Signal transmission device

A magnetic detection element includes a magnetoresistance effect portion composed of a magnetoresistance effect material and a pair of yoke portions. The pair of yoke portions is composed of a soft magnetic material and are respectively arranged so as to be electrically connected to both sides of the magnetoresistance effect portion. The pair of yoke portions guides magnetic flux into the magnetoresistance effect portion. The magnetic detection element also includes a bypass portion, which is composed of a soft magnetic material and is saturated with magnetic flux at lower magnetic field intensity than the yoke portions, and which guides a part of the magnetic flux generated in the yoke portions so as to divert the magnetic flux from the magnetoresistance effect portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One or more embodiments of the present invention relate to a magnetic detection element for detecting a magnetic field intensity and a signal transmission device for transmitting a signal by means of a magnetic coupling.

2. Description of the Related Art

Patent literature 1, for instance, discloses a magnetic coupling type of signal transmission device comprising a coil which generates a magnetic field in accordance with a input signal and a bridge circuit which includes a magnetoresistance effect element (magnetic detection element) to detect the intensity of the magnetic field generated by the coil.

Patent literature 2, for instance, discloses a granular in gap (GIG) configuration in which a pair of yoke films consisting of a soft magnetic material is arranged to guide a large amount of magnetic flux into both side of the granular film exhibiting a giant magnetoresistance effect (generically electric resistance of a material varies by amount more than few % with an external magnetic field), in order to enhance a variation sensitivity of the electric resistance of the granular film exhibiting a giant magnetoresistance effect.

In such GIG configuration, when external magnetic field is inputted, first the yoke consisting of a soft magnetic material having a large magnetic flux density is magnetized, the magnetic flux generated by the large magnetization passes through the granular film exhibiting a giant magnetoresistance effect to achieve large amount of variation in the electric resistance with a small variation of the external magnetic field. However, in the GIG configuration, a linear range where magnetic field intensity can be linearly detected is limited in a significantly narrow range, because of a nonlinear magnetic flux increasing characteristic according to a magnetizing procedure of the soft magnetic material yoke film and to a nonlinear resistance variation characteristic in the magnetoresistance effect of the granular film.

Patent literature 3, for instance, discloses a technique for detecting a very small variation of magnetic flux by providing a magnetic path with a bypass to reduce magnetic flux applied to the detecting coil. In this technique, the magnetic flux variation detection range is widened by reducing the sensitivity, but the range having high linearity in electric resistance can not be widened, and therefore the linearity of the magnetoresistance effect element can not be improved.

PATENT LITERATURES

SUMMARY OF THE INVENTION

One or more embodiments of the present invention may provide a magnetic detection element with a high linearity and a signal transmission device with a high linearity.

A magnetic detection element according to one or more embodiments of the present invention has a magnetoresistance effect portion composed of a magnetoresistance effect material, a pair of yoke portions which is composed of a soft magnetic material and respectively arranged so as to be electrically connected to both sides of the magnetoresistance effect portion, and which guides magnetic flux into the magnetoresistance effect portion, and a bypass portion which is composed of a soft magnetic material and saturated with magnetic flux at lower magnetic field intensity than the yoke portions, and which guides a part of the magnetic flux generated in the yoke portions so as to divert the magnetic flux from the magnetoresistance effect portion.

With this configuration, in a condition that the bypass portion is not yet saturated with a low external magnetic field intensity, a portion of magnetic flux generated in the yoke portion with the external magnetic field passes through the bypass portion to reduce a magnetic flux passing thorough the magnetoresistance effect portion. In contrast, with an increased external magnetic field, the bypass portion is saturated before the yoke portions, and therefore all of increase in magnetic flux generated in the yoke portions passes thorough the magnetoresistance effect portion. As a result, electric resistance variation profile of the magnetoresistance effect portion varies so as to enhance the linearity.

Further, in the magnetic detection element according to one or more embodiments of the present invention, the bypass portion may be electrically isolated from the magnetoresistance effect portion and the yoke portions.

