JPS6022704A - Demodulating method of vertical magnetic record information - Google Patents

Abstract

PURPOSE:To attain the recording/reproducing characteristics equivalent to an auxiliary magnetic pole exciting system with a main magnetic pole exciting system, by obtaining two-time differential waveforms of the output of a magneto-resistance effect type magnetic head when the information written to a vertical recording medium of a compound double-layer film recording medium and detecting the zero cross point of said differential waveforms. CONSTITUTION:The information is written to a compound double-layer film recording medium 6 by a unipolar type recording head 1 and then reproduced by a magneto-resistance effect (MR) type magnetic head 11. In this case, an isolated reproduction waveform similar to a function tan<-1> is obtained. Then a differential waveform (Fig. a) of said isolated waveform is obtained, and the effect of the DC component of said differential waveform is eliminated. This differential waveform is differentiated again to obtain a waveform (Fig. b), and the zero cross point of said waveform is detected. Therefore the zero cross point is detected for said isolated reproduction waveform. When the information is read out by the head 11, a sense current is supplied to the head 11. As a result, the resistance change of the head 11 due to the magnetic field of a vertical magnetic recording medium 3 is converted into a voltage change. This voltage is amplified by a preamplifier 13 and then differentiated two times by the 1st and 2nd differentiation circuits 14 and 15 to be supplied to a zero cross point detector 17 via an LPF16 for detection of the zero cross point.

Description

[Detailed description of the invention] (al Technical field of invention The present invention relates to a method for demodulating perpendicular magnetic recording information.

(bl) Prior Art and Problems Various types of magnetic heads have been proposed for conventional perpendicular recording systems, and the representative one is the so-called auxiliary pole excitation type head shown in Figure 1. , 1 is a main magnetic pole made of NiFe permalloy, 2 is an auxiliary magnetic pole made of a high permeability magnetic material such as ferrite, and 3 is cobalt-chromium (G.

-Cr) having perpendicular anisotropy, and 4 indicates a coil winding wound around an auxiliary magnetic pole for recording and reproducing, respectively.

As shown in the figure, this auxiliary magnetic pole excitation method requires two magnetic poles to be placed between the recording medium. It is difficult to precisely position the two heads, and the mechanism is also complicated. Furthermore, the width of the auxiliary magnetic pole 4 that has been reported so far ranges from several 100 [μm] to several (
m m ), and therefore the inductance of the head is much larger than that of a thin film head, etc., which has the disadvantage that the usable frequency is limited to a low frequency range.

Currently, the data transfer speed of magnetic disk devices is 3 [MBy
te/S) has been realized, but such high-speed data transfer is not possible with the auxiliary magnetic pole excitation method. The auxiliary magnetic pole excitation method has a low transfer rate, and its applicability is limited to magnetic devices in which the magnetic head is fixed, such as magnetic tape devices.

In order to solve the problems of the auxiliary magnetic pole excitation method as described above, a single magnetic pole type head alone (main magnetic pole excitation method) or a conventional bulk ring type head is used to record and read from one direction of the recording medium. A method for doing this has also been proposed. In the case of the main pole excitation method, it is known that in order to efficiently write information to a perpendicular medium, it is practically essential to provide a high magnetic permeability material under the perpendicular medium. However, even when such a 2M film medium is used, the recording efficiency of the head is poor, so there is a drawback that recording cannot be performed with a low magnetomotive force, and the reproduction output is also smaller than that of a ring head. On the other hand, in the ring-shaped head used in conventional horizontal recording, the head writing magnetic field contains many horizontal components, making it difficult to fully utilize the excellent performance inherent in the perpendicular recording method.

[C] Object of the Invention An object of the present invention is to provide a perpendicular magnetic recording information demodulation method that can achieve excellent recording and reproducing characteristics comparable to the above-mentioned auxiliary magnetic pole excitation method using the main magnetic pole excitation method.

