JPS5942602A - Erasing head device - Google Patents

Abstract

PURPOSE:To execute an erasion without generating a noise, by forming a magnetic pole of a ferromagnetic field on the upstream side in the tape running direction of the head surface, forming a nonmagnetized part adjacently on the downstream side, and forming plural magnetic poles of a gradually reducing magnetic field toward the downstream side from said nonmagnetized part. CONSTITUTION:When a magnetic head device 10 is placed in a position of a full line against a ferromagnetic material 8 and an electric current is made to flow in the prescribed direction to a magnetic coil 15, an S-pole and an N-pole are magnetized and formed to a part 8a and a part 8b, respectively, in the ferromagnetic material 8. Subsequently, when the magnetic head device 10 is moved by length being equal to a magnetic pole array pitch (p) in the direction A, and an electric current whose polarity becomes opposite is made to flow to the magnetic coil 15, the part 8b is opposed to a magnetized effective face 13a, but since the direction of the electric current is reversed, it is magnetized to the N-pole side in the same way as the previous time, and a part 8c opposed to a magnetized effective face 14a is magnetized to the S-pole side. Subsequently, when magnetizing and forming a gradually reducing magnetic field magnetizing part 6 of an erasing head 3, it is executed by varying a quantity of an electric current which is made to flow by reverse-switching it at every intermittent relative movement of the pitch (p) each. In this way, a good erasion by which a residual magnetic flux is converged to zero is executed.

Description

[Detailed Description of the Invention] [Industrial Application Section 1f] The present invention relates to an erasing head device such as a tape recorder,
In particular, the present invention relates to an erasing head device using a permanent magnet with N and S poles alternately magnetized in the tape running direction.

[Background technology and its problems]

When erasing signals magnetically recorded on the magnetic tape of a tape recorder, two methods are used: a DC erasing method that applies a DC saturation magnetic field to leave a certain amount of residual magnetization, and a DC erasing method that applies an AC saturation magnetic field. That magnetic field? Gradually reduce the size K
There are known AC erasing methods that converge the residual magnetization to zero, and for each of these methods, erasing heads that flow a current through a coil and erasing heads that use permanent magnets are known. In the case of the above DC erasing method, DC noise is generated as erasing noise due to the residual magnetization of the tape, and the head and running system become magnetized, so the AC erasing method is often used. has been done.

By the way, small and portable tape recorders often use things with limited power, such as dry cell batteries or rechargeable batteries, as a power source, and there is a desire to reduce power consumption as much as possible, so permanent magnet erasure is required. In order to perform the alternating current erasure using a head, it is desirable to use a tape running method in which N and S poles are alternately magnetized and the strength thereof gradually weakens (gradually decreasing magnetic field).

Here, FIG. 1 shows an example of a permanent magnet erasing head 1 that performs the above-mentioned AC erasing.
The 1S poles are alternately arranged at equal intervals along the tape running direction (direction of arrow P) and are magnetized so that the magnetic field gradually decreases. Next, when assuming two types of tapes having hysteresis characteristics as indicated by the solid line ha or the broken line b in Fig. 2 as the magnetic tape 2 to be used, the residual magnetic flux will eventually be The erasure is carried out in such a way that it becomes a liability.

That is, according to the tape running direction of the erasing head 1 (arrow direction), the first magnetic pole (N pole) generates a magnetic field H1, the second magnetic pole (S pole) generates a magnetic field 11□, and the third magnetic pole (N pole) generates a magnetic field H1.
H3 is caused by the fourth magnetic pole (S pole), and H4 is caused by the fourth magnetic pole (S pole).
When applied to the magnetic tape 2 in sequence, if the magnetic tape has the hysteresis characteristic shown by the solid line ha in FIG. By passing through &4, the residual magnetic flux finally disappears. Also, if the magnetic tape has the hysteresis characteristic shown by the broken line hb in FIG. Each point b1 y b2' of one characteristic curve hb, bs
'! By passing through b4, the residual magnetic flux finally becomes zero.

In this way, the erasing head 1 can erase two types of magnetic tapes with different pre-specified hysteresis characteristics.
AC erasure that reduces the residual magnetic flux to zero can be performed, but for magnetic tapes that have hysteresis characteristics other than these characteristics, erasure that reduces the residual magnetic flux to zero is not necessarily performed. Rather, some residual magnetic flux often remains.