With this configuration, because the bypass portion is electrically isolated, the electric resistance of the magnetoresistance effect portion is accurately detected. Therefore, the influence of the bypass portion to the detection accuracy can be reduced as much as possible to enhance the linearity of variance of the electric resistance of the magnetoresistance effect portion to the magnetic field intensity.

Further, in the magnetic detection element according to one or more embodiments of the present invention, the magnetoresistance effect portion and the yoke portions may be formed in film like forms on a same plane, and the bypass portion may be formed in a film like form so as to lap at least partially over the magnetoresistance effect portion and to be spaced from the yoke portions.

With this configuration, the magnetic detection element can be produced by a common semiconductor manufacturing method in which thin film material layers are stacked on a substrate by a microfabrication technology.

Further, in the magnetic detection element according to one or more embodiments of the present invention, a reluctance of a magnetic path diverted from the magnetoresistance effect portion via the bypass portion may be smaller than a reluctance of the magnetoresistance effect portion between the yoke portions at a magnetic field intensity which does not saturate the bypass portion with magnetic flux.

With this configuration, more flux is diverted from the magnetoresistance effect portion at a low magnetic field intensity, and therefore the bypass portion has large effect to the resistance variation characteristic so as to significantly improve the linearity of the resistance variation characteristic.

Further, in the magnetic detection element according to one or more embodiments of the present invention, the bypass portion may be partially saturated with magnetic flux at different magnetic field intensities.

With this configuration, by each saturation of the parts of the bypass portion, a ratio of bypassing flux is varied so as to cause the resistance variation characteristic of the magnetoresistance effect portion to be more linier with respect to the external magnetic field.

Further, in the magnetic detection element according to one or more embodiments of the present invention, the bypass portion may comprise portions with different lengths in a direction of guiding magnetic flux.

With this configuration, by a planer shape of the bypass portion, the magnetic field intensity saturating the bypass portion with magnetic flux can be partially differed.

Furthermore, a signal transmission device according to one or more embodiments of the present invention has any one of the aforesaid magnetic detection element, and a coil which applies a magnetic field to the magnetic detection element in accordance with an input signal.

With this configuration, it has a high transmission efficiency and an input-output transmission with better linearity can be made by one or more embodiments of the present invention. Accordingly, a high quality signal transmission can be achieved.

In accordance with one or more embodiments of the present invention, in a condition that the bypass portion is not yet saturated with a low external magnetic field intensity, a part of magnetic flux generated in the yoke portion with the external magnetic field passes through the bypass portion to reduce a magnetic flux passing thorough the magnetoresistance effect portion. In contrast, with an increased external magnetic field, the bypass portion is saturated before the yoke portions, and therefore all of increase in magnetic flux generated in the yoke portions passes thorough the magnetoresistance effect portion. As a result, electric resistance variation profile of the magnetoresistance effect portion varies so as to enhance the linearity.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one with ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention.FIG. 1shows a circuit configuration of a signal transmission device (magnetic coupling type isolator)1as first embodiment of the present invention. The signal transmission device1comprises a primary circuit4having two excitation coils3a,3bwhich generate magnetic fields according to currents inputted to input terminals2a,2b, and a secondary circuit6which is magnetically coupled with the primary circuit4and outputs an electric voltage to output terminals5a,5bin accordance with the input voltage.

The secondary circuit6is a bridge circuit that comprises two magnetic detection elements7a,7bof which electric resistance value varies according to the intensity of the magnetic field generated by the exciting coils3a,3b, and two fixed resistances8a,8bof which resistance value is unchangeable, and that is connected to a power source Vcc.

FIG. 2shows a practical configuration of the signal transmission device1(in plane view). The signal transmission device1is configured by layer stacking of each component on a silicon substrate9on which surface insulation film is formed. The exciting coils3a,3bare respectively formed so as to surround the magnetic detection elements7a,7b.

