JPH07153032A - Magnetic head and magnetic recording/reproducing method - Google Patents

Abstract

PURPOSE:To obtain a high reproducing output, a high S/N, a high sensitivity and a high signal detection accuracy by a method wherein a phenomenon that an impedance is significantly varied by an external magnetic field in a radio frequency range. CONSTITUTION:A magnetic head (r) is composed of a coil winding 11, a magnetic core 12, a nonmagnetic insulator 13 filling a space in the core 12 and electrodes 14a and 14b to which a DC bias current is applied at the time of reproducing. A gap 12d formed in the core 12 traces the recording surface of a magnetic recording medium 17. Further, a V-shaped detecting conductor 15 and a horizontal bottom end part 15a are buried in the insulator 13 in the core 12. Detecting conductor electrodes 16a and 16b are formed on the top parts of the wing parts 15a and 15b of the conductor 15 continuously with the wing parts 15a and 15b respectively. If a ratio frequency current is applied to the conductor 15 at the time of reproducing, an electromagnetic wave is reflected and absorbed by the core 12 and, if the core 12 is getting magnetized by an external magnetic field, a relative permeability is reduced and becomes zero when the core 12 reaches a saturated magnetizing state. As an impedance in the core 12 is increased in a ratio frequency range at that time, a very large S/N can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head and a magnetic recording reproducing method using the same.

[0002]

2. Description of the Related Art In the field of magnetic recording, small storage devices
With the demand for larger capacity, it is desired to improve the recording density of a recording medium applied to the recording apparatus. Here, a structure of a conventional thin film ring type inductive magnetic head and a recording / reproducing method using the magnetic head will be described with reference to the drawings [see Masaaki Nishikawa: "Theory of Magnetic Recording" (Asakura Shoten)].

FIG. 9 (a) is a vertical sectional front view of a conventional ring type inductive magnetic head, and FIG. 9 (b) is the same as IXb-IX.
It is a b line sectional view. In the figure, α is a conventional ring-type inductive magnetic head, 1 is a winding coil, 2 is a magnetic core, 2a is a gap, 3 is a non-magnetic insulator, 4a and 4b are electrodes, and 5 is a magnetic recording medium.

In the conventional ring-type inductive magnetic head α, in the recording process, a current is passed through the winding coil 1 to magnetize the magnetic core 2, and the leakage magnetic field from the gap 2a magnetizes the magnetic recording medium 5. Record the signal.
On the other hand, in the reproducing process, the medium magnetic field generated from the magnetic recording medium 5 is picked up in the gap 2a to magnetize the magnetic core 2, and the signal is reproduced by the induced electromotive force induced in the winding coil 1.

On the other hand, a magnetoresistive head has been proposed as a magnetic head capable of reproducing even with a weak medium magnetic field strength. FIG. 10 shows a magnetoresistive head. In the figure, β is a magnetoresistive head (hereinafter referred to as “MR head”), 6 is a magnetoresistive element (hereinafter referred to as “MR element”), 7a and 7b are detection electrodes, and 8 is for DC bias. Conductors, 9a and 9b are DC bias current supply electrodes,
Reference numeral 10 is a magnetic recording medium.

Although the MR head β shown in FIG. 10 is a read-only head, the reproducing principle is that a constant DC current is passed between the detection electrodes 7a and 7b to reduce the magnetic field strength from the magnetic recording medium 10. The change in the electric resistance value of the MR element 6 due to the change is extracted as a change in the voltage of the detection electrodes 7a and 7b, and the recording signal is detected.

Conventionally, as the MR head β, one utilizing the magnetoresistive effect of a ferromagnetic material has been widely used. M
The change in the resistance value R due to the R effect is expressed by the following equation (1). R = R ₀ + ΔR cos ² θ (1) R ₀ : Resistance when magnetization direction is perpendicular to current direction ΔR: Difference between resistance and resistance R ₀ when magnetization direction and current direction are parallel θ: Magnetization Angle between direction and current direction

[0008]

However, in general, in the magnetic recording medium, as the recording density increases, the magnetized area occupied by one piece of information decreases, and therefore the magnetic field strength obtained therefrom decreases. Therefore, in the ring-type inductive magnetic head α shown in FIG. 9, there is a problem that the reproduction output level sharply decreases as the recording density increases, making it difficult to reproduce the recorded information.

