JPS6035731B2 - magnetoresistive transducer - Google Patents

Description

[Detailed description of the invention] The present invention relates to magnetoresistive transducers.

The present invention is particularly suited to the succession of information recorded on magnetic recording media such as rigid or flexible magnetic disks and magnetic tape. It is well known that in a magnetic disk, information is carried on circular recording tracks, which have a radial width of a few hundredths of a millimeter or less, and usually occupy most of both sides of the magnetic disk. .

In magnetic tape, information is carried on tracks parallel to the length of the tape. Normally, a series of magnetic information recorded on one track of a magnetic disk or magnetic tape is distributed over the entire length of the track, and is distributed over the entire length of the track, and in the same module, a series of magnetic information called "fundamental magnetic domains" having opposite magnetic induction directions are distributed over the entire length of the track. This is the shape of a small magnetic domain.

The number of information per unit length measured along the circumference of one track in the case of a magnetic disk, and the number of information per unit length measured along the longitudinal direction of the tape in the case of a magnetic tape, is called the longitudinal density (or linear density). ).

Means capable of writing or capturing information on a disk or tape, or alternatively performing both functions, are referred to as magnetic transducer devices.

Typically, one or several magnetic transducer devices are coupled to a given recording medium and the medium is passed in front of the device. Currently, in order to continue information on a track or tape, one
Transducing devices, referred to as "magnetoresistive transducers", containing one or more magnetoresistive elements are increasingly being used. In particular, the above-mentioned conversion device is often used when the traveling speed of the recording medium is slow or the speed fluctuations of the recording medium are large (which is particularly likely to occur with magnetic tape). Magnetic resistance is
An electrical resistor in the form of a very thick diagonal, thin layer or film (from a few hundred angstroms to a few microns thick), with a length that is extremely large compared to its width.

These magnetoresistors are then used attached to a substrate made of electrically insulating material.

The value of its resistance changes when subjected to the action of a magnetic field. When a magnetoresistive resistor of magnitude R as described above is connected to the terminals of a generator and a current 1 is supplied along the length of the resistor, the resistor is a type of magnetoresistive transducer coupled to a magnetic recording medium. It can be thought of as being placed in close proximity to, for example in contact with, the medium.

Each elementary domain of the medium generates a leakage field Hf near the surface of the medium as it sequentially passes in front of the magnetoresistor, and the leakage field Hf causes a resistance change ΔR of the magnetoresistor.

Therefore, a change of V=1×ΔR occurs at the terminal. As a result, the formula △V/V=△R/R is established, and △R/R is referred to as a "magnetoresistance coefficient." This coefficient is typically on the order of 2% and is often a negative value. The electrical signal collected at the magnetoresistive terminals has an amplitude that is independent of the speed of the recording medium.

It is known that the term "initial permeability of a magnetic material" refers to the ratio of magnetic field to magnetic induction (B/H) as it appears on the first magnetization curve when 8 is close to 0.

The first magnetization curve is a curve whose origin is an initial magnetic state where B and day are close to 0 when a magnetizing magnetic field is applied to a magnetic body, and which shows the change in B as a function of the magnetic field day. In other words, the initial magnetic permeability of the magnetic material is equal to the slope of the first magnetization curve near the points B=0 and H=0. On the other hand, a magnetically isotropic material that exists in one plane (i.e., a magnetically isotropic material that has a very small thickness compared to its length and width) has two layers inside the material itself, usually perpendicular to each other. It is known that it has a specific magnetization direction of .

One is designated as the "easy magnetization direction" and the other is designated as the "hard magnetization direction." The initial permeability of the material in the direction of hard magnetization is much greater than the initial permeability of the material in the direction of easy magnetization.

The value of the magnetic field acting in the direction of hard magnetization of the material and saturating the material in that direction is designated as the anisotropy field HK.

Usually the magnetoresistive material used consists of a magnetically anisotropic material, for example an iron-nickel alloy (18% iron and 82% nickel).

The easy axis of magnetization of the magnetoresistive member is parallel to the direction of the current 1 and the longitudinal direction of the magnetoresistive member, and the hard axis of magnetization is perpendicular to the longitudinal direction. The magnetoresistance (or magnetoresistances) of the magnetoresistive transducer is such that the hard axis of magnetization perpendicular to the surface of the medium is parallel to the stray field of the fundamental domain of the medium with respect to the recording medium to which it is coupled. It is arranged like this. When no magnetic field acts on the magnetoresistive resistor, the magnetization of the resistor (ie magnetic induction inside the resistor) occurs along the direction of the easy axis of magnetization.

By applying a polarizing magnetic field parallel to the hard axis to a magnetoresistive resistor made of anisotropic material, the sensitivity of the resistor can be improved, i.e., the output signal voltage can be increased as a function of the applied magnetic field. This is well known.

