JPH0376015A - Parametric playback head for perpendicular magnetic recording - Google Patents

Abstract

PURPOSE:To obtain high reproduced output and high S/N in spite of high-density recording by confining the thickness in the track direction of the end face of a main magnetic pole facing a magnetic layer to <=2mum and executing the parametric reproduction of perpendicular recording signals. CONSTITUTION:This head has the main magnetic pole 10, one end of which extends to face the magnetic layer of the magnetic recording medium, a pair of leads which are connected between the prescribed positions in the longitudinal direction of the main magnetic pole 10 and a coil wound on the main magnetic pole 10. The thickness in the track direction of the end face of the main magnetic pole 10 facing the magnetic layer on the front end part 15 side is <=2mum, more preferably 0.1 to 2mum, more specifically preferably 0.1 to 1mum. About 120dB sensitivity to the magnetization recorded on the medium and about 100d/B S/N are obtd. with this parametric playback head for perpendicular magnetic recording. The sufficient reproduced output and S/N are obtd. in this way in spite of the high-density recording and the ultra-high density recording system is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a parametric read head for perpendicular magnetic recording.

<Conventional technology> A perpendicular magnetic recording system suitable for high-density recording is known.

The mainstream magnetic heads used in this system include auxiliary pole excitation type single magnetic pole heads and main pole excitation type single magnetic pole heads.

As an example, FIG. 4 shows an auxiliary magnetic pole excitation type single magnetic pole head.

This magnetic head is composed of a main magnetic pole 21 and an auxiliary magnetic pole 25 around which a coil 27 is wound.

To perform recording, a signal current is passed through the coil 27 of the auxiliary magnetic pole 25.

This current causes a magnetic flux change, the magnetic flux concentrates on the main magnetic pole 21, and the magnetic recording medium 3 is magnetized perpendicularly.

Reproduction is performed in the reverse order, and the magnetization recorded on the medium 3 causes a magnetic flux change in the auxiliary magnetic pole 25, and a reproduction signal is induced in the coil 27.

Incidentally, the higher the density of recording on the medium 3, the more the magnetization decreases.

Therefore, in the conventional magnetic head, since the magnetic head itself is a passive element, sufficient reproduction output cannot be obtained.

In addition, there is a limit to the recording density in order to increase the S/N ratio to 40 to 45 dB or more, and it is difficult to increase the recording density.

On the other hand, the 12th Academic Lecture Summary of the Japanese Society of Applied Magnetics (19
No. 88), page 265, discloses a parametric reproducing head for perpendicular magnetic recording having an amplification effect.

This reproducing head has a groove in the auxiliary magnetic pole of a conventional magnetic head, and has a smaller signal sensing portion.

In this reproducing head, the LC resonance circuit is operated by the inductance L of the reproducing head and the time-varying capacitance C at tlH5!2L, and reproduction is performed as described below.

First, when the value of C is changed periodically by some method, an oscillation voltage with a frequency half the frequency at which C changes is generated in the circuit under certain conditions.

Since this oscillation voltage is a function of L, the oscillation voltage undergoes amplitude modulation depending on the externally applied magnetic field.

By demodulating this amplitude modulated wave, a constant output proportional to the signal magnetic field is obtained regardless of the frequency of the signal magnetic field.

However, in this reproducing head, since the area for sensing signals is large, it is difficult to prevent crosstalk when the recording density becomes high.

For this reason, the S/N ratio is particularly insufficient for high-density recording.

<Problems to be Solved by the Invention> An object of the present invention is to provide a parametric reproducing head for perpendicular magnetic recording that can obtain high reproduction output and high S/N ratio even in high-density recording.

Means for Solving the Problems> These objects are achieved by the present inventions (1) to (7) below.

(1) A main magnetic pole whose one end extends to face the magnetic layer of the magnetic recording medium, a pair of leads connected between predetermined positions in the longitudinal direction of the main magnetic pole, and a coil wound around the main magnetic pole. A parametric reproducing head for perpendicular magnetic recording, characterized in that the end face of the main pole facing the magnetic layer has a thickness in the track direction of 2- or less, and performs parametric reproduction of a perpendicular recording signal.

(2) The main pole has a distributed capacitance coil (1).
) A parametric reproducing head for perpendicular magnetic recording.

(3) The parametric reproducing head for perpendicular magnetic recording according to the above (1), wherein a capacitor is connected between the lead pair in parallel with the main magnetic pole.