For example, the solid line hc in FIG. 3 shows a hysteresis characteristic different from the above-mentioned hysteresis characteristic curves ha and hb,
Even if the above-mentioned magnetic fields H□, H2, H3, and H4 are applied to a magnetic tape having such characteristics, the characteristic curve ll
Each point cl F(!21 passing through C3t04 on c,
Eventually, the residual magnetic flux density converges to Be's residual magnetic flux density.

Furthermore, the relationship between the vertical distance from the surface on which the magnetic poles of the erasing head 1 are magnetized and the magnetic field strength H is expressed, for example, as shown in FIG. (
attenuation rate) is large. Therefore, when the tape runs in contact with the surface of the magnetic pole of the erasing head 1 (the position where the distance 1 is approximately zero), if the contact state of the tape changes, the strength of the magnetic field H changes due to a slight change in the distance. changes greatly, and each of the magnetic fields H1 to H4 becomes, for example, the 54th magnetic field H1 to f
', respectively, and are applied to the tape after being attenuated. At this time, even if a magnetic tape having the characteristics specified in advance is used, for example, in the case of the characteristic curve ha, each point /, ~a will be affected by the magnetic fields H'□ to H'4.
'4, it finally converges to the residual magnetic flux density B'a, and in the case of the characteristic curve hb, each point b'L-b'
4 and finally converges to the residual magnetic flux density B'b, neither of which becomes zero.

By the way, if it were possible to increase the number of magnetic poles on the surface of the erase head and obtain a gradually decreasing magnetic field that smoothly continues from a strong magnetic field to a weak magnetic field, it would be possible to reduce the residual magnetic flux to almost zero without depending on the hysteresis characteristics of the magnetic tape. It is possible to converge to In this case, the above-mentioned strong magnetic field needs to be strong enough to reach the resonance region K of the Major loop of the hysteresis curve in order to completely erase even high-level signals magnetically recorded on metal tapes with high coercive force. Furthermore, in consideration of variations in the distance of the tape from the magnetic pole surface, it is necessary to have a strength that can saturate the magnetic material of the tape even in the farthest state.

However, it is difficult to magnetize magnetic poles that generate such a strong magnetic field with narrow spacing, and if the spacing between magnetic poles is extremely narrow, the magnetic field generated by other magnetic poles will be affected during or after magnetization. It is easy to be influenced. For this reason, it is necessary to set the magnetic pole spacing of the strong magnetic field to a certain length, and in the conventional erasing head with an equally spaced magnetic pole structure, this magnetic pole spacing limits the number of magnetic poles that can be arranged on the surface of the erasing head. There is,
A smooth gradually decreasing magnetic field cannot be obtained.

[Purpose of the invention]

In view of these conventional circumstances, the present invention provides a magnetic pole with a strong magnetic field that can completely saturate even a magnetic recording medium with a large coercive force such as a metal tape, and a magnetic pole that can finally converge the residual magnetic flux to zero. The object of the present invention is to provide an erasing head device which uses a permanent magnet as a head body, which is effectively magnetized with a large number of magnetic poles that produce a smoothly gradually decreasing magnetic field, and which can perform good erasing without noise.

[Summary of the invention]

That is, the erase head device according to the present invention is characterized in that the erase head device has a head body including a permanent magnet having a plurality of magnetic poles magnetized along the tape running direction vc on the head surface. A magnetic pole of a strong magnetic field is magnetized and formed on the upstream side of the magnetic field, and a non-magnetized part is formed adjacent to the magnetized part of the strong magnetic field magnetic pole on the downstream side in the tape running direction,
It is formed by magnetizing a plurality of magnetic poles with a gradually decreasing magnetic field in which the magnetic field becomes progressively weaker toward the downstream side in the tape running direction from this non-magnetized portion.

Therefore, a magnetic pole with a strong magnetic field and a large number of magnetic poles with a smoothly gradually decreasing magnetic field can be effectively magnetized on the surface of the erase head. Good characteristics can be erased such that the magnetic flux finally converges to zero, and adverse effects such as generation of erase noise can be prevented.

〔Example〕

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 6 shows an erasing head 3 as a main part of an embodiment of the present invention.
The area near the contact surface with the tape is poorly shown.