This is due to the Compagnie International Pour l'Ormatake filed on December 22, 1971.
C. mpagnie lntemati. na
le p. French Patent No. 2,165,206 "Improved magnetoresistive devices and electromagnetic transducers incorporating them"
nceper to ctionn'eesettranSd
uCteur e'leCtromag fertilization
It is described in que leSIMorporanr. The value of the polarization field field pol is chosen to rotate the magnetization of the magnetoresistive element by an angle of 8.

Preferably, the value of 8 is close to 450 (in which case the magnetization forms an angle of 45° with the easy magnetization direction).

In this case, the magnetoresistive sensitivity is maximized.

That is, for a given change in the applied magnetic field (other than the magnetic field Hpol), a maximum resistance change and therefore a maximum output voltage change will occur. Practical magnetoresistive transducers include two parallel (ie longitudinally parallel) magnetoresistive elements spaced apart on the order of a tenth of a micron.

The spacing between said elements is always substantially less than the length of the elementary domains contained in each recording track of the magnetic medium, so that two magnetoresistances are equal to affected by leakage magnetic fields. That is, the o2 magnetoresistive elements, in which the values of the leakage magnetic fields acting on the two magnetoresistive elements are equal, are polarized so that their magnetizations rotate by 450 degrees and form an angle of about 90 degrees with respect to each other.

This is reflected in French Characteristics No. 2, 24 & 566 by the Compagnie International pour l'Informatake, filed on October 23, 1973.
The output signal AV of the first magnetoresistive element is supplied to the first input of the differential amplifier, and the output signal AV of the second magnetoresistive element is
V2 is fed to the second input of the same differential amplifier. Substantially △V. =-ΔV2, so a signal proportional to 2×lΔV,l is obtained from the outputs of the two differential amplifiers. It is clear that the use of a differential amplifier can substantially reduce the noise signal for signals proportional to 2×ΔV. The noise signal is particularly attributable to all magnetic fields other than the field disturbances in the magnetoresistors and the fringing fields produced by the magnetic domains facing the two magnetoresistors.

As the magnetic field acting on the two magnetoresistive elements, in addition to the leakage magnetic field of the magnetic domains facing the two magnetoresistive elements, the resultant force of the leakage magnetic fields generated by the magnetic domains located on both sides of the magnetic domains is considered. It is clear that there must be.

Even if the resultant force is relatively small compared to the value of the leakage magnetic field of the magnetic domain, when the linear density of information is relatively small, the resultant force is different from the case where the linear density is large. It is considered to be relatively large compared to the magnetic field. Therefore, it is necessary to arrange magnetic shielding means on both sides of the two magnetoresistive elements. The means usually consist of an assembly of thin films of magnetic material separated by thin non-magnetic layers bonded together.

The planes of these individual films are perpendicular to the direction of travel of the recording medium and tracks. Preferably, the film constituting the magnetic shielding means is made of a magnetically anisotropic material, and the hard axis of magnetization of the film is oriented in a direction perpendicular to the magnetic medium.

Therefore, all the lines of magnetic force generated by the magnetic domains surrounding the magnetic field opposite the magnetoresistive element are collected by the film rather than by the two magnetoresistive elements. Preferably, each magnetoresistive element of a magnetoresistive transducer as described above is polarized by a magnetic field created by the passage of current through the other magnetoresistive element.

Therefore, if the magnetic field generated when the current 1 passes through the first magnetoresistive element is 1, then the second magnetoresistive element is polarized by the magnetic field 1. Similarly, if the magnetic field generated by the same current 1 in the second magnetoresistive element is 2, then the first magnetoresistive element is polarized by the magnetic field 2. It is clear that, normally, day 2 and day 2 have substantially equal absolute values and opposite signs. Therefore, by simply adjusting the intensity of the current 1 applied to the two magnetoresistive elements, it is possible to polarize each of the two elements by an angle of the order of 45o and make the magnetizations of the two magnetoresistive elements 90o with respect to each other. it is obvious. When a magnetoresistive transducer with two magnetoresistive elements includes magnetic shielding means arranged on both sides of the elements, the following phenomenon appears.

- the magnetic shielding means located on the side of the first magnetoresistive element are subjected to the action of the magnetic field generated by the passage of the current 1 through the element;

A magnetic quantity distribution occurs inside the magnetic shielding means depending on the magnetic field. The magnetic quantity distribution consists of a volume magnetic quantity and a surface magnetic quantity inside and on the surface of the area of the magnetic shielding means under the action of the tin field. These magnetic quantities increase as the volume of the magnetic shielding means under the action of the field increases and on the other hand as the field strength increases. As a document that explains this phenomenon in more detail,
W. F. BROWN “Principedeferromagnetism”
isme'' Chapter 0, M, published by DUNOD, 1970, and DURAND's book, Chapter W, Section 1, Section 3 and Windmill, published by MASSON, 1968.

It is clear that a similar phenomenon occurs inside the magnetic shielding means, which is arranged on the side of the second magnetoresistive element and is affected by the magnetic field ratio produced by the passage of the current 1 through the element.

