JPH0935236A - Magnetic recording media - Google Patents

Abstract

(57) [Summary] [Object] To provide a magnetic recording medium suitable for an inductive head, which has a large Br · δ while using CoSm, and thus has a large read signal intensity. In a magnetic recording medium in which a non-magnetic base metal layer and a magnetic layer of a ferromagnetic alloy are sequentially laminated on a non-magnetic substrate, the magnetic layer is a magnetic layer 31 made of CoCrTa and a magnetic layer 31 on the magnetic layer. Magnetic layer 33 made of CoSm laminated on
A two-layer magnetic layer consisting of
a magnetic layer, an intermediate layer made of a non-magnetic material laminated on this layer, and a Co layer laminated on this intermediate layer.
A composite magnetic layer composed of a magnetic layer composed of Sm. Reference numeral 4 is a protective layer, and 5 is a lubricating layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a longitudinal thin film magnetic recording medium for a hard disk device used as a magnetic recording device for computers and the like.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view of a conventional magnetic recording medium. A nonmagnetic layer 12 is formed on the surface of a nonmagnetic substrate 11 made of Al or the like, a magnetic layer 3 is formed thereon as a recording layer, and a protective layer 4 and a lubricating layer 5 are further formed on the magnetic layer 3. ing. In response to the demand for increased recording density, the magnetic layer 3 is changed from the coated magnetic layer to a metal thin film magnetic layer formed by sputtering. Usually, in order to improve the coercive force characteristics of the magnetic layer for magnetic recording, the magnetic layer is thinned and the coercive force is improved by the shape anisotropy in the in-plane direction (longitudinal direction) and the film thickness direction. Is being done.

In order to increase the recording density of the magnetic recording medium, the magnetic properties of the magnetic layer are high coercive force (Hc), the product of the residual magnetic flux density (Br) and the film thickness (δ) of the magnetic layer. It is necessary that Br · δ be large and the S / N ratio at the time of recording / reproduction be large. One of the magnetic materials with this feature
Although CoCrTa having a large S / N ratio has been used as a seed although the coercive force is not remarkably high, CoCrPtTa has come to be used as a material for improving the coercive force. However, this material has a limitation in reducing noise as compared with CoCrTa, and further increase in recording density cannot be expected. Therefore, research on CoSm is underway as a material that is expected to have a coercive force of 3000 Oe or more and has low noise.

[0004]

Co, which is a ferromagnetic material,
Even in the magnetic layer using Sm, when the nonmagnetic metal underlayer is Cr and the film thickness is about 20 nm, the coercive force is 32.
A magnetic recording medium with 00 Oe and Br · δ of 138 Gauss · μm is known. However, since Br · δ is slightly small, the recording / reproducing signal level is low, and the S / N ratio by the inductive head is insufficient at 32.1 dB.

This is the saturation magnetic flux density (Bs) of CoSm.
Is 650 emu / cm ³ and that of CoCrTa or CoCrPtTa is smaller than 800 emu / cm ³ , so the external leakage magnetic flux density from the magnetic layer traversed by the signal reading head is small. The object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a magnetic recording medium having a large Br · δ while using oSm, and thus having a large read signal strength and suitable for an inductive head.

[0006]

In order to achieve the above object, the present invention is a magnetic recording medium in which a non-magnetic metal underlayer and a ferromagnetic alloy magnetic layer are sequentially laminated on a non-magnetic substrate. In the above, the magnetic layer is a two-layer magnetic layer including a magnetic layer made of CoCrTa and a magnetic layer made of CoSm laminated on the magnetic layer.

Further, in a magnetic recording medium in which a non-magnetic metal underlayer and a magnetic layer of a ferromagnetic alloy are sequentially laminated on a non-magnetic substrate, the magnetic layer is made of CoCrTa, and the magnetic layer is made of CoCrTa. It is assumed that the composite magnetic layer is composed of an intermediate layer made of a non-magnetic material and laminated on the intermediate layer, and a magnetic layer made of CoSm laminated on the intermediate layer.

[0008]

According to the present invention, the magnetic layer in the magnetic recording medium is a two-layer magnetic layer comprising a magnetic layer made of CoCrTa and a magnetic layer made of CoSm laminated on the magnetic layer, or the magnetic layer is Since the composite magnetic layer includes a magnetic layer made of CoCrTa, an intermediate layer made of a non-magnetic material laminated on the layer, and a magnetic layer made of CoSm laminated on the intermediate layer, a high CoSm protective layer is obtained. The magnetic force and the high saturation magnetic flux density of CoCrTa are simultaneously expressed in the laminated magnetic layer, the coercive force is larger than that of the CoCrTa single layer, and the average saturation magnetic flux density of the entire magnetic layer is larger than that of the CoSm single layer.

Further, since the layers having different magnetic properties are adjacent to each other, the magnetic exchange action between these layers is reduced, and the noise due to the magnetic exchange action is reduced. When the non-magnetic intermediate layer is interposed between the two magnetic layers, the magnetic exchange action is further reduced and the noise is further reduced.

[0010]

【Example】

Example 1 FIG. 1 is a sectional view of a magnetic recording medium of an example according to the present invention. The disc-shaped non-magnetic substrate 1 includes a non-magnetic substrate 11 made of an Al alloy and a Ni-P plated non-magnetic layer 12 on the surface thereof.
And the surface of the non-magnetic layer 12 was subjected to texture treatment in the circumferential direction. The non-magnetic substrate 1 uses a glass plate as a non-magnetic substrate 11 and a non-magnetic layer 12 of Cr thereon.
May be laminated.

