JPS60173820A - Manufacture of vertical anisotropic magnetized film - Google Patents

Abstract

PURPOSE:To give magnetic characteristics proper to vertical magnetic recording while obtaining the titled film having excellent abrasion-resistant characteristics and corrosion resistance by thermally treating the film of a thin-film mainly comprising iron oxide, to which osmium is added, while vertically applying a magnetic field. CONSTITUTION:The film of a thin-film mainly comprising iron oxide, to which osmium is added, is thermally treated while vertically applying a magnetic field. An Os pellet is arranged on a target such as an iron target, and an alpha-Fe2O3 film in which Os is added at a ratio only of a metallic element of 5.0atom% is prepared throug corresponding sputtering in a mixed gas atmosphere at the ratio of 1:1 of argon to oxygen, and film thickness is brought to 0.1mum. The alpha-Fe2O3 film is heated for 1hr at 250 deg.C in a hydrogen gas current and changed into Fe2O4, and heated for 4hr at 310 deg.C in atmospheric air and turned into gamma-Fe2O3. The Os added gamma-Fe2O3 film is heated for 15min within a range of 350-400 deg.C in atmospheric air again, and an external magnetic field of 10kOe is applied vertically to the film surface at that time.

Description

[Detailed Description of the Invention] [Technical Field] Fuhayu is a method for producing iron oxide thin films with magnetic anisotropy perpendicular to the film surface, which are used as magnetic media for high-density magnetic recording devices, especially magnetic disks. It is related to.

<Technical outlook and problems> The so-called perpendicular magnetization recording method, which records information by magnetizing perpendicular to the film surface using a magnetic medium with magnetic anisotropy perpendicular to the film surface, has a high recording density. The further the bit is placed, the more the bit shape extends in the recording magnetization direction, so the demagnetizing field decreases and the recording magnetization becomes more stable. Therefore, it has been found that a higher recording density can be achieved compared to the conventionally used in-plane magnetized film in which magnetic anisotropy is imparted parallel to the film surface. This material includes (S, Iwasa'rLetal:
IEEE Trans Magn, MAG-13
(1977) 1272).

As a magnetic medium used in such a perpendicular magnetization recording system, a cobalt (Co) based alloy metal film such as a cobalt-chromium alloy or a cobalt-ruthenium alloy has been used. This material includes (S, IwasLk-1etal;
IEEE Trans Magn, , MAG-14,
(1978) 849, S. Hirono et al.
: Jpn, J., Apol.

PH3's, 20 (1981) L571).

The Co-based alloy thin film has a structure in which the C-axis is aligned perpendicular to the surface. In addition, since the magnetocrystalline anisotropy of Co is uniaxial and the easy axis of magnetization is the C axis, the Co-based alloy thin film ends up having magnetic anisotropy perpendicular to the film surface, a so-called perpendicularly anisotropic magnetized film. It is.

Incidentally, a perpendicularly anisotropic magnetized film in which the residual magnetization when measured perpendicular to the film surface is larger than the residual magnetization when measured parallel to the film surface is particularly called a perpendicularly magnetized film.

The drawbacks of such a Co-based alloy thin film, which is a perpendicularly anisotropic magnetization film, are that since this film is a metal film, it is easily corroded, and furthermore, the surface hardness is insufficient.

<Objective of the Invention> The present invention eliminates the drawbacks of the above-mentioned Co-based alloy thin film, and provides a perpendicular anisotropy in which an induced magnetic anisotropy is imparted perpendicularly to the film surface for an iron oxide thin film that has high corrosion resistance and excellent surface hardness. The purpose of the present invention is to provide a method for manufacturing a magnetic film.

<Structure of the Invention> The present invention that achieves the above object is characterized in that a magnetic field is applied perpendicularly to the film surface of a thin film whose main component is iron oxide with osmium (08) added, and heat treatment is carried out.

<Example> Example 1 Osmium (O8) and Co pellets were placed on an iron (Fe) target with a diameter of 20 ctrr, and argon (
Hematite (α-Fe20a) was sputtered by reactive sputtering in a mixed gas atmosphere of 1=1 of Ar) and oxygen (0□).
) A thin film is formed on the basal root. The sputtering method is a high frequency two-pole sputtering method and the sputtering power is 3
00W, sputtering atmosphere pressure is 2 x 10” Tor
It is r. A glass substrate is used as the substrate. O into the membrane
The addition of carbon dioxide and CO can be controlled by increasing or decreasing the amount of pellets on the target. α-Fe with a film thickness of 0.1 μm
O8 and CO were added to the 20B film at a ratio of only metal elements of 2.3 and 3.6 at%, respectively. Next, this α
-The following three types of heat treatment are performed on the Fe203 thin film.

