JP2006284571A - Digital magnetoresistive sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetoresistive sensor, having a high resistance ratio which shows a discontinuous resistance value change over approximately thousand% by the presence of external magnetic field or the direction of the magnetic pole. <P>SOLUTION: The system comprises a first magnetic body part and a second magnetic body part, which is selectively contacted or isolated to the first magnetic body part by a magnetic force induced elastic deformation generated between the first magnetic body part and the second magnetic body part magnetizing by the external magnetic field. The magnetoresistance sensor detects a change of the resistance value between the first and second magnetic body parts. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetoresistive sensor, and more particularly to a magnetoresistive sensor that detects a magnetic field using a change in electrical resistance between two magnetic bodies due to a change in an external magnetic field.

  Currently, hard disk drives (HDDs) that are widely used as information recording devices use magnetic materials as information recording media. Information is recorded by adjusting the magnetization direction, and at this time, a magnetic sensor generated by the magnetization direction is detected by a magnetic sensor to reproduce the information. Therefore, in order to realize a high recording density, it is an important factor how to efficiently detect a magnetic field generated from a magnetic pole that becomes smaller as the recording density increases.

  In order to detect a magnetic field efficiently, a method of detecting a magnetic field using a change in the electric resistance value of a magnetic substance due to a change in the magnetic field has been widely used, and in particular, an effort to improve the magnetic field detection performance. Have developed various magnetoresistive sensors such as AMR (Anisotropic Magneto Resistance), GMR (Giant Mangeto Resistance), and TMR (Tunneling Magneto Resistance). Through these developments, the initial AMR sensor representing a magnetoresistance ratio of 1 to 2% has evolved into a GMR sensor having a magnetoresistance ratio of about 10%, and recently, a magnetoresistance of about 40%. A TMR sensor with a ratio is refraining from commercialization.

However, in order to accurately reproduce information on a magnetic recording medium having a degree of integration of several terabits per square inch (Tb / in ² ) beyond the performance of the TMR sensor, a magnetic material having a higher magnetoresistance ratio is used. A resistance sensor is required.

  The problem to be solved by the present invention is to provide a high resistance ratio magnetoresistive sensor that exhibits a discontinuous change in resistance value of about several thousand% or more depending on the presence or absence of an external magnetic field or the direction of a pole.

  The digital magnetoresistive sensor according to the present invention is magnetized by a first magnetic body portion and an external magnetic field, and is elastically deformed by a magnetic force generated between the first magnetic body portion and the first magnetic body portion. And a second magnetic body portion that is contacted and separated from each other. Detection of the resistance value between the first magnetic body part and the second magnetic body part is performed by a resistance value detecting means of a general magnetoresistive sensor.

  In terms of material, at least a part of the first magnetic part is made of a hard magnetic material, a soft magnetic material or a semi-hard magnetic material, and at least a part of the second magnetic part is a soft magnetic material. Made of material or semi-rigid magnetic material. As the hard magnetic material, for example, Alnico (an alloy obtained by adding aluminum, nickel, or cobalt to iron), a rare earth magnet, or hard ferrite is used. As the soft magnetic material, for example, iron having a coercive force of 50 Oe or less. -Silicon alloys, permalloy (nickel-iron alloys), amorphous magnetic alloys such as iron-cobalt-boron, nanocrystalline alloys such as iron-tantalum-nitrogen or soft ferrites can be used. A semi-hard magnetic material having a coercive force of about 5 to 50 Oe may be used instead of the soft magnetic material. It is desirable that the soft magnetic material and the semi-hard magnetic material have a perpendicular magnetization curve so that the magnetic field emitted from the magnetic recording medium can react only in a well-defined region.

  In terms of shape and structure, at least one of the first and second magnetic parts is integrally formed using an elastically deformable magnetic material and connected to the magnetic member and the magnetic member. It may be provided with a structure in which an elastic member that changes the position of the magnetic member by being elastically deformed is coupled.

  A magnetoresistive element according to one aspect of the present invention includes a first magnetic layer formed on a substrate, an insulating layer partially formed on the first magnetic layer, and a part in contact with an upper surface of the insulating layer. The remaining portion extends outside the insulating layer, and the extended portion includes a second magnetic layer facing a part of the first magnetic layer, and the second magnetic layer is magnetized by an external magnetic field. The first magnetic layer is elastically deformed by a magnetic force generated between the first magnetic layer and selectively contacted and separated from the first magnetic layer.

