JPS61224123A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled medium having excellent resistance to corrosion and weather by composing the alloy magnetic thin film of a Co-base alloy contg. >=1 kind among Al, Si and Cu and nitrogen. CONSTITUTION:The magnetic thin film consists of a Co-base alloy contg. >=1 kind among 2-12atom% Al or Si or 2-8atom% Cu and 0.5-5atom% N. The content of Al or Si is regulated to 2-12atom% and that of Cu to 2-8atom%, because the corrosion resistance is deteriorated at <2atom% contents of the additives. Meanwhile, the saturation magnetization becomes too low at >8atom% Al or Si and the merit of the thinness of the alloy magnetic thin film suitable for high-density recording can not be fully exhibited. Reasons for regulating the N content to 0.2-5atom% are mainly related to the production and because >=0.2atom% N remains in the film. On the other hand, the squareness ratio S among magnetic characteristics is deteriorated at >5atom%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording medium having an alloy magnetic thin film, and in particular, the alloy magnetic thin film is made of aluminum, silicon,
The present invention also relates to a magnetic recording medium made of a cobalt-based alloy containing at least one of copper.

[Prior Art] Research and development of magnetic recording media having alloy magnetic thin films with high recording density has been greatly promoted in recent years, and one of them is cobalt (CO)-nickel (cobalt (CO))-nickel (
There is one using a Ni)-phosphorus (P) alloy magnetic thin film.

However, the Co-N1-P alloy has a problem in corrosion resistance, and recording media using the alloy magnetic thin film are inferior in reliability such as recording errors when used for many years. For example, the alloy magnetic thin film was heated for 2 hours at a temperature of 57°C and a humidity of 85%.
When left for a week, the saturation magnetization deteriorates by 30%.
Furthermore, when left in pure water for one week, the rate reaches 40%. Such deterioration of characteristics causes a decrease in output when used in actual equipment, and the presence of corroded parts causes an increase in errors.

[Problems to be Solved by the Invention] As described above, the Co-Ni-P alloy magnetic thin film produced by electroless plating has problems in corrosion resistance and weather resistance, which result in a decrease in reliability such as a decrease in output and an increase in errors. was there.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors conducted studies from various viewpoints, and found that 2 to 12 atomic % aluminum (AI
) or silicon (Si), or 2 to 8 atomic percent copper (
It has been found that a Co-based alloy magnetic thin film containing one or more of C1) has extremely excellent corrosion resistance and #4 weatherability.

That is, the present invention provides a magnetic recording medium having an alloy magnetic thin film formed on a substrate.
2 atomic % A1 or Si, or 2 to 8 atomic % CO
It is characterized by being made of a Co-based alloy containing one or more of the above and 0.2 to 5 atomic % of nitrogen.

The configuration of the present invention will be explained in more detail below.

The magnetic thin film used in the present invention has a content of 2 to 12 atomic %.
It is made of a Co-based alloy containing any one or more of Al or Si, or 2 to 8 atomic % of CO, and 0.5 to 5 atomic % of N.

The reason why the A1 or Sl content was set to 2 to 12 at % and the Cu content was set to 2 to 8 at % is that if the content of these additives is less than 2 at %, the corrosion resistance will decrease. be. On the other hand, in the case of Cu, it is 8 at%, AI or S
This is because, in the case of i, when it exceeds 12 atom %, the saturation magnetization becomes too low, and the advantage of the alloy magnetic thin film, which is suitable for high-density recording, such as thin layer formation, cannot be utilized.

In addition, the reason why N was set at 0.2 to 5 at% was mainly due to 1
This is due to a structural relationship, and for example, in the manufacturing method according to the present invention described later, N of 0.2 atomic % or more remains. On the other hand, if the content exceeds 5 at %, the so-called squareness ratio S of the magnetic properties will decrease. Normally, the squareness ratio S of a magnetic recording medium is required to be 0.1 or more, but in the present invention, a particularly preferable N content is 0.2 to 3 atomic %.