The magnetic detection elements7a,7bcomprise, as further shown inFIG. 3(perspective view) andFIG. 4(sectional view) specifically, of magnetoresistance effect portions (called as MR portions bellow)10a,10bcomposed of a giant magnetoresistance effect material and yoke portions11a,12aand11b,12bwhich is composed of a soft magnetic material and which is arranged at both sides of the MR portions10a,10bso as to maintain respective contacts with the MR portions10a,10b. These yoke portions have significantly lower specific resistances than the above giant magnetoresistance effect material to function also as electrodes to supply current to the MR portions10a,10b(so called GIG). Further, the magnetic detection elements7a,7bhave bypass portions13a,13bwhich is composed of a soft magnetic material and which is arranged so as to lap over the MR portions10a,10band to form a gap d between with yoke portions11a,12aand11b,12bfor electric isolation.

The gap d between the bypass portions13a,13band the MR portions10a,10b, also and the yoke portions11a,12a,11b,12bcan be a air layer, but practically is an insulation film (protection film) made of nonmagnetic material and formed between the bypass portions13a,13band the MR portions10a,10b, also and the yoke portions11a,12a,11b,12b.

As giant magnetoresistance effect materials for forming the MR portions10a,10b, cited are nano-granular film materials, for instance, Co39Y14O47, Co43Y24O33and Co35Mg20F45having specific resistances typically of 3×106μΩm, 0.4×103μΩm and 1×106μΩm respectively. In addition, as giant magnetoresistance effect materials, Cox—(Y2O3)(100-X)nano-granular alloys, Cox—(Al2O3)(100-X)nano-granular alloys, Cox—(Sm2O3)(100-X)nano-granular alloys, Cox—(Dy2O3)(100-X)nano-granular alloys, (FeCO)x—(Y2O3)(100-X)nano-granular alloys, fluoride nano-granular alloys such as Fex—(Mg2F2)(100-X), (FeCO)x—(Mg2F2)(100-X)can be used. Notably, composition ratios are indicated in at % in the present application.

The yoke portions11a,12aand11b,12bare formed in film forms on a same plane in a rectangular shape, for instance, with a length of 250 μm in a longitudinal direction (the direction of magnetic flux), a width of 80 μm and a thickness of 0.5 μm, so that end portions of each pair oppose to each other with a gap G respectively. The MR portions10a,10bare formed so as to be electrically connected with the yoke portions11a,12aand11b,12bwithin the gap G.

The bypass portions13a,13bhas for instance a length of 5 μm, a width of 5μ and a thickness of 0.1 μm, and is formed with 0.1 μm of gap d between with the MR portions10a,10band the yoke portions11a,12aand11b,12b.

FIG. 5shows a configuration of the magnetic detection elements7a,7bin magnetic path reluctance (magnetic circuit diagram). This magnetic path reluctance can be considered as one in which a reluctance consisting of a reluctance RGAPof the air or nonmagnetic insulating portion between the yoke portions11a,11band the bypass portions13a,13b, a reluctance RBPSof the bypass portions13a,13b, and reluctance RGAPof the air or nonmagnetic insulating portion between the bypass portions13a,13band the yoke portions12a,12bconnected in series is further connected in parallel with a reluctance RGMRof the MR portions10a,10b, between reluctances RYOKof the yoke portions11a,11band the yoke portions12a,12b.

Therefore, in the magnetic detection elements7a,7b, magnetic flux generated by the exciting coils3a,3band guided by the yoke portions11a,12a,11b,12bis at first divided into the bypass portions13a,13band the yoke portions11a,12a,11b,12b. This meaning that the bypass portions13a,13battract a part of the number of magnetic flux generated in the yoke portions11a,12a,11b,12bto divert from the MR portions10a,10band thereby reduce the amount of the magnetic flux passing thorough the MR portions10a,10b.

Notably, the reluctance RYOK, RGMR, RBPSrespectively vary in its value according to the magnetic field intensity. Generally, a reluctance value increases with increasing of amount of passing magnetic flux according to a rising of magnetic field intensity. And, because saturation with magnetic flux is caused at certain magnetic field intensity, the reluctance value comes to increase in a significantly higher rate compared to at low magnetic field intensity, and the reluctance value stops increasing any further amount of magnetic flux passing thorough when saturation is completed. Specifically, the reluctances RGMRof the bypass portions13a,13brapidly increase at lower magnetic field than other reluctances.