(d) Structure of the Invention The present invention is characterized by the perpendicular recording medium surface of a composite two-layer film recording medium in which a perpendicular recording medium having perpendicular anisotropy in the film thickness direction is formed on a high permeability magnetic film. A magnetoresistive magnetic head scans the surface of the perpendicular recording medium by scanning it with a single-pole type recording head to read information written by forming a magnetization reversal on the perpendicular recording medium in response to a predetermined signal. The purpose of the present invention is to detect the magnetization reversal of the perpendicular recording medium by detecting the zero crossing points of the output waveforms obtained by scanning the two same-machine waveforms.

tel Embodiment of the Invention An embodiment of the invention will be described below with reference to FIGS. 2 to 5.

Figures 2 to 4 are diagrams showing the principle of the above embodiment.
The figure shows the isolated reproduction waveform obtained in this example.
1 and 2) respectively indicate the waveforms of the above-mentioned isolated reproduction waveforms for one time and two times. Further, FIG. 4 shows the frequency characteristics of this embodiment. FIG. 5 is a system configuration diagram showing the main parts of the perpendicular magnetic recording information demodulation circuit used in this example.

Composite 2 in which a perpendicular recording medium having perpendicular anisotropy in the film thickness direction, such as cobalt-chromium (Co-Cr), is laminated on a high permeability magnetic layer such as permalloy (Fe-Ni).
When information is written to a layered recording medium using a single-pole type recording head and then reproduced using a magnetoresistive magnetic head, an isolated reproduced waveform similar to the jan'' function shown in Figure 2 is obtained. The zero-crossing point of this isolated reproduction waveform corresponds to the information written on the perpendicular recording medium such as the Co-Cr film, that is, the magnetization reversal formed in the perpendicular recording medium.Therefore, this zero-crossing point However, when reading continuously written information, level fluctuations due to the influence of the DC component called base shift occur, making it difficult to accurately detect the zero cross point. difficult or impossible.

Therefore, if the differential waveform of the reproduced waveform is obtained as shown in FIG. 3(a), the influence of the above-mentioned DC component is removed and a sharp waveform is obtained, so it is sufficient to detect the peak value of this waveform. To do this, by further differentiating this one aircraft waveform and detecting the zero crossing point of the two aircraft waveforms shown in the same figure (bl), we can easily find the zero crossing point of the reproduced output waveform in Figure 2. can be detected.

Moreover, in this case, unlike the conventional method described above, no base shift occurs due to the influence of the DC component.

Curves A and B in FIG. 4 show normalized frequency characteristics when the reproduced output shown in FIG. 2 and the waveforms of the two same machines are used. In the figure, the vertical axis is the normalized output, and the horizontal axis is the recording density CFCI: fluxchange pe.
r 1nch ). By dividing the reproduced output obtained using the magnetoresistive head into two equal parts and detecting the zero cross point, the perpendicular magnetic recording information written on the composite dual-layer film recording medium can be accurately and It becomes possible to read out stably, and since the frequency characteristics are improved, the reading speed can be increased.

The perpendicular magnetic recording information demodulation circuit used in this example and its operation will be explained with reference to FIG. do.

In the figure, ■ is a single magnetic pole head, 3 is a perpendicular recording medium such as cobalt-chromium (Co-Cr) that has perpendicular anisotropy in the film thickness direction, 4 is a coil winding, and 5 is a Ni-Fe permalloy. 6 is a perpendicular recording medium 3.
and a high permeability magnetic film 5, a composite two-layer film recording medium, 7
1 is a write drive circuit, 11 is a magnetoresistive magnetic head consisting of a magnetoresistive element, which is an important part of the present invention, 12 is a current source, 13 is a preamplifier, and 14 and 15 are first and second
16 is a low-pass filter, and 17 is a zero cross point detector.

