ku=3. lX10'e
A perpendicular magnetization film of rg/cc was obtained.

(Example 12) With the compositions Fe@@N, d3w and Fe@aNd*o, the substrate temperature Ts was +290°C, +250°C, and Ar
The pressure is 2xto-ITorr, and the film thickness is 1265OA each.

A sputtered film with a thickness of 4860λ was created. Fe@6Nd4.
The torque curve obtained from 4.2 to 300 is
(1), (2) As shown in the figure.

Further, FIG. 10 shows temperature changes in Ku and rotational hysteresis loss W at low temperatures in a 15 kOe magnetic field.

At low temperatures, Ku increases and 1 e.g. F e HN d
4 (+ composition) Ku
It can be seen that it reaches a maximum value of 3XlO' erg/cc.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention: F e 100-iN
d, a graph showing the magnetization temperature characteristics of a sputtered thin film.
Graph showing Curie temperature Tc, crystallization temperature Tcry, and saturation magnetization Ms (77K and 300K) of I, third
Figures (a) to (C) show Fe+ao-1Ndx (X=3
0.35.40) Spar/Yuu thin film (F) 77K and 3
A graph showing each magnetization curve at 00, Fig. 4 is F e
@, Graph showing the relationship between substrate temperature and perpendicular magnetic anisotropy constant Ku of N d B sputtered thin film, Figure 5 is F e 6
A graph showing the X-ray diffraction pattern of m N d 3f sputtered thin film depending on each substrate temperature, Figure 6 is Fe-based N d 3
Graph showing the relationship between the thickness of g-sputtered thin film and Ku. Figure 7 shows the Ar of F66*Nd31 sputtered thin film.
A graph showing the relationship between pressure and Ku, Figure 8 is Fe1°. -xNd, graph showing the relationship between the amount of Nd in the sputtered thin film and Ku, Figures 9 (1)' and (2) are F e @6 N d4
6 shows the torque curve obtained from 4.2 to 300, and the 10th (1) and (2) figures are Fe1g10
1 is a graph showing temperature changes in perpendicular magnetic anisotropy constant Ku and hysteresis loss W of a -1 Ndx (x=35.40) sputtered thin film. Applicant Sumitomo Special Metals Co., Ltd. Agent Patent Attorney Kato Hado Temperature T(K) X(m%hυ) ArIHPb104TORR) 7th m Fe,, Ne4. :M, 'Jiii layer qA
r/f- and 4#aa*'llB sex m diagram 7ov) pua number (;L 廁(NhenX (ep≦Nd) Fig. 8 Modified axial temperature anisotropy IF of twit drawing (no change in content) Figure q(2) Fe6gNd@ZunoheriMoon->4.
2.7 otsu 300 and 7℃F @. ~Noburu 2 Curve Procedure Amendment Form) December 28, 1980 Manabu Shiga, Commissioner of the Patent Office 1, Indication of Case Patent Application No. 236661, 1982
No. (filed on November 12, 1980) 2. Name of the invention Perpendicular magnetic recording medium and its manufacturing method 3. Person making the amendment Relationship to the case Name of patent applicant Sumitomo Special Metals Co., Ltd. 4. Agent 5. Amendment Date of order Spontaneous 6, number of inventions increased by amendment None (Procedure Nakaminami Seisho Yakusho) June 2, 1985 [1]

Claims (1)

[Claims] 1) The rare earth element R is 31 to 60 at% (however, 70 at% or more of R is the sum of Nd+Pr, and the remainder of R is Y, L
a, Ce, Sm, Gd, Tb, Dy, Ho, Er and Y
(b), the remainder being Fe, and having perpendicular magnetic anisotropy. 2) Perpendicular magnetic anisotropy constant Ku is 2.5×10^6erg
Claim 1 characterized in that it is equal to or more than /cc
The perpendicular magnetic recording medium described in . 3) 31 to 60 atomic% rare earth element R (70 atomic% or more of R is the sum of Nd + Pr, and the remainder of R is Y, La, Ce
, Sm, Gd, Tb, Dy, Ho, Er, and Yb), the balance being Fe and less than 30 atomic % of Co, and having perpendicular magnetic anisotropy. 4) 31 to 60 atomic% rare earth element R (70 atomic% or more of R is the sum of Nd + Pr, and the remainder of R is Y, La, Ce
, Sm, Gd, Tb, Dy, Ho, Er and Yb), Ni, Zr, Nb, V, Ta within 10 atomic %
, Cr, Mo, W, Mn, Bi, Al, Si, Pb, G
1. A perpendicular magnetic recording medium comprising at least one of e, Sn, and Hf with the balance being Fe, and having perpendicular magnetic anisotropy. 5) 31 to 60 atomic% rare earth element R (70 atomic% or more of R is the sum of Nd + Pr, and the remainder of R is Y, La, C
e, Sm, Gd, Tb, Dy, Ho, Er and Yb), Ni, Zr, Nb, V, T within 10 atomic %
a, Cr, Mo, W, Mn, Bi, Al, Si, Pb,
1. A perpendicular magnetic recording medium comprising at least one of Ge, Sn and Hf, the balance being Fe and less than 30 atomic % of Co, and having perpendicular magnetic anisotropy. 6) In a method for manufacturing perpendicular magnetic recording media in which a thin film is formed on a substrate by a metal gas agglomeration method, the substrate temperature is set at 180°C.
~ held at a temperature below the crystallization temperature of the alloy, the formula R(Fe
, Co)M, R31 to 60 atom %
, M0 to 10 atomic%, and the remainder Fe (however, Co replaces less than 30 atomic% of Fe), R is the sum of Nd and Pr among the rare earth elements, and 70 atomic% or more of R, and the remainder R Y
, La, Ce, Sm, Gd, Tb, Dy, Ho, Er and Yb, and M is Ni, Zr, Nb, V, T
a, Cr, Mo, W, Mn, Bi, Al, Si, Pb,
1. A method for producing a perpendicular magnetic recording medium, comprising forming a thin film having a perpendicular magnetic anisotropy and having a thickness of 0.3 to 3 μm and having a composition of at least one of Ge, Sn, and Hf.