It is noted that the reluctance RGMRcan be described as bellow expression, wherein the GGMRrepresents the length of the MR portions10a,10bin the direction where the magnetic flux is applied (magnetic path length), μGMRrepresents the magnetic permeability of the MR portions10a,10b, tGMRrepresents the thickness of the MR portions10a,10band WGMRrepresents the width of the MR portions10a,10b(magnetic path width).
RGMR=GGMR/(μGMR×tGMR×WGMR)

FIG. 6shows a result of a simulation of variation of the electric resistance between the yoke portions11a,11band the yoke portions12a,12bincluding the MR portions10a,10bwith respect to the input magnetic field intensity applied to the magnetic detection elements7a,7b, in MR ratio in which the resistance at zero of magnetic field intensity is 100%. Notably, the result is illustrated in comparison to an electric resistance of a magnetic detection element with conventional configuration without the bypass portion13a,13b. Remarkably, the bypass portion13a,13bis electrically insulated from the MR portions10a,10band the yoke portions11a,11b,12a,12b, and therefore does not influent the electric resistance of the electrical path including the MR portions10a,10b.

In this simulation, used are a nano-granular film composed of (FeCo)30—(MgF2)70with 14% of MR ratio at 10 Oe as the MR portion10and amorphous Co78Fe4Si9B9films which have 12 KG of magnetic flux density at 10 Oe and single axis induced magnetic anisotropy, and of which magnetic permeability varies almost linearly form the zero magnetic field to the saturated magnetic field, as the yoke portions11,12. And an amorphous film composed of the same material with the yoke portions11,12is used as the bypass portion13.

The MR portions10a,10bdecrease its electric resistance with increasing of passing magnetic flux. However when the bypass portions13a,13bare not yet saturated, parts of the magnetic flux generated in the yoke portions11a,11b,12a,12bare induced into the bypass portions13a,13b, and therefore the electric resistance reducing rate of the MR portions10a,10bis lower than that in a conventional element. In the Figs. the variation characteristics of the MR ratio (shape of the diagram) are expanded in the lateral direction with reference to that of the conventional one.

However, because the sectional areas (thickness×width) of the bypass portions13a,13bare sufficiently smaller than the sectional areas (thickness×width) of the yoke portions11a, llb,12a,12b, the input magnetic field comes to strong. Therefore, when the amount of the magnetic flux generated by the exciting coils3a,3bincreases (the intensity of the magnetic field which is generated by the exciting coils3a,3band applied to the magnetic detection elements7a,7bis increased), the bypass portions13a,13bare saturated with magnetic flux so as to be impossible to guide any more magnetic flux. Accordingly, when the intensity of the input magnetic field is high, the magnetic flux bypassing function of the bypass portions13a,13bis low, and therefore most increase of magnetic flux generated in the yoke portions11a,11b,12a,12bare guided into the MR portions10a,10b. In the diagram, with reaching to saturation of the bypass portions13a,13b, the degree of lateral expansion of the curve with reference to the conventional curve get smaller. Accordingly the linearity of the MR ratio variation characteristic is enhanced.

In the magnetic detection elements7a,7b, when the intensity of the input magnetic field is further increased, the bypass portions13a,13bare completely saturated before the yoke portions11a,11b,12a,12b. As a result, all increase of magnetic flux generated in the yoke portions11a,11b,12a,12bpasses through the MR portions10a,10b, after the bypass portions13a,13bare completely saturated. According to this function, the decrease of the electric resistance varying rate due to increasing of the reluctances of the MR portions10a,10band the yoke portions11a,11b,12a,12bis compensated, so as to obtain a variation characteristic of the electric resistance (MR ratio) with higher linearity. This means that magnetic detection elements7a,7bprovided with the bypass portions13a,13bhas a wider range where the linearly is excellent in the variation characteristic of the electric resistance (MR ratio) with respect to the variation of the input magnetic field, compared to conventional magnetic detection elements.