The magnetic mass inside the magnetic shielding means generates a magnetic field referred to as the "return field".

The magnetic field opposes the magnetic field that generated the magnetic quantity (here, we are dealing with the first magnetic shielding means disposed on the side of the first magnetoresistive element, but the phenomenon caused by the other magnetic shielding means is also the same). it is obvious). Let this return magnetic field be Hr. The absolute value of the magnetic field Hr is substantially equal to 1/3 of the absolute value of the magnetic field Hr. In this case, the polarizing magnetic field of the second magnetoresistive element is no longer 1, but 1, 1, r. Similarly, the polarizing field of the first magnetoresistive element is 2-Hr instead of 2-Hr.

The magnetoresistance is polarized at a smaller value of the angle instead of 45o and therefore has less sensitivity (
That is, the ratio ΔR/ΔH) decreases. Furthermore, the transmitted signal loses its linearity. To eliminate this drawback, it is necessary to increase the current strength in the two magnetoresistors to increase the relative strength and restore a polarization angle of the order of 450 in the magnetoresistors.

Such an increase in current entails, on the one hand, excessive heating of the magnetoresistor and, on the other hand, an increase in the energy for magnetoresistive polarization. In order to eliminate the above-mentioned disadvantages, the present invention reduces, on the one hand, the volume of the magnetic shielding means which is affected by the magnetic field generated by the passage of current in the magnetoresistive element, and, on the other hand, reduces the strength of the magnetic field.

The above object is achieved by arranging a magnetic deflection means between the magnetoresistive element and the magnetic shielding means, which deflects the magnetic field generated by the magnetoresistive element to the part of the magnetic shielding means furthest from the magnetic recording medium.

The magnetic deflection means for magnetic field deflection serve as a screen for the magnetic field generated by the magnetoresistive element. The magnetoresistive transducer of the present invention for the acquisition of information recorded inside a plurality of tracks of a magnetic medium comprises: - at least one magnetoresistive transducer arranged perpendicular to the direction of information propagation and passing a current in the longitudinal direction; a magnetoresistive element; - first and second magnetic shielding means disposed on both sides of the element for collecting the magnetic flux of the information group around the information on the track facing the element; a transducer, said transducer comprising means for deflecting a magnetic field produced by a current flowing in said element, said deflection means being arranged between said element and said first shielding means and between said element and said element; It is characterized in that it is respectively arranged between the second shielding means and the second shielding means.

Further characteristics and advantages of the invention will become apparent from the following description based on a non-limiting example illustrated in the attached drawings.

In order to understand more fully the construction of the magnetoresistive transducer of the invention, the working principle of the magnetoresistive system will be explained somewhat by means of figures la, lb and 2 on the one hand, and figures 3a, 3b, 3c, 4
, 5, 6a and 6b, it may be appropriate to describe a prior art magnetoresistive transducer comprising two magnetoresistors.

Figures 1a and 1b show a basic magnetoresistive transducer TMRE consisting of only one magnetoresistive element M. In Figure la, the magnetoresistive MR is connected to a magnetic recording medium S such as a magnetic tape.
It is arranged opposite to the track P of M. The length L of the magnetic resistance is approximately the same as the width LP of the track P, and the height h' measured perpendicular to the surface of the medium S is, for example, 30 to 4
It is on the order of 0 microns. The length L is greater than the width.
The two terminals of the magnetoresistive MR are (omitted in Figure la)
includes a connecting conductor, which conductor connects the magnetoresistive medium SM
It can be connected to the electronic circuit of the information stored in the . Magnetic resistance M
The easy magnetization axis Axf of R is parallel to the longitudinal direction, and the hard magnetization axis AXd is perpendicular to the longitudinal direction and the medium SM. A current 1 is supplied to the magnetoresistive MR, e.g.
It flows in the direction shown in figure b, that is, parallel to the easy axis of magnetization AXf. The magnetic resistance M is affected by the leakage magnetic field Hf of the basic magnetic domain of the medium.

(Some of these magnetic domains are A,, A2, Ai, Aj
is shown in Figure la). The leakage field is perpendicular to the recording medium and therefore parallel to the hard axis Axd of the magnetoresistive member M. Figure 2 shows the change △R in the resistance R of the magnetoresistive MR,
Figure 2 is a graph shown as a function of the magnetic field acting along the hard axis Axd, allowing a better understanding of the operation of the basic magnetoresistive transducer TMRE;

If the value of h is equal to the anisotropic magnetic field Hk of the magnetoresistive material, the material is saturated in the hard magnetization direction and the resistance R does not change. By applying a polarizing magnetic field Hpo to the magnetoresistance and moving the coordinate axes in FIG. 2 from the origin ○, to the origin 02, it is possible to give the magnetoresistance MR the highest sensitivity. This is described in the aforementioned French patent no. 2165206. The polarization magnetic field (generated by an external source omitted in Figure 1) is the hard magnetization axis Axd of the magnetoresistive MR.
Therefore, it is parallel to the information leakage magnetic field Hr of the medium SM. That is, it is perpendicular to the surface of the recording medium. When a polarizing magnetic field acts on magnetoresistance, the change in magnetoresistance ΔR is relatively large. ΔR may be maximum when the polarization magnetic field Hpo has a value that rotates the magnetization direction by about 45°. (When no magnetic field acts on the magnetoresistance, the magnetization is parallel to the easy axis of magnetization Axf). Therefore, a relatively small change ΔH' in the magnetic field acting on the magnetoresistance causes a relatively large change ΔR in the resistance value.

