WO2023074440A1

WO2023074440A1 - Magnetoresistance effect element and magnetoresistance effect sensor

Info

Publication number: WO2023074440A1
Application number: PCT/JP2022/038597
Authority: WO
Inventors: 雅彦市村; 直人深谷
Original assignee: 株式会社日立ハイテク
Priority date: 2021-11-01
Filing date: 2022-10-17
Publication date: 2023-05-04
Also published as: JP2023067488A

Abstract

In order to be able to detect a magnetic field of a magnetic object to be detected, even if the magnetic object touches a GMR sensor, the present invention provides a magnetoresistance effect element that has, upon a substrate, an antiferromagnetic layer, a ferromagnetic fixed layer, a non-magnetic intermediate layer, a ferromagnetic free layer, and a protective layer. The aspect ratio between the horizontal width and the length of the magnetoresistance effect element is 1:5 to 1:300. The magnetoresistance effect element has a linear shape having a horizontal width of 190–620 nm.

Description

Magnetoresistive element and magnetoresistive sensor

The present disclosure relates to magnetoresistive elements and magnetoresistive sensors.

In recent years, magnetic sensors using magnetoresistive elements are capable of detecting minute changes in magnetic fields, and are used in various applications such as read heads of hard disk drives. A typical giant magnetoresistive element has a GMR (Giant Magneto Resistance) laminated film consisting of a ferromagnetic pinned layer, a non-magnetic intermediate layer and a ferromagnetic free layer stacked in order from the bottom as a basic structure. are doing. The magnetization direction of the free layer changes sensitively to changes in the external magnetic field. Laminated structure is designed. In such a basic structure, a phenomenon in which the relative angle between the magnetization directions of the free layer and the fixed layer is changed by an external magnetic field and the electrical resistance is greatly changed is called a giant magnetoresistive effect (GMR effect).

When the GMR laminated film is used as a GMR sensor, it is processed into a fine wire shape so that its electrical resistance value changes linearly with respect to an external magnetic field. In order to protect the processed GMR sensor from deterioration factors such as oxygen and moisture, it is generally necessary to protect the entire GMR sensor with an insulating film.

Patent Document 1 discloses that a magnetoresistive effect element processed into an elongated shape can prevent chattering and the like, obtain stable operation, and easily control the magnetic sensitivity according to the application. An enabling magnetic sensor is described. Further, Patent Document 2 describes a method of manufacturing a current-perpendicular-current-type GMR element in which a patterned GMR multilayer film is covered with an insulating film, which is used for a large-capacity magnetic recording/reproducing head.

JP 2007-273528 A JP 2010-87293 A

In the above-mentioned Patent Document 1, a magnetoresistive element processed into an elongated shape is used as a GMR sensor. However, since the GMR disclosed in Patent Document 1 is a non-contact magnetic sensor, the magnetic material to be detected does not come into direct contact with the magnetic sensor. Therefore, when detecting a magnetic material that is in direct contact using the GMR according to Patent Document 1, signals with opposite polarities are generated depending on whether the detection target is directly above the sensor or next to the sensor, and the signals cancel each other out. becomes smaller.

Further, the above-mentioned Patent Document 2 discloses a current-perpendicular-type GMR element covered with an insulating film. However, since this is also a non-contact type magnetic sensor and is not processed into an elongated shape, the magnetic field range in which the electrical resistance value linearly changes with respect to the external magnetic field is extremely small. As described above, it is difficult for the conventional GMR sensor to obtain a large signal when the magnetic substance to be detected is in contact with the magnetic sensor.
In view of such circumstances, the present disclosure proposes a technique that enables detection of the magnetic field of a magnetic material to be detected even when the magnetic material is in contact with the GMR sensor.

In order to solve the above problems, the embodiments disclosed in the present application have an antiferromagnetic layer, a ferromagnetic fixed layer, a nonmagnetic intermediate layer, a ferromagnetic free layer, and a protective layer on a substrate. A magnetoresistive effect element, which has an aspect ratio of width to length of the magnetoresistive effect element of 1:5 or more and 1:300 or less and a width of which is 190 nm or more and 620 nm or less. make a proposal about

Further features related to the present disclosure will become apparent from the description of the specification and the accompanying drawings. In addition, the aspects of the present disclosure are achieved and attained by means of the elements and combinations of various elements and aspects of the detailed description that follows and the claims that follow. It should be noted that the descriptions in this specification are merely typical examples, and are not intended to limit the scope of claims or application examples in any way.

According to the technology of the present disclosure, it is possible to improve the performance of the GMR sensor. In particular, it is possible to efficiently detect the magnetic field of the magnetic material in contact with the GMR sensor.

