CN117626181A - In-plane magnetization film, in-plane magnetization film multilayer structure, hard bias layer, magnetoresistance effect element, and sputtering target - Google Patents
In-plane magnetization film, in-plane magnetization film multilayer structure, hard bias layer, magnetoresistance effect element, and sputtering target Download PDFInfo
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Abstract
The present invention provides a method for realizing coercive force Hc of 2.00kOe or more and residual magnetism Mrt of 2.00memu/cm per unit area without using a nonmagnetic underlayer for promoting in-plane orientation of a magnetic layer and without performing heating film formation 2 The above in-plane magnetization film, in-plane magnetization film multilayer structure, hard biasLayer, magneto-resistive effect element and sputtering target. The in-plane magnetization film has: an initial magnetic layer (12A) containing Co, pt and a non-magnetic grain boundary material and having a thickness of 1-32 nm; and a magnetic layer main body portion (12B) which is formed on the initial magnetic layer (12A) and contains Co, pt and a non-magnetic oxide, wherein the non-magnetic grain boundary material of the initial magnetic layer (12A) contains at least one of Zn oxide and Ta oxide.
Description
Technical Field
The present invention relates to an in-plane magnetization film, an in-plane magnetization film multilayer structure, a hard bias layer, a magnetoresistance effect element, and a sputtering target, and more particularly to a film formation method capable of realizing a coercive force Hc of 2.00kOe or more and a residual magnetism Mrt of 2.00memu/cm per unit area without performing film formation by heating a substrate (hereinafter, sometimes referred to as a heating film formation) 2 The above-mentioned in-plane magnetization film and in-plane magnetization film multilayer structure of magnetic properties, and a hard bias layer having the above-mentioned in-plane magnetization film or in-plane magnetization film multilayer structure, and a magnetoresistance effect element and sputtering target associated with them.
It is considered that if the coercive force Hc is 2.00kOe or more and the remanence Mrt per unit area is 2.00memu/cm 2 The hard bias layer has a coercive force and remanence per unit area equal to or higher than those of the current magnetoresistive element. In the present application, the term "remanence per unit area" of an in-plane magnetization film means a value obtained by multiplying the remanence per unit volume of the in-plane magnetization film by the thickness of the in-plane magnetization film.
In the present application, the hard bias layer refers to a thin film magnet that applies a bias magnetic field to a magnetic layer that exhibits a magnetoresistance effect (hereinafter, may be referred to as a free magnetic layer).
In the present application, the metal Co may be abbreviated as Co, the metal Pt may be abbreviated as Pt, and the metal Ru may be abbreviated as Ru. The same applies to other metal elements.
Background
Magnetic sensors are now used in many fields, and as one of the widely used magnetic sensors, there is a magneto-resistive effect element.
The magnetoresistance element includes a magnetic layer (free magnetic layer) that exhibits magnetoresistance and a hard bias layer that applies a bias magnetic field to the magnetic layer (free magnetic layer), and it is required that the hard bias layer be capable of stably applying a magnetic field having a magnitude equal to or greater than a predetermined magnitude to the free magnetic layer.
Therefore, for the hard bias layer, high coercive force and remanence are required.
However, the coercive force of the hard bias layer of the current magnetoresistance effect element is about 2kOe (for example, fig. 7 of patent document 1), and it is desirable to achieve coercive force of not less than that.
In addition, it is desirable that the remanence per unit area is about 2memu/cm 2 The above (for example, paragraph 0007 of patent document 2).
In order to form a hard bias layer capable of stably applying a magnetic field of a predetermined magnitude or more to a magnetoresistive element portion including a free magnetic layer, conventionally, an in-plane magnetization film in which the c-axis of a CoPt alloy of an hcp structure is oriented in-plane has been used, and as a technique for obtaining such an in-plane magnetization film, there is a technique in which a nonmagnetic underlayer (Cr, ti, cr alloy, ti alloy, or the like) that promotes the c-axis of a CoPt alloy of an hcp structure to be oriented in-plane has been used (for example, paragraph 0028 of patent document 2).
However, in this technique, it is necessary to use a nonmagnetic underlayer (Cr, ti, cr alloy, ti alloy, or the like) that promotes in-plane orientation of the c-axis of the CoPt alloy of the hcp structure, and the distance between the magnetoresistive element portion and the hard bias layer is reduced by an amount corresponding to the thickness of the nonmagnetic underlayer, and the magnetic field applied to the magnetoresistive element portion by the hard bias layer is reduced.
