JPS5857806B2 - magnetic recording method - Google Patents

Description

[Detailed Description of the Invention] When a magnetic head records a signal on a magnetic medium such as a magnetic tape, if the signal has a fairly high frequency (short wavelength), it is magnetized in the thickness direction rather than along the tape surface. It is known that it is more advantageous.

Therefore, if you use a magnetic medium with an axis of easy magnetization in the thickness direction and record by magnetizing it in the thickness direction, it becomes possible to record at a considerably high frequency. It becomes possible to record density.

However, until now, a magnetic head that magnetizes in the thickness direction has not been realized, and therefore high-frequency, high-density recording has been difficult.

Conventional magnetic heads generally have two magnetic heads, as shown in FIG.
It is composed of magnetic poles 1 and 2 that are brought together,
A magnetic gap g is formed on the side of the tape 3 that should face the magnetic layer 4.

The opposing surfaces 1a and 2a of the magnetic poles 1 and 2 forming this magnetic gap g are parallel to each other, and moreover, they form a surface perpendicular to the tape contact surface.

Therefore, the direction of the depth of the gap g, indicated by arrow 5, is perpendicular to the direction of movement of tape 3, indicated by arrow 6.

Note that the magnetic gap g is actually formed with a so-called gap spacer interposed therebetween.

7 is a coil.

However, in such conventional magnetic heads, the direction of magnetization is mainly in the longitudinal direction of the tape 3, making it difficult to record at high frequencies and therefore at high density.

That is, if we look at the magnetic field generated at the air gap g in this head, it will be as shown by the broken line in the figure, and this will be divided into a component Hx in the longitudinal direction of the tape 3 and a component Hy in the thickness direction of the tape 3 perpendicular to this. When it is disassembled and expressed, it becomes as shown in Fig. 2.

The component Hx in the longitudinal direction of the tape 3 is the longitudinal component Hx of the gap g (
The maximum value Mx is exhibited at the center position in the left-right direction of the figure (the direction perpendicular to the plane of the drawing is the width direction that determines the track width), and exhibits symmetrical characteristics.

On the other hand, the component Hy in the thickness direction of the tape 3 is the gap g
Since the tape 3 is traveling in the direction shown by the arrow 6, the opposite surface of the magnetic pole 2 on the side of the traveling direction, that is, the side where the tape 3 finally comes off. 2a
It exhibits a maximum value My at the position of , and exhibits asymmetric characteristics.

The maximum value My of the magnetic field component Hy in the thickness direction is smaller than the maximum value Mx of the magnetic field component Hx in the longitudinal direction, and the magnetic field component Hy gradually attenuates on the magnetic pole 2 side.

This gradual attenuation is caused by the tape 3 of magnetic pole 2.
This is because the surface 2b facing the tape 3 is formed to extend along the surface of the tape 3.

As described above, in conventional general magnetic heads, magnetization in the longitudinal direction of the tape is predominant, making it difficult to record at high frequencies and high density.

A head that magnetizes in the thickness direction of the tape could be a rod-shaped core with a coil wound around it, but this rod-shaped head has extremely poor recording efficiency, requires a very large recording current, and is easily saturated. It's not practical.

However, the present inventor has developed a new magnetic head that can be magnetized in the thickness direction of the tape, thus enabling high-frequency, high-density recording, and with recording sensitivity comparable to that of conventional general heads. I came up with this.

FIG. 3 shows an example of this magnetic head, which is composed of two magnetic poles 11 and 12 that are brought together like a conventional general magnetic head, but are parallel to each other to form the magnetic gap g. For example, the facing surfaces 11a and 12a are made oblique to the tape facing surface.

Therefore, the depth direction of the magnetic gap g shown by arrow 15 is
It is oblique to the traveling direction of the tape 13 shown by.

17 is a coil. Therefore, the tape contact portion is asymmetrical with respect to the magnetic gap g, and in this case, the tape 13
The width Wc (see FIG. 4) of the gap g in the magnetic pole 12 on the traveling direction side, that is, on the side where the tape 13 finally comes off, in the length direction (in the horizontal direction in the figure as described above) (see FIG. 4) is made sufficiently small.

According to this head, the magnetic field component Hy in the thickness direction of the tape 13 becomes large, and moreover, this exhibits a steep characteristic in the longitudinal direction of the tape 13.

That is, if we look at the magnetic field generated at the gap g, it will be as shown by the broken line in the figure, and as shown in FIG. The maximum value Mx at a position slightly closer to the magnetic pole 11 than the position
, and exhibits asymmetrical characteristics with respect to the center position.

The component Hy in the thickness direction of the tape 13 is zero at the center position in the longitudinal direction of the gap g, and has a maximum value My at the end position of the gap g on the magnetic pole 12 side. It is slightly larger than the maximum value Mx of the component Hx.

Moreover, the component Hy in the thickness direction sharply attenuates from the end position of the tape contacting surface 12b on the opposite side to the gap g side to the traveling direction side of the tape 13.

According to this magnetic head, the magnetization in the thickness direction of the tape 13 exhibits characteristics that are sufficiently large and steep, so that high-frequency and therefore high-density recording is possible.