1 is a diagram showing a configuration example of a GMR laminated film according to a first embodiment; FIG. It is a figure which shows the cross section when the example of arrangement|positioning configuration of several GMR sensors is seen from a longitudinal direction. FIG. 10 is a diagram showing a structural example of a GMR laminated film forming a GMR sensor according to the second embodiment; FIG. 10 is a diagram showing a structural example of a GMR laminated film forming a GMR sensor according to a third embodiment; FIG. 10 is a diagram showing signals obtained from leakage magnetic fields of top magnetic particles and side wall magnetic particles, respectively, and a total signal obtained by adding them together when magnetic particles are attached to the entire GMR sensor according to the conventional example. FIG. 3 is a diagram showing evaluation results (signals with respect to GMR sensor line width) of experiments according to Example 1; FIG. 10 is a diagram showing the relationship between the MR ratio that determines the magnitude of a sensor signal and the aspect ratio of a GMR thin line in Example 2; FIG. 10 is a diagram showing the relationship between the operating magnetic field range (operating magnetic field region) in which the sensor operates and the aspect ratio of the GMR wire in Example 2; FIG. 10 shows experimental results according to Example 3, showing the results of the same experiment as in Example 1 for aspect ratios of a plurality of GMR sensors.

The present disclosure relates to a magnetoresistive effect element, for example, a magnetoresistive effect element and a magnetoresistive effect device that cause a huge magnetoresistance change in a low magnetic field region. Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing for explaining this embodiment, members having the same function are denoted by the same reference numerals, and repeated description thereof will be omitted. Also, in this embodiment, the description of the same or similar parts will not be repeated in principle unless particularly necessary.

(1) First Embodiment In the following, GMR (Giant Magneto Resistance , giant magnetoresistive) is fine-fabricated into thin wires and a layer for preventing adhesion of magnetic particles is formed to improve the performance of the GMR sensor. Specifically, more efficient detection of the magnetic field leaking from the magnetic material to be detected attached to the upper portion of the GMR sensor will be described. The main feature of this embodiment is that an upper limit is imposed on the fine line width corresponding to the aspect ratio of the GMR sensor processed into a fine line.

<Structure example of magnetoresistive element>
FIG. 1 is a diagram showing a configuration example of a GMR laminated film according to the first embodiment. The GMR laminated film according to this embodiment has a substrate 101 and an underlying layer 102 formed on the substrate 101 . The underlying layer 102 has a role of forming a flat GMR laminated film and a role of crystallizing the constituent films of the GMR laminated film formed on the underlying layer 102 . Underlayer 102 contains a metal such as Ta (tantalum), Ti (titanium), Ni (nickel), Cr (chromium), or Fe (iron). Specifically, the underlying layer 102 contains one or more kinds of materials, and can be formed of a laminated film containing two layers, for example, a Ta layer and a NiCr (nickel chromium) layer. If the film thickness of the underlayer 102 is thin, it will not function as an underlayer. Therefore, the base layer 102 can be a layer having a thickness of 1 nm or more.

An antiferromagnetic layer 103 is formed on the underlayer 102 . The antiferromagnetic layer 103 must maintain its magnetism at room temperature or higher at which the GMR laminated film operates. Therefore, the material forming the antiferromagnetic layer 103 can be an oxide containing at least one of Ni, Cr, Fe, Co (cobalt), and Mn (manganese). Alternatively, the material forming the antiferromagnetic layer 103 can be a metal containing one or more elements of Fe, Mn, Pt (platinum), and Ir (iridium). Antiferromagnetic layer 103 comprises a material that has no magnetic moment as a whole. However, from a microscopic point of view, the magnetic moments of the magnetic atoms in the antiferromagnetic layer 103 are regularly arranged alternately in opposite directions. The antiferromagnetic layer 103 according to this embodiment has, for example, only two kinds of magnetic moments that are directed along the upper surface of the substrate 101 and in opposite directions. As a result, since the spontaneous magnetization cancels each other, the spontaneous magnetization of the antiferromagnetic layer 103 is zero as a whole.

A ferromagnetic pinned layer 104 is formed on the antiferromagnetic layer 103 . The ferromagnetic fixed layer 104 is a ferromagnetic layer whose magnetization direction is not fixed by itself. The antiferromagnetic layer 103 and ferromagnetic pinned layer 104 are magnetically coupled at their interfaces. Thereby, the magnetization direction of the ferromagnetic fixed layer 104 is fixed. The magnetization direction of the ferromagnetic pinned layer 104 must not change easily even when the external magnetic field (external magnetic field) is large. Thus, the ferromagnetic pinned layer 104 material may include at least one of Fe, Ni, Co, or alloys thereof.