As a technique using an in-plane magnetization film in which the c-axis of Co is aligned in-plane, there is a technique of forming an in-plane magnetic recording film (for example, paragraph 0010 of patent document 3), but this technique is a technique of forming a film by heating a substrate to 200 ℃. Since the magnetoresistive element portion formed of an extremely thin film is easily broken by heating, film formation accompanied by substrate heating is not suitable as a method for forming a hard bias layer.
As a film forming method without heating a substrate, there is a technique in which a Ru underlayer is used as an underlayer for forming a co—pt based in-plane magnetization film, and the coercive force Hc of the co—pt based in-plane magnetization film formed on the Ru underlayer is increased by setting the atmospheric pressure at a high atmospheric pressure at the time of forming the Ru underlayer (for example, paragraph 0016 of patent document 3 and non-patent document 1). However, in this technique, in order to increase the coercive force Hc, it is necessary to increase the thickness of the Ru underlayer to about 15nm or more, and the distance between the magnetoresistive element portion and the hard bias layer is set to an amount corresponding to the thickness of the nonmagnetic Ru underlayer, so that the magnetic field applied to the magnetoresistive element portion by the hard bias layer is reduced, and thus there is a problem similar to the technique described in patent document 2.
Prior art literature
Patent literature
Patent document 1: japanese patent application laid-open No. 2008-283016
Patent document 2: japanese patent publication No. 2008-547150
Patent document 3: japanese patent laid-open No. 2003-123240
Non-patent literature
Non-patent document 1: basic oxygen therapy, dasen Guangdong, qian Ming Hong, dai Di with Ru, a ternary Co-Pt film with a ternary magnetic property (the structure and magnetic property of Co-Pt film using Ru substrate) ", a ternary magnetic property Japanese applied magnetic society, vol.26, no.4,2002, p.269-273
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made in view of the above-described problems, and provides a magnetic material capable of achieving a coercive force Hc of 2.00kOe or more and a residual magnetism Mrt per unit area of 2.00memu/cm without using a nonmagnetic underlayer for promoting in-plane orientation of a magnetic layer and without performing a heating film formation 2 The above-mentioned magnetic properties are subject to an in-plane magnetization film, an in-plane magnetization film multilayer structure, and a hard bias layer, and a magnetic resistance element and a sputtering target are provided in association with the above-mentioned in-plane magnetization film, the above-mentioned in-plane magnetization film multilayer structure, or the above-mentioned hard bias layer.
Means for solving the problems
The present invention is an invention for solving the above-described problems, and is an in-plane magnetization film, an in-plane magnetization film multilayer structure, a hard bias layer, a magnetoresistance effect element, and a sputtering target as described below.
That is, aspect 1 of the present invention is an in-plane magnetization film used as a hard bias layer of a magnetoresistance effect element, comprising: an initial magnetic layer containing metal Co, metal Pt and a nonmagnetic grain boundary material and having a thickness of 1nm to 32nm, wherein the metal Co is contained in an amount of 44 to 82 at%, the metal Pt is contained in an amount of 18 to 56 at%, and the nonmagnetic grain boundary material is contained in an amount of 2.0 to 31.0 vol%, based on the total volume of the metal components; and a magnetic layer main body portion formed on the initial magnetic layer and containing a metal Co, a metal Pt and a non-magnetic oxide, wherein the metal Co is contained in an amount of 44 to 82 at% inclusive, the metal Pt is contained in an amount of 18 to 56 at% inclusive, the non-magnetic oxide is contained in an amount of 2.0 to 31.0 at% inclusive, and the non-magnetic grain boundary material of the initial magnetic layer contains at least one of a Zn oxide and a Ta oxide.
The 2 nd mode of the in-plane magnetization film of the present invention is as follows: in the in-plane magnetization film according to the above-described aspect 1, the initial magnetic layer further contains metal Fe, and contains metal Co and metal Fe in a total amount of 44 to 82 at% and metal Pt in an amount of 18 to 56 at% based on the total metal components.
The 3 rd mode of the in-plane magnetization film of the present invention is as follows: in the in-plane magnetization film according to the 1 st or the 2 nd, the nonmagnetic oxide of the magnetic layer main body portion contains boron oxide.
The 4 th mode of the in-plane magnetization film of the present invention is as follows: in the in-plane magnetization film according to any one of the 1 st to 3 rd aspects, the initial magnetic layer is formed on a underlayer having a surface roughness of 0.1nm or more and 1.5nm or less.