When various characteristics were investigated for a conventional magnetic head having the structure shown in FIG. 1 and a magnetic head having the structure shown in FIG. 3, the following results were obtained.

However, the conventional magnetic heads (shown in Figure 1) are RF-140RO3 manufactured by Sony Corporation (gap length is 10μ), and the tape is a general magnetic tape also manufactured by Sony Corporation. Using a certain 5LH-81,
The tape speed was 9.5 crn/sec.

In each case, the reproducing magnetic head was a PF140-4202 manufactured by Sony Corporation (the gap length was 1 μm).
), and a reproducing amplifier with flat frequency characteristics was used.

Further, the recording signal was a rectangular wave pulse in all cases.

Note that the measurement was performed using a synchroscope. First, if we look at how the characteristics of the reproduction voltage level with respect to the recording signal level change with frequency, in the conventional head it is as shown in Figure 5, while in the head in Figure 3 it is as shown in Figure 6. and as shown in Figure 7.

In both cases, the horizontal axis is a uniform scale, and the vertical axis is also a uniform scale.

In addition, Fig. 6 shows that the length WG of the air gap g (see Fig. 4) is 9
．． 45μ, the length Wc of the tape contacting surface 12b of the magnetic pole 12 is 17.01μ, therefore: = 1.8 (hereinafter referred to as sample I). In Fig. 7, WG is 8.7μ, Wc is 3.78μ, so when "=2.22" (hereinafter referred to as sample 2), WG is obtained.

As is clear from this, in the conventional head, the reproduction output decreases significantly as the frequency increases, whereas in the head of FIG. 3, the attenuation of the reproduction output at high frequencies is small.

Next, if we look at the value of the reproducing voltage at the recording current where the reproducing voltage becomes the maximum at each frequency, it becomes as shown in FIG.

The frequency on the horizontal axis is on a logarithmic scale, and PCI replaces this with the number of changes in magnetic flux per inch of tape.

The vertical axis is a logarithmic scale. 20 is a conventional head;
1 is the case where the sample is sampled with the head shown in FIG.

As is clear from this, it is recognized that there is almost no difference in the characteristics of the maximum reproduction output voltage compared to the conventional one.

The recording pulse has a pulse width T as shown in FIG. 9A.

When the pulse width To is small, the reproduced waveform becomes continuous as shown in Figure 10B, and when the pulse width To is large as shown in Figure 10A, the reproduced waveform becomes continuous as shown in Figure 10B. However, the positional deviation of the positive peak and negative peak of this reproduced waveform with respect to the rising and falling edges of the recording pulse will affect the interference between bits when recording a pulse code signal. , which affects recording density.

Therefore, in each case of Fig. 9 and Fig. 10, we looked at how much the time width TP from the positive peak to the negative peak of the reproduced waveform changes with respect to the pulse width To of the recording pulse, and found the following. It became so.

First, as shown in FIG. 9, the relationship between when the reproduced waveform becomes a continuous wave (to) is as shown in FIG. 11.

The horizontal axis is a logarithmic scale.

In the figure, 22 is a conventional head, and 23 is the head shown in FIG. 3 in the case of sample (2).

As is clear from this, with the head of FIG. 3, the rate of change of the time width TP of the reproduction waveform with respect to the pulse width To of the recording pulse is significantly smaller than that of the conventional head.

Therefore, if a head having a structure as shown in FIG. 3 is used, interference between bits will be reduced in recording pulse code signals, and high-density recording will be possible.

Figures 12 to 17 show the reproduced waveforms observed with an oscilloscope, and the large one on the horizontal axis is O, l m
sec.

Figures 12 to 14 show conventional heads;
Figures 5 to 17 are for the head in Figure 3 and sample ■, and Figures 12 and 15 are for T□ = 300.
When μsec, FIGS. 13 and 16 show T□ =
lOO/! jsec, FIGS. 14 and 17 are for TQ=50 μsec.

It can be seen that when the pulse width To of the recording pulse becomes smaller, there is a significant difference in the time width TP of the reproduction waveform between the head shown in FIG. 3 and the conventional head, and this becomes smaller in the case of the head shown in FIG.

If we look at the relationship at 100 (%), it becomes as shown in Figure 18.

24 is a conventional head, and 25 is the head shown in FIG. 3 for sample (2).

Note that the pulse width of the recording pulse is 83 μsec (PCI
This is a case of approximately 3221).

As is clear from this, according to the head shown in FIG. 3, the time width TP of the reproduced waveform does not change much depending on the magnitude of the recording current and is stable.

On the other hand, Figures 19 and 20 show the positive polarity waveform of the reproduced waveform on the side corresponding to the rising edge of the recording pulse observed with an oscilloscope in the case of a solitary wave as shown in Figure 10. The large Ichimoku dust on the horizontal axis is 0.1 m5ec.

The recording pulse has a frequency of 300 Hz and a duty factor of 1, and its current value is 8 mAp-p.

FIG. 19 shows the conventional head, and FIG. 20 shows the head of FIG. 3 in the case of sample (2).