A nonmagnetic intermediate layer (nonmagnetic layer) 105 is formed on the ferromagnetic fixed layer 104 . A ferromagnetic free layer 106 is formed on the nonmagnetic intermediate layer 105 . The nonmagnetic intermediate layer 105 has a thickness sufficiently large to eliminate the magnetic coupling between the ferromagnetic free layer 106 above the nonmagnetic intermediate layer 105 and the ferromagnetic pinned layer 104 below the nonmagnetic intermediate layer 105 . must have. The film thickness of the non-magnetic intermediate layer 105 can be, for example, 1 nm or more. Also, the GMR effect appears in a region including ferromagnetic fixed layer 104 , nonmagnetic intermediate layer 105 and ferromagnetic free layer 106 . For this reason, the non-magnetic intermediate layer 105 can contain a highly conductive material in order to efficiently pass current through the region. As a material for the non-magnetic intermediate layer 105, for example, Cu or the like can be used.

The ferromagnetic free layer 106 formed on the nonmagnetic intermediate layer 105 is a ferromagnetic layer whose magnetization direction is not fixed by itself. The ferromagnetic free layer 106 is a sensing position where the magnetization direction changes when detecting a weak magnetic field generated from an object to be inspected above the magnetoresistance effect element. Therefore, the ferromagnetic free layer 106 must be made of a material whose magnetization direction can be easily changed in response to changes in the external magnetic field. In other words, the ferromagnetic free layer 106 should exhibit good soft magnetic properties. Thus, the material of the ferromagnetic free layer 106 can include at least one of Fe, Ni, Co, or alloys thereof. In particular, the Ni ratio can be 50% or more.

A protective layer 107 is formed on the ferromagnetic free layer 106 . Thus, the GMR multilayer film includes a substrate 101, an underlayer 102, an antiferromagnetic layer 103, a ferromagnetic pinned layer 104, a nonmagnetic intermediate layer 105, a ferromagnetic free layer 106 and a protective layer, which are sequentially stacked on the substrate 101. It has layer 107 . The protective layer 107 is in contact with the upper surface of the ferromagnetic free layer 106 and covers the entire upper surface of the ferromagnetic free layer 106 .

The protective layer 107 has the role of preventing the ferromagnetic free layer 106 from deteriorating due to the external environment of the GMR laminated film. In other words, the protective layer 107 has the role of preventing the ferromagnetic free layer 106 from being altered by a chemical reaction such as oxidation, thereby reducing the reliability of the magnetoresistive element. The protective layer 107 has a thickness of at least 0.5 nm because it is necessary to maintain its crystallinity.

<Features of the GMR sensor>
One of the main features of this embodiment is that the GMR laminated film is processed into a fine line. At this time, the magnetization direction of the ferromagnetic fixed layer 104 is fixed in the short axis direction of the wire, and the magnetization direction of the ferromagnetic free layer is directed in the long axis direction of the wire due to shape magnetic anisotropy. Specifically, the shape of the fine wire is a fine wire shape with an aspect ratio of 1:5 or more and 1:300 or less. With an aspect ratio of 1:5 or more, the electrical resistance value changes linearly with respect to the external magnetic field. Further, since the aspect ratio is 1:300 or less, it becomes possible to fix the magnetization direction of the ferromagnetic pinned layer in the minor axis direction of the thin wire, and the sensor functions as a GMR sensor. Here, the GMR sensor is composed of at least one fine wire, and may be electrically connected in series or in parallel.

<Application to chemical sensors>
In this embodiment, application to chemical sensors of target substances is possible. A capturing substance of a target substance is previously immobilized on the outermost surface of the GMR sensor. A label is prepared by previously binding a target substance and a substance that generates a leakage magnetic field. The relationship between the label concentration and the signal intensity generated when the GMR sensor on which the label and capture substance are immobilized is allowed to react is recorded as a calibration curve. A target substance sample of unknown concentration, a labeled substance of known concentration, and a GMR sensor preliminarily immobilized with a capture substance are allowed to react, and the concentration of the target substance sample can be calculated based on the difference from the calibration curve.

<Confirmation of the crystal structure of the GMR sensor>
The crystal structure of the GMR sensor can be easily confirmed by X-ray diffraction (XRD). Further, the structure of the GMR sensor can be confirmed by observing it with an electron microscope such as a TEM (Transmission Electron Microscope) or a SEM (Scanning Electron Microscope). In addition, the single-crystal or polycrystalline crystal structure and laminated structure of the GMR laminated film can be confirmed by observing a spot-like pattern or a ring-like pattern in an electron beam diffraction image. The composition distribution of each layer of the GMR sensor can be confirmed using EPMA (Electron Probe Micro Analyzer) such as EDX (Energy dispersive X-ray spectrometry). In addition, the composition distribution can be confirmed using techniques such as SIMS (Secondary Ion Mass Spectrometry), X-ray photoelectron spectroscopy, or ICP (Inductively Coupled Plasma) emission spectrometry. .