(4) (1) or 3) above, wherein the thickness of the end face of the main pole facing the magnetic layer in the track width direction is 10 - or less.
A parametric reproducing head for perpendicular magnetic recording according to any one of the above.

(5) The parametric reproducing head for perpendicular magnetic recording according to any one of (1) to 4) above, wherein the main pole is formed as a thin film on a base material.

(6) The parametric reproducing head for perpendicular magnetic recording according to (5) above, wherein the base material is a conductive wire, and a magnetic layer is provided on the surface of the wire.

(7) The parametric read head for perpendicular magnetic recording according to any one of (1) to 6) above, wherein the main pole has an axis of easy magnetization that intersects with the longitudinal direction.

<Examples> The present invention will be described in detail below with reference to preferred examples of the present invention.

FIG. 1 shows an example of a parametric reproducing head for perpendicular magnetic recording according to the present invention.

The reproducing head 1 of the present invention has a main magnetic pole 10. In addition to the main magnetic pole 10, an auxiliary magnetic pole (not shown) may be provided.

Recording prior to playback is generally similar to normal perpendicular recording.
For example, this is done using a normal main magnetic pole and an auxiliary magnetic pole.

Then, reproduction is performed by the illustrated reproduction head l.

The main pole 10 used in the present invention may be made of any material as long as it can be saturated by the excitation magnetic field.

As shown in the figure, the shape is one in which one end extends facing the magnetic layer of the magnetic recording medium, such as a needle or rod shape, or even a strip shape, which extends in the axial direction. Preferably.

In addition, it may have a bent shape due to its structure.

With such a shape, the end face facing the magnetic layer can be made small and can be adapted to high recording density. Furthermore, the diameter of the coil can be made small and evenly wound, and furthermore, it can be saturated with a small excitation current.

The thickness of the end surface of the main pole 10 facing the magnetic layer on the side of the tip 15 in the track direction is 2JJJI or less, preferably 0.
1 to 2-1, particularly preferably 0.1 to 1-.

The thickness of the end surface of the main pole 10 on the side of the tip 15 in the track width direction is 10 - or less, more preferably 0.1 to 10
4, more preferably 0.1 to 2μ, particularly preferably 0
．． It is preferably 1 to 1 pR.

With such a size, a high S/N ratio can be obtained even for high-density recording.

The thickness of the main magnetic pole is a maximum value of 10 μm from the tip of the main magnetic pole 10.

In order to make the tip end face of the main magnetic pole 10 such a size, the main magnetic pole can also be formed by processing a 1 Mi wire.

However, in order to process more accurate shapes and dimensions,
The main pole is preferably formed as a thin film on the base material.

In this case, the thin film may be formed using various methods such as electroplating, electroless plating, and sputtering, but the thickness should be about 0.1 to 2-1, more preferably about 0.5 to 2-2. is preferred.

Further, the material of the main pole 10 may be any soft magnetic material, but the main pole 10 must be electrically conductive, and for example, a magnetic alloy such as permalloy is suitable as the material.

On the other hand, various base materials are possible as long as they are non-magnetic.
It may be insulating or conductive.

The main magnetic pole 10 shown in FIG. 2 has a magnetic film 11 coated on the surface of a conducting wire 13, which is a conductive wire.

For example, it is preferable to use a copper wire for the conducting wire 13 and a magnetic alloy such as permalloy for the magnetic film 11.

In such a case, the tip 15 of the main pole 10 shown in FIG. 2 is shaped like a truncated cone.

Such a shape can prevent interference such as crosstalk even when the recording density is high.

Note that electrolytic etching, for example, is suitable for processing the tip end 15 of the conductive wire 13 of the main pole 10 into a truncated cone shape.

Alternatively, the reproducing head 1 may be formed as a thin film on a non-magnetic base material. Further, a turn magnetic pole may be formed just as the main magnetic pole 10.

In these cases, it is preferable to provide the magnetic film 11 with a linear easy axis of magnetization inclined with respect to the longitudinal direction of the main magnetic pole 10 or an easy axis of magnetization with in-plane rotation (rotation curve shape).

The inclination angle of the straight axis of easy magnetization is O~4 with respect to the longitudinal direction.
Approximately 5° is suitable.

Furthermore, in order to provide an axis of easy magnetization with in-plane rotation, magnetic fields with different phases may be applied in the longitudinal direction and the direction perpendicular thereto (circumferential direction), and plating or the like may be performed in the magnetic field.

In this way, an axis of easy in-plane magnetization, such as a trochoidal shape, can be formed.

