JPS6134722A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain excellent recording and reproducing characteristics by providing a Co-Cr vertical magnetic film directly or through a mono/multilayered thin film on a soft magnetic thin film having a negative magnetostriction constant and which is formed on a nonmagnetic substrate. CONSTITUTION:A soft magnetic thin film 3 is provided between a substrate 1 consisting of a nonmagnetic material and a Co-Cr vertical magnetic film 2 to obtain a 2-layered film medium, and a nonmagnetic thin film 4 of Ti, SiO2, or an amorphous material is arranged between the magnetic film 2 and the thin film 3. The orientation of the Co-Cr vertical magnetic film can be improved by arranging the nonmagnetic thin film 4.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to perpendicular magnetic recording media.

(Structure of Conventional Example and its Problems) Conventionally, there is a perpendicular magnetic recording method as a magnetic recording method with excellent short wavelength recording characteristics. This method requires a perpendicular magnetic recording medium whose axis of easy magnetization is substantially perpendicular to the film surface of the medium. When a signal is recorded on such a medium, the residual magnetization is oriented almost perpendicular to the film surface of the medium, so that the shorter the wavelength of the signal, the smaller the demagnetizing field within the medium, resulting in excellent reproduction output. Co-Cr perpendicular magnetic recording media, called single-layer media, are made by depositing a perpendicularly magnetized film mainly composed of Co-Cr on a substrate made of a non-magnetic material using a sputtering method or vacuum evaporation method (such as ion blating method). (including a method in which a portion of evaporated atoms are ionized and deposited). For a single-layer film medium having such a structure, a so-called two-layer film in which a soft magnetic thin film 3 is provided between a substrate 1 made of a non-magnetic material and a Co-Cr perpendicularly magnetized film 2 as shown in FIG. It is known that recording efficiency and reproduction output can be improved by using a structure called a medium. In particular, when recording and reproducing using a known auxiliary magnetic pole excitation type vertical head, the recording efficiency is improved by about 20 dB, and the reproduction output is approximately 20 dB.
Improve by dB.

As described above, excellent recording and reproducing characteristics can be obtained by using a dual-layer film medium, but considering the increasing density and miniaturization of magnetic recording and reproducing devices, the characteristics are still insufficient and even better characteristics are required. was required.

(Objective of the Invention) An object of the present invention is to improve the characteristics of the conventional example and provide a perpendicular magnetic recording medium with extremely excellent recording and reproducing characteristics.

(Structure of the Invention) The perpendicular magnetic recording medium of the present invention includes a non-magnetic substrate, a soft magnetic thin film having a negative magnetostriction constant formed on the non-magnetic substrate, and a layer formed on the soft magnetic thin film directly or in a single layer or in a multi-layered manner. The structure includes a Co--Cr perpendicular magnetization film formed through a structural thin film.

(Description of Embodiment) An embodiment of the present invention will be described based on FIGS. 1 to 4.

The results of an experiment in which the magnetostriction constant of the soft magnetic thin film 3 of the two-layer film medium shown in FIG. 1 was varied will be explained. As the soft magnetic thin film 3,
A permalloy film was selected, and recording and reproduction were performed on five types of samples shown in Table 1 using an auxiliary magnetic pole excitation type vertical head. Note that the present invention regarding the magnetostriction constant can also be applied to soft magnetic thin films other than permalloy. The sample substrate is a heat-resistant polymer film with a thickness of 12 μm.

Table 1 The recording and reproducing characteristics were measured by cutting the sample into a tape with a width of 3.81 wn and setting the tape running speed to 9.5 ann.
/second. Table 2 shows the reproduction output and noise level of each sample based on sample C.

10 KFRPI in the table is the recording state of digital signals with 10,000 magnetization reversals per inch.Table 2 shows that the output and recording density characteristics of all samples are almost the same, but there is a large difference in noise level. I understand.

In Table 2, Sample C has a magnetostriction constant λ of 0, whereas Samples A and B, which have a positive λ, have large noise and λ.

Samples D and E with negative values have small noise. Therefore, samples with negative λ have excellent S/N. In addition, Ni-Fe
In the case of two-element permalloy, if the Ni amount is approximately 90% or more, the initial magnetic permeability decreases, resulting in a deterioration of the reproduction output, so it is preferably 90% or less.

Next, as shown in FIG. 2, even when a nonmagnetic thin film 4 of Ti, Sin, or amorphous is disposed between the Co-Cr perpendicularly magnetized film 2 and the soft magnetic thin film 3, The above results remain unchanged. Note that by arranging the nonmagnetic thin film 4 in this manner, the orientation of the Co--Cr perpendicularly magnetized film is improved. Furthermore, as shown in FIG. 3, even if there is a soft magnetic thin film 5 between the nonmagnetic thin film 4 and the Co--Cr perpendicularly magnetized film 2, the above results do not change. It is better for the soft magnetic thin film 5 to have a negative λ, but even if it is not negative, the effects of the present invention can be seen as long as the soft magnetic thin film 3 has a negative λ. In addition, when the soft magnetic thin film is made into a multilayer structure in this way,
A thin film with a single layer or multilayer structure is present between the Go-Cr perpendicularly magnetized film 2 and the soft magnetic thin film 3, as shown in 0 or more, which has a higher initial magnetic permeability than a single layer and improves recording and reproducing characteristics. The present invention is also very effective in this case.

A concrete example will be explained with reference to FIG. A polyamide heat-resistant film with a film thickness of 10 μm was used as the substrate 1,
A magnetic layer is formed thereon by vacuum evaporation. Co-C
The thickness of the r-perpendicular magnetization film 2 is 1200 mm. 3 and 5 are permalloy films as soft magnetic thin films, and the film thicknesses are 1500 and 1000, respectively. Note that the reproduction characteristics were measured while changing λ8 of the soft magnetic thin films 3 and 5 as shown in Table 3.

Table 3 6.7 shows Ti films with a thickness of 100 and 200, respectively, and the Ti film 6 is provided to improve the orientation of the Co--Cr perpendicular magnetization film 2.

The reproduction characteristics were measured by slitting the medium into a tape having a width of 3.81 mm and using an auxiliary magnetic pole excitation type vertical head.6The reproduction output and noise level in Table 3 are based on Sample F. The playback output at 100 KFRPI is the same for all samples, but samples G and H of the present invention have a higher reproduction output than conventional sample F.

It is obvious that the noise level is lower.

(Effects of the Invention) According to the present invention, there is an effect that extremely excellent recording and reproducing characteristics can be improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the basic structure of a two-layer film medium, FIGS. 2 and 3 are cross-sectional views of a two-layer film medium according to the present invention, and FIG. 4 is a perpendicular magnetic recording medium according to an embodiment of the present invention. FIG. 1...Substrate made of non-magnetic material, 2...Co-
Cr perpendicular magnetization film, 3, 5... Soft magnetic thin film, 4...
・Nonmagnetic thin film, 6,7...Ti film. Patent applicant: Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] a nonmagnetic substrate, a soft magnetic thin film having a negative magnetostriction constant formed on the nonmagnetic substrate, and a Co-Cr formed directly on the soft magnetic thin film or via a thin film having a single layer or multilayer structure.
A perpendicular magnetic recording medium comprising a perpendicular magnetization film.