JPS5853024A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a reproduced output with excellent frequency characteristics without thinning a magnetic substance layer, by decreasing residual magnetization to the lower magnetic layer of multilayered magnetic substance layers. CONSTITUTION:Residual magnetization is decreased to the lower magnetic substance of multilayered magnetic substance layers. Fox example, on a substrate 5 such as an aluminum-made disc, a magnetic paint is coated so that the weight ratio gamma/B of magnetic powder (gamma-Fe2O3) to a binder can be halved to that of the upper magnetic layer 7 to form the lower magnetic layer 6, and the upper magnetic layer 7 is provided on the layer 6 to form a magnetic recording medium consisting of a double magnetic layer. The magnetic layer is egually well to form three layers or multilayers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic recording media such as magnetic disks and magnetic tapes used for magnetic recording.

Conventionally, in this type of magnetic recording apparatus, as shown in FIG. 1, recording is performed by changing the magnetization of a magnetic recording medium 4 by leakage magnetic flux 3 from a gap 2 of a magnetic head 1, and Conversely, a magnetic head reads the changes in the magnetic field generated by the magnetization recorded on the medium and converts it into an electrical signal.

Further, the frequency characteristics of the magnetic recording medium used in this type of magnetic recording device can be expressed by the sharpness of the reproduction waveform from isolated inversion magnetization, and the sharper the reproduction waveform, the higher the writing frequency can be.

Generally, the half-width Wl of the reproduced waveform from isolated reversed magnetization is Wl-(a+d+δ) (a+d) """(1
) a: magnetization reversal width d: head-medium 111Iff distance ζ: medium thickness. Here, magnetization reversal @a corresponds to the length of the transition region required for magnetization to reverse, and depends on the magnetic properties of the magnetic recording medium, and is approximately az2aIr/Hc Ir: Medium residual magnetization Hc:
It is expressed in terms of media retention force.

However, as shown in FIG. 2(a), since the distance @d from the head of the upper magnetic layer 4 and the lower magnetic layer 4b becomes large, as shown in FIG. 2(b), the vPI@ is large. Become something. Therefore, since the output from the entire magnetic layer is the superposition of the contribution from the upper magnetic layer 4m and the contribution from the lower magnetic layer 4b (more precisely, the output from the upper magnetic layer to the lower magnetic layer), The half-width property from the lower magnetic layer deteriorates.

In order to prevent the above phenomenon, conventional magnetic recording media have a medium thickness of a
Improvements have been made in the direction of making the media thinner, but there is a limit to this improvement, as reducing the media thickness increases media noise and reduces output.

An object of the present invention is to provide a magnetic recording medium that can provide a reproduction output with good frequency characteristics without making the magnetic layer of the medium thin.

According to the present invention, it is possible to obtain a magnetic recording medium having multilayered magnetic layers in which the residual magnetization of the lower magnetic layer is smaller than that of the upper magnetic layer.

In the present invention, the half width Wl of the reproduced waveform is 12 (!l+d+δ)(Kaede+d)...
The magnetization reversal width a in equation (1) is a-2δIr/Hc...
・(1) I": Medium residual magnetization HC; expressed by medium coercive force.

That is, the magnetization reversal width a is proportional to the residual magnetization Ir.

Therefore, in the lower magnetic layer 4'I, the magnetization reversal width a is made smaller by the amount of d in equation (1) that is larger than that of the lower magnetic layer 4'I, so that the half-value width w#s for 9Ir is also reduced by the signal from the upper magnetic layer 4m. It is possible to prevent a decrease in resolution by reducing the size to the same size as a minute. Note that since the magnetization reversal width becomes smaller, the decrease in output due to the smaller residual magnetization is quickly offset, and the peak value of the output hardly changes.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 4 shows a coating used in a storage device of an electronic computer.

In a normal magnetic disk drive, each parameter in equation (1) is about IgmlJ, d-αδμ, and a-1 voice m.

When the magnetic layer is made into two layers and the thickness of the upper and lower layers is set to αssm as shown in FIG. 4, the magnetic layer is applied downward onto the aluminum disc. As a result, the magnetization is halved, so a=
lIα5 μm is achieved.

In this example, a magnetic layer 11 with an r/B of α1 using Y-Fegog as magnetic powder was applied (coated on a disk and cured, and then a magnetic layer with an r/B of L4 was coated and cured. Forms a double layer.

As another example 1a of the present invention, it is possible to have three magnetic layers or a multilayer magnetic layer. However, in this case as well, it is assumed (according to equation 11) that Wse for m force from each layer is always adjusted to be constant by changing the residual magnetization Ir.

As described above, the present invention has the effect of increasing the resolution of the head output by making the magnetic layer of the medium multilayered so that the residual magnetization at the bottom is small.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a medium and a head, FIG. 2 is a schematic diagram of a conventional medium, and a diagram showing the output of the conventional medium.
FIG. 3 is a diagram showing the output from the medium of the present invention, and FIG. 4 is a diagram showing a cross section of a magnetic disk plate.0, 1...Head, 2...Gap, 3・
...Magnetic flux from the head, 4...Medium, 5
・・・・・・Arun disk, 6 enemy once (shi) 2 Wa police 5ffi

Claims (1)

[Claims] 1. A magnetic recording medium having multilayered magnetic layers, characterized in that the residual magnetization of the lower magnetic layer is reduced.