  A magnetoresistive element according to another aspect of the present invention includes a first carbon nanotube elastic member having one end fixed to a substrate, a first magnetic member provided at a free end of the first carbon nanotube elastic member, and one end on the substrate. A second carbon nanotube elastic member provided adjacent to the first carbon nanotube elastic member, and a second magnetic member provided at a free end of the second carbon nanotube elastic member, The second magnetic member is magnetized by an external magnetic field, is displaced by a magnetic force generated between the second magnetic member and the first magnetic member, and is selectively contacted and separated from the first magnetic member.

  The digital magnetoresistive sensor according to the present invention can represent a discontinuous change in resistance value of about several thousand% or more depending on the presence or absence of an external magnetic field or the direction of a pole. Thereby, highly integrated magnetic information can be accurately reproduced.

Hereinafter, embodiments of a digital magnetoresistive sensor according to the present invention will be described in detail with reference to the accompanying drawings. The features and advantages of the present invention can be more clearly understood through the description of preferred embodiments. In the accompanying drawings, the same reference numeral represents the same member or part.
1 and 2 are schematic views illustrating a magnetoresistive sensor according to a first embodiment of the present invention. The sensor 100 according to the first embodiment of the present invention includes a substrate 101, a first magnetic layer 102 formed on the substrate 101, an insulating layer 104 partially formed on the first magnetic layer 102, A second magnetic layer 105 disposed on the insulating layer 104, a part of the second magnetic layer 105 being in contact with the upper surface of the insulating layer 104, and the remaining part being the insulating layer 104. The extended portion is formed so as to face a part of the first magnetic layer 102. That is, the second magnetic layer 105 has a structure in which an empty space 106 is formed between the second magnetic layer 105 and the first magnetic layer 102, and an end portion thereof can move elastically in the thickness direction.

  The first magnetic layer 102 and the second magnetic layer 105 are mainly made of a soft magnetic material and can be provided in the form of a single layer or a multilayer thin film. That is, the first magnetic layer 102 and the second magnetic layer 105 are soft magnetic material thin films, and can be formed by sputtering, vacuum evaporation, or electroplating. Although the thickness of the thin film is not limited, it is desirable that the end of the second magnetic layer 105 is thin in order to react quickly to a small magnetic force. Desirably, it is formed by cutting an end close to the magnetic recording medium, and the magnetic field emitted from the magnetic recording medium can be concentrated on the chip area.

  When both the first magnetic layer 102 and the second magnetic layer 105 are made of a soft magnetic material, the second magnetic layer 105 is not affected by an external magnetic field as shown in FIG. It is formed so as to be in mechanical contact with the magnetic layer 102 side. Such mechanical contact is due to the spring characteristic built into the second magnetic layer 105, and it is desirable that the mechanical contact be maintained without being separated by accidental movement.

Such a spring characteristic may be realized by various methods. For example, a material having a different thermal expansion coefficient may be overlapped on one surface of the second magnetic layer 105 to apply mechanical stress, or Ions may be implanted into one surface of the second magnetic layer 105 to be warped.
All of the magnetoresistive sensors according to the present invention have a resistance detection unit similar to a normal magnetoresistive sensor, which is connected to the first magnetic body unit and the second magnetic body unit to detect a resistance value. . The sensor resistance detection unit 301 according to the present embodiment is connected to the first magnetic layer 102 which is the first magnetic body unit and the second magnetic layer 105 which is the second magnetic body unit. Thus, even if not shown in the drawing, it has a resistance detector connected to the structure corresponding to the first and second magnetic parts in this way.

  The operation of the magnetoresistive sensor according to the first embodiment of the present invention will be described as follows. FIG. 2 shows a state in which the upward pole information area 11 of the magnetic recording medium 10 approaches one side of the sensor 100 according to the first embodiment. When an upward magnetic field is applied to the sensor 100, an upward magnetic field is formed in the soft magnetic first magnetic layer 102 and the second magnetic layer 105 in the same manner. Accordingly, a repulsive force is generated between the first magnetic layer 102 and the second magnetic layer 105, and the second magnetic layer 105 is elastically deformed in a direction away from the first magnetic layer 102 and separated from each other.

  When the magnetic layers are in contact with each other, the electrical resistance between them is close to 0, and when they are separated from each other, the electrical resistance between them is close to infinity. A discontinuous signal can be generated.