In the present invention, the composition other than AI, Si, Cu, and N may be (a) only Co (b) a part of Co replaced with Ni and/or l"e. (b) In the case of composition, some of the CO is replaced by N
The substitution ratio when replacing with i and/or Fe is 2 of CO
The content is preferably 5 at % or less. When the substitution ratio exceeds 25 atomic %, an fcc phase appears in the hcp host crystal, resulting in a decrease in the in-plane magnetic properties of the film.

Furthermore, in the case of l''e substitution, if the substitution ratio exceeds 25 atomic %, the corrosion resistance and weather resistance of the thin film will also be reduced.

The magnetic recording medium of the present invention can be manufactured, for example, as follows. That is, AI, s+
, or CD, and an alloy thin film containing CO and N (and optionally further Ni and/or Fe) is formed on a substrate, and then heat-treated to release N and reduce the N content. The ratio is set to 0.2 to 5 at%.

In this manufacturing method, the thin film that is first formed on the substrate is amorphous or microcrystalline with a grain size of about 50 to 100 A, and is crystallized or crystallized by heat treatment in a later step.
The crystal grains grow to about 00A, forming a magnetic recording medium having an appropriate HC and a high squareness ratio.

The temperature of this heat treatment is preferably 280° C. or higher, and if the temperature of the heat treatment is lower than 280° C., the active sites for deNization are not activated and deNization does not proceed. Furthermore, if the heat treatment temperature is too high, crystal grains will grow abnormally, leading to a decrease in coercive force HC. Therefore, the preferred heat treatment temperature is 280-500℃
It is.

In addition, as the substrate used in the present invention, various conventionally used non-magnetic substrates can be used, and alloy-based substrates (for example, alloys made of A1 with a few percent or less of magnesium added, titanium alloy substrates), various ceramics, or glass substrates. Further, in addition to a hard underlayer made of chromium, titanium, alumite, N1-P, etc., various nonmagnetic intermediate layers for increasing the adhesion strength of the magnetic thin film may be provided between the substrate and the magnetic thin film. Further, a nonmagnetic metal intermediate layer and/or a protective film made of carbon, polysilicate, etc. may be provided on the magnetic fill. Furthermore, a lubricant may be applied onto this protective film.

[Action] 2 to 12 atom% of A1 or Si, or 2 to 8 atom%
A CO-based alloy magnetic thin film containing any one or more of Cu and having an N content of 0.2 to 5 at% has appropriate magnetic properties, and has good corrosion resistance as shown in the examples below.・Excellent weather resistance.

[Example 1 Hereinafter, the present invention will be explained in detail using specific examples.

In addition, although the embodiment described below uses a magnetron sputtering device, it goes without saying that the effects of the present invention can also be obtained by ion beam sputtering, etc., which can be said to be similar in terms of ion technology. be.

Example 1 Using r, f, planar magnetron sputtering equipment,
Go-based alloy magnetic films having various compositions were formed on glass substrates under the following conditions.

Initial exhaust 1~2x10-' TorrTotal atmospheric pressure (Ar+N2) 10~20mTorr (% of N2 partial pressure to total pressure) 50~80% input power
1 kW Target composition CO (When matching the composition of the target H film, do so by appropriately placing chips of each additive on the target.) Pole spacing 108 mm (during thick sputtering) 700 A thin film formation speed 250 ~500A/glin substrate temperature
After forming the sputtered film at 200° C., the 300° C.-b film was crystallized in a vacuum of 10″’ Torr or less, and the nitrogen contained in the film was released. Afterwards, we investigated corrosion resistance and weather resistance.

Here, the corrosion resistance evaluation is as follows:
By soaking for a week, the weather resistance was evaluated at a temperature of 57℃.
The test was carried out by leaving it for two weeks under the condition of 80% humidity.

The results are shown in Table 1.