Because when the ratio of magnetic flux which is guided by the bypass portions13a,13bso as to be diverted from the MR portions10a,10b, to whole magnetic flux generated in the yoke portions11a,11b,12a,12bis low, the room for changing the MR ratio characteristic of the MR portions10a,10bis small. Therefore, when the magnetic field intensity is low, between the yoke portions11aand12band between the yoke portions11band11b, the reluctances of magnetic paths via the bypass portions13a,13b(2RYOK+2RGAP+RBPS) are preferably smaller than the reluctances of magnetic paths via the MR portions10a,10b(2RYOK+RGMR).

In a case that the reluctances of magnetic paths via the bypass portions13a,13b(2RYOK+2RGAP+RBPS) is excessively smaller than the reluctances of magnetic paths via the MR portions10a,10b(2RYOK+RGMR), too much magnetic flux is guided into the bypass portions10a,10b, and therefore, inFIG. 6, the line profile of the MR ratio variation characteristic with the bypass portions13a,13bis too expanded laterally. Accordingly, the varying rate of the electric resistance of the MR portions10a,10bwith respect to the input magnetic field is law, and hence the sensitivity of detection of magnetic field is reduced. In contrast, in a case that the reluctances of magnetic paths via the bypass portions13a,13bare excessively large, magnetic flux can not be guided into the bypass portions10a,10b, and therefore the function to divert the magnetic flux from the MR portions10a,10bhas almost disappeared. Accordingly, the function to improve the electric resistance variation characteristic is not obtained. As the above, the balance between the reluctances of magnetic paths via the bypass portions13a,13b(2RYOK+2RGAP+RBPS) and the reluctances of magnetic paths via the MR portions10a,10b(2RYOK+RGMR) should be considered.

FIG. 7andFIG. 8show a magnetic detection element7cas second embodiment of the present invention. The magnetic detection element7cof the second embodiment comprises yoke portions11,12of which end facing to each other with a gap G is reduced in thickness in a tapered shape, a MR portion10formed by filling magnetoresistance effect material into a region from tapered portion on one side of the yoke portions11,12to the middle of the gap G, and a bypass portion13formed so as to lap over the MR portion10with interposition of unshown isolation film.

The yoke portions11,12have a length of 50 μm in a direction where the magnetic flux is guided (a direction to sandwich the MR portion10), a width of 80 μm and a thickness of 0.5 μm, and face to each other so as to form a gap G. And, the yoke portions11,12have a face respectively inclined in a tapered shape for a length of 2 μm from the end face of the MR portion10in the guiding direction for magnetic flux, on the bypass portion13side, and 2 μm of thickness defining the gap G. Bypass portion has a length of 5 μm in the guiding direction for magnetic flux that is as same as the whole length of the MR portion including a part covering the tapered portion of the yoke portions11,12. The gap d between the MR portion10and the bypass portion13(thickness of a isolation film made of a spatter SiO2film) is 0.05 μm.

In this magnetic detection element7c, as the MR portion10, a nano-granular film with 0.3 μm of film thickness in the gap G made of (FeCO)30—(Mg2F2)70with 14% of MR ratio at 10 Oe is used, as the yoke portions11,12, amorphous Co78Fe4Si9B9films which have 12 KG of magnetic flux density at 10 Oe and single axis induced magnetic anisotropy, and of which magnetic permeability varies almost linearly form the zero magnetic field to the saturating magnetic field. And, as the bypass portion13, an amorphous film of the same material with the yoke portions11,12is used.

FIG. 9shows measured results of variations of electric resistances (MR ratios) between the yoke portion11and the yoke portion12including the MR portion10with respect to the intensity of the input magnetic field, with the magnetic detection elements7cof the present embodiment having thickness of the bypass portion13of 0.2 μm and respectively the widths of the bypass portion13of 80 μm as same as the yoke portions11,12, of 40 μm as half of the yoke portions11,12, of 20 μm as quarter of the yoke portions11,12, and of 10 μm as one eighth of the yoke portions11,12.

As shown in the diagram, in the magnetic detection element7c, in the range with input magnetic field lower than 10 (Oe), the curves of the MR ratios expanded in the horizontal axis direction by the bypass portion similar to the first embodiment, and after the bypass portion13has been fully saturated with stronger input magnetic field, drawn curves generally coincide the parallel translated curves of the conventional magnetic detection elements without a bypass portion. Further, in this embodiment, the yoke portions11,12are also saturated at about 20 (Oe) of the magnetic field intensity. Therefore, at higher magnetic field intensity, the decreasing rates of the MR ratios are significantly lowered.