Here, in the present application, the surface roughness means an arithmetic average roughness Ra.
The 5 th mode of the in-plane magnetization film of the present invention is as follows: in the in-plane magnetization film according to the 4 th aspect, the underlayer is an insulating layer.
An in-plane magnetization film multilayer structure according to aspect 1 of the present invention is an in-plane magnetization film multilayer structure used as a hard bias layer of a magnetoresistance effect element, comprising: an initial magnetic layer containing metal Co, metal Pt and a nonmagnetic grain boundary material and having a thickness of 1nm to 32nm, wherein the metal Co is contained in an amount of 44 to 82 at%, the metal Pt is contained in an amount of 18 to 56 at%, and the nonmagnetic grain boundary material is contained in an amount of 2.0 to 31.0 vol%, based on the total volume of the metal components; a non-magnetic initial intermediate layer formed on the initial magnetic layer; and a magnetic layer main body portion formed on the nonmagnetic initial intermediate layer and containing a metal Co, a metal Pt and a nonmagnetic oxide, wherein the metal Co is contained in an amount of 44 to 82 at% inclusive, the metal Pt is contained in an amount of 18 to 56 at% inclusive, the nonmagnetic oxide is contained in an amount of 2.0 to 31.0 at% inclusive, and the nonmagnetic grain boundary material of the initial magnetic layer contains at least one of a Zn oxide and a Ta oxide.
An in-plane magnetization film multilayer structure according to claim 2 is an in-plane magnetization film multilayer structure used as a hard bias layer of a magnetoresistance element, comprising an initial magnetic layer, two or more magnetic layer main body portions, and a nonmagnetic intermediate layer, wherein the initial magnetic layer contains metal Co, metal Pt, and nonmagnetic material, contains metal Co of 44 atomic% or more and 82 atomic% or less with respect to the total of metal components, contains metal Pt of 18 atomic% or more and 56 atomic% or less with respect to the total volume, contains 2.0 volume% or more and 31.0 volume% or less of the nonmagnetic grain boundary material, the initial magnetic layer main body portions each contain metal Co, metal Pt, and nonmagnetic oxide, contains metal Co of 44 atomic% or more and 82 atomic% or less with respect to the total of metal components, contains metal Pt of 18 atomic% or more and 56 atomic% or less with respect to the total volume, contains 2.0 volume% or more and 31.0 volume% or less of the nonmagnetic material, and the two or more magnetic layer main body portions each contain Zn, and the two or more magnetic layer main body portions are formed in a thickness of 1nm or less than 32nm, and the initial magnetic layer main body portions are arranged in a magnetic layer main body portion, and the nonmagnetic material is a non-magnetic layer main body portion is formed between the adjacent to each other.
Here, the lowermost magnetic layer body of the two or more magnetic layer body is formed at a position closest to the initial magnetic layer of the two or more magnetic layer body.
An in-plane magnetization film multilayer structure according to claim 3 is an in-plane magnetization film multilayer structure used as a hard bias layer of a magnetoresistance element, comprising an initial magnetic layer, a non-magnetic initial intermediate layer formed on the initial magnetic layer, two or more magnetic layer main body portions, and a non-magnetic intermediate layer, wherein the initial magnetic layer contains metal Co, metal Pt, and a non-magnetic grain boundary material, contains 44 at% or more and 82 at% or less of metal Co with respect to the total of metal components, contains 18 at% or more and 56 at% or less of metal Pt with respect to the total volume, contains 2.0 at% or more and 31.0 at% or less of the non-magnetic grain boundary material, the initial magnetic layer main body portions each contain metal Co, metal Pt, and a non-magnetic oxide, contains 44 at% or more and 82 at% or less of metal Co with respect to the total of metal components, contains 18 at% or more and 56 at% or less of metal Co, and the non-magnetic intermediate layer main body portions each other contains 2.0 at least 2 to 31.0 at% by volume of the non-magnetic layer main body portions, and the non-magnetic intermediate layer main body portions are disposed in the non-magnetic layer main body portions are adjacent to each other.
The 4 th mode of the in-plane magnetization film multilayer structure of the present invention is as follows: in the in-plane magnetization film multilayer structure according to claim 1 or 3, the nonmagnetic initial interlayer is made of Ru or a Ru alloy.