In FIG. 6, the surface of the erasing head 3 is magnetized with a plurality of magnetic poles arranged overflowing in the tape running direction (direction of arrow P). Tape running direction P on head surface
A strong magnetic field magnetized section 4 consisting of at least a pair of strong magnetic field magnetic poles is magnetized on the upstream side (left side in the figure) of the strong magnetic field magnetized section 4 in the tape running direction P ( 7'1, - “ - Non-magnetized part 5
is provided, and a gradually decreasing magnetic field magnetized section 6 is formed with a plurality of magnetic poles such that the magnetic field becomes progressively weaker toward the downstream side of the non-magnetized portion 5.

For example, when erasing a recording medium having a high coercive force such as a metal tape, the strong magnetic field magnetization section 4 generates an extremely large initial magnetic field at the tape introduction section (upstream side in the tape running direction) to moderate the medium. It is for. In this way, after applying a strong magnetic field that reaches the saturation region I/C of the hysteresis characteristic described above, erasing can be performed with a relatively weak gradually decreasing magnetic field, and the magnetic pole spacing of the gradually decreasing magnetic field magnetized section 6 can be narrowed. You can take it. Further, by providing the non-magnetized portion 5 between the strong magnetic field magnetized section 4 and the gradually decreasing magnetic field magnetized section 6, it is possible to prevent the magnetic pole of the strong magnetic field magnetized section 4 from influencing other magnetic poles. FIG. 7 is a graph showing the magnetic field on the surface of the erasing head 3. As shown in FIG.

In order to magnetize and form such an erase head, a magnetic head device for magnetization and a magnetization method as shown in FIGS. 8 to 11 are effective.

In FIGS. 8 to 11, the above-mentioned erasing head 3 is obtained by magnetizing and forming a magnetic pole as described above on a ferromagnetic material 8 serving as a magnetized material.

The magnetic core 11 of the magnetic head device 10 for performing this magnetization has a pair of arm portions 13 and 14 disposed CC symmetrically in one direction (in the direction of the arrow) with a magnetic gap 12 interposed therebetween. 11 and a magnetic gap 12 at a predetermined position in the magnetic circuit loop, for example, at the base 11 of the magnetic core 11.
-a includes a magnetic coil 1 for generating a magnetic field for magnetization;
5 is wound.

The magnetized body that becomes the erase head 3 after being magnetized, that is, the unmagnetized ferromagnetic body 8 (the magnetic core arm portions 13, 1
Magnetizing effective surfaces 13a and 14a parallel to the surface of the ferromagnetic material 8 are disposed close to the distal end side of the magnetic core arm portions 13 and 14 of the magnetic core arm portions 13 and 14, and the portions facing the ferromagnetic material 8 have effective magnetization surfaces 13a and 14a parallel to the surface of the ferromagnetic material 8, respectively. each formed. Here, a magnetic pole pattern is formed on the surface of the ferromagnetic material 8 facing the magnetic head device 11 in which N and S poles are arranged alternately in one direction (the direction of the arrow) at a constant arrangement pitch P. When magnetized and formed, is the length a of the magnetization effective surface 13a of at least one of the magnetic core arm portions 13 and 14 in one direction (arrow direction) and the distance of the magnetic gap 12 in the same direction? The sum a+sF is set (VC) so that it is equal to the arrangement pitch pVC of the magnetic poles (a+f=1). In this embodiment, the length of the effective magnetization surface 14a of the other magnetic core arm 14 in the above-mentioned one direction (the direction of the arrow) is also set as a, and as described later, rare earth magnetic materials such as samarium cobalt (rare earth The structure also makes it possible to magnetize ferromagnetic materials made from cobalt magnet materials.

Furthermore, the shape of the vicinity of the tip of each magnetic core arm portion 13.
The depth dl of b and 14b, that is, the length d in the direction perpendicular to the surface of the ferromagnetic material 8, is made as short as possible, and the distance between the arms 13 and 14 increases rapidly as the distance from the magnetic gap 12 increases. The magnetic flux is formed in such a manner as to minimize the amount of invalid magnetic flux (a flux that does not contribute to the magnetization of the magnetic material). Further, the cross-sectional area of each magnetic core arm portion 13, 14 is formed so as to become smaller as it approaches the magnetic gap 12 from the main body side of the magnetic core 11, forming a part of a so-called tapered square shape. , the other core parts are prevented from being magnetically fed before the arm parts 13 and 14 near the magnetic gap 12 are magnetically saturated.