With a wider width of the bypass portion13, the amount of the magnetic flux diverted from the MR portion10is increased, the behavior is nonlinearly changed significantly with respect to the increasing of the amount of the magnetic flux. Therefore, the effect of enhancing the linearity around an intensity of input magnetic field where the bypass portion13is saturated get grater, accordingly the range where the MR ratio is linear is widened. At the same time, because with wider width of the bypass portion13, the amount of the magnetic flux diverted from the MR portion10is increased, the varying rate of the MR ratio with respect to the variation of the input magnetic field is decreased. It is noted that when the yoke portions11,12are saturated, the linearity is impaired, and therefore the range of magnetic field intensity where the MR ratio characteristic is enhanced by the bypass portion13should be a lower range than the magnetic field intensity where the yoke portions11,12are saturated. Consequently, in this embodiment, in the case that the linear range is widest, the linear range is from where the bypass portion13starts to be saturated to where the yoke portions11,12start to be saturated.

FIG. 10shows measured results of variations of electric resistances (MR ratios) between the yoke portion11and the yoke portion12including the MR portion10with respect to the intensity of the input magnetic field, with the magnetic detection elements7cof the present embodiment having a width of the bypass portion13of 0.2 μm and respectively the thicknesses of the bypass portion13of 0.2 μm, 0.1 μm, and without bypass portion13.

As shown in the diagram, with larger thickness of the bypass portion13, the degree of laterally expanding the curve of the MR ratio when the intensity of input the magnetic field is lower, and therefore the intensity of the magnetic field where the bypass portion13is saturated get higher. And the curve of the MR ratio with the bypass portion13having a with of 80 μm and a thickness of 0.1 μm in theFIG. 10almost coincide to the curve with the bypass portion13having a with of 40 μm and a thickness of 0.2 μm in theFIG. 9. That means the MR ratio characteristic is generally same as far as the cross sectional area of the bypass portion13is same in the case that the other condition is same.

Also, the saturabilities of the yoke portions11, and the bypass portion13depend on the each cross sectional area. In this embodiment, because the yoke portions11,12and the bypass portion13are made from the same material, the cross sectional area of the by pass portion13should be smaller than the cross sectional area of the yoke portions11,12. It is noted that the term “cross sectional area” here means an effective sectional area that limits the amount of passing magnetic flux through it.

Therefore, in the magnetic detection elements7c, by choosing the ratio between the cross sectional area of the bypass portion13and the cross sectional area of the yoke portions11,12, the balance between the reluctance of the magnetic path via bypass portion13(2RYOK+2RGAP+RBPS) and the reluctance of the magnetic path via MR portion10(2RYOK+RGMR) can be adjusted.

In the magnetic detection elements7cof the present embodiment, also by changing the over lapping area of the bypass portion13and the yoke portions11,12seen from the top, the balance between the reluctance of the magnetic path via bypass portion13(2RYOK+2RGAP+RBPS) and the reluctance of the magnetic path via MR portion10(2RYOK+RGMR) can be adjusted.

Further in the present embodiment, by changing the amount of the gap d between the bypass portion13and the yoke portions11,12, the reluctance between the bypass portion13and the yoke portions11,12RGAPcan be varied.

While, in the present embodiment, the bypass portion13is arranged so as to lap over the one side of the MR portion10, the bypass portion13can be in any form as far as the bypass portion13can guide the magnetic flux generated in the yoke portions11,12to divert from the MR portion10. For instance, the bypass portion13may be arranged on both or one side of the MR portion10(the gap G between the yoke portions11,12). In a case that the MR portion10occupies only a part of the gap G between the yoke portions11,12, the bypass portion13may be arranged in the gap G between the yoke portions11,12.

FIG. 11shows a magnetic detection element7dbeing third embodiment of the present invention,FIG. 12shows a magnetic detection element7ebeing fourth embodiment of the present invention, andFIG. 13shows a magnetic detection element7fbeing fifth embodiment of the present invention.