The 5 th mode of the in-plane magnetization film multilayer structure of the present invention is as follows: in the in-plane magnetization film multilayer structure according to the 1 st or 3 rd aspect, the thickness of the nonmagnetic initial intermediate layer is 0.3nm or more and 2nm or less.
The 6 th mode of the in-plane magnetization film multilayer structure of the present invention is as follows: in the in-plane magnetization film multilayer structure according to the 2 nd or the 3 rd, the nonmagnetic intermediate layer is made of Ru or a Ru alloy.
The 7 th mode of the in-plane magnetization film multilayer structure of the present invention is as follows: in the in-plane magnetization film multilayer structure according to the 2 nd or the 3 rd, the thickness of the nonmagnetic intermediate layer is 0.3nm or more and 2nm or less.
The 8 th mode of the in-plane magnetization film multilayer structure of the present invention is as follows: in the in-plane magnetization film multilayer structure according to any one of the 1 st to 7 th aspects, the initial magnetic layer further contains metal Fe, and the metal Co and the metal Fe are contained in a total amount of 44 atomic% to 82 atomic% and the metal Pt is contained in an amount of 18 atomic% to 56 atomic% with respect to the total of the metal components.
The 9 th mode of the in-plane magnetization film multilayer structure of the present invention is as follows: in the multilayer structure of an internal magnetization film according to any one of the aspects 1 to 8, the nonmagnetic oxide of the magnetic layer main body portion contains boron oxide.
The 10 th mode of the in-plane magnetization film multilayer structure of the present invention is as follows: in the in-plane magnetization film multilayer structure according to any one of the 1 st to 9 th aspects, the initial magnetic layer is formed on a underlayer having a surface roughness of 0.1nm or more and 1.5nm or less.
The 11 th mode of the in-plane magnetization film multilayer structure of the present invention is as follows: in the in-plane magnetization film multilayer structure according to the 10 th aspect, the underlayer is an insulating layer.
The 1 st aspect of the hard bias layer of the present invention is a hard bias layer comprising the in-plane magnetization film of the 5 th aspect.
The 2 nd aspect of the hard bias layer of the present invention is a hard bias layer having the above 11 th aspect of the in-plane magnetization film multilayer structure.
A magnetoresistance effect element according to claim 1 is the magnetoresistance effect element, wherein the hard bias layer of claim 1 is provided.
A magneto-resistive effect element according to claim 2 of the present invention is the magneto-resistive effect element, wherein the hard bias layer of claim 2 is provided.
The sputtering target of the present invention is a sputtering target used for forming an in-plane magnetization film used as at least a part of a hard bias layer of a magnetoresistance element by room temperature film formation, and is characterized by comprising a metal Co, a metal Pt, and a nonmagnetic grain boundary material, wherein the metal Co is contained in an amount of 60 to 82 at% and the metal Pt is contained in an amount of 18 to 40 at% relative to the total metal components of the sputtering target, and the nonmagnetic grain boundary material is contained in an amount of 6 to 30 at% relative to the total sputtering target, and wherein the nonmagnetic grain boundary material contains at least one of a Zn oxide and a Ta oxide.
Effects of the invention
According to the present invention, it is possible to provide a magnetic material capable of realizing a coercive force Hc of 2.00kOe or more and a residual magnetism Mrt per unit area of 2.00memu/cm without using a nonmagnetic underlayer for promoting in-plane orientation of a magnetic layer and without performing a heating film formation 2 The above-mentioned in-plane magnetization film, in-plane magnetization film multilayer structure, and hard bias layer having magnetic properties, and a magnetoresistance effect element and a sputtering target related to the above-mentioned in-plane magnetization film, in-plane magnetization film multilayer structure, or the above-mentioned hard bias layer may be provided.
Drawings
Fig. 1 is a cross-sectional view schematically showing a magnetoresistance effect element 10, an in-plane magnetization film 12, and a hard bias layer 14 according to embodiment 1 of the present invention, and is a cross-sectional view schematically showing a state in which the in-plane magnetization film 12 according to embodiment 1 of the present invention is applied to the hard bias layer 14 of the magnetoresistance effect element 10.
Fig. 2 is a sectional view schematically showing a magnetoresistance effect element 200 of the related art.
Fig. 3 is a cross-sectional view schematically showing the magnetoresistance effect element 20, the in-plane magnetization film multilayer structure 22, and the hard bias layer 24 according to embodiment 2 of the present invention, and is a cross-sectional view schematically showing a state in which the in-plane magnetization film multilayer structure 22 according to embodiment 2 of the present invention is applied to the hard bias layer 24 of the magnetoresistance effect element 20.