By adding anisotropy in this way, when an excitation current is applied,
Parametric oscillation becomes easier and the oscillation margin becomes wider.

Further, the size of the main magnetic pole IO may be appropriately determined depending on the application, but when it is in a needle-like form, the following sizes are preferable, for example.

Length in the longitudinal direction of the main magnetic pole 1: about 0.5 to 10 cm Diameter φ of the conductor 13: about 0.1xO, Fz++m Further, a pair of leads 5 for supplying exciting current is connected to both ends of the main magnetic pole 1O.

As the material of the lead pair 5, any known material can be used as long as it is for current-carrying purposes, and examples thereof include formal resin-coated wire, polyurethane-coated wire, and the like.

The connection position of the lead pair 5 is arbitrary as long as a distributed capacitance coil 41 and an output coil 43, which will be described later, can be formed between the connection parts 53 and 55. All you have to do is connect.

In this case, in order to reduce leakage magnetic flux, it is preferable to connect the coil with a slight spacing. In addition, on the tip end 15 side, it is preferable to connect at a little distance from the tip in order to prevent disconnection due to contact with the medium.

In such a case, the lead pair 5 or the coils 43 and 4 described later
The first layer may be provided using a thin film forming technique.

Note that an excitation current I2f at frequency 2 is passed through the lead pair 5 to perform reproduction.

In addition, in the illustrated example, the main magnetic pole 10 includes a distributed capacitance coil 4.
1 is formed.

The distributed capacitance type coil 41 may be formed by a bobbin having a distributed capacitance type coil, or may be formed by winding a coated conducting wire directly around the main pole lO.

In any case, it is not necessary to wire both terminals of the distributed capacitance coil 41.

Moreover, it is preferable that the distributed capacitance coil 41 be formed with one layer or multiple layers of parallel winding.

By winding in this manner, the distributed capacitance C can be increased, and the setting of the distributed capacitance C is easy.

The distributed capacitance C set here has a constant width determined by the tuning frequency f and the inductance L of the tuning circuit, and is appropriately determined so as to satisfy the resonance condition.

Note that it is also possible to set the tuning frequency f and inductance L so as to satisfy the resonance conditions.

In this case, the tuning frequency f is usually a frequency divided by 1/2, that is, 1/2 of the excitation frequency 2f. Also,
The inductance L is approximated by the inductance of the distributed capacitance coil 41 because the number of turns of the output coil 43, which will be described later, is small.

Note that the resonance conditions may be set using a capacitor, an inductor, or the like instead of or in addition to the distributed capacitance coil 41.

Set capacitance C and inductance L of the distributed capacitance coil 41
may be determined appropriately depending on the application and the excitation frequency 2f. For example, in the case of 1/2 frequency division, the excitation frequency 2f is 2
If Ml(z), oscillation will occur if the distributed capacitance coil 41 is wound in three layers in parallel and has about 500 to 2000 tangents.

Above the distributed capacitance coil 41 is an output coil 43.
is wound.

Any material can be used for the output coil 43 as long as it is suitable for current-carrying.

The number of turns is also arbitrary, but usually about 1 to 10 turns is suitable.

The distributed capacitance coil 41 and the output coil 43 are connected to the main magnetic pole 1.
It may be wound only around the return wire 51 connected to the tip 15 of the main magnetic pole 10 and both the main magnetic pole 10, each having its own effect, but it is particularly preferable to wind it around both. If it is wound only around the main pole 10, it can be wound in close contact with the magnetic material. Furthermore, by winding the wire around both sides, the magnetic flux generated by the excitation current flowing through the main pole 10 and the magnetic flux generated by the current flowing through the return wire 51 cancel each other out, resulting in an even higher S/N ratio.

In the present invention, the component corresponding to the oscillation frequency f is used as a seed signal, for example, at a frequency of -120 to -4 with respect to the oscillation voltage.
The coupling may be approximately 0 dB.

Specifically, for example, another coil may be provided by branching off between the winding portion of the output coil 43 and the terminal.

Next, another embodiment of the parametric reproducing head for perpendicular magnetic recording of the present invention will be explained.

FIG. 3 shows an example of another embodiment of the reproducing head 1.

In this case, the excitation current 1 xt is passed through the coil 45 to magnetize the magnetic film 11 of the main pole 10 in the longitudinal direction.

In this case, to facilitate parametric oscillation,
It is preferable to provide an easy axis of magnetization that is inclined with respect to the circumferential direction of the main pole 10 or an easy axis of magnetization that is in the form of in-plane rotation (rotation curve) as described above.