Here, if the magnetic pole arrangement pitch p of the magnetization pattern is about 400 μm, then a should be about 150 μm, 2 should be about 250 μm, and the depth d should be about 50 μm.
It is preferable to set it to 0 μIn or less. In addition, the lengths of each part are set according to the required magnetic pole arrangement pitch p.
should be selected appropriately, and in this case d is a + 9 and 1
It is preferable to set the length to about the same length.

FIG. 11 is a diagram for explaining a magnetization recording process using such a magnetic head device 10.

In FIG. 11, it is assumed that the ferromagnetic material 8, which is the material of the erase head and is the magnetized material, is magnetized without moving the magnetic head device 10 in the right direction (in the direction of the arrow) in the drawing. . In this case, the magnetic hennod device 10 is fixed,
Of course, the ferromagnetic body 8 may be moved to the left in the figure (in the opposite direction to arrow A).

First, the magnetic head device 10 is placed at the position indicated by the solid line in FIG. 10 with respect to the ferromagnetic body 8, and the magnetic coil 1
5 in a predetermined direction, for example, the magnetic core arm 13
The north pole is made to appear on the side, and the south pole is made to appear on the arm portion 141i111. At this time, the direction of the magnetic lines of force is Q as shown by the solid arrow in FIG. Portion 8 of arm portion 14 facing effective magnetization surface 14a
N poles are respectively magnetized and formed at b.

Next, the magnetic head device 10 is moved in the direction of the arrow by a length equal to the magnetic pole arrangement pitch p with respect to the ferromagnetic body 8, and placed at the position indicated by the imaginary line in FIG.
A current in the opposite direction to the above-mentioned predetermined direction, that is, a current with opposite polarity is passed through the magnetic core arm 13 side KS pole to the arm 1
Make sure that the N poles appear on each of the 4 sides. in this case,
In the ferromagnetic material 8, the effective magnetization surface 14a of the arm portion 14 is first
and b The opposing partial sum is the effective magnetization surface 1 of the arm 13 this time.
3a, but since the direction of the current in the magnetic coil 15 is reversed, the magnetic poles gathered on the core arm side VC are the same S
As with the pole, the portion 8b of the ferromagnetic material 8 is magnetized to the north pole side as in the previous case. At this time, in the ferromagnetic body 8, a portion 8c facing the effective magnetization surface 14a of the magnetic core arm portion 14
is magnetized toward the south pole.

Similarly, the magnetic head device 10 is sequentially fed in steps in a fixed direction (in the direction of the arrow) by K magnetic pole array intervals p to the ferromagnetic material 8, and the magnetizing current of the magnetic coil 15 is By reversing the direction, the polarity of the magnetic poles appearing on each magnetic core arm part 13 and 14 is sequentially reversed, so that magnetic poles of the same polarity are formed in the same part of the ferromagnetic hand. .

The magnetization pattern magnetized and recorded on the ferromagnetic material 8 in this way is one in which N1 and N poles are arranged alternately with a fixed length p as an arrangement pinch in a fixed direction A VCG. The arrangement pitch p is 1/ of the so-called magnetic recording wavelength λ.
2 (p=λ/2).

According to such a magnetic head device 10 for magnetization, the magnetic core arm portions 13 and 14 have a substantially tapered C shape, and the effective magnetization surface 13
Since magnetization is performed using the magnetic head device 10 in which the lengths a and 14a and the depth d of the magnetic gap 12 are formed to be small, a concentrated magnetic flux is obtained near the gap portion at the tip of the arm portions 13° and 14. Therefore, a large magnetizing current can be taken, and magnetic saturation does not occur.For example, a magnetization pattern with a magnetic pole spacing of less than one cabinet (magnetic pole arrangement pinch) is applied to a ferromagnetic material with a high coercive force of several thousand oersted or more. can be sufficiently strongly magnetized. In addition, each magnetic core arm portion 13. . 1
Let the respective lengths of the effective magnetization surfaces 13a and 14a of No. 4 be equal a, and the magnetic gap interval ? The sum of this length a and the length a + ? is set equal to the magnetic pole arrangement pitch p, so that the magnetic head device 10 is not moved relative to the ferromagnetic material 8, which is the magnetized material, intermittently (in steps) by the above-mentioned pinch p. Due to the magnetization method that switches the polarity of the magnetic current, a part that was previously magnetized with one magnetic polarity (for example, N pole) will be magnetized with the same magnetic polarity (for example, N pole) during the next magnetization. be done. Therefore, each of the magnetic poles is sequentially magnetized with the same magnetic polarity during each of the above intermittent movements, and the magnetization of the already magnetized magnetic poles is strengthened rather than attenuated, allowing efficient magnetization. .