Fig. 4 is a cross-sectional view schematically showing the magnetoresistance effect element 30, the in-plane magnetization film multilayer structure 32, and the hard bias layer 34 according to embodiment 3 of the present invention, and is a cross-sectional view schematically showing a state in which the in-plane magnetization film multilayer structure 32 according to embodiment 3 of the present invention is applied to the hard bias layer 34 of the magnetoresistance effect element 30.
Fig. 5 is a sectional view schematically showing the magnetoresistance effect element 40, the in-plane magnetization film multilayer structure 42, and the hard bias layer 44 according to embodiment 4 of the present invention, and is a sectional view schematically showing a state in which the in-plane magnetization film multilayer structure 42 according to embodiment 4 of the present invention is applied to the hard bias layer 44 of the magnetoresistance effect element 40.
Fig. 6 is a bar graph showing the experimental results of reference examples 1 to 8, in which the type of the nonmagnetic grain boundary oxide is shown on the horizontal axis and the coercive force Hc (kOe) is shown on the vertical axis.
Fig. 7 is an observation image (cross-sectional TEM photograph) obtained by taking a vertical cross section (cross section in a direction orthogonal to the in-plane direction) of the CoPt in-plane magnetization film (initial magnetic layer) of reference example 8 by a scanning transmission electron microscope.
Fig. 8 is a graph showing the experimental results of examples 1 to 6 and comparative example 1, in which the thickness of the initial magnetic layer of the in-plane magnetization film is shown on the horizontal axis and the coercivity Hc (kOe) is shown on the vertical axis.
Fig. 9 is a graph showing the experimental results of examples 4, 7 to 15 and comparative examples 2 and 3, in which the ZnO content in the initial magnetic layer of the in-plane magnetization film is shown on the horizontal axis and the coercive force Hc (kOe) is shown on the vertical axis.
Fig. 10 is a graph in which the horizontal axis represents the Pt content (atomic%) relative to the total of Co and Pt, which are metal components, of the initial magnetic layer, and the vertical axis represents the coercive force Hc (kOe).
Detailed Description
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Here, the tunnel magnetoresistance effect element is described in consideration of the magnetoresistance effect element according to the embodiment of the present invention, but the magnetoresistance effect element of the present invention is not limited to the tunnel magnetoresistance effect element. The in-plane magnetization film and the hard bias layer of the present invention are not limited to the hard bias layer applied to the tunnel magnetoresistance effect element, and can be applied to, for example, a giant magnetoresistance effect element and an anisotropic magnetoresistance effect element.
(1) Embodiment 1
(1-1) schematic configuration of the magnetoresistive element 10 according to embodiment 1
Fig. 1 is a cross-sectional view schematically showing a magnetoresistance effect element 10, an in-plane magnetization film 12, and a hard bias layer 14 according to embodiment 1 of the present invention, and is a cross-sectional view schematically showing a state in which the in-plane magnetization film 12 according to embodiment 1 of the present invention is applied to the hard bias layer 14 of the magnetoresistance effect element 10. Fig. 2 is a sectional view schematically showing a magnetoresistance effect element 200 in the related art.
The magnetoresistance effect element 10 (here, tunnel magnetoresistance effect element) of embodiment 1 has an in-plane magnetization film 12 (hard bias layer 14), a magnetic shield layer 50, a seed layer 52, an antiferromagnetic layer 54, a pinning layer 56, a blocking layer 58, a free magnetic layer 60, a cap layer 62, and an insulating layer 70.
The pinned layer 56 and the free magnetic layer 60 are both ferromagnetic layers separated by a very thin barrier layer 58 that acts as a nonmagnetic tunnel barrier. The pinned layer 56 is fixed by exchange coupling with the adjacent antiferromagnetic layer 54, or the like, so that the magnetization direction thereof is fixed. The free magnetic layer 60 is free to rotate in its magnetization direction relative to the magnetization direction of the pinned layer 56 in the presence of an external magnetic field. When the free magnetic layer 60 is rotated with respect to the magnetization direction of the pinned layer 56 by an external magnetic field, the resistance changes, and thus, by detecting the change in the resistance, the external magnetic field can be detected. A seed layer 52 is provided on the magnetic shield layer 50, and an antiferromagnetic layer 54 is provided on the seed layer 52. A capping layer 62 is disposed on the free magnetic layer 60.