<Effect of GMR sensor>
In order to quantitatively detect a weak leakage magnetic field in a GMR sensor, it is necessary that the electrical resistance value of the sensor changes linearly with respect to the external magnetic field. For this reason, the GMR laminated film is processed into a thin line. At this time, the magnetization direction of the ferromagnetic pinned layer is fixed in the short axis direction of the wire, and the magnetization direction of the ferromagnetic free layer is directed in the long axis direction of the wire due to shape magnetic anisotropy. In the initial state without a magnetic field, the relative angle between the magnetization directions of the ferromagnetic fixed layer and the ferromagnetic free layer is 90°. When magnetic particles adhere and an external magnetic field such as a leakage magnetic field acts, the relative angle between the magnetization directions of the ferromagnetic fixed layer and the ferromagnetic free layer deviates from 90°, and the electrical resistance value changes as the relative angle increases and decreases. Increase or decrease. Here, the GMR sensor consists of at least one fine wire, and may be electrically connected in series or in parallel.

<Example of arrangement of GMR sensors>
FIG. 2 is a diagram showing a cross section of an example of arrangement configuration of a plurality of GMR sensors when viewed from the longitudinal direction. When the GMR sensor 201 detects an attachment such as a magnetic particle, the signal of the GMR sensor is opposite in positive and negative when the magnetic particle is attached to the upper part of the GMR sensor and when the magnetic particle is attached to the side wall of the GMR sensor. When magnetic particles adhere to the entire GMR sensor, signals cancel each other out and attenuate (conventional example). When the aspect ratio of the GMR sensor is 1:125, if the width is 440 nm or less, the sign of the GMR sensor signal will be the same when the magnetic particles adhere to the upper part of the GMR sensor and when the magnetic particles adhere to the side walls of the GMR sensor. In agreement, no signal cancellation occurs and the total signal of the GMR sensor can be improved.

(2) Second Embodiment FIG. 3 is a diagram showing a structural example of a GMR laminated film forming a GMR sensor according to a second embodiment. The GMR laminated film can have a laminated structure as shown in FIG.

The GMR laminated film according to this embodiment includes an underlayer 302, an antiferromagnetic layer 303, a first ferromagnetic pinned layer 304, a nonmagnetic coupling layer 305, and a second ferromagnetic pinned layer 306, which are formed in order on a substrate 301. , a nonmagnetic intermediate layer 307 , a ferromagnetic free layer 308 and a protective layer 309 .

Unlike the structure shown in FIG. 1, here a first ferromagnetic pinned layer 304 and a second ferromagnetic pinned layer 306 are layered, with a non-magnetic coupling layer (non-magnetic layer) 305 between them. is formed. The magnetization direction of the first ferromagnetic fixed layer 304 is fixed by the antiferromagnetic layer 303 . The magnetization direction of the second ferromagnetic pinned layer 306 formed on the first ferromagnetic pinned layer 304 via the non-magnetic coupling layer 305 is pinned in the direction opposite to that of the first ferromagnetic pinned layer 304 . It is The magnetization direction of the second ferromagnetic pinned layer 306 is determined by the film thickness of the non-magnetic coupling layer 305 , that is, the distance between the first ferromagnetic pinned layer 304 and the second ferromagnetic pinned layer 306 .

The magnetization directions of the first ferromagnetic pinned layer 304 and the second ferromagnetic pinned layer 306 are opposite to each other. In other words, the magnetization direction of the first ferromagnetic pinned layer 304 and the magnetization direction of the second ferromagnetic pinned layer 306 are antiparallel. Thus, the magnetic field emitted from each of the first ferromagnetic pinned layer 304 and the second ferromagnetic pinned layer 306 loops between the first ferromagnetic pinned layer 304 and the second ferromagnetic pinned layer 306. . That is, most of the leakage magnetic field emitted from the first ferromagnetic pinned layer 304 passes through the second ferromagnetic pinned layer 306, and most of the leakage magnetic field emitted from the second ferromagnetic pinned layer 306 passes through the first ferromagnetic pinned layer 306. Through fixed layer 304 . Therefore, the magnetic field emitted from each of the first ferromagnetic pinned layer 304 and the second ferromagnetic pinned layer 306 does not affect the external environment.