Further, the magnetoresistive element 6 used as the detecting element of the MR head β is in principle capable of only one-way conversion from magnetism to electric resistance value and has no reversibility. . Therefore, the MR head β cannot be used as a recording head because its application is limited to a read-only head.

The S / N ratio of the MR head β is ΔR / R
It is represented by ₀ . NiFe, NiCo, and NiCu, which are typical ferromagnetic materials that have been conventionally used for the MR head β.
In the case of alloys and the like, the MR ratio was as low as several% (room temperature), and ΔR itself was only a small value. Therefore, in the MR head β using these, it was difficult to realize sufficient S / N ratio and sensitivity when the track width became several μm.

Recently, in the Fe / Cr multilayer film, the phenomenon that the MR ratio becomes 50% (giant magnetoresistive effect: MNBaibich,
JMBroto, A.Fert, F.Nguyen Van Dau, F.Petroff,
P.Eitenne, G.Creuzet, A.Friedrich and J.Chazelas,
Phys. Rev. Lett., 61, 2472'88) was discovered, but it is not suitable for practical use because its operating temperature is 4.2K and it is extremely low, and a large magnetic field of 20 kOe is required. Furthermore, since a large hysteresis appears in the dependence of the resistance on the external magnetic field, there is a problem that the signal detection accuracy is lowered.

Further, as is clear from the equation (1), M
Since the R effect is symmetrical with respect to the magnetic field reversal, it is necessary to apply a DC bias magnetic field in order to have a polarity detection function, and a current bias method has been proposed as a method therefor. The current bias method uses a DC bias magnetic field due to a DC bias current flowing through the DC bias conductor 8 by electrically insulating the DC bias conductor 8 from the MR element 6 adjacent to the MR element 6. Is the way to do it.

However, in this current bias method,
There is a problem that the number of constituent parts increases and complexity is involved in part design and part manufacture. As described above, in the conventional ring-type inductive magnetic head α, the problem that the reproduction output sharply decreases when the recording density is improved is that the MR head β has a low S / N ratio, sensitivity and signal detection accuracy, and the current If the bias method is adopted, there is a problem that the component structure becomes complicated.

In this case, the present invention provides a magnetic head and a magnetic recording / reproducing method that solve the problems of low reproduction output, S / N ratio, sensitivity, low signal detection accuracy, and complexity of component structure. To do.

The solution of the above-mentioned conventional problems can be achieved by the present invention by adopting the novel characteristic construction means and methods listed below. That is, the device of the present invention is characterized in that, in the ring-type inductive magnetic head, a magnetic material core made of a single plate-shaped material consisting of only magnetic layers or a plywood-shaped material in which magnetic layers and nonmagnetic insulating layers are alternately laminated And a winding coil wound outside the magnetic core, and at least one pair of detecting conductor electrodes disposed inside or outside the magnetic core directly or through a nonmagnetic insulator for detection. A magnetic head including a conductor.

A first feature of the method of the present invention is a magnetic material core made of a single plate material consisting of only magnetic layers, or a plywood material in which magnetic layers and non-magnetic insulating layers are alternately laminated. A winding coil wound outside the magnetic core, and a detection conductor in which at least one pair of detection conductor electrodes are arranged inside or outside the magnetic core directly or via a non-magnetic insulator. A high frequency current is applied to the detection conductor of the magnetic head provided, and the impedance of the detection conductor changes according to the magnetization state of the magnetic core that reflects the recorded information of the magnetic medium. It is a magnetic recording / reproducing method for reproducing recorded information on the magnetic medium.