The hard bias layer 14 has an effect of applying a bias magnetic field to the free magnetic layer 60 and stabilizing the magnetization direction axis of the free magnetic layer 60. In the magnetoresistance effect element 10 of embodiment 1, the in-plane magnetization film 12 constitutes the hard bias layer 14.
The insulating layer 70 is formed of an electrically insulating material and has a function of suppressing shunt of sensor current flowing through the sensor stack (free magnetic layer 60, barrier layer 58, pinned layer 56, antiferromagnetic layer 54) in the vertical direction into the hard bias layer 14 on both sides of the sensor stack (free magnetic layer 60, barrier layer 58, pinned layer 56, antiferromagnetic layer 54). As the insulating layer 70, for example, silicon oxide, aluminum oxide, or the like can be specifically used.
(1-2) general constitution of in-plane magnetization film 12 and hard bias layer 14 according to embodiment 1
As shown in fig. 1, in the magnetoresistance effect element 10 of embodiment 1, the in-plane magnetization film 12 is used as the hard bias layer 14, and the in-plane magnetization film 12 can apply a bias magnetic field to the free magnetic layer 60 which exhibits the magnetoresistance effect. The hard bias layer 14 is constituted only by the in-plane magnetization film 12 of embodiment 1.
The in-plane magnetization film 12 of embodiment 1 includes an initial magnetic layer 12A and a magnetic layer main body 12B. The initial magnetic layer 12A and the magnetic layer main body 12B are each an in-plane magnetization film having a particle structure in which magnetic metal particles are separated by a nonmagnetic grain boundary material.
The initial magnetic layer 12A is a layer directly laminated on the insulating layer 70, and has the following functions: the magnetic metal particles (CoPt-based alloy particles having an hcp structure) formed on the magnetic layer main body 12B of the initial magnetic layer 12A are promoted to grow with the active easy axis (c-axis) aligned in the plane, a columnar particle layer of a CoPt-based alloy having an hcp structure having a c-axis in the in-plane direction is well formed in the magnetic layer main body 12B, and the initial magnetic layer 12A itself also has an action of applying a bias magnetic field to the free magnetic layer 60 as a part of the hard bias layer 14. In the [ example ] described later, it is proved that it is important that the non-magnetic grain boundary material of the initial magnetic layer 12A contains at least one of Zn oxide and Ta oxide in terms of the initial magnetic layer 12A exerting these functions.
The magnetic layer main body 12B is a magnetic layer formed on the initial magnetic layer 12A, and as described in the text, is a main body that occupies most of the in-plane magnetization film 12 (hard bias layer 14), and has an action of applying a bias magnetic field to the free magnetic layer 60.
Since the in-plane magnetization film 12 of embodiment 1 is configured to have the initial magnetic layer 12A and the magnetic layer main body 12B as described above, when the in-plane magnetization film 12 of embodiment 1 is formed, the in-plane magnetization film 12 exhibits good magnetic characteristics even if the non-magnetic Ru underlayer 202 (see fig. 2) having a thickness of about 15nm or more is not formed after the non-magnetic Ru underlayer 202 is formed on the insulating layer 70 as in the prior art. By directly forming the initial magnetic layer 12A as a part of the in-plane magnetization film 12 on the insulating layer 70 and forming the magnetic layer main body 12B as the remaining part of the in-plane magnetization film 12 thereon, the in-plane magnetization film 12 exhibits good magnetic characteristics (coercive force Hc of 2.00kOe or more, remanence per unit area of 2.00memu/cm 2 The above).
The in-plane magnetization film 12 exhibited excellent magnetic characteristics (coercive force Hc of 2.00kOe or more, residual magnetism per unit area of 2.00 memu/cm) 2 The thickness of the initial magnetic layer 12A is normally 1nm to 32nm, and from the standpoint of greatly satisfying both the coercive force Hc and the remanence Mrt per unit area, the thickness of the initial magnetic layer 12A is preferably 2nm to 30nm, more preferably 8nm to 20 nm. Since the initial magnetic layer 12A has a particle structure in which the magnetic metal is separated by the nonmagnetic grain boundary material and is part of the in-plane magnetization film 12, even when the initial magnetic layer 12A is as thick as 30nm, for example, the free magnetic layer 60 and the in-plane magnetization film 12 are separated by only the distance corresponding to the arrangementBy the amount of distance of the insulating layer 70 between the magnetic layer 60 and the in-plane magnetization film 12. Therefore, in the magnetoresistance effect element 10 of embodiment 1, the amount of attenuation of the bias magnetic field applied to the free magnetic layer 60 by the hard bias layer 14 is small.