Such a structure is called a laminated antiferromagnetic structure. The laminated antiferromagnetic structure reduces the magnetic field emanating from the GMR laminated film. For this reason, when detecting a very weak magnetic field of a magnetic material, it is possible to detect the magnetic field of the magnetic material without changing the magnetic state of the magnetic material to be detected before and after the detection, thereby detecting the magnetic state more accurately. can be done. At least one of the first ferromagnetic fixed layer 304 and the second ferromagnetic fixed layer 306 contains either Co or a Co—Fe alloy, and the nonmagnetic coupling layer 305 contains Ru (ruthenium) and Ir. can include at least one of

A laminated film consisting of the first ferromagnetic pinned layer 304, the non-magnetic coupling layer 305 and the second ferromagnetic pinned layer 306 can be regarded as one ferromagnetic pinned layer. That is, in the magnetoresistive element of the present embodiment, the ferromagnetic pinned layer 104 of the first embodiment consists of the first ferromagnetic pinned layer 304, the nonmagnetic coupling layer 305, and the second ferromagnetic pinned layer 306. can be considered to be composed of a laminated film composed of

(3) Third Embodiment FIG. 4 is a diagram showing a structural example of a GMR laminated film forming a GMR sensor according to a third embodiment. The GMR laminated film can have a laminated structure as shown in FIG.

The GMR laminated film according to this embodiment includes an underlying layer 402, a first antiferromagnetic layer 403, a first ferromagnetic pinned layer 404, a first nonmagnetic coupling layer 405, and a second antiferromagnetic layer 404, which are formed on a substrate 401 in this order. ferromagnetic pinned layer 406, first nonmagnetic intermediate layer 407, ferromagnetic free layer 408, second nonmagnetic intermediate layer 409, third ferromagnetic pinned layer 410, second nonmagnetic coupling layer 411, second 4 ferromagnetic pinned layer 412 , a second antiferromagnetic layer 413 and a protective layer 414 .

Unlike the structure shown in FIG. 2 antiferromagnetic layers 413 are layered. These reverse the first antiferromagnetic layer 403, the first ferromagnetic pinned layer 404, the first nonmagnetic coupling layer 405, the second ferromagnetic pinned layer 406, and the first nonmagnetic intermediate layer 407. They are stacked in order and have the same role. However, the constituent materials may not be the same.
Such a structure is called a dual stacked antiferromagnetic structure. In the dual-type laminated antiferromagnetic structure, the amount of change in electrical resistivity due to an external magnetic field increases.

(4) Example (i) Example 1
The present inventors fabricated a GMR sensor and evaluated signals obtained from magnetic particles attached to the top and sidewalls of the GMR sensor. The structure of the GMR laminated film used here is the same as that shown in FIG. In Example 1, the underlying layer 102, which is a laminated film composed of a film containing Ta and having a thickness of 5 nm and a film containing NiCr and having a thickness of 5 nm, is formed on a Si substrate whose surface is covered with a thermal oxide film. It is Also formed are an antiferromagnetic layer 103 containing Ir ₂₀ Mn ₈₀ and having a thickness of 6 nm, and a ferromagnetic pinned layer 104 containing Co ₉₀ Fe ₁₀ and having a thickness of 1.6 nm. Further, a non-magnetic intermediate layer 105 containing Cu and having a thickness of 2.5 nm, a film containing Co ₉₀ Fe ₁₀ and having a thickness of 1.0 nm, and a film containing Ni ₈₁ Fe ₁₉ and having a thickness of 3.5 nm. A ferromagnetic free layer 106 is formed by a film having a A protective layer 107 containing Ru and Ta is also formed. The shape of the GMR sensor can be easily confirmed using SEM, TEM, or an optical microscope.

The cross section of the GMR sensor according to Example 1 is as shown in FIG. FIG. 5 is a diagram showing signals obtained from leakage magnetic fields of the upper magnetic particles and the side wall magnetic particles, respectively, and the total signal obtained by adding them when the magnetic particles are attached to the entire GMR sensor according to the conventional example. . As can be seen from FIG. 5, the signals obtained from the stray magnetic fields of the upper magnetic particles and the side wall magnetic particles are positive and negative, respectively. In other words, the signal obtained from the magnetic particles attached to the top of the GMR sensor is always negative. At this time, the dimensions of the conventional GMR sensor are 800 nm in width and 100 μm in length, and the aspect ratio (width:length) is 1:125.