As is clear from this, in the head of FIG. 3, even when the reproduced waveform becomes a solitary wave, its pulse width becomes small.

The structure of the head is similar to those shown in FIGS. 21 to 23.

21 has the structure shown in FIG. 3, but a non-magnetic material 50 such as ceramic is attached to the side of the magnetic pole 12 opposite to the air gap g side to improve contact with the tape 13 and provide wear resistance. In this case, the coil 17 is wound across the magnetic pole 12 and the non-magnetic material 50.

22 has the structure shown in FIG. 3, but a magnetic thin film 51 of ferrite, sendust, etc. is formed on the opposite side of the magnetic pole 12 from the air gap g side by sputtering, vapor deposition, or vapor deposition. A non-magnetic material 50 is attached to the thin film 51 side.

In the one shown in FIG. 23, the above-mentioned magnetic thin film 51 is attached to one side of a block in which a magnetic body 53 is bonded to a non-magnetic material 52, and this is used as the other magnetic pole and joined to one magnetic pole 11 via a spacer 54. It is something.

By the way, in the case of a head having a special structure as described above, if the recording signal is a pulse, spikes may appear in the reproduced waveform.

For example, under the above measurement conditions, WQ=8.19μ,
WO = 9.45μ, so = = 1.15, w
Using G, the pulse width To is 0.3 m as shown in Figure 24.
When a 5 ec pulse was recorded, the reproduced waveform became as shown in FIG. 25, with spikes occurring as indicated by arrows.

When such a spike occurs, it is undesirable to cause an error during reproduction when recording a pulse code signal.

That is, for example, when a 2-bit code signal is recorded using the NRZI method as shown in FIG. 26A, if a spike occurs in the reproduced waveform as shown in FIG. Since spikes also exist in the rectified output, if a detection signal is obtained by slicing this at the level shown by the chain line 30, error pulses will occur in the detection signal as shown by the broken line in the figure.

The present invention provides a recording method that prevents the above-mentioned harmful spikes from occurring in the reproduced waveform.

In the present invention, a current that saturates the head is caused to flow instantaneously in relation to a change in the recording current.

FIG. 27 shows an example of this, in which the pulse P1 from the input terminal 31 is supplied to the above-mentioned head 33 through the constant current recording amplifier 32, and the pulse P1 is also supplied to the differentiating circuit 34 to obtain a differentiated pulse P2, which is converted into a waveform. A pulse P3 from this is supplied to the head 33 through a constant current recording amplifier 36.

In this way, the recording signal P supplied to the head 33
4, the level that saturates the head 33 is reached only at the rising and falling moments, as shown in FIG.
The head 33 is saturated at the rising and falling points.

FIG. 28 shows another example in which the input pulse P1 is input to the pulse amplifier 3.
7, and is supplied to the above-mentioned head 33 via a parallel circuit of a current limiting resistor 38 and a speed-up capacitor 39.

In this way, the recording signal P supplied to the head 33
5 reaches a level that saturates the head 33 at the rising and falling moments, as shown in FIG. 30, resulting in overshoot, and the head 33 is saturated at the rising and falling points.

It has been found that when recording by the method described above, the above-mentioned harmful spikes do not occur in the reproduced waveform.

Under the above measurement conditions, using the same head as in FIGS. 24 and 25, and overshooting the recorded waveform using the method shown in FIG. 27, as shown in FIG. 31, the reproduced waveform is as follows: As shown in FIG. 32, it was confirmed that no spikes occurred.

As described above, according to the method of the present invention, when a pulse signal or the like is recorded using a special high-frequency, high-density head,
It is possible to prevent harmful spikes from occurring in the reproduced waveform.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional general head, FIG. 2 is a diagram for explaining it, FIG. 3 is a diagram showing an example of a special magnetic head, and FIG. 4 is a diagram for explaining it. Figures 5 to 20 are diagrams for explaining the measurement results of the differences in characteristics between conventional general magnetic heads and special magnetic heads, and Figures 21 to 23.
The figure shows another example of a special magnetic head, Figures 24 and 25 are diagrams to show that spikes occur in the reproduced waveform, and Figure 26 is a diagram to explain the inconvenience when spikes occur. Waveform diagrams, Figures 27 and 28 are system diagrams of an example of the present invention, Figures 29 and 30 are waveform diagrams for explaining each, and Figures 31 and 32 are waveforms reproduced by the present invention. FIG. 2 is a diagram showing that no spike occurs in 11 and 12 are magnetic, g is a magnetic gap, 13 is a tape, 1
7 is a coil, Pl is an input pulse, and P4 and P are recording waveforms.

Claims (1)

[Claims] 1 One of the magnetic pole peaks of a pair of magnetic poles facing the magnetic medium is
For a perpendicular magnetic head that is narrower than the magnetic gap formed by the pair of magnetic poles and records a spike waveform in response to changes in the recording current, the present invention is configured to substantially saturate the head in response to changes in the recording current. . A magnetic recording method in which the spike waveform is substantially removed by superimposing a pulse current having a pulse width sufficiently narrower than the pulse width of the recording current on the recording current.