On the other hand, as shown in fig. 2, the magnetoresistance effect element 200 of the conventional example has a nonmagnetic Ru underlayer 202 having a thickness of about 15nm or more provided on the insulating layer 70, and an in-plane magnetization film 204 is provided on the nonmagnetic Ru underlayer 202. Therefore, the non-magnetic Ru underlayer 202 having a thickness of about 15nm or more is present between the free magnetic layer 60 and the in-plane magnetization film 204 in addition to the insulating layer 70, and the free magnetic layer 60 and the in-plane magnetization film 204 are separated by not only an amount corresponding to the distance formed by the thickness of the insulating layer 70 but also an amount corresponding to the distance formed by the thickness of the non-magnetic Ru underlayer 202, and the distance between the free magnetic layer 60 and the in-plane magnetization film 204 of the magnetoresistance effect element 200 of the conventional example is just larger than the distance formed by the thickness of the non-magnetic Ru underlayer 202 in comparison with the magnetoresistance effect element 10 of embodiment 1. Therefore, in the magnetoresistance effect element 200 of the conventional example, the amount of attenuation of the bias magnetic field applied to the free magnetic layer 60 by the hard bias layer 206 becomes larger than that of the magnetoresistance effect element 10 of embodiment 1.
(1-3) constituent Components of initial magnetic layer 12A
As described above, the in-plane magnetization film 12 of embodiment 1 is constituted by the initial magnetic layer 12A and the magnetic layer main body 12B, and the initial magnetic layer 12A and the magnetic layer main body 12B are each in-plane magnetization films each having a particle structure in which magnetic metal particles are separated by a non-magnetic grain boundary material.
In order to allow the initial magnetic layer 12A to exert the above-described function (to promote the growth of the active easy axis (c-axis) by orienting the magnetic metal particles (CoPt-based alloy particles of hcp structure) of the magnetic layer main body 12B in the plane, to satisfactorily form a columnar particle layer of a CoPt-based alloy having an hcp structure with a c-axis in the in-plane direction in the magnetic layer main body 12B, and to allow the initial magnetic layer 12A itself to act as a part of the hard bias layer 14 and to apply a bias magnetic field to the free magnetic layer 60), the initial magnetic layer 12A contains at least one of Zn oxide and Ta oxide as a non-magnetic grain boundary material, and contains Co and Pt as metal components.
The metal Co and the metal Pt are components of magnetic metal particles (micro magnets) in the initial magnetic layer 12A of the in-plane magnetization film 12 formed by sputtering.
Co is a ferromagnetic metal element and plays a central role in the formation of magnetic crystal grains (minute magnets) in the initial magnetic layer 12A of the in-plane magnetization film 12.
From the standpoint of increasing the magnetocrystalline anisotropy constant Ku of the CoPt alloy grains (magnetic grains) and maintaining the magnetic properties of the CoPt alloy grains (magnetic grains), the initial magnetic layer 12A contains Co in an amount of 44 atomic% or more and 82 atomic% or less relative to the total of the metal components of the initial magnetic layer 12A, and from the standpoint of the above, the more preferable range of the content ratio of Co in the initial magnetic layer 12A is preferably 55 atomic% or more and 80 atomic% or less, and more preferably 65 atomic% or more and 75 atomic% or less relative to the total of the metal components of the initial magnetic layer 12A.
Pt has a function of reducing the magnetic moment of an alloy by alloying with Co in a predetermined composition range, and has a function of adjusting the magnetic strength of a magnetic crystal grain. On the other hand, the CoPt alloy grains (magnetic grains) in the initial magnetic layer 12A of the in-plane magnetization film 12 obtained by sputtering have a function of increasing the magnetocrystalline anisotropy constant Ku and increasing the coercive force of the initial magnetic layer 12A of the in-plane magnetization film 12.