Therefore, it is defined that the operating point PF and the abscissa 0,02 are equal to Hpo. When the leakage magnetic field Hf of the information of the medium acts on the magnetoresistive element, the change in resistance value is ΔRf, and the voltage collected at the terminal of the magnetoresistive member is ΔV=1×ΔRf. Around the operating point PF, the resistance change is therefore a linear function of the leakage field acting on the reluctance in the direction of the hard axis. Figures 3a, 3b and 3c show prior art magnetoresistive transducers in practical use.

This converter is designated TMRA. The transducer TMRA includes: - a first magnetoresistive member M; - a second magnetoresistive member M2; - a first magnetic shielding means M2; - a second magnetic shielding means M2; .

It is clear that in Figures 3a, 3b and 3c, the spacing between the various elements making up the transducer TMRA has been considerably enlarged for clarity.

For the same reason, the nonmagnetic layers that separate the elements, ie, elements Mold and MR, elements MR and MR2, and elements MR2 and Mold2, are also not shown. Furthermore, these non-magnetic layers are also electrically insulating. The illustrated transducer TM A is arranged opposite to a track P of the recording medium SM, which corresponds to several basic regions of the track, namely magnetic domains A, , A2, A.
i-1, Ai, Ai, Ai 10. are illustrated. Elements MR and MR2 are completely identical to element MR in FIGS. 1a and 1b, and a current 1 flows in the longitudinal direction. L,,Axf,,
Axd. are the length of magnetic resistance M, the axis of easy magnetization, and
Indicates the hard axis of magnetization. Similarly, L2, Axf2, and AXd2 indicate the length of the magnetic resistance M old 2, the easy axis of magnetization, and the axis of difficult magnetization, respectively. The lengths L and L2 are substantially equal to each other and have values close to the width LP of the track P. The two magnetoresistances are polarized as follows.

Magnetization of magnetoresistance MR, AM. forms an angle of 1450 with the axis of easy magnetization AXf. That is, it forms an angle of 1450 with respect to the position of the magnetization AM, of the magnetoresistive cape K, which is at rest. Magnetization AM2 of magnetoresistance M level 2 is -45 with easy magnetization axis AXf2
form an angle of 0. That is, for the position of the magnetization AM2 of the (resting) magnetoresistive Mold 2 in the absence of an acting magnetic field -
Forms an angle of 45o. Therefore, magnetoresistance M town, and MR
The two magnetizations AM and AM2 form an angle of 900 degrees with each other. The magnetic shielding means M, , M&, preferably made of a magnetically anisotropic material, each have an easy axis of magnetization AF, , AF2 and a hard axis of magnetization AD, , AD2.

The axes AF and AF2 are parallel to the axes Axf and Axf2, and the hard magnetization axes AD, AD2 are parallel to the hard magnetization axes A, A, and A.
It is parallel to Xd2. Preferably magnetic shielding means MB,,
M old 2 consists of a plurality of magnetic thin films parallel to each other and separated by non-magnetic layers.

These membranes are not shown in FIG. 3 for simplicity of illustration. In particular, as shown in Figure 3c, two magnetoresistive elements M
The spacing between R, and MR2 must be sufficiently small and arranged such that the two reluctances are subjected to virtually the same stray magnetic field Hf.

MR and MR2 are magnetic domains Ai- of track P of medium SM.
, and Ai become substantially equidistant from the boundary FRi, the information is read. As shown in Fig. 3b, the shielding means MB, M old 2 is configured to prevent leakage caused by magnetic domain groups other than the magnetic domains A; The magnetic field lines of the resultant force of the magnetic fields can be collected.

That is, since the shielding means MB, MB are present, the magnetic resistance M
R,, MR2 are not affected by the resultant force. Next, FIG. 4 will be explained. Let d be the distance between the magnetic resistances MR and MR2. The width of the reluctance is much smaller compared to the spacing d. This means that the distance d between the magnetoresistive elements M and MR2 is equal to the distance between the symmetrical distances of the magnetic resistances MR and MR2 perpendicular to the recording medium SM, as shown in FIG. Next, FIG. 6 will be explained. Hpo evening,
IHpo between and Hpo2, l=IHposo2
Considering that l holds true, the angles 8, 82 formed by the polarization magnetic fields of magnetoresistances MR, MR2 with respect to the easy magnetization axes AXf, AXf2 are 1450 and 1, respectively, similar to the magnetizations AM, , A. Equal to 450.