The second feature of the method of the present invention is that the magnetic material core is made of a single plate material consisting of only magnetic layers, or a plywood material in which magnetic layers and nonmagnetic insulating layers are alternately laminated. A winding coil wound outside the magnetic core, and a detection conductor in which at least one pair of detection conductor electrodes are arranged inside or outside the magnetic core directly or via a non-magnetic insulator. A high-frequency current is applied to the detection conductor of the magnetic head provided, and a DC bias current is applied to the detection conductor or the winding coil, depending on the magnetization state of the magnetic core that reflects the recorded information on the magnetic medium. Then, the magnetic recording / reproducing method comprises reproducing the recorded information on the magnetic medium based on the change of the impedance of the detecting conductor.

The third feature of the method of the present invention is that the frequency of the high frequency current applied to the detecting conductor in the first or second feature of the method of the present invention is the magnetic property of the magnetic substance used for the magnetic core. This is a magnetic recording / reproducing method in the vicinity of the resonance frequency.

[0019]

Since the present invention takes the above-mentioned method and means,
In the reproducing process of the magnetic head, the phenomenon that the impedance largely changes in the external magnetic field at a high frequency is utilized, so that a high reproducing output, a high S / N ratio, a high sensitivity, and a high signal detection accuracy can be obtained. Further, since the detection conductor or the winding coil also serves as the DC bias conductor, the polarity of the signal magnetic field can be detected with a simple component configuration.

[0020]

【Example】

(Example of Device) An example of the device of the present invention will be described with reference to the drawings. Figure 1
(A) is a longitudinal sectional view of a magnetic head showing an example of the apparatus of the present invention,
1B is a sectional view taken along line Ib-Ib in FIG.
[Fig. 4] is a model diagram showing variations of the arrangement positions of detection ends.

In the figure, γ is the magnetic head of this embodiment, 11 is a winding coil, 12 is a magnetic core, 13, 13 ', 13 ".
Is a non-magnetic insulator, 14a and 14b are winding coil electrodes,
Reference numeral 15 is a detection conductor, 16a and 16b are detection conductor electrodes, 17 is a magnetic recording medium, 18 is a high-frequency current oscillator, 1
Reference numeral 9 is a DC bias power source, and 20 is a wave detector.

The magnetic head γ of the example of the present apparatus has a winding coil 11 spirally wound outward from the center and two single plates that hold a part of the lower side of the winding coil 11. Magnetic material 12a, 12b adhered at the upper end 12c, and a magnetic core 12 having a gap 12d having a minute gap at the lower end, and the above-mentioned magnetic material which is supported while maintaining insulation of the winding coil 11. From the non-magnetic insulator 13 filled in the gap of the body core 12 and the electrodes 14a and 14b electrically connected to both the center and peripheral ends of the winding coil 11 and supplied with a DC bias current during reproduction. The gap 12d formed in the magnetic core 12 traces the recording surface of the magnetic recording medium 17.

Further, in the magnetic core 12, a detection end 15a at the horizontal lower end of the V-shaped detection conductor 15 is embedded in the non-magnetic insulator 13 via the vicinity of the gap 12d, and the detection is carried out. The detection conductor electrodes 16a, 16 are provided at the upper ends of the wing-shaped portions 15b, 15c of the conductor 15 for spreading upward and downward.
b are integrally connected to each other.

Variations of the mutual arrangement positions of the magnetic core 12 and the detection end 15a are shown in FIGS. As long as the energy of the high-frequency electromagnetic wave generated by the high-frequency current supplied to the detection conductor 15 can be applied to the magnetic core 12, the detection end 15a is arranged as shown in (b) of FIG.
As shown in (d), (g), (k), and (n), the inside of the magnetic core 12 or (a), (c), and
(E), (f), (h), (i), (j), (l),
As shown in (m) and (o), it can be arranged in any place in the vicinity, and various variations other than those shown in FIG. 2 are possible. The detection conductor electrodes 16a,
Even if a plurality of 16b are provided and the detection end 15a is directly installed on the magnetic core 12, the same effect can be obtained.

(Example of Method) A recording / reproducing method in the magnetic head γ of the present invention will be described. As a recording method, recording is performed using the same principle as that of the conventional ring-type inductive magnetic head α shown in FIG.

On the other hand, in the reproducing process, a high frequency current is applied to the detecting conductor 15 and reproduction is performed based on the impedance of the detecting conductor 15 changing according to the magnetization state of the magnetic core 12. The operation principle of the reproducing process will be described below.

When a current of frequency f is applied to the detection conductor 15, the electromagnetic wave is reflected and absorbed by the magnetic core 12, and the impedance Z (f) between the detection conductor electrodes 16a and 16b is expressed by the following equation (2) )become that way. Z (f) = Z ₀ (f) + ΔZ _mag (f) (2) Z ₀ (f): Impedance derived only from the detection conductor 15 ΔZ _mag (f): For reflection / absorption in the magnetic core 12. Derived impedance increase

In the above formula (2), Z ₀ (f) is almost constant and does not depend on the frequency when the frequency is several GHz or less. On the other hand, ΔZ _mag (f) is the magnetic core 1
The relative permeability μr (f) of 2 and ΔZ _mag (f) ∝ f · μr (f) (3) are satisfied.

When the magnetic core 12 is magnetized by the external magnetic field, the relative permeability μr (f) gradually decreases, and the relative permeability μr (f) becomes zero in the magnetization saturation state. This time,
The voltage V (pe) generated between the detection conductor electrodes 16a and 16b
The external magnetic field H dependency of ak to peak) is conceptually shown in FIG.

Assuming that the current is almost constant, the S / N ratio is ΔV / V (0) = {V (0) -V (H)} / V (0) ≈ΔZ _mag (f) / {Z ₀ ( f) + ΔZ _mag (f)} (4) V (0): voltage value when the external magnetic field H is zero V (H): voltage value when the magnetic core 12 is saturated ΔV: V (0) -V ( H), Z ₀ (f) is small, and ΔZ _mag (f) is large in the high frequency range, so the S / N ratio becomes a very large value. Further, since the magnetic core 12 of the magnetic head γ has a characteristic that it is saturated in a weak magnetic field and has a small hysteresis,
The sensitivity and signal detection accuracy are also improved.

By the way, in order to have a polarity detection function, a DC current is passed through the detection conductor 15 or the winding coil 11 to generate a DC bias magnetic field H _bias, and the operation on the VH curve shown in FIG. 3 is performed. Move point to P ₀ .

At this time, in the magnetic head γ used in this example of the method, the detecting conductor 15 or the winding coil 11 has a structure shown in FIG.
Since it also serves as the DC bias conductor of the ring-type inductive magnetic head β of the conventional example shown in (3), the component structure is simplified. Further, by setting P ₀ to the point where the gradient of the VH curve is maximized, it becomes possible to further improve the detection sensitivity.

FIG. 4 shows a block diagram of the reproducing process, and FIGS. 5A to 5E show signal waveforms at points A to E in FIG. 4, respectively. A high-frequency current of, for example, 800 MHz from the high-frequency current oscillator 18 to the detection conductor 15 as shown in FIG.
From 9, a DC bias current as shown in FIG. 5B is applied to the detection conductor 15 or the winding coil 11.

A DC bias magnetic field H _bias is generated by this DC bias current, and the operating point moves to point P ₀ shown in FIG. As the signal magnetic field, here, for example, a magnetic field of 30 MHz shown in FIG.
The voltage V between 6a and 16b is V (P ₁ ) and V shown in FIG.
Go back and forth on (P ₂ ).

800 MHz between the electrodes 16a and 16b
A voltage obtained by amplitude-modulating the signal of 30 MHz with the signal of 30 MHz is generated as shown in FIG. By passing this through the wave detector 20, a 30 MHz signal can be reproduced as the output voltage shown in FIG.

In the magnetic head γ of the example of the present device, a phenomenon in which high frequency electromagnetic waves are reflected and absorbed by the magnetic core 12 is utilized. At this time, the effective volume of the magnetic core 12 is reduced due to the skin effect. However, the amount of reflection / absorption is reduced.

In order to avoid this, as shown in FIG. 6, instead of the single-plate magnetic materials 12a and 12b of the magnetic core 12, magnetic layers 12e and nonmagnetic insulating layers 12f are alternately laminated in multiple layers. It is effective to have a multilayer structure, and
In this case, the thickness of the magnetic layer 12e may be formed to be thinner than the skin depth which is the limit that can be passed by the skin effect, and the thickness of the non-magnetic insulating layer 12f may maintain the electrical insulation between the magnetic layers 12e. It is more effective if it is formed more than the thickness.

(Measurement Example) FIG. 7 shows a measurement example of this method example using this apparatus example. In this measurement example, the magnetic head γ shown in FIG.
The magnetic layers 12e of 2a 'and 12b' are made of Ni of 50 nm thickness.
Fe alloy is used for the non-magnetic insulating layer 12f, and Si of 50 nm thickness is used.
O ₂ was used and a multi-layer structure as shown in FIG. 6 was adopted.

Further, the total thickness of the magnetic core 12 is 3 μm.
m, the width of the tip of the magnetic core 12 is 10 μm, the gap 12d is 0.3 μm in width, and the detection conductor 15 has a width of 1 μm.
Cu having a thickness of μm was used, and the width of the detection conductor 15 was 10 μm. All measurements were performed at room temperature.

FIG. 7 shows the frequency f dependence of the voltage change ratio ΔV / V (0). ΔV / V (0) is from several hundred MHz to 1G
It becomes a large value of 60 to 70% near Hz. The reason why ΔV / V (0) becomes large in this frequency band is that this frequency band coincides with the magnetic resonance frequency of 600 MHz to 1 GHz of the NiFe alloy used for the magnetic core 12.

Here, in FIG. 8, the voltage V at 800 MHz
The dependence of (peak to peak) on the external magnetic field H is shown. The voltage V greatly decreases around 5 Oe, which is the anisotropic magnetic field of the NiFe alloy, and has a substantially constant value at approximately 20 Oe.

As described above, in this measurement example, 60 to 70
%, A large S / N ratio is obtained, and a large voltage change is generated even with a small external magnetic field H of several Oe, so that the sensitivity is high.
It should be noted that no hysteresis was observed even when the external magnetic field H was repeatedly increased and decreased, and it was confirmed that the signal detection sensitivity was high.

As can be seen from FIG. 7, ΔV / V
(0) becomes maximum when the frequency of the high frequency current is set near the magnetic resonance frequency of the magnetic material used for the magnetic core 12.
Therefore, in order to obtain a high S / N ratio and high sensitivity, it is effective to operate the device example γ in the vicinity of the magnetic resonance frequency of the magnetic material used for the magnetic core 12.

The material of the magnetic layer 12e is F
e, Co, Ni to Fe, Co, Ni, Zr, Nb, Y,
Of Hf, Ti, Mo, W, Ta, Si, B, Re,
The non-magnetic insulating layer 12f may be made of SiO ₂ , AlN, Al ₂ O ₃ , or B, which may be made of a single material or a material containing a plurality of elements.
N, TiN, SiC, and the detection conductor 15 are
Cu, Al, Ag, Au, Pt, Sn, Cr, Zn, I
When n is used, the same effect can be obtained.

[0045]

As described above, according to the present invention, compared with the conventional apparatus and method, reproduction output, S /
Since both N and sensitivity are extremely high, they are very useful for increasing the recording density of magnetic recording.
In addition, compared with the conventional magnetoresistive head that applies the current bias method, the detection conductor or winding coil also serves as the DC bias conductor, reducing the number of components and reducing the manufacturing cost by simplifying the configuration. The manufacturing process can be reduced, and mass productivity and economic efficiency are excellent.

Further, when compared with the conventional giant magnetoresistive effect, it is possible to operate at room temperature, reduce the amount of application of the DC bias magnetic field, and have a low magnetic field response. It does not need to be set, has a small hysteresis, enables highly accurate detection, has a simple configuration of the detection system, has high sensitivity, and has high reliability.

[Brief description of drawings]

FIG. 1A is a vertical sectional front view of a magnetic head showing an example of the device of the present invention, and FIG. 1B is a sectional view taken along line Ib-Ib of FIG.