On the other hand, in Example 1, GMR sensors were produced with the aspect ratio of the GMR sensor fixed at 1:125, and the widths were changed to 400, 500, and 700 nm, respectively, and the GMR sensor was attached near the center of the upper part of the GMR sensor. The signal obtained from one magnetic particle was evaluated. FIG. 6 is a diagram showing evaluation results of an experiment according to Example 1. FIG. As shown in FIG. 6, the sign of the signal is positive in the GMR sensor with a lateral width (line width) of 400 nm, and the sign of the signal is negative in the range of 500 nm to 800 nm. Also, from FIG. 6, the upper limit of the lateral width at which the signal sign of the side wall magnetic particles and that of the upper magnetic particles match can be estimated to be 440 nm (the limit at which a positive signal can be obtained). Therefore, when the aspect ratio of the GMR sensor is fixed at 1:125, the direction of the leakage magnetic field of the side wall magnetic particles and the direction of the leakage magnetic field of the upper magnetic particles can be matched by setting the lateral width of the GMR sensor to 440 nm or less. can be used to increase the total signal obtained.

(ii) Example 2
Regarding the GMR sensor according to Example 2, the dimensional ratio of the thin wire shape that can operate as a sensor will be described. The structure of the GMR laminated film forming the GMR sensor used here is the same as the structure shown in FIG. However, as the structure of the GMR laminated film, not only the structure shown in FIG. 3 but also the structure shown in FIG. 1 or 4 may be employed.

In Example 2, the underlying layer 302, which is a laminated film composed of a film containing Ta and having a thickness of 5 nm and a film containing NiCr and having a thickness of 5 nm, is formed on a Si substrate whose surface is covered with a thermal oxide film. It is Also formed are an antiferromagnetic layer 303 containing Ir ₂₀ Mn ₈₀ and having a thickness of 6 nm, and a first ferromagnetic pinned layer 304 containing Co ₉₀ Fe ₁₀ and having a thickness of 1.6 nm. Further, a non-magnetic coupling layer 305 containing Ru and having a thickness of 0.85 nm, a second ferromagnetic pinned layer 306 containing Co ₉₀ Fe ₁₀ and having a thickness of 1.6 nm, and a thickness of 2.5 nm containing Cu. A non-magnetic intermediate layer 307 having a thickness of . A ferromagnetic free layer 308 is formed of a film containing Co ₉₀ Fe ₁₀ and having a thickness of 1.0 nm and a film containing Ni ₈₁ Fe ₁₉ and having a thickness of 3.5 nm. A protective layer 309 containing Ru and Ta is formed on the ferromagnetic free layer 308 .

FIG. 7 is a diagram showing the relationship between the MR ratio that determines the magnitude of the sensor signal and the aspect ratio of the GMR thin line. It can be seen from FIG. 7 that the MR ratio decreases significantly as the aspect ratio increases. Therefore, in order to use it as a sensor for detecting magnetic particles, the MR ratio must exceed at least 1% and the GMR effect must be expressed, so it can be seen that the aspect ratio of the GMR thin wire must be 1:300 or less.

FIG. 8 is a diagram showing the relationship between the operating magnetic field range (operating magnetic field region) in which the sensor operates and the aspect ratio of the GMR wire. It can be seen from FIG. 8 that the operating magnetic field range (operating magnetic field region) decreases as the aspect ratio decreases. The operating magnetic field range (operating magnetic field region) indicates the detectable magnetic field range, and at least 10 Oe or more is required to detect magnetic particles. Therefore, the aspect ratio should be 1:5 or less.
As described above, the aspect ratio of the GMR thin wire that can be used as a GMR sensor for detecting magnetic particles is 1:5 or more and 1:300 or less.

(iii) Example 3
In Example 1, as shown in FIG. 6, under the condition that the aspect ratio of the GMR sensor is fixed at 1:125, the upper limit of the width at which the signal sign of the side wall magnetic particles and that of the upper magnetic particles match is set to 440 nm. could be estimated. FIG. 9 is a diagram showing the results of the same experiment as in Example 1 for multiple aspect ratios of GMR sensors. Looking at FIG. 9, the aspect ratio values of the GMR sensors used in the experiment are 1:300, 1:200, 1:50, and 1:5, and the corresponding upper limit values of the width are 190, 300, 550 and 620 nm could be estimated.

Therefore, for each aspect ratio of the GMR sensor, by making the lateral width equal to or less than the upper limit, the direction of the stray magnetic field of the side wall magnetic particles and the direction of the stray magnetic field of the upper magnetic particles can be matched, and the total obtained signal can be increased.

(iv) Example 4
In Example 4, a GMR sensor composed of a film having an amorphous structure and a film thickness of _3.5 nm containing _Ni70Fe27B3 in the ferromagnetic free layer 106 _of Example 1 (using the structure of FIG. 1) was formed. bottom. Further, a GMR sensor was produced by fixing the aspect ratio of the GMR sensor to 1:125 and changing the width, and the signal obtained from one magnetic particle attached near the center of the upper part of the GMR sensor was evaluated. Conventionally, an alloy (crystallized structure) called a permaalloy was used, but in Example 4, part of Fe and B in the alloy are replaced to make it amorphous (non-crystallized). As a result, it is possible to improve the followability to a magnetic field (a signal can be easily obtained without applying a strong magnetic field). Therefore, a larger signal can be obtained by using a GMR sensor that uses an amorphous material from which signals can be easily obtained.