In this way, the operating points PF and PF2 are determined. M old,
When the same leakage magnetic field Hf acts on MR2 and MR2, the voltage changes at the terminals of the magnetic resistances are ΔV, ΔV2, respectively. The voltage changes are applied to the inputs E, , E of the differential amplifier AMPDIF, respectively.
2 (see Figure 5).

The first input therefore receives the signals ΔV, 1B. B, is a noise signal (the noise signal is generated particularly from magnetic information of a group of tracks adjacent to track P, thermal disturbance within the two magnetic resistors, etc.). Input E of differential amplifier AMPDIF
2 receives the signal ΔV2+&. Examining FIG. 6a, we obtain ΔV2=−ΔV.

Therefore, the absolute value of the signal obtained at the output of the amplifier AMPDIF is proportional to l2ΔV,l+B=l2ΔV2l+B.

In the formula, B=B-B2, and since B has a value close to B2, B is extremely small. It will be appreciated that the use of a differential amplifier provides an output signal that is proportional to twice the output signal of a single magnetoresistor.

First, it is assumed that the magnetic shielding means MB, MB2 do not affect the magnetic field generated by the current 1 passing through the magnetic resistance within a distance d from the magnetic resistance.

(The distribution of the magnetic field generated within the magnetoresistive device is the same as in the case where the magnetoresistive transducer TMRA does not have the shielding means MB, MB). Therefore, within the range of distance d from the magnetoresistor, the magnetoresistive force M calm. , MR2 are assumed to produce magnetic fields 1, 2, which are equal to Hpo, , Hpo2, respectively.

Let lsB be the strength of the current that can pass through the magnetoresistor and give the above value to the ratio. (The above values result in a polarization of approximately 45° in the two magnetoresistances). The operating points are PF and PF
2 (see Figure 6a). However, the magnetic shielding means M
B,,M old 2 has magnetic resistance M old,,MR2 with intensity ls
It is thought that this not only affects the distribution of the magnetic field lines 1, 2 caused by the current 1 of B, but also affects the strength of the magnetic field.

As mentioned above, a magnetic field acts on the means MB.

Magnetic field day. generates a magnetic quantity inside and on the surface of the magnetic means M, and the group of magnetic quantities is generated by a return magnetic field Hr, which is in the opposite direction to the field Hr,
generate. Similarly, the shielding means Mold2, which is acted upon by the field 52, generates a return magnetic field Hr2, which is at the level of the magnetic resistance MR2 and has a direction opposite to that of the field. Return magnetic field Hr, and Hr2
The intensity of is close to 1/3 of the intensity of ba day and day 2, and on the one hand is a function of the amount of magnetism contained in the magnetic shielding means MB and M old 2, and on the other hand is a value of ba day and day 2. It is a function of intensity. Said magnetic quantity is a function of the volume and surface area of the means MB, MB2 subjected to the influence of the magnetic fields 1, 2. Therefore, if the composite polarization magnetic fields acting on the magnetoresistances M old, MR2 are respectively H'poso, Hpo〆2, then Hpo,=day, dayr, and Hposo2=uniform Hr2.

Therefore, IHpo〆l<IHpo〆l and IH'po〆l
<IHpoZ2 l.

As a result, the operating point is not PF,,PF2 but PF',,P
It is F'2.

At this time, the sensitivity of the magnetoresistive device is considerably reduced, so that the change in resistance of the magnetoresistive device and hence the terminal voltage change is no longer a linear function of the acting leakage field. In order to return the initial operating point of MR,, MR2 to PF,, PF2, H'po so,, H'p
o〆2 is Hpo so. , Hpo〆2 needs to be increased in intensity so that it becomes substantially equal to Hpo〆2.

This means that it is necessary to substantially increase the intensity of the current flowing through the magnetoresistive element, ie to obtain an intensity IB much greater than IsB. It is clear that this results in extra heating of the magnetoresistor and requires the use of a more powerful power supply. Additionally, the noise signal generated by the magnetoresistive device is significantly increased. Figures 7a and 7b and Figures 8a and 8b illustrate two examples of the magnetoresistive transducer of the present invention, which can eliminate the disadvantages of prior art magnetoresistive transducers such as the transducer TM old A. Specific examples TMR1, TMR12 are shown. The principle of the invention is that the magnetic field of the two magnetoresistances of the transducer,
, 2 to minimize the volume and surface area of the shielding means subjected to the action of the magnetic shielding means, thereby reducing the intensity of the magnetic shielding means inside and on the surface of the magnetic shielding means, thereby significantly reducing the return magnetic field Hr,, Hr2. or to erase it. In this method, a magnetic deflection means for deflecting a magnetic field generated by current passing through the magnetic resistance is arranged between the first magnetic resistance and the adjacent magnetic shielding means, and a magnetic deflection means is arranged between the first magnetic resistance and the adjacent magnetic shielding means. In between, there is a second magnetic field that deflects the magnetic field generated by the second magnetic resistance.
This is achieved by arranging magnetic deflection means. Figures 7a and 7b show a first preferred embodiment of the magnetoresistive transducer of the invention, TMR1.