In either case, the magnetic recording medium has a nonmagnetic metal underlayer 2 of 100 nm in thickness, a magnetic layer 31 of CoCrTa, a magnetic layer 33 of CoSm, and a protective layer of carbon on the nonmagnetic substrate 1. 4, lubrication layer 5 of liquid lubricant
To have a layered structure in which Film formation of the magnetic recording medium of the present invention was carried out using a magnetron sputter film forming film arrangement. The target used was a Cr target for the non-magnetic metal underlayer, CoCr ₁₄ Ta ₄ for the magnetic layer, and a C target for the protective layer. The gas is Ar.

After forming a non-magnetic metal underlayer 2 of Cr having a thickness of 100 nm on a non-magnetic substrate 1, Co having a thickness of 20 nm is formed.
A CrTa magnetic layer 31 and a CoSm magnetic layer 33 having a thickness of 30 nm were successively laminated. The laminated magnetic layers are C-axis oriented in the plane of the medium according to the texture. Further, an amorphous carbon layer having a thickness of 20 nm was laminated as the protective layer 4, and a fluorocarbon liquid lubricant was applied to a thickness of 2 nm to form a lubricating layer.

The magnetic recording medium thus manufactured is
The coercive force is 3250 Oe, Brδ is 254 Gauss · μm, and the S / N ratio is 3 when the inductive head is used.
It was 5.2 dB. It can be seen that the coercive force, Br · δ and S / N ratio are all improved as compared with the magnetic layer of SmCo alone. Embodiment 2 FIG. 2 is a sectional view of a magnetic recording medium of another embodiment according to the present invention. Example 1 up to non-magnetic substrate 1 and underlayer 2
I used the same one. The magnetic layer is a composite magnetic layer having the following constitution. The magnetic layer 31 is CoCrTa, and the magnetic layer 31 is
Was CoSm. The nonmagnetic intermediate layer 32 is made of Cr and M.
o sputtered films were used as different magnetic recording media. The thickness of the non-magnetic intermediate layer 32 was set to 2 to 3 nm. The magnetic layer, the protective layer and the lubricating layer were formed in the same manner as in Example 1.

The magnetic recording medium thus manufactured is
The coercive force is 3300 Oe, Br · δ is 258 Gauss · μm, and the S / N ratio is 3 when the inductive head is used.
7.2 dB, which is a coercive force compared to the magnetic layer of SmCo alone,
It can be seen that the S / N ratio is improved although the change in Br · δ is small. This is due to the effect of weakening only the exchange coupling between the magnetic layers that causes noise by preserving the magnetostatic coupling by inserting the extremely thin non-magnetic intermediate layer between the two magnetic layers. We were able to provide a medium of noise. Further, when the non-magnetic intermediate layer was a Cr layer, it became easy to obtain a microcrystalline structure, which is a mechanism for manifesting the magnetization of CoSm, and a higher coercive force could be achieved.

[0015]

According to the present invention, the magnetic layer in the magnetic recording medium is a two-layer magnetic layer comprising a magnetic layer made of CoCrTa and a magnetic layer made of CoSm laminated on the magnetic layer, or Since the layer is a composite magnetic layer composed of a laminated magnetic layer composed of CoCrTa, an intermediate layer composed of a non-magnetic material laminated on this layer, and a magnetic layer composed of CoSm laminated on this intermediate layer, Both high coercive force and low noise can be achieved. Further, the introduction of the non-magnetic intermediate layer can weaken the exchange coupling between the magnetic layers and further reduce the noise. The magnetic recording medium of the present invention is improved in coercive force, Br · δ and S / N ratio in comparison with the medium having a magnetic layer of SmCo alone, and a magnetic recording medium having a high recording density suitable for an inductive head can be obtained. To be

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic recording medium according to an embodiment of the present invention.

FIG. 2 is a sectional view of a magnetic recording medium of another embodiment according to the present invention.

FIG. 3 Conventional magnetic recording medium

[Explanation of symbols]

 1 non-magnetic substrate 11 non-magnetic substrate 12 non-magnetic metal layer 2 non-magnetic metal underlayer 3 magnetic layer 31 CoCrTa magnetic layer 32 intermediate layer 33 CoSm magnetic layer 4 protective layer 5 lubricating layer

Claims (2)

[Claims] 1. A magnetic recording medium in which a non-magnetic metal underlayer and a magnetic layer of a ferromagnetic alloy are sequentially laminated on a non-magnetic substrate, wherein the magnetic layer is made of CoCrTa and the magnetic layer is made of CoCrTa. A magnetic recording medium comprising a two-layer magnetic layer comprising a magnetic layer made of CoSm laminated on the magnetic layer. 2. A magnetic recording medium in which a non-magnetic metal underlayer and a magnetic layer of a ferromagnetic alloy are sequentially laminated on a non-magnetic substrate, wherein the magnetic layer is made of CoCrTa, and
An intermediate layer made of a non-magnetic material laminated on this layer,
A magnetic recording medium comprising a composite magnetic layer comprising a CoSm magnetic layer laminated on the intermediate layer.