(1) Heating at 250°G for 1 hour in a humidified hydrogen (H2) stream to obtain a magnetite (Fe, 04) film. .

At this time, an external magnetic field of 10 KOe is applied perpendicular to the film surface.

(2) After heating to 250°C for 1 hour in a humidified H2 stream to obtain a Fe3O4 film, heating to 310"C for 4 hours in the air to obtain maghemite (γ-Fe2Q3). In the air When heating, apply an external magnetic field 10 perpendicular to the film surface.
Add KOe.

(3) Heating at 250°C for 1 hour in a humidified H2 stream to remove Fe, 0. After obtaining the film, it was heated at 310° C. for 4 hours in the air to form a γ-Fe2O3 film. This γ-Fe, OB
The film is heated to 3-80° C. for 1 hour in air while applying an external magnetic field of 10 KOe perpendicular to the film surface. In this process, r
-The state of 20g of Fe is maintained.

After performing the three types of heat treatments described above, hysteresis loops were measured in the direction parallel to and perpendicular to the film surface. Table 1 shows the values of coercive force (He) and residual magnetization (Mr) after each heat treatment.

[-12,3 at%Os + 3.6 at%CO Magnetic properties of fallen iron oxide thin film As can be seen from Table 1, the coercive force in the direction perpendicular to the film surface (on He) is higher in all samples. The coercive force (He//) parallel to the film surface is also larger, indicating that the film is a perpendicularly anisotropic magnetized film. In particular, heat treatment (3
), residual magnetization in the direction perpendicular to the film surface (Mr
The residual magnetization (Mr//) in the direction parallel to the film surface is also larger than that in the upper case, indicating that it is a so-called perpendicularly magnetized film, which is more stable when magnetized perpendicularly to the film surface than parallel to the film surface. It shows.

Example 2 Under the same manufacturing conditions as Example 1, only O8 was used at a ratio of only metal elements of 5. Oat% added α-Fe, 0. A membrane was prepared. The film thickness is 1 μm. This α-Fe, 0° film was heated to 250°C for 1 hour in a humidified hydrogen stream, and Fe3O
4, then heated to 310°C in the air for 4 hours to obtain γ-F.
Let e, O, be. This OB addition-Fe20. The film is heated again in the air at a temperature in the range of 250°C to 680°C for 15 minutes. Note that at this time, an external magnetic field of 10 KOe is applied perpendicular to the film surface.

FIG. 1 shows the dependence of coercive force (He) and residual magnetization (Mr) on the heat treatment temperature in a magnetic field. Heat treatment temperature in magnetic field is 350℃
When the temperature is above .degree. C., Hc+Mr measured perpendicular to the film surface is larger than Hc and Mr measured parallel to the film surface, and a perpendicularly magnetized film is formed.

Example 3 Contains O8 at 0 to 9.5 at% under the same conditions as Example 2.
．． An α-Fe, 03 thin film with a thickness of 2 μm was formed. This thin film was heated to 250 to 320°C for 1 hour in a humidified hydrogen stream, and then heated to 310°C for 4 hours in the air.
A thin film containing B as the main component was obtained. According to X-ray diffraction, the film containing 9.5 at% Oa contained γ-Fe and 0.5 at%. It has been confirmed that a trace amount of α-Fe203 phase is present in addition to the phase. This OB-added-Fe20° thin film was heated for 400° in the atmosphere while applying an external magnetic field of 10 KOe perpendicular to the film surface.
℃ for 15 minutes.

The coercive force (H
c) and the dependence of residual magnetization (Mr) on the amount of O8 added is shown in FIG. He top and Karado indicate the coercive force and residual magnetization measured perpendicular to the film surface, and Hc // and Mr // indicate the coercive force and residual magnetization measured parallel to the film surface, respectively. 08 Addition plate sail 37
In the range of ~9.5 at%, He>He// holds true,
A perpendicular magnetic anisotropic film has been obtained. Especially when the amount of O8 added is 3
．． In the range of 5 to 9.5 at%, Mr±>Mr// holds true, and a perpendicularly magnetized film is obtained. Note that similar effects were obtained when the external magnetic field during magnetic field heat treatment was 4 KOeO.

Example 4 A silicon (Si) disk with a diameter of 50 mm and whose surface was thermally oxidized was used as the substrate, and the other parts were made in the same manner as in Example 2.
A γ-Fe203 thin film with a thickness of 0.2 μm was formed by adding 6% of γ-Fe203. This γ-Fe, O, thin film was heated at 400° C. for 30 minutes in the air while applying an external magnetic field of 7 KOe perpendicularly to the surface to form a perpendicularly magnetized film.

The magnetic properties of this perpendicularly magnetized film are as follows.

He top = 14000e, He //= 5000
e, Mr upper = 100 Gauss, Mr / =
30 Gauss.