The transducer comprises: - two magnetoresistive resistors MR1, , parallel to each other;
MR12, -magnetic shielding means M old 1, MB12, -
It includes magnetic deflection means MMD, , MMD2.

The two magnetoresistances MR1, MR12 are exactly equal to the two magnetoresistances MR1, MR2 of the secondary technology transducer TMRA.

The magnetoresistor is made of magnetically anisotropic material and has a length of
substantially equal to the width LP of the medium SM arranged opposite the transducer TMR1.

The easy magnetization axis and the hard magnetization axis are the converter TMR shown in Figure 3a.
Magnetic resistance Mold of A,, easy axis of magnetization Axf of MR2,,A
They are arranged similarly to xf2 and the hard magnetization axes Axq and Axd2. Further, the two magnetic resistors MR1, MR12 are polarized in the same manner as the magnetic resistors M, MR2.

The magnetic shielding means MB1, MB12 are completely equivalent to the magnetic shielding means MB, MB12 of the prior art transducer TMRA.
The magnetic deflection means MMD, MMD2 of the magnetic field generated by the two magnetoresistive resistors MR1, MR12 are completely equal to each other.

The means each consist of a plurality of parallel magnetic thin films parallel to each other and separated from each other by non-magnetic thin layers. Therefore, the means Mhm, of FIG.
,,LAM2,LAM3,LAM4,LAM5,LAM
6, and a film LIS.6 of non-magnetic material is provided between each film. ,L
IS2, LIS3, LIS4, and LIS5 are arranged.

Similarly, the magnetic deflection means MMD2 includes a non-magnetic thin film LIS6.
~ LIS, . It includes a plurality of magnetic thin films LAM7 to LAM,2 separated from each other by.

The films LAM, to LAM6 and LAM7 to LAM,2 are preferably made of a magnetically anisotropic material, and their easy and hard axes of magnetization are parallel to the easy and hard axes of the magnetoresistors MR1, MR12, respectively. be. Insulating thin layers LIS, to LIS5 and LIS6 to LIS, . The thickness of each layer is selected such that the magnetic coupling between adjacent magnetic films of each layer is relatively small.

The magnetic deflection means MMD, are separated from the magnetic shielding means M1, by a thin layer of non-magnetic material CAM, and the magnetic deflection means MMD2 are separated from the magnetic shielding means M1, by a thin layer CAM of non-magnetic material. It is isolated from the magnetic shielding means MB12 by a non-magnetic layer CA ground similar to the above. The two magnetoresistive resistors MR1, MR12' are separated from each other by an electrically insulating non-magnetic thin layer, and each magnetoresistive member is separated from the adjacent magnetic resistor by an electrically insulating non-magnetic layer which is also omitted in FIG. 7a. isolated from deflection means.

According to Figures 7a and 7b, the height of the magnetic and non-magnetic films of the magnetic deflection means (approximately 30 to 50 microns) is smaller than the height of the magnetic shielding means (approximately 200 microns).

(Height is the dimension of the film measured perpendicular to the recording medium).
FIG. 7b particularly shows the function of the magnetic deflection means MMD, , MMD2.

In FIG. 7b, the lines of magnetic force caused by the passage of the current 1 in the magnetoresistive element MR are indicated by dotted lines. Assuming no magnetic deflection means are present (and also assuming that said means are not activated), the magnetic field lines are
12 to polarize the resistor at 45°. In this case, the magnetic field is within the region Z inside the magnetic shielding means MBI. invade inside. Area B is located near the magnetic recording medium and has a height substantially close to the height of the magnetoresistive elements MR, MR2. Assuming that the magnetic deflection means MMD of the converter TMRA is in operation, let HD be the magnetic field generated by passing the same current 1 through the magnetoresistive resistor MR1.

The magnetic field lines HD are shown as solid lines. Magnetic field line HD, is magnetic resistance M
Polarize the resistor 45o through R12. These lines of magnetic force are
It is deformed with respect to the magnetic field lines by the magnetic deflection means MMD. HD, is deflected with respect to the sun, and inside the region Z, the upper region Z2, the magnetic shielding means M old 1. to invade. (In other words, area Z2 is farther from recording medium SM than area Z). Field HD in area Z2. is smaller than the intensity in the area Z when the deflection means MMD is not present, and the volume and surface area of the magnetic shielding means MB1 under the action of the magnetic deflection means is The same magnetic shielding means MB1 under the action of
, is clearly smaller than the volume and surface area of . Therefore, the amount of magnetism generated by the magnetic field HD inside and on the surface of the magnetic shielding means MD1, inside and on the surface of the territorial sea Z
, is clearly smaller than the amount of magnetism generated inside and on the surface of .