  FIG. 3 is a schematic diagram illustrating a magnetoresistive sensor according to a second embodiment of the present invention. The sensor according to the present invention further includes an insulating film on at least one side of the opposing surfaces of the first magnetic layer 102 and the second magnetic layer 105, and the sensor 110 according to the second embodiment of the present invention includes the first magnetic layer. An insulating film 103 is provided on the upper surface of the layer 102, that is, the surface facing the second magnetic layer 105. The insulating layer 104 and the insulating film 103 are both made of an electrically insulating material, and the insulating film 103 functions as a tunneling barrier between the first magnetic layer 102 and the second magnetic layer 105. It is desirable that it is relatively thin. As such an insulating material, an oxide insulator such as aluminum oxide or magnesium oxide, or a nitride or fluoride can be used.

  When an external magnetic field is not applied, the first magnetic layer 102 and the second magnetic layer 105 are magnetized in different directions, and an attractive force is generated between them, whereby the second magnetic layer 105 is The insulating film 103 on the first magnetic layer 102 is contacted. At this time, the first and second magnetic layers 102 and 105 form a tunneling structure, and the resistance detector 301 detects a tunneling resistance value. If a magnetic field is applied to the sensor 110, the first and second magnetic layers are spaced apart from each other in the same manner as the sensor 100 according to the first embodiment. Therefore, at least several times to several tens of times the tunneling resistance value. A resistance value that is at least twice as large is detected.

  4 and 5 are schematic views showing a magnetoresistive sensor according to a third embodiment of the present invention. The sensor 120 according to the present embodiment is structurally identical to the sensor 100 according to the first embodiment described above, but there is a difference in the material. According to the present embodiment, the first magnetic layer 102 is made of a hard magnetic material, and the second magnetic layer 105 is mainly made of a soft magnetic material. As described above, a semi-hard magnetic material can be used instead of the soft magnetic material.

  As shown in FIG. 4, when the downward pole information region 12 approaches the sensor 120 according to the third embodiment of the present invention, the same downward pole magnetic field is formed in the second magnetic layer 105 depending on the property of the material. . Accordingly, a repulsive force acts between the first magnetic layer 102 that maintains a downward pole as a hard magnetic material, and the second magnetic layer 105 is deformed in a direction in which the two magnetic layers 102 and 105 are separated from each other. . Conversely, as shown in FIG. 5, when the upward pole information area approaches the sensor 120, the first magnetic layer 102 is a hard magnetic material and maintains the downward pole, and the second magnetic layer 105 An upward pole magnetism is formed, and an attractive force acts between the two magnetic layers 102 and 105 to mechanically contact each other. In this case, even when compared with the tunneling structure shown in FIG. 3, the resistance value is remarkably low at the time of contact, which is advantageous for realizing a high resistance ratio.

  6 to 8 are schematic views illustrating a magnetoresistive sensor according to a fourth embodiment of the present invention. The sensor 200 according to the fourth embodiment of the present invention includes a substrate 20 and a pair of carbon nanotube elastic members 50 each having one end fixed to the substrate, that is, a first carbon nanotube elastic member 51 and a second carbon nanotube elastic member 52. Have. Magnetic members 80 are respectively provided at the free ends of the pair of carbon nanotube elastic members 50. At this time, the first magnetic member 81 of the first carbon nanotube elastic member 51 is preferably made of a hard magnetic material, and the second magnetic member 82 of the second carbon nanotube elastic member 52 is preferably made of a soft magnetic material.

  The fixed ends of the first and second carbon nanotube elastic members 51 and 52 are preferably fixed to the first and second electrodes 21 and 22 of the substrate 20, respectively. Are preferably electrically insulated from each other by an insulator 23. The first and second electrodes 21 and 22 are connected to both ends of the resistance detector 301, respectively. Thus, the sensor 200 having one end fixed to the substrate 20 can be disposed adjacent to the recording medium 10 to the extent that the magnetic member 80 is affected by the magnetic field formed in the information area of the recording medium.

The size of the sensor 200 according to the present embodiment can be reduced to several to several tens of nanometers. For example, the pair of carbon nanotube elastic members 50 has an interval of about 5 to 10 nm so as to correspond to the size of the information area (about 12 nm in diameter) of the recording medium stored at an integration degree of about 1 Tb / in ^2. Can do.