From FIG. 6 described above, the upper limit of the lateral width at which the signal sign of the side wall magnetic particles and that of the upper magnetic particles match can be estimated to be 400 nm. Therefore, by fabricating the lateral width of _the GMR sensor composed of the ferromagnetic free layer of the _Ni70Fe27B3 amorphous _structure to 400 nm or less, the direction of the stray magnetic field of the side wall magnetic grains and the direction of the stray magnetic field of the upper magnetic grains can be can be matched and the total signal obtained can be increased.

(5) Summary (i) The above-described embodiment relates to a magnetoresistive effect element having an aspect ratio of width to length of 1:5 or more and 1:300 or less and a width of 190 nm or more and 620 nm or less. Disclose. With such a structure, when a GMR sensor is configured with at least one magnetoresistive element, it can be stably operated in a minute magnetic field, and the upper and side portions of the magnetoresistive element can be stably operated. Since the magnetic particles adhering (contacting) to (the sidewall portion) align the directions of the local magnetic fields acting on the element, it is possible to detect the magnetic material with high accuracy. Therefore, it is possible to make the GMR sensor function as a chemical sensor.

Specifically, when the aspect ratio is 1:125, the width is 440 nm or less, when the aspect ratio is 1:300, the width is 190 nm or less, and when the aspect ratio is 1:200, the width is 300 nm or less, and the aspect ratio is 1:1. When 50, the width can be 550 nm or less.

(ii) As shown in FIG. 1, the magnetoresistive element has an antiferromagnetic layer, a ferromagnetic fixed layer, a nonmagnetic intermediate layer, a ferromagnetic free layer, and a protective layer formed on a substrate. It is Here, the non-magnetic intermediate layer may be made of, for example, Cu, and the ferromagnetic fixed layer or ferromagnetic free layer may be made of, for example, Fe, Ni, Co, or alloys thereof. By doing so, the GMR effect can be efficiently expressed. In other words, it becomes possible to efficiently flow a current through the region including the ferromagnetic fixed layer, the nonmagnetic intermediate layer, and the ferromagnetic free layer. Also, the antiferromagnetic layer may be composed of an oxide containing Ni, Cr, Fe, Co or Mn, or a metal containing Fe, Mn, Pt or Ir. By using such a material, the magnetism can be maintained in an environment of room temperature or higher in which the magnetoresistive effect element operates.

(iii) In the magnetoresistive element, the underlayer formed under the antiferromagnetic layer may be composed of a metal containing Ta, Ti, Ni, Cr, Al or Fe, or an oxide. By using these materials for the underlying layer, it becomes possible to reliably crystallize the constituent laminated films of the magnetoresistive effect element.

(iv) In the magnetoresistive element, the ferromagnetic free layer may be composed of Fe, Ni, B, or an alloy of these amorphous structures. By making the ferromagnetic free layer having a crystallized structure into an amorphous structure, it is possible to secure or improve the followability to the magnetic field even if a magnetic field smaller than the magnetic field applied to the crystallized structure is applied. .

(v) As shown in FIG. 3, the magnetoresistive element has an antiferromagnetic layer, a first ferromagnetic pinned layer, a nonmagnetic coupling layer, and a second ferromagnetic pinned layer on the substrate. A layer, a nonmagnetic intermediate layer, a ferromagnetic free layer, and a protective layer are formed. That is, in the structure shown in FIG. 3, the ferromagnetic pinned layer in the structure shown in FIG. 1 is the first ferromagnetic pinned layer, the second ferromagnetic pinned layer, and the and a non-magnetic coupling layer formed on the substrate.

(vi) Furthermore, as shown in FIG. 4, the magnetoresistive effect element has a first antiferromagnetic layer, first and second ferromagnetic fixed layers, and the first and second ferromagnetic fixed layers on the substrate. a first nonmagnetic coupling layer formed between the ferromagnetic pinned layers; first and second nonmagnetic intermediate layers; and a ferromagnetic layer formed between the first and second nonmagnetic intermediate layers. a magnetic free layer, third and fourth ferromagnetic pinned layers, a second nonmagnetic coupling layer formed between the third and fourth ferromagnetic pinned layers, and a second antiferromagnetic layer and a protective layer are formed. By adopting the dual-type laminated antiferromagnetic structure in this manner, it is possible to increase the amount of change in electrical resistivity due to an external magnetic field.