The magnetic detection element7dof the third embodiment, as shown inFIG. 11, has the same configuration with the magnetic detection element7cof the second embodiment, excepting the bypass portion13is formed so as to lap over only a part of the MR portion10locating the gap G.

The magnetic detection element7eof the fourth embodiment, as shown inFIG. 12, has a bypass portion13with a shape as defined by that the bypass portion13of the magnetic detection element7dof the third embodiment is non-uniformly expanded in the longitudinal direction of the yoke portions11,12, that is the direction where the bypass portion13guides the magnetic flux. Specifically, the bypass portion13has a generally cross star shape of which both ends in the direction of the width (the direction perpendicular to the direction of guiding of the magnetic flux) laps over only the portion in the gap G, the length of which gets longer as at more inside in the direction of guiding of the magnetic flux the widthwise portion, particularly so that the widthwise central portion protrudes as in a triangle shape of which tip ends reaches to the position opposite to the starting positions of the taper of the yoke portions11,12.

The magnetic detection element7fof the fifth embodiment, as shown inFIG. 13, has a bypass portion13with a star shape sharper than the bypass portion13of the magnetic detection element7eof the fourth embodiment. In the bypass portion13of this embodiment, the both widthwise ends is sharpened to have a length of zero in the direction of guiding magnetic flux, and the projecting portion at the widthwise center has sharp shape with a small apex angle. Therefore, the length of the bypass portion13in the direction of guiding magnetic flux is extremely varied.

FIG. 14shows simulation results of variation characteristics of electric resistances (MR ratio) between the yoke portion11and yoke portion12including the MR portion with respect to the intensity of the input magnetic field with the magnetic detection elements7d,7e,7fand a conventional magnetic detection element consisting only of the MR portion10and the yoke portions11,12without the bypass portion13.

The magnetic detection element7dof the third embodiment, similar to the magnetic detection element7cof the second embodiment, has a low decreasing rate of MR ratio at less than about 10 (Oe) where the bypass portion begins to be saturated (the amount of the caught magnetic flux comes to increase not in proportion to the magnetic field intensity), and therefore has low linearity. In contrast, in the magnetic detection element7eof the fourth embodiment and the magnetic detection element7fof the fifth embodiment, the MR ratios linearly decrease in a wide range from low magnetic field intensity to about 20 (Oe) where the bypass yoke portions11,12begin to be saturated, and therefore the linearity is significantly enhanced in comparison to the magnetic detection element7dof the third embodiment.

Because the bypass portions13of the magnetic detection elements7e,7fhave projecting widthwise central portions, the magnetic flux is attracted to this portions, and therefore the magnetic flux concentrates in the widthwise central portions. For this reason, widthwise central portions of the bypass portions13are saturated at low magnetic field intensity, earlier than the other portions. And, as the magnetic field intensity increases, the saturated area of the bypass portion13progressively expands from the widthwise central portion in the widthwise direction to both ends and in the longitudinal direction. Accordingly, the effect for enhancing the linearity of the MR ratio by saturation of the bypass portion is gradually produced in the widthwise direction at different timings, so as to linearly vary the MR ratio in a wide range from a low to a high magnetic field intensity.

Similarly to the above, in order to obtain the effect for enhancing linearity of the MR ratio by partially saturating the bypass portion13at different magnetic field intensity, as the magnetic detection element7gof the sixth embodiment shown inFIG. 15, the bypass portion13may be formed in a divided manner as a plurality of separated parts respectively having different length in the direction of guiding magnetic flux. Also, as the magnetic detection element7hof the seventh embodiment shown inFIG. 16, the bypass portion13may be formed with thickness varied in the widthwise direction.

Furthermore, in one or more embodiments of the present invention, by forming the bypass portion13from the different material, the characteristic of the profile of the electric resistance variation of the MR portion10with respect to the magnetic field intensity can also be altered. Here is examined a difference in MR ratio varying profile with forming the bypass portion13of a magnetic detection element7iof the eighth embodiment shown inFIG. 17.