  The operation principle of the sensor 200 according to the present embodiment will be described as follows. The pole direction of the first magnetic member 81 may be either upward or downward, but here, the upward pole will be described as an example. As shown in FIG. 7, when the downward pole information area 12 of the recording medium 10 reaches a position corresponding to the second magnetic member 82, the second magnetic member is affected by the magnetic field of the downward pole information area 11. The same downward pole magnetic field is formed at 82. At this time, since the first magnetic member 81 and the second magnetic member 52 each have an upward pole and a downward pole, an attractive force is generated between them. Due to such attractive force, the first and second carbon nanotube elastic members 51 and 52 are bent in a direction approaching each other, and thus the first magnetic member 81 and the second magnetic member 82 are brought into contact with each other.

  On the other hand, as shown in FIG. 8, when the upward pole information area 11 of the recording medium 10 reaches a position corresponding to the second magnetic member 82, the second pole information area 11 is affected by the magnetic field of the upward pole information area 11. The same upward magnetic field is formed on the magnetic member 82. At this time, since the first magnetic member 81 and the second magnetic member 52 both have upward poles, a repulsive force is generated between them. Due to such repulsive force, the first and second carbon nanotube elastic members 51 and 52 are bent in a direction away from each other.

The resistance value between the first electrode 21 and the second electrode 22 which is close to infinity decreases discontinuously to a value close to 0 due to such contact. Therefore, the sensor 200 according to the present embodiment can generate a discrete signal corresponding to the digital information recorded on the recording medium 10.
The magnetic member 80 includes a nanostructure such as a nanoparticle, a nanowire, or a nanosheet having a size of several to several tens of nm in at least one dimension. Any structure that can be provided fixed to the end of the carbon nanotube elastic member is sufficient.

  The magnetoresistive sensor according to various embodiments of the present invention may be used in a magnetic information recording apparatus such as a hard disk drive (HDD) according to the above-described features and advantages. A magnetic information recording apparatus includes a magnetic recording medium, a magnetic recording head that magnetizes a predetermined area of the magnetic recording medium and records information, and a magnetic reading head that senses and reproduces magnetic information stored in the information area The magnetoresistive sensor according to the present invention can be used as a magnetic read head. In particular, it is very useful for a magnetic information recording apparatus for recording digital information.

  Although the preferred embodiment of the present invention has been described above, this is merely an example, and those skilled in the art will appreciate that various modifications and other equivalent embodiments are possible. I will. Therefore, the protection scope of the present invention must be determined by the claims.

  The present invention is applicable to a technical field related to a magnetic information recording apparatus such as an HDD.

It is the schematic which shows the magnetoresistive sensor by 1st Embodiment of this invention. It is the schematic which shows the magnetoresistive sensor by 1st Embodiment of this invention. It is the schematic which shows the magnetoresistive sensor by 2nd Embodiment of this invention. It is the schematic which shows the magnetoresistive sensor by 3rd Embodiment of this invention. It is the schematic which shows the magnetoresistive sensor by 3rd Embodiment of this invention. It is the schematic which shows the magnetoresistive sensor by 4th Embodiment of this invention. It is the schematic which shows the magnetoresistive sensor by 4th Embodiment of this invention. It is the schematic which shows the magnetoresistive sensor by 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Sensor 101 Board | substrate 102 1st magnetic layer 104 Insulating layer 105 2nd magnetic layer 106 Space 301 Resistance detection part

Claims (23)