From the standpoint of increasing the coercivity of the initial magnetic layer 12A and adjusting the magnetic strength of the CoPt alloy grains (magnetic grains) in the initial magnetic layer 12A, the initial magnetic layer 12A contains Pt at 18 atomic% or more and 56 atomic% or less with respect to the total of the metal components of the initial magnetic layer 12A, and from the standpoint of the above, the more preferable range of the content ratio of Pt in the initial magnetic layer 12A is preferably 20 atomic% or more and 45 atomic% or less, and more preferably 25 atomic% or more and 35 atomic% or less with respect to the total of the metal components of the initial magnetic layer 12A.
The metal component of the initial magnetic layer 12A of the in-plane magnetization film 12 according to the present embodiment may contain Fe in addition to Co and Pt in an amount of 0.5 atomic% to 1.5 atomic% based on the total metal component of the initial magnetic layer 12A.
The non-magnetic grain boundary material of the initial magnetic layer 12A of the in-plane magnetization film 12 according to embodiment 1 contains at least one of Zn oxide and Ta oxide. In addition, in the initial magnetic layer 12A, the CoPt alloy magnetic grains are separated from each other by a nonmagnetic grain boundary material containing at least one of Zn oxide and Ta oxide, forming a grain structure. That is, the grain structure of the initial magnetic layer 12A is composed of CoPt alloy grains and grain boundaries surrounding the CoPt alloy grains, the grain boundaries being composed of a non-magnetic grain boundary material containing at least one of Zn oxide and Ta oxide.
When the content of the non-magnetic grain boundary material in the initial magnetic layer 12A is increased, it is easy to reliably separate the magnetic crystal grains from each other and to make the magnetic crystal grains independent from each other, and therefore, from this point of view, it is standard to set the content of the non-magnetic grain boundary material contained in the initial magnetic layer 12A of the in-plane magnetization film 12 of embodiment 1 to 2.0% by volume or more, preferably 3.0% by volume or more, and more preferably 4.0% by volume or more, relative to the entire volume of the initial magnetic layer 12A.
However, if the content of the non-magnetic grain boundary material in the initial magnetic layer 12A is too large, the non-magnetic grain boundary material may be mixed into the CoPt alloy grains (magnetic grains) and adversely affect the crystallinity of the CoPt alloy grains (magnetic grains), and the proportion of structures other than hcp in the CoPt alloy grains (magnetic grains) may increase. From this point of view, the content of the non-magnetic grain boundary material contained in the initial magnetic layer 12A of the in-plane magnetization film 12 according to embodiment 1 is set to 31.0% by volume or less, preferably 15.0% by volume or less, and more preferably 10.0% by volume or less, based on the entire volume of the initial magnetic layer 12A.
Therefore, in embodiment 1, the content of the non-magnetic grain boundary material in the initial magnetic layer 12A is set to 2.0% by volume or more and 31.0% by volume or less, preferably 3.0% by volume or more and 15.0% by volume or less, and more preferably 4.0% by volume or more and 10.0% by volume or less, based on the entire volume of the initial magnetic layer 12A.
The non-magnetic grain boundary material of the initial magnetic layer 12A of the in-plane magnetization film 12 of embodiment 1 contains at least one of Zn oxide and Ta oxide, which is proved to be important in improving the magnetic characteristics (coercive force Hc and remanence Mrt per unit area) of the in-plane magnetization film 12 in [ example ] described later.
(1-4) constituent Components of the magnetic layer Main body portion 12B
As described above, the magnetic layer main body 12B is a magnetic layer formed on the initial magnetic layer 12A, and as described in the text, is a main body that occupies most of the in-plane magnetization film 12 (hard bias layer 14), and has an effect of applying a bias magnetic field to the free magnetic layer 60. To exert this effect, the magnetic layer main body portion 12B contains Co and Pt as metal components and an oxide as a non-magnetic grain boundary material.
The metal Co and the metal Pt are constituent components of magnetic metal particles (micro magnets) in the magnetic layer main body portion 12B of the in-plane magnetization film 12 formed by sputtering.
As described above, co is a ferromagnetic metal element and plays a central role in the formation of magnetic crystal grains (micro magnets) in the magnetic layer main body portion 12B of the in-plane magnetization film 12.
In the magnetic layer main body 12B as well, in the same manner as in the initial magnetic layer 12A, from the viewpoint of increasing the magnetocrystalline anisotropy constant Ku of the CoPt alloy crystal grains (magnetic crystal grains) and from the viewpoint of maintaining the magnetism of the CoPt alloy crystal grains (magnetic crystal grains), the magnetic layer main body 12B contains Co in an amount of 44 atomic% or more and 82 atomic% or less with respect to the total of the metal components of the