Note that the angle of inclination is preferably about 0 to 45 degrees with respect to the circumferential direction.

By the way, in this embodiment, the monodistributed capacitance type coil 41 is not wound.

As for the capacitance C of the tuning circuit, the lead pair 5.
A capacitor C1 is connected in parallel with the main magnetic pole 10 between the main magnetic poles 10 and 10.

Further, the inductance of the magnetic film 11 becomes the inductance L of the tuned circuit.

In this case, the tuning current I, is capacitor C1 - lead 5
- main pole 10 - flows in a closed loop formed by lead 5.

The reproduced output may be obtained by measuring, for example, the V induced between the lead pair 5.5 in the same manner as described above, and reading the presence or absence of oscillation and the phase.

Note that it is of course possible to demodulate and read the amplitude modulated wave.

<Effect> An explanation will be given by taking the reproducing head 1 shown in FIG. 1 as an example.

An excitation current 11f is passed through the lead pair 5 connected to the main magnetic pole 10 to magnetize the magnetic film 11 of the main magnetic pole 10.

The excitation frequency 2f is preferably about 0.1 to 100 MHz.

Oscillation at a low frequency is not suitable for high-density recording, but at too high a frequency, the inductance cannot be increased.

In this case, the magnitude of Iff is such that the magnetic film 11 is magnetized to near saturation.

In this way, negative inductance is generated in the magnetic film 11.

Next, the medium 3 is run or rotated at a predetermined speed while bringing the tip of the main pole 10 into contact with the magnetic recording medium 3.

When the recording point of the medium 3 passes through the main magnetic pole lO, the recorded magnetization causes a DC current component to be processed. . occurs, I
ff and IDC.

Note that the oscillation or tuning frequency f is such that the excitation frequency 2f is 1
The frequency is divided by /2 and is about 2.5 to 50 MHz.

The capacitance C and inductance L of the tuned circuit are the frequency f
It is set to a predetermined value so that it oscillates at

In this way, the tuned 1/2 frequency wave is transmitted to the output coil 43 as a signal.

In this case, since oscillation occurs at the recording point and not at the unrecorded portion, the presence or absence of oscillation is read by measuring the tuning voltage (2) and tuning current Ir induced in the output coil 43.

Therefore, even if the magnetization recorded on the medium 3 is small, a high output and a high S/N ratio can be obtained.

Note that it is more effective if Ixt is superimposed on the DC bias current as an excitation current.

Here, in the reproducing head 1 of the present invention, an output coil 43 for signal detection is wound in the circumferential direction of the main magnetic pole 10.

Therefore, the excitation current 1. The influence of magnetic flux generated when f or DC bias current is caused to flow can be almost ignored, and a high S/N ratio can be obtained.

In addition to the above-mentioned amplification effect, parametric excitation has a shaping effect that corrects the waveform to a standard shape, and the reproduced output is
It vibrates in either O phase or π phase.

Therefore, whether the magnetization recorded on the medium 3 is an S-pole-N-pole signal or a N-pole-8 scratch signal can be determined based on the difference in the phase of vibration.

In this case, it is more effective to couple the component corresponding to the tuning frequency f as a seed signal.

In addition, in the present invention, by amplitude modulation of the tuned 172 frequency divided wave,
You can also play it.

In this case, the magnetic film 11 is saturated with only the excitation current Iff or with Iir and a DC bias current to cause oscillation in advance.

Then, it is sufficient to demodulate the amplitude modulated wave that changes depending on whether or not IDI is present.

With either method, it is possible to perform reproduction regardless of the frequency of the recorded signal.

In the example shown in FIG. 3, the excitation circuit is the coil 45 and the tuning circuit is between the lead pair 5.5, and oscillation and reproduction are performed in substantially the same manner as described above.

The reproducing head of the present invention can reproduce any conventionally known perpendicular magnetic recording type media, such as disk-shaped or tape-shaped media.

The reproducing head l of the present invention may be of a sliding type or a floating type.

<Effects of the Invention> According to the parametric reproducing head for perpendicular magnetic recording of the present invention, the sensitivity to magnetization recorded on the medium is 120.
dB and an S/N ratio of about 100 dB.

Therefore, it provides sufficient playback output even for high-density recording.
A high S/N ratio can be obtained, and an ultra-high density recording method can be realized.

The present inventors conducted various experiments to confirm the effects of the present invention. An example is shown below.