Comparative Example 1 A Co-Ni-P alloy magnetic film was created on an appropriately surface-treated glass substrate under the following conditions, and then corrosion resistance,
Weather resistance was evaluated. The results are shown in Table 1.

Plating bath Cobalt sulfate 0.06 mol /
lNickel sulfate 0.04 Hypophosphorous acid 0.2 Ammonium sulfate 0.1 Sodium malonate 0.3 Sodium malate 0.4 Sodium succinate 0.5 pH-8.9-9.3 Temperature 75-85°C Membrane Thickness 70
0A Comparative Example 2 1ll with 0% N content was prepared in the same manner as in Example 1 except that the atmosphere during sputtering was 100% Ar.
I created li. In addition, alloy thin films in cases where residual N1 degree exceeds 5 at%, Ni111 degree exceeds 25 at%, and when additives exceeding the specified amount are contained are similarly prepared under the conditions of Example 1. did.

Its magnetic properties are shown in Table 1.

From Table 1, it can be seen that AI, st, or C according to the present invention
The Cam alloy magnetic thin film containing u is similar to the conventional Co-Ni-
It is recognized that it exhibits far superior corrosion resistance and weather resistance compared to P electroless plated magnetic thin film.

In addition, in order to satisfy the characteristics as a magnetic recording medium,
It is also recognized that the film must be formed under a mixed atmosphere of argon and nitrogen.

Example 2 On a substrate made of a surface-polished aluminum alloy subjected to alumite treatment, 51% was applied under the same conditions as described in Example 1 so as to obtain the desired composition as shown in Table 2. /4“
After a φ disk was prepared and subjected to heat treatment at 350° C. x Ahr in vacuum, an amorphous carbon film of 400 A was formed using an R, F, planar magnetron device.

Next, corrosion resistance and weather resistance were evaluated using these disks. The results are shown in Table 2. The electromagnetic conversion characteristics of the magnetic recording medium were evaluated under the following conditions.

Head used: Mn-Zn ferrite head (track width 16μ11 gap length 1.1μ11 gap depth 20μ
Akebono, number of turns 19Tx 2) Levitation l0034μm Writing frequency 1F: 1.25 MH22F
; 2.5 MHz Disc rotation speed 3600 rpm Measurement point Distance from the center of the disk R-30nui Comparative Example 3 On a 5 1/4"φ disk substrate with a Ni-P plating base layer on a surface-polished aluminum alloy. A co-Jli-P alloy magnetic film was formed under the same conditions as in Comparative Example 1, and then a 400A amorphous carbon film was formed in the same manner as in Example 2.

Next, these were used for evaluation of corrosion resistance and weather resistance.

The results are shown in Table 2. The electromagnetic conversion path characteristics were evaluated under exactly the same conditions as in Example 2.

From the above, it was proven that the magnetic recording medium of the present invention has excellent corrosion resistance and weather resistance.

Claims (4)

[Claims] (1) In a magnetic recording body having an alloy magnetic thin film formed on a substrate, the alloy magnetic thin film is made of one or more of 2 to 12 atomic % aluminum or silicon, or 2 to 8 atomic % copper. A magnetic recording medium comprising a cobalt-based alloy containing. (2) The magnetic recording medium according to claim 1, wherein the alloy magnetic thin film is formed by sputtering and heat-treating the substrate. (3) The alloy magnetic thin film contains at least one of 2 to 12 atomic % of aluminum or silicon, or 2 to 8 atomic % of copper, and 0.2 to 5 atomic % of nitrogen, with the balance being cobalt. A magnetic recording medium according to claim 1 or 2, characterized in that the magnetic recording medium comprises: (4) The alloy magnetic thin film contains at least one of 2 to 12 atomic % of aluminum or silicon, or 2 to 8 atomic % of copper, and 0.2 to 5 atomic % of nitrogen, with the balance being Claims 1 or 2 consist of cobalt and nickel and/or iron, and the content of nickel and/or iron is an amount that replaces 25 atomic percent or less of cobalt. The magnetic recording medium described.