A first magnetic body part;
A second magnetic body portion magnetized by an external magnetic field, elastically deformed by a magnetic force generated between the first magnetic body, and selectively contacted and separated from the first magnetic body portion; Digital magnetoresistive sensor provided.   The magnetoresistive sensor according to claim 1, wherein at least a part of each of the first and second magnetic parts is made of a soft magnetic material or a semi-hard magnetic material. The first magnetic part is at least partially made of a hard magnetic material,
2. The digital magnetoresistive sensor according to claim 1, wherein at least a part of the second magnetic part is made of a soft magnetic material or a semi-hard magnetic material.   2. The digital magnetoresistive sensor according to claim 1, wherein the second magnetic part is integrally formed of a soft magnetic material that is elastically deformed. The second magnetic part is
A magnetic member;
And an elastic member that changes the position of the magnetic member by being elastically deformed with one end fixed to the substrate and the other end connected to the magnetic member. Item 2. The digital magnetoresistive sensor according to Item 1. The first magnetic part is
A hard magnetic member;
And an elastic member that changes the position of the hard magnetic member by being elastically deformed with one end fixed to the substrate and the other end connected to the hard magnetic member. The digital magnetoresistive sensor according to claim 5.   The magnetoresistive sensor according to claim 1, wherein a thickness of the second magnetic body portion is smaller than a thickness of the first magnetic body portion.   The magnetoresistive sensor according to claim 1, wherein the second magnetic body portion includes an end portion disposed adjacent to the recording medium, and the end portion includes a sharpened chip. A first magnetic layer formed on a substrate;
An insulating layer partially formed on the first magnetic layer;
A part of which is in contact with the upper surface of the insulating layer, and the remaining part extends outside the insulating layer, and the extended part includes a second magnetic layer facing a part of the first magnetic layer;
The second magnetic layer is
A digital magnetoresistive sensor characterized by being magnetized by an external magnetic field and elastically deformed by a magnetic force generated between the first magnetic layer and selectively contacting and separating from the first magnetic layer.   The digital magnetoresistive sensor according to claim 9, wherein at least a part of each of the first and second magnetic layers is made of a soft magnetic material or a semi-hard magnetic material. The first magnetic layer is made of a hard magnetic material,
The digital magnetoresistive sensor according to claim 9, wherein the second magnetic layer is made of a soft magnetic material or a semi-hard magnetic material.   The digital magnetoresistive sensor according to claim 9, further comprising an insulating film on at least one side of opposing surfaces of the first magnetic layer and the second magnetic layer.   The magnetoresistive sensor according to claim 12, wherein the insulating film is any one of aluminum oxide, magnesium oxide, nitride, or fluoride. A first carbon nanotube elastic member having one end fixed to a substrate;
A first magnetic member provided at a free end of the first carbon nanotube elastic member;
A second carbon nanotube elastic member having one end fixed to the substrate and provided adjacent to the first carbon nanotube elastic member;
A second magnetic member provided at a free end of the second carbon nanotube elastic member,
The second magnetic member is
A digital magnetoresistive sensor characterized by being magnetized by an external magnetic field and displaced by a magnetic force generated between the first magnetic member and selectively contacting and separating from the first magnetic member. The first magnetic member is made of a hard magnetic material,
The digital magnetoresistive sensor according to claim 14, wherein the second magnetic member is made of a soft magnetic material or a semi-hard magnetic material. The substrate includes a first electrode and a second electrode which are mutually insulated,
The digital magnetoresistive sensor of claim 14, wherein the fixed ends of the first and second carbon nanotube elastic members are fixed to the first and second electrodes, respectively.   15. The digital magnetoresistive sensor according to claim 14, wherein the first magnetic member is any one of hard magnetic nanoparticles, nanowires, and nanosheets.   The digital magnetoresistive sensor according to claim 14, wherein the second magnetic member is one of nanoparticles, nanowires, or nanosheets having soft magnetism or semi-hard magnetism.   15. The digital magnetoresistive sensor of claim 14, wherein the first and second carbon nanotube elastic members are formed in a single shape and are elastically bent. In a magnetic read head that senses magnetic information recorded in an information area of a magnetic recording medium and generates a reproduction signal,
A first magnetic layer formed on a substrate;
An insulating layer partially formed on the first magnetic layer;
A part of the upper surface of the insulating layer is in contact with the other part, and the remaining part extends outside the insulating layer, and the extended part of the second magnetic layer faces a part of the first magnetic layer;
A resistance detection unit that has one end connected to the first magnetic layer and the other end connected to the second magnetic layer and detects a resistance value between the two ends.
The second magnetic layer is
A magnetic read head, wherein the magnetic read head is magnetized by an external magnetic field, elastically deformed by a magnetic force generated between the first magnetic layer, and selectively contacted and separated from the first magnetic layer.   The magnetic read head according to claim 20, wherein the external magnetic field is generated by an information area of the magnetic recording medium. In a magnetic read head that senses magnetic information recorded in an information area of a magnetic recording medium and generates a reproduction signal,
A first carbon nanotube elastic member having one end fixed to a substrate;
A first magnetic member provided at a free end of the first carbon nanotube elastic member;
A second carbon nanotube elastic member having one end fixed to the substrate and provided adjacent to the first carbon nanotube elastic member;
A second magnetic member provided at a free end of the second carbon nanotube elastic member;
A resistance detection unit that has one end connected to the fixed end of the first carbon nanotube elastic member and the other end connected to the fixed end of the second carbon nanotube elastic member to detect resistance values at both ends. ,
The second magnetic member is
A magnetic read head characterized by being magnetized by an external magnetic field and displaced by a magnetic force generated between the first magnetic member and selectively contacting and separating from the first magnetic member.   The magnetic read head according to claim 22, wherein the external magnetic field is generated by an information area of the magnetic recording medium.

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