Experimental Example Parametric reproducing head sample No. 1 for perpendicular magnetic recording of the type shown in FIG. 1 and sample No. 1 of an auxiliary pole excitation type single magnetic pole head shown in FIG. 4 for comparison.
, 2 were prepared.

Sample No. 1 (Invention) The main magnetic pole 10 was made into a needle-like shape by forming a permalloy film with a thickness of 1- by electroplating on a copper wire having a diameter φ of 0.5 m111.

Further, the length of the main magnetic pole 10 in the longitudinal direction is 4 cm.

The diameter φ at a height of 10- from the most extreme part was set to 1-.

The permalloy film was plated in a magnetic field to provide a linear axis of easy magnetization with an inclination angle of 5 degrees to the longitudinal direction of the main magnetic pole 10.

The distributed capacitance coil 41 was formed by a distributed capacitance coil bobbin, and was wound around both the main pole 10 and the return wire 51.

In this case, the distributed capacitance coil 41 was made of a polyurethane coated wire with a diameter of 30 mm, and was wound in three layers in parallel for 1200 turns.

The output coil 43 had five turns.

Sample No. 2 (Comparison) For the main pole 21, a Co-Zr-Nb film was formed on a non-magnetic substrate.

Furthermore, Mn--Zn ferrite was used for the auxiliary magnetic pole 25. The coil 27 had 60 turns.

Each sample is used to reproduce a perpendicular recording signal recorded on the same magnetic recording medium, and the reproduction output and S
/N ratio was determined.

Note that as the excitation current for sample No. 1 of the present invention, 30 mA of alternating current with a frequency of 2 MHz was superimposed on 100 mA of direct current bias current.

Then, it was oscillated in advance at a frequency of I MHz, and the amplitude modulated wave was demodulated and reproduced.

As a result, in sample No. 1 of the present invention, the reproduced output was 50 mV% and the S/N ratio was 1200 dB.

On the other hand, in comparison sample No. 2, the playback output is l
The voltage was about mV or less, and the S/N ratio was about 20 to 30 dB or less.

From these, the effects of the present invention are obvious.

Incidentally, when a reproducing head sample of the type shown in FIG. 3 was manufactured and a similar test was conducted, results equivalent to those described above were obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a parametric reproducing head for perpendicular magnetic recording according to the present invention. FIG. 2 is a sectional view showing an example of the main pole of the parametric reproducing head for perpendicular magnetic recording of the present invention. FIG. 3 is a perspective view showing another embodiment of the parametric reproducing head for perpendicular magnetic recording of the present invention. FIG. 4 is a perspective view showing a conventional perpendicular magnetic recording head. Explanation of symbols 1...Reproducing head 1O121...Main magnetic pole 11...Magnetic film 13...Conducting wire 15...Tip portion 25...Auxiliary magnetic pole 3...Magnetic recording medium 41...Distribution Capacitive coil 25.45...Coil 43...Output coil 5...Lead pair 51...Return wire 53.55...Connection point C1...Capacitor Applicant TDC Co., Ltd. Patent Attorney Ishii Seikan Patent Attorney
Increase 1) Tatsuya FIG, 1 FIG, 3 FIG, 4

Claims (7)

[Claims] (1) A main magnetic pole whose one end extends to face the magnetic layer of the magnetic recording medium, a pair of leads connected between predetermined positions in the longitudinal direction of the main magnetic pole, and a coil wound around the main magnetic pole. A parametric reproducing head for perpendicular magnetic recording, characterized in that the end face of the main pole facing the magnetic layer has a thickness in the track direction of 2 μm or less, and performs parametric reproduction of a perpendicular recording signal. (2) Claim 1 in which the main magnetic pole has a distributed capacitance coil.
A parametric reproducing head for perpendicular magnetic recording described in . (3) The parametric reproducing head for perpendicular magnetic recording according to claim 1, wherein a capacitor is connected between the lead pair in parallel with the main magnetic pole. (4) The parametric reproducing head for perpendicular magnetic recording according to any one of claims 1 to 3, wherein the thickness of the end face of the main pole facing the magnetic layer in the track width direction is 10 μm or less. (5) The parametric reproducing head for perpendicular magnetic recording according to any one of claims 1 to 4, wherein the main pole is formed as a thin film on a base material. (6) The parametric reproducing head for perpendicular magnetic recording according to claim 5, wherein the base material is a conductive wire, and a magnetic layer is provided on the surface of the wire. (7) The parametric reproducing head for perpendicular magnetic recording according to any one of claims 1 to 6, wherein the main pole has an axis of easy magnetization that intersects with the longitudinal direction.