This 08-added γ-Fe20B perpendicular magnetization film has a diameter of 2.2
9 Mn-Zn 7 Push the light ball and rotate the disk so that the relative velocity is 1 m/sec.
The depth of scratches on the medium surface after passing 1000 times was measured. or,
81 on a Si substrate whose surface was thermally oxidized by sputtering.
．． A 3 at% Co -18,7 at% Cr perpendicularly magnetized film was prepared and subjected to a similar wear test. C.

The conditions for producing the -Cr film are as follows. Tergut is 81.3 at%Co -18,7 at% with a diameter of 100.
Cr disk, sputtering atmosphere is 2 x 10-2 Torr
0.2 by adding 200W of high-frequency power and Ar gas of
A Co-Cr film with a thickness of μm was obtained. The magnetic properties of this Co-Cr film are as follows: Hc = 17000e, Hc //=
9000e, Mr upper = 90 Gauss, M
r // = 48 Gauss. FIG. 3 shows the relationship between the load on the ferrite ball and the depth of the wear scar. OIs
It can be seen that the wear depth of the added γ-Fe, 03 film A is smaller than that of the C0-Cr film B.

Next, the above r-Fe, 0. The recording and reproducing characteristics of the film and Co-CrH were evaluated using a Winchester-type Mn-Zn ferrite head. The core width of the head is 70 μm1, the number of coil turns is 20, and the length of the coil is 0.
．． Measurements were made at a thickness of 3 μm and a circumferential speed of 5 m/sec. The head flying height at this time is 0.05 μm. The recording density &(D50) that provides the highest output of solitary wave reproduction output is r −F
e20g membrane is 3200 FRPM (FluxReYe
rsals per Millimeter), Co
-The Cr film is 3170F'RPIvl. Immediately,
It has been confirmed that the 7'-Fe2O3 perpendicularly magnetized film according to the present invention can provide almost the same recording density as the conventionally used Co--Cr perpendicularly magnetized film.

Finally, the above Os-doped r-Fe,,03 thin film and Co
-Cr thin film was placed in an atmosphere with a humidity of 90 parts and a temperature of 80°C.
The sample was left to stand for 00 days, and its 1I11 symptoms were examined. 08 addition γ-
In the Fe20s auxiliary film, no signs of corrosion were observed either visually or by optical microscopy, but the Co-C
In the R film, corrosion was observed at 92 to 3 locations per atl.
゛ko.

<Effects of the Invention> As explained above, the O8-doped iron oxide perpendicularly anisotropic magnetization film produced according to the present invention has magnetic properties suitable for perpendicular magnetic recording, and at the same time has magnetic properties suitable for perpendicular magnetic recording.
-Compared with metal thin films such as Cr films, it has advantages such as excellent wear resistance and corrosion resistance, which significantly improves reliability in practical use.

[Brief explanation of the drawings] Figure 81 is a graph showing the relationship between heat treatment temperature in a magnetic field, coercive force (Hc) and residual magnetization (Mr), and Figure 2 is a graph showing the relationship between the amount of OB added and the coercive force (He) after heat treatment in a magnetic field. and residual magnetization (Mr'
), and FIG. 3 is a graph showing the relationship between ferrite ball indenter load and wear scratch depth. In the figure, Mr-1-il is the residual magnetization in the direction perpendicular to the film surface, Mr/ is the residual magnetization in the direction parallel to the film surface, Hcl is the coercive force in the direction perpendicular to the film surface, and Ha/ is the coercive force in the direction parallel to the film surface. Patent applicant: Nippon Telegraph and Telephone Public Corporation Patent attorney Dobe Mitsuishi (and 1 other person) Fig. 1ajIA hsa', *s-t'c) Fig. 2 0 (24G B 7゜Os4 force Djt (at%)

Claims (3)

[Claims] (1) A method for producing a perpendicularly anisotropic magnetized film, which is characterized by performing heat treatment while applying a magnetic field perpendicular to the film surface of a thin film whose main component is iron oxide doped with osmium-08. (2) The above iron oxide is hematite α-Fe20. year,
Claim 1, characterized in that simagnetite Fe504 is formed by performing the above-mentioned heat treatment of heating in a hydrogen stream. A method for manufacturing a perpendicularly anisotropic magnetized film described in liI. (3) The above iron oxide is made of magnetite Fe50. 2. The method for producing a perpendicularly anisotropic magnetized film according to claim 1, wherein simaghemite γ-Fe, Os is formed by performing the heat treatment in which the perpendicularly anisotropic magnetized film is heated in the atmosphere. (4) The method for producing a perpendicularly anisotropic magnetized film according to claim 1, characterized in that the iron oxide is magnetite γ-Fe203, and the heat treatment is performed by heating in the atmosphere.