Also, here, the second ferromagnetic pinned layer or the third ferromagnetic pinned layer contains Co or a Co--Fe alloy, and the second non-magnetic coupling layer contains Ru or Ir. At this time, the magnetization direction of the second ferromagnetic pinned layer and the magnetization direction of the third ferromagnetic pinned layer are antiparallel to each other. Thereby, the magnetic field emitted from each of the first ferromagnetic pinned layer and the second ferromagnetic pinned layer can be looped, and the influence of the magnetic field on the external environment can be suppressed.

(vii) Although the present embodiments and examples have been described specifically and in detail above, the technology of the present disclosure is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the scope of the present disclosure. is.

101, 202, 301, 401 substrates 102, 302, 402 underlayers 103, 303 antiferromagnetic layer 104 ferromagnetic fixed layers 105, 307 nonmagnetic intermediate layers 106, 308, 408 ferromagnetic free layers 107, 309, 414 protective layers 201 GMR sensor 304, 404 First ferromagnetic pinned layer 305 Non-magnetic coupling layer 306, 406 Second ferromagnetic pinned layer 403 First antiferromagnetic layer 405 First non-magnetic coupling layer 407 First non-magnetic Intermediate layer 409 Second nonmagnetic intermediate layer 410 Third ferromagnetic pinned layer 411 Second nonmagnetic coupling layer 412 Fourth ferromagnetic pinned layer 413 Second antiferromagnetic layer

Claims

A magnetoresistive element having an antiferromagnetic layer, a ferromagnetic fixed layer, a nonmagnetic intermediate layer, a ferromagnetic free layer, and a protective layer on a substrate,
A magnetoresistive element having an aspect ratio of width to length of 1:5 or more and 1:300 or less, and having a linear width of 190 nm or more and 620 nm or less.
In claim 1,
A magnetoresistive element, wherein the lateral width is 440 nm or less when the aspect ratio is 1:125.
In claim 1,
A magnetoresistive element, wherein the lateral width is 190 nm or less when the aspect ratio is 1:300.
In claim 1,
A magnetoresistive element, wherein the lateral width is 300 nm or less when the aspect ratio is 1:200.
In claim 1,
A magnetoresistive element, wherein the lateral width is 550 nm or less when the aspect ratio is 1:50.
In claim 1,
The non-magnetic intermediate layer contains Cu,
A magnetoresistance effect element, wherein the ferromagnetic fixed layer or the ferromagnetic free layer contains Fe, Ni, Co, or an alloy thereof.
In claim 1,
The ferromagnetic fixed layer includes a first ferromagnetic fixed layer, a second ferromagnetic fixed layer, and a nonmagnetic coupling layer formed between the first and second ferromagnetic fixed layers. , a magnetoresistive element.
In claim 1,
a first antiferromagnetic layer, first and second ferromagnetic pinned layers, and a first nonmagnetic coupling layer formed between the first and second ferromagnetic pinned layers on the substrate; and first and second nonmagnetic intermediate layers, the ferromagnetic free layer formed between the first and second nonmagnetic intermediate layers, and third and fourth ferromagnetic pinned layers; A magnetoresistive element comprising a second nonmagnetic coupling layer formed between the third and fourth ferromagnetic fixed layers, a second antiferromagnetic layer, and the protective layer.
In claim 8,
the second ferromagnetic pinned layer or the third ferromagnetic pinned layer comprises Co or a Co—Fe alloy;
The magnetoresistive effect element, wherein the second non-magnetic coupling layer contains Ru or Ir.
In claim 8,
The magnetoresistive element, wherein the magnetization direction of the second ferromagnetic pinned layer and the magnetization direction of the third ferromagnetic pinned layer are antiparallel to each other.
In claim 1,
The antiferromagnetic layer is composed of an oxide containing Ni, Cr, Fe, Co or Mn, or a metal containing Fe, Mn, Pt or Ir.
In claim 1, further:
an underlayer formed under the antiferromagnetic layer;
a substrate formed under the underlying layer;
The magnetoresistive effect element, wherein the underlayer is composed of a metal containing Ta, Ti, Ni, Cr, Al, or Fe, or an oxide.
In claim 1,
The ferromagnetic free layer is composed of Fe, Ni, B, or an amorphous structure alloy thereof, in the magnetoresistive effect element.
A magnetoresistive sensor having at least one magnetoresistive element according to claim 1.
In claim 14,
Having a plurality of the magnetoresistive effect elements,
A magnetoresistive sensor comprising a plurality of magnetoresistive elements electrically connected in series or in parallel.