JPS60231924A - Production of thin film type magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which has the magnetic characteristic approximately equal to the magnetic characteristic of a magnetic recording medium formed by using iron as an essential material and by depositing diagonally cobalt thereon by evaporation and is highly resistant to corrosion even if a protective film is not formed thereon by ionizing a gaseous mixture composed of nitrogen and oxygen simultaneously with vapor deposition of iron on a non-magnetic base material. CONSTITUTION:Iron having 99.9% purity is used as a vapor source 1 and a 35mm. square glass substrate 2 is used as a non-magnetic base material. A magnetic film is formed thereon. More specifically, the atm. pressure in a vacuum vessel is maintained under a vacuum state of <=10<-6>Torr and electron rays are irradiated from an electron gun 5 to the source 1 to evaporate the source 1 so that the vapor of the iron generated therefrom is irradiated onto the substrate 2 at 80 deg. incident angle. A gaseous mixture composed of gaseous nitrogen and gaseous oxygen is introduced into an ion gun 3 of a Kaufmann type via a valve 4 and is ionized in the gun 3. The ionized gaseous mixture is irradiated onto the substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a thin film magnetic recording medium mainly made of iron.

[Prior art]

So-called thin-film magnetic recording media are being put into practical use as high-density magnetic recording media.

Conventionally, in the best high-density magnetic recording media of this type, a magnetic film is created by diagonally vacuum-depositing a ferromagnetic material such as cobalt or a cobalt alloy onto a non-magnetic base material. The produced magnetic film has a coercive force of 10,000e.
The squareness ratio is 0.9 or more.

However, there are two major problems with the practical use of cobalt-based thin film magnetic recording media. First, the cobalt-based magnetic film itself does not have sufficient corrosion resistance for practical use, and conventionally, the magnetic film is used with a protective film applied thereto. but,
Even with the same protective film, the corrosion resistance is not sufficient; for example, after being immersed in salt water with a concentration of 5%, no change in appearance or magnetic properties is observed for about two days at most. Regarding this corrosion resistance, there is a demand for corrosion resistance that can withstand about one month in the same salt water.

Secondly, since cobalt is a scarce resource and is expensive, it has been desired to use materials such as iron, which is abundant in resources and inexpensive.
A high-density magnetic recording medium having a squareness ratio of 00e or more, a squareness ratio of 0.9 or more, and excellent corrosion resistance could not be obtained.

[Purpose of the invention]

The present invention was made to meet the above-mentioned needs for thin-film magnetic recording media, and aims to provide a method for manufacturing a magnetic recording medium that is mainly made of iron and has excellent magnetic properties and corrosion resistance. purpose.

[Structure of the invention]

The method for manufacturing a thin film magnetic recording medium according to the present invention simultaneously evaporates iron onto a nonmagnetic base material.

A magnetic film is fabricated on the substrate by ionizing a mixed gas containing nitrogen and oxygen and irradiating it onto the base material. For ionization of mixed gas, use an ion gun or high frequency discharge type.

Known ionization means used for direct current discharge type, arc discharge type ring, and various types of ion brating can be used.

In this case, when the concentration of nitrogen gas in the mixed gas increases, the squareness ratio tends to deteriorate in the magnetic properties of the magnetic film, and conversely, when the concentration of oxygen gas increases, the magnetism tends to decrease. There is. Therefore, practically, it is appropriate that the concentration of oxygen gas contained in the mixed gas is in the range of 10 to 30%.

In particular, the best results are obtained at a concentration of around 20%.

〔Example〕

Next, an embodiment of the present invention will be described. As shown in FIG. 1, iron with a purity of 99.9% is used as the evaporation source 1, and a glass substrate 2 with a diameter of 35 mm is used as the non-magnetic base material. A magnetic film was formed on this.

That is, the atmospheric pressure in the vacuum chamber is set to a vacuum state of 10-6 Torr or less, and the electron beam is irradiated from the electron gun 5 to the evaporation source 1 to evaporate the evaporation source 1, and the iron vapor generated from it is heated at 80°. The light was irradiated onto the substrate 2 at an incident angle of . At the same time, a mixed gas containing nitrogen gas and oxygen gas was introduced into the Kauffman type ion gun 3 through the valve 4, and the ion gun 3 ionized this gas, and irradiated it onto the substrate 2. The degree of vacuum in the vacuum chamber at this time is lXl0-'Torr
In addition, the amount of introduced mixed gas is 1 to 2 sec/m
in, the ion current density on substrate 2 is 0.2111A/C
It was designated as IA. At this time, the evaporation rate from the evaporation source 1 is measured by a sensor installed adjacent to and at the same height as the substrate 2, while the quartz crystal film thickness meter (XTM) linked to the sensor indicates the evaporation rate. II so that the number of staff in charge will be 20/S.
I controlled J.

For mixed gases, the concentration of oxygen gas is 0.5°10%, 20.50% of the total of oxygen gas and nitrogen gas.
It was conducted in five stages.

Next, the M-H characteristics of the magnetic film of each of the magnetic recording media thus produced were measured using a sample vibrating magnetometer, and the coercive force and squareness ratio were determined.

Further, the thickness of the magnetic film was measured using an optical interference type film thickness meter. The results are shown in Table 1. The thickness of the magnetic film was approximately 1000 to 1500 in all magnetic recording media.

Next, after immersing these magnetic recording media in salt water with a concentration of 5% for 3 months, the appearance and magnetic properties (Table 1) were examined, and no change was observed in the magnetic film compared to before immersion.

As a result, the oxygen gas concentration in the magnetic recording medium was 10
%, magnetic properties equivalent to those of cobalt-based magnetic films can be obtained, especially when the oxygen gas concentration is close to that of air, 20%.
%, better magnetic properties were obtained. Also.

This magnetic film was confirmed to have excellent corrosion resistance comparable to that of iron nitride in the above corrosion resistance test.

〔Effect of the invention〕

As explained above, according to the present invention, the magnetic recording medium is made of iron, which is relatively inexpensive and can be expected to be supplied stably, as the main material, and has magnetic properties equivalent to that of a magnetic recording medium made by obliquely evaporating cobalt. A magnetic recording medium with excellent corrosion resistance can be obtained without applying a film.

[Brief explanation of the drawing]

The drawing is an explanatory diagram schematically showing an example of an apparatus for implementing the present invention. 1- Evaporation source (iron) 2- Substrate (non-magnetic base material) Patent applicant Taiyo Yuden Co., Ltd. Agent Patent attorney Kazuyoshi Hojo

Claims (1)

[Claims] 1. A method for manufacturing a thin-film magnetic recording medium by vacuum-depositing a magnetic material on a non-magnetic base material. A magnetic film is created on the base material by injecting heated evaporated iron vapor onto the base material and at the same time irradiating the base material with ions of a mixed gas containing nitrogen and oxygen. A method for manufacturing a thin film magnetic recording medium characterized by: 2. The method for manufacturing a thin film magnetic recording medium according to claim 1, wherein the reactive gas is air.