In the magnetic detection element7i, the material and the shape of the MR portion10and the yoke portions11,12are same with the above second embodiment. And, the bypass portion13has a length of 5 μm as same as the total length of the MR portion10, a thickness of 0.2 μm, a width of 80 μm as same as the MR portion10and the yoke portions11,12, and a gap of 0.05 μm between with the MR portions10.

FIG. 18shows B-H curves (profile of amount of magnetic flux with respect to magnetic field intensity) of three soft magnetic materials for forming the bypass portion13. A normal material is a usual soft magnetic material film formed in an oriented magnetic field from metallic material as same as yoke portions11,12, for instance amorphous CO78Fe4Si9B9films, similar to that in the above second embodiment. Therefore the normal material has a characteristic in which amount of magnetic flux linearly increases in proportion to increasing of magnetic field intensity and is saturated at a certain intensity of input magnetic field in which amount of magnetic flux linearly does not increases even if the input magnetic field increases. First alternative material has a same composition as the yoke portions11,12, but is formed in randomly oriented magnetic field to eliminate single axis induced magnetic anisotropy, different from conventional production methods for magnetic materials. As a result, the first alternative material has a non-linear B-H profile in which increasing rate of magnetic flux density with respect to input magnetic field increasing gets gradually lower. And, the second alternative material is that a material, such as Co65Fe3Si15B17, which is as the material used for the yoke portions11,12with more added nonmagnetic material, such as Si, B and the like, is formed in a randomly oriented magnetic field. As a result, the second alternative material has a B-H profile that is as a compressed first alternative material to half in the direction of vertical axis, so that the magnetic flux density with respect to the input magnetic field intensity is half of the first alternative material.

FIG. 19shows simulation results of profile of electric resistances (MR ratio) between the yoke portion11and yoke portion12including the MR portion with respect to magnetic field intensity with the magnetic detection elements7irespectively with bypass portions formed from the materials of different magnetic characteristics shown inFIG. 18. As shown in the diagram, the bypass portion13made of the first alternative material can enhance the linearity of the MR ratio profile in comparison to the bypass portion13made from the normal material. It can be considered that the bypass portion13made of the second alternative material provides a MR ratio profile generally similar to the bypass portion13made from the first alternative material with a cross sectional area reduced in half.

As described above, by forming the bypass portion13from a soft magnetic material with a nonlinear B-H profile, the nonlinearity of the MR portion10and the yoke portions11,12can be adequately canceled, to vary the electric resistance (MR ratio) between the yoke portion11and yoke portion12including the MR portion linearly with respect to magnetic field intensity. As methods for providing nonlinear B-H profile to the bypass portion13, other than forming in a randomly oriented magnetic field, methods of heat treatment and methods for adjusting crystal size or orientation depending conditions of speed, temperature, atmosphere gas and the like of film formation. Further, with respect to the material composition, cobalt-iron amorphous and materials of nickel-iron, iron-silicone and silicon-aluminum can be used.

Furthermore, as a magnetic detection element7jof ninth embodiment of the present invention shown inFIG. 20, the bypass portion13may be formed by arranging a plurality of materials having different magnetic properties in a row in the direction of guiding magnetic flux. Thus, the bypass portion as whole can have more preferable property, that is, a characteristic capable of varying the bypassing amount with respect to variation of magnetic field intensity to compensate the linearity of the MR portion10and the yoke portions11,12with respect to magnetic field intensity.

Moreover, as a magnetic detection element7kof tenth embodiment of the present invention shown inFIG. 21, by forming the insulation film (insulation layer)14which insulates the MR portion10and the yoke portions11,12from each other from a semiconducting magnetic material having a very small electric conductivity, small magnetic conductivity and nonlinear magnetic property (B-H curve), amount of magnetic flux bypassed to the bypass portion13can be varied nonlinearly so as to compensate the linearity of the MR portion10and the yoke portions11,12with respect to magnetic field intensity. As materials for this insulation film14, it is cited, for instance, MnZn ferrite film, NiZn ferrite film, Cuzn ferrite film, CuZnMg ferrite film, and the like.

EXPLANATION OF REFERENCE