(The latter is always the case assuming that the magnetic deflection means MMD, are not present or in operation). Therefore, the means M
The return magnetic field Hrd. is extremely small. The first reason is that the amount of magnetism generated within region Z2 is small, and the second reason is that region Z is relatively far from magnetoresistive regions MRI, MR12. As mentioned above, the presence of the magnetic deflection means MMD, very significantly reduces the return magnetic field Hrd, and eliminates the influence of the magnetic shielding means MB1, on the magnetic field HD, polarizing the magnetoresistive MR12.

In other words, because of the presence of the magnetic deflection means MMD, there is no need to increase the value of the current applied to the magnetoresistor in order to obtain a polarization angle of approximately 45°. Figures 8a and 8b are
Second preferred embodiment TMR of the magnetoresistive transducer of the present invention
12 is shown.

The magnetoresistive transducer TMR12 of the present invention shown in FIG. 8 includes various components as described below. Magnetoresistances MR1, MR1, M-law 2 and parallel magnetoresistances MR13, MR14 (dimensions, type of magnetic anisotropic material,
The arrangement of the easy magnetization track and the hard magnetization axis and the polarization angle are MR1
,,same as MR12).

- deflection shielding means MD&, MDB4;

The non-magnetic insulating thin layer on the other hand has two magnetoresistive elements M old 13 and M
R14, and on the other hand between each magnetoresistor and the deflection shielding means MD&, MDB4 proximate to the magnetoresistor, but are not shown in FIG. 8a for the sake of simplicity.

The magnetic deflection deflection means MDB3 includes a magnetic thin film L3. ,,L3.
2, L3.3, L3.4, and L bottles, each film having a non-magnetic insulating thin layer LIS3. ,,LIS3.2,LIS3.
3. Isolated from each other by LISM.

For example, the layer LISM is arranged between the magnetic films LM and L3.2. Regarding the thickness of the magnetic films LM to L3.5, the farther from the magnetoresistive films 13 and MR14, the thicker the film, and regarding the thickness of the non-magnetic layer between various magnetic films, the farther from the magnetoresistive film the thicker the film. 4. Sashi. In other words, for example, the membrane L3. , is smaller than the thickness of the membrane L3.2, which is smaller than the thickness of the membrane L3.3, and so on. Insulating film LIS3. , is greater than the thickness of the membrane LIS3.2, which is greater than the thickness of the membrane LIS3.3,
The same applies hereafter. This means that the magnetic coupling between the films close to the magnetoresistor is smaller than the magnetic coupling between the films remote from the magnetoresistor.

For example, the magnetic coupling between films LM and L3.2 is substantially less than the magnetic coupling between magnetic films L3.4 and L3.5. The deflection shielding means MDB4 is completely equal to the deflection shielding means MDB3, and is made of an insulating thin film LISM to LIS made of a non-magnetic material.
Magnetic thin films L4. ,～L
Contains 4.5.

As in the case of means MDB, the magnetic coupling between magnetic thin films close to the magnetoresistor is smaller than the magnetic coupling between magnetic thin films remote from the magnetoresistor. FIG. 8b shows the converter TMR12 of the present invention.
This shows the operation. FIG. 8b shows the magnetic field lines generated by the passage of current 1 in magnetoresistive MR 13. FIG.

The magnetic field lines pass through magnetoresistive MR14, increasing the magnetoresistive force to about 4
Can be polarized 5o. The transducer TM eye 12 has a magnetic deflection shielding means MDB3 consisting of two parts, namely a shielding means Mold 3 and a deflection means M
It operates as if it were composed of D3.

The operation of the converter TMold 12 is therefore exactly the same as the operation of the converter TMR12 described in FIG. 7b. The magnetic field lines 3 generated by the passage of the current 1 in the magnetoresistive element MR13 when it is assumed that the deflection means MD3 are not present or activated are shown in dotted lines.

If the area of the shielding means MB3 that is affected by the magnetic field 3 at this time is Z, then Z generates a return magnetic field that cannot be ignored. The lines of magnetic force passing through the magnetic field HD3 and the magnetic resistance MR14 are shown by solid lines when it is assumed that the deflection means MD3 exists and operates.

At this time, magnetic shielding means M old 3 subjected to the action of tin HD3
The area is indicated by O. In this case, the return magnetic field Hrd3 is HD
It is extremely small compared to 3 and has virtually no effect.
Therefore, there is no need to increase the intensity of the current 1 to obtain a polarization angle value of approximately 45°. It is clear that the description of the magnetoresistive transducer of the invention comprising two magnetoresistive elements is also valid for magnetoresistive transducers comprising one or more than two magnetoresistive elements.