Written information in the same figure? II&yo, write drive circuit 7,
through the coil 4 wound around the single-pole head 1.
By supplying a magnetomotive force of 5AT, the perpendicular recording medium 3
will be written to. To single magnetic pole type - Nod 1 has a thickness of 0.5
Due to the strong interaction with the NiFe permalloy film 5 of ~1 [μm], the Co-Cr perpendicular recording medium 3 with a thickness of approximately 0.5 [μm] separated by about 0.15 to 0.2 [μm] is sufficiently Generates a write magnetic field sufficient to magnetize.

In this embodiment, the perpendicular magnetic recording information written in this manner is transferred to a magnetoresistive magnetic head with a thickness of approximately 0.04 to 0.05 [μm] that is biased by a bias magnetic field generating means (not shown). 11. This magnetoresistive magnetic head 11 is connected to a current source 12 approximately 1
A sense current of 5 mA is supplied. Magnetoresistive magnetic head 11 generated by the magnetic field generated by the perpendicular magnetic recording medium 3
The resistance change is converted into a voltage change by flowing the sense current, and this voltage is input to the preamplifier 13. The preamplifier 13 amplifies the voltage to a predetermined level. The reproduced output signals obtained in this way are the first and second
After going through two differentiating operations using the differentiating circuit 14.15,
Noise is removed by the low-pass filter 16 and input to the zero cross point detector 17. The zero cross detector 17 detects the zero cross of the analog input signal and generates a pulse signal indicating the zero cross detection. This zero cross detection pulse is sent to the latter stage (
The signal is sent to a digital signal processing circuit (not shown).

According to this embodiment, not only can perpendicular magnetic recording information written on a composite two-layer magnetic recording medium be detected accurately and at high speed, but also the configuration of the perpendicular magnetic recording information demodulation circuit can be simplified.

Furthermore, according to this embodiment, the magnetoresistive magnetic head 11
Since the head can be manufactured using thin film technology in the same way as the single-pole type head, it is possible to form both into an integral structure, which also has the advantage that the mutual positional relationship of both heads can be manufactured accurately.

ff) Detailed Description of the Invention As described in detail, the present invention provides a method for demodulating perpendicular magnetic recording information having excellent recording and reproducing characteristics using a recording/reproducing head disposed on one side of a recording medium, and is capable of demodulating a rigid disk. Even in the magnetic disk device used, it becomes possible to achieve a recording density that exceeds that of current horizontal recording.

[Brief explanation of drawings]

Figure 1 is a side view of a conventional perpendicular magnetic head, Figures 2-
FIG. 5 is a diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing an isolated reproduction waveform obtained by the above embodiment, and FIG.
Figures (al and (b) are waveform diagrams showing the single and double waveforms of the above isolated reproduction waveform, Fig. 4 is a curve diagram showing the frequency characteristics of the above embodiment, and Fig. 5 is a waveform diagram showing the frequency characteristics of the above embodiment). It is a main part system configuration diagram showing the perpendicular magnetic recording demodulation circuit used. In the figure, 1 is a single magnetic pole type head, 3 is a perpendicular recording medium,
4 is a winding, 5 is a high permeability magnetic film, 6 is a composite double layer film recording medium, 11 is a magnetoresistive magnetic head, 12 is a current source,
13 is a preamplifier, 14 and 15 are first and second differentiating circuits, 16 is a low-pass filter, and 17 is a zero cross point detector. Figure 1 Figure 4 Figure 5ryj 7

Claims (1)

[Claims] Scanning the surface of the perpendicular recording medium with a single magnetic pole type recording head of a composite two-layer recording medium in which a perpendicular recording medium having perpendicular anisotropy in the film thickness direction is formed on a high permeability magnetic film,
When reading information written by forming magnetization reversal in the perpendicular recording medium in response to a predetermined signal,
The output waveform obtained by scanning the surface of the perpendicular recording medium with the magnetoresistive magnetic head twice is calculated.
A method for demodulating perpendicular magnetic recording information, characterized in that magnetization reversal of the perpendicular recording medium is detected by detecting zero crossing points of a waveform for the number of times.