FIG. 2 is a model diagram showing variations of the positions where the detection ends are arranged.

FIG. 3 is a voltage V and an external magnetic field H illustrating an example of the method of the present invention.
It is a correlation characteristic diagram with.

FIG. 4 is a block diagram of a reproduction process of the same.

5 is a waveform diagram of points A to E in FIG.

FIG. 6 is a partially enlarged vertical side view of a magnetic core.

FIG. 7 is a correlation characteristic diagram of a voltage change ratio ΔV / V (0) and a frequency f for explaining a measurement example according to the method example of the present invention.

FIG. 8 is a correlation characteristic diagram of the voltage V and the external magnetic field H of the above.

9A is a vertical sectional front view of a conventional ring-type inductive magnetic head, and FIG. 9B is a sectional view taken along line IXb-IXb.

FIG. 10 is a structural principle diagram of a conventional magnetoresistive head (MR head) to which a current bias method is applied.

[Explanation of symbols]

 α ... Ring-type inductive magnetic head β ... Magnetoresistive head γ ... Magnetic head of the present invention 1, 11 ... Winding coil 2, 12 ... Magnetic core 3 ... Nonmagnetic insulator 4a, 4b ... Electrode 5, 10, 17 ... Magnetic recording medium 6 ... Magnetoresistive element 7a, 7b ... Detection electrode 8 ... DC bias conductor 9a, 9b ... DC bias current supply electrode 12a, 12b ... Single plate magnetic material 12a ', 12b' ... Ply plate magnetic Material 12c ... Upper end 2a, 12d ... Gap 12e ... Magnetic layer 12f ... Nonmagnetic insulating layer 13, 13 ', 13 "... Nonmagnetic insulator 14a, 14b ... Winding coil electrode 15 ... Detection conductor 15a ... Detection end Numerals 15b, 15c ... upward divergent wings 16a, 16b ... detection conductor electrode 18 ... high-frequency current oscillator 19 ... DC bias power supply 20 ... detector

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yasuhiro Koshimoto 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (4)

[Claims] 1. In a ring-type inductive magnetic head, a magnetic core made of a single plate-shaped material consisting of only magnetic layers or a plywood-shaped material in which magnetic layers and non-magnetic insulating layers are alternately laminated in multiple layers, A winding coil wound outside the body core; and a detection conductor in which at least one pair of detection conductor electrodes are arranged inside or on the outer surface of the magnetic core directly or via a non-magnetic insulator. A magnetic head characterized by: 2. A magnetic material core made of a single plate material composed only of a magnetic layer or a plywood material in which magnetic layers and non-magnetic insulating layers are alternately laminated in multiple layers, and wound around the outside of the magnetic material core. A magnetic head comprising: a winding coil; and a detection conductor in which at least one pair of detection conductor electrodes are arranged inside or on the outer surface of the magnetic body directly or via a non-magnetic insulator. When a high-frequency current is applied to the recording conductor, the recorded information on the magnetic medium is reproduced based on the impedance of the detecting conductor changing according to the magnetization state of the magnetic core that reflects the recorded information on the magnetic medium. A magnetic recording / reproducing method characterized by: 3. A magnetic material core made of a single plate material consisting only of a magnetic layer, or a plywood material in which magnetic layers and non-magnetic insulating layers are alternately laminated in multiple layers, and wound around the outside of the magnetic material core. A magnetic head comprising: a winding coil; and a detection conductor in which at least one pair of detection conductor electrodes are arranged inside or on the outer surface of the magnetic body directly or via a non-magnetic insulator. A high-frequency current is applied to the detection conductor, a DC bias current is applied to the detection conductor or the winding coil, and the impedance of the detection conductor is changed according to the magnetization state of the magnetic core that reflects the recorded information of the magnetic medium. The magnetic recording / reproducing method is characterized in that the recorded information on the magnetic medium is reproduced on the basis of the change of. 4. The magnetic recording according to claim 2, wherein the frequency of the high frequency current applied to the detecting conductor is in the vicinity of the magnetic resonance frequency of the magnetic material used for the magnetic core. How to play.