In exactly the same way as the above description of the operation of the inventive transducer with two magnetoresistives, the operation of a transducer containing one or more than two magnetoresistors can be explained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operating principle of a basic magnetoresistive transducer including one magnetoresistive unit made of magnetically anisotropic material;
Fig. a is a perspective view of a magnetoresistive device arranged opposite to one track of a magnetic recording medium, Fig. lb is an explanatory diagram showing the positional relationship of the magnetic resistance with respect to a leakage magnetic field of information recorded on a recording track, and Fig. Figure 2 shows changes in magnetoresistance made of magnetically anisotropic materials in order to fully understand the polarization principle of magnetoresistance.
FIG. 3 is an illustration of a prior art magnetoresistive transducer comprising two parallel magnetoresistive transducers and shielding means;
Figure a is a perspective view of the above-mentioned magnetoresistive transducer, Figure 3b is a side view, and Figure 3c is a diagram of two magnetoresistive transducers viewed from the magnetic domain of the recording track of the medium facing the magnetoresistive elements. 4 is a plan view, and FIG. 4 is a cross-sectional view of the magnetoresistive transducer of FIG. 3 showing the main magnetic field lines of each magnetic field generated by the passage of current in the first and second magnetoresistors, and FIG. 5 is a sectional view of the magnetoresistive terminals. Figure 6 is an explanatory diagram showing how the signals collected in the differential amplifier are supplied to the differential amplifier. FIG. 7 shows a preferred embodiment of the magnetoresistive transducer of the present invention, FIG. 7a is a perspective view, and FIG. The figure shows two magnetoresistive cells of the transducer of the present invention. FIG. 8 shows a second specific example of the magnetoresistive transducer of the present invention, and FIG. 8a is a perspective view. , FIG. 8b shows two of the converters of the present invention.
FIG. 3 is a side view showing the deformation of one of the main magnetic field lines of the magnetic field caused by one of the magnetoresistances; MR... Magnetoresistive, TMRE... Magnetoresistive converter,
SM...magnetic medium, P...track,
Hf... Leakage magnetic field, TMRA... Magnetoresistive converter, MB... Magnetic shielding means, AM circle D
IF... Differential amplifier, TMR1... Magnetoresistive converter, MR1... Magnetoresistive, MMD.
...Magnetic deflection means, MDB...Deflection shielding means. FIG. loFIG. lb FIG, 2 FIG. 3o FIG. 3b FIG-Yo [FIG. MuFIG. 5 FIG. 6o F'G. 6b FIG. 7o FIG. 7b FIG. 8o FIG. 8b

Claims (1)

[Scope of Claims] 1. In order to read information recorded inside a plurality of tracks of a magnetic medium, - at least one magnetic medium is arranged perpendicularly to the direction of travel of the information and allows a current to pass in the longitudinal direction; A magnetoresistive transducer comprising: a magnetoresistive element; - first and second magnetic shielding means disposed on opposite sides of the element to collect magnetic flux of a group of information surrounding information on a track facing the element; wherein the transducer includes means for deflecting a magnetic field generated by a current flowing in the element, the deflection means being between the element and a first shielding means and between the element and a second shielding means. A magnetoresistive transducer characterized in that the magnetoresistive transducer is disposed between the two. 2. The magnetic field deflecting means includes two magnetoresistive elements parallel to each other and a magnetic field deflecting means, and the magnetic field deflecting means is arranged between the first element and the first shielding means and between the second element and the second shielding means. A transducer according to claim 1, characterized in that the transducers are arranged respectively. 3. The deflection means is composed of a plurality of magnetic thin films parallel to each other, the magnetic thin films are separated from each other by a non-magnetic thin film, and the thickness of the magnetic thin film is equal to that of two adjacent magnetic thin films. 3. A magnetoresistive transducer according to claim 1, wherein the magnetoresistive transducer has a thickness such that magnetic coupling between the magnetoresistive transducers is relatively small. 4. A magnetoresistive transducer including a magnetic shielding means consisting of a group of magnetic thin films separated by a non-magnetic film and configured such that the coupling between two adjacent magnetic films is relatively large;
The magnetic film group and the non-magnetic film group of the deflection means and the shielding means have the same dimensions, so that the deflection means and the shielding means constitute a single deflection shielding assembly, and the thickness of the magnetic thin film group Regarding the thickness of the non-magnetic film group, the farther away from the magnetoresistive layer the thinner the magnetic film is, the thinner the film is. 4. The magnetoresistive transducer according to claim 3, wherein the magnetic coupling is smaller than the magnetic coupling between the magnetic films further away from the magnetoresistive transducer. 5. A patent claim characterized in that the magnetic thin film of the magnetoresistive and deflection means and the magnetic thin film of the shielding means are manufactured from magnetically anisotropic materials, and their easy and hard axes of magnetization are respectively parallel to each other. A magnetoresistive transducer according to any one of items 1 to 4 in the range 1 to 4.