By the way, in rare earth magnetic materials such as long-marium cobalt magnetic materials, the hysteresis characteristic due to a weak magnetic field is expressed as a point-symmetric characteristic curve centered on the origin, similar to that of general ferromagnetic materials, but when a strong magnetic field After receiving the magnetic field, it exhibits asymmetric hysteresis characteristics with respect to positive and negative magnetic fields.

Even when magnetizing such a special magnetic material, according to the magnetizing force method using a magnetic head device having the above-described structure, the polarity that is first magnetized in the unmagnetized part of the magnetized object can be detected. Since the next magnetization is performed with the same polarity as , there is no influence from the asymmetric hysteresis characteristic, and effective magnetization can be performed.

Next, using such a magnetizing magnetic head device 10,
In order to magnetize the gradually decreasing magnetic field magnetized portion 6 of the erasing head 3, it is sufficient to change the amount of current flowing while switching inversion every intermittent relative movement (step feeding) of the pitch p. . However, when magnetizing and forming the above-mentioned gradually decreasing magnetic field pattern, considering that the part that was magnetized first is magnetized with the same magnetic polarity and the magnetization is strengthened, the magnetic pole with the weaker magnetic field is It is more rational to sequentially magnetize the magnetic poles from 71 to the stronger magnetic poles, and it is possible to obtain a magnetization pattern in which the magnetic field 71 is gently attenuated.

In addition, the strong magnetic field magnetizing section 4 of the erasing head 3 is used for the above-mentioned magnetization.
B' can be sufficiently strongly magnetized using the magnetic head device 10, but by using another magnetizing magnetic head device with a wider magnetic gap spacing 1, the magnetic pole spacing can be made wider than the magnetic pole spacing of the gradually decreasing magnetic field magnetization section 6. The strong magnetic field magnetized portion 4 may be formed by magnetization.

Of course, the non-magnetized portion 5 of the erasing head 3 may be moved by moving the head relative to the ferromagnetic material without passing current through the magnetic coil of the magnetizing magnetic head device.

Next, it is preferable to form a non-magnetic thin film layer 7 as shown in FIG. 12 on the surface of the erase head 3 magnetized in this manner. This takes into account the variation in the contact state of the magnetic tape with the erase head surface, that is, the variation in the distance from the head surface mentioned above.
By selecting the thickness of the thin film layer 7 to a value near distance 11 at which the magnetic field intensity change is slow in the relationship between distance E and magnetic field strength H shown in the figure, the magnetic tape can pass near this distance. , even if the contact shape S of the magnetic tape changes, the change in the magnetic field can be reduced by 1a. Also,
If it is possible to prevent the adverse effects caused by variations in unevenness on the head surface and to reduce noise, it may be formed by sputtering, thermal spraying, or other methods.

In addition, in the case of general ferromagnetic materials (those whose hysteresis characteristics are symmetrical curves with respect to the origin), Fig. 13 r
Using the magnetizing magnetic head 7 disposed 20 as shown in tc, it is possible to effectively magnetize and form the above-mentioned first shield pole.

The magnetic core 21 of the magnetic head device 2o has a pair of arm portions 23, 24 that are arranged opposite to each other in one direction (in the direction of the arrow) with a magnetic gap 22 in between. Similar to the magnetic core arm portion 13 described above, the effective magnetization surface 2 faces parallel to the surface of the ferromagnetic material 8 that is the magnetized material.
The sum a + of the length a of 3a and the distance 1 of the magnetic gap 22
It' is formed to be equal to the magnetic pole' arrangement pitch p, while the length of the effective magnetization surface 24a of the other magnetic core arm 24 is formed to be longer than a. The magnetizing magnetic coil 25 is still wound around the base 21a of the magnetic core 21.

When using such a magnetic head 20, as described above, the ferromagnetic material 8 is fed in the direction indicated by the arrow by step-feeding by pinch p in the direction indicated by the arrow, and then reversed and magnetized the magnetizing current. It is possible to magnetize and form a magnetization pattern in which N and S poles are arranged alternately with a pitch of p, and it is easy to increase the strength of the magnetizing magnetic field by increasing the current. Sufficient V magnetization can be achieved with a narrow magnetic pole spacing.

In this case, if the length of the wide effective magnetization surface 24a of the magnetic core arm 24 is greater than or equal to the magnetic pole array pitch 9, the unmagnetized strongly magnetic body 8 is first magnetized by the effective magnetization surface 24a. Although some parts are finally magnetized with a polarity different from the polarity when the magnetic core arm part 24 is magnetized, a strong magnetizing magnetic field appears in the effective magnetizing surface 24a of the magnetic core arm part 24. Since the magnetizing magnetic field in the extremely narrow part near the gap 25 and the remaining part is very weak, even if the area is magnetized by the effective magnetizing surface 24a of the ferromagnetic material 8, the above-mentioned step transfer is not possible. Finally, a magnetic pole of the polarity when strongly magnetized on the narrow effective magnetization surface 23a of the magnetic core arm portion 23 is formed.

For this reason, the magnetic head device 20 has the magnetic core arm 2
4 is forward and the arm 23 is backward (step feeding is required. In other words, at least the downstream side (or strong It is necessary to set the length a in the feed direction of the effective magnetization surface 23a of the magnetic core arm portion 23 on the side from which the magnetic body 8 comes out) to be the above-mentioned a+7-p.

Next, FIG. 14 shows another embodiment of the present invention.
The distance between the magnetic poles of the gradually decreasing magnetic field magnetized portion 6' of the magnetic field 3' is gradually shortened as the magnetic field weakens. This is because, in general, when magnetizing a magnetic material with high coercive force, it is desirable to have a wide distance between the magnetic poles of a strong magnetic field, and weak detection is possible even if the distance between the magnetic poles is relatively short. As a result, a large number of poles can be efficiently magnetized and formed.

〔Effect of the invention〕

As is clear from the above description, the erasing head device according to the present invention can effectively magnetize and form a magnetic pole with a strong magnetic field and a large number of magnetic poles with a smoothly gradually decreasing magnetic field. By lighting a wide variety of media, including magnetic recording media with large oscillation forces such as metal tapes, it is possible to perform erasure with good characteristics such that the residual magnetic flux eventually converges into a valley, causing erasure noise, etc. can prevent the negative effects of

[Brief explanation of drawings]

Figures 1 to 5 are for explaining the AC erasing operation using a permanent magnet. Figure 1 is a schematic front view of the erasing head, Figures 2 and 3 are graphs showing hysteresis characteristics, and Figure 4 is a diagram showing the hysteresis characteristics. The figure is a graph showing the relationship between the distance 1 from the head surface and the magnetic field H, and FIG. 5 is a graph showing the hysteresis characteristics. 6 to 13 are for explaining one embodiment of the present invention, FIG. 6 is a front view showing the main parts of the erasing head, and FIG. 7 is a graph showing the magnetic field on the surface of the erasing head. , FIGS. 8 to 11 show a magnetizing head device and a magnetizing method for forming the erase head by magnetizing the erase head. FIG. 8 is a perspective view, FIG. 9 is a front view, and FIG. Figure 10 is an enlarged front view N of the main part, Figure 11 is a schematic front view showing the magnetizing operation, and Figure 1 is a schematic front view showing the magnetizing operation.
FIG. 2 is a front view showing essential parts of an erasing head as a specific example of this embodiment, and FIG. 13 is a front view showing another specific example of the magnetizing magnetic head device. FIG. 14 is a front view showing the main parts of an erasing hesode according to another embodiment of the present invention. 3, 23... Erasing head 4... Strong magnetic field magnetized section 5... Non-magnetized section G, 6'... Gradually decreasing magnetic field magnetized section 10.20... Magnetic head device for magnetization patent application Person Sony Corporation Representative Patent Attorney Koji Koike 1) Sakae Mura - Figure 6P Figure 7 Figure 14

Claims (1)

[Claims] In an erasing head device whose head body is a permanent magnet in which a plurality of magnetic poles are magnetized and formed along the tape running direction on the head surface, a strong magnetic field magnetic pole is magnetized and formed on the upstream side of the head surface in the tape running direction. Then, a non-magnetized part is formed adjacent to the magnetized part of the strong magnetic field pole on the downstream side in the tape running direction, and the magnetic field gradually weakens from this non-magnetized part toward the downstream side in the tape running direction. An erasing head device formed by magnetizing and forming multiple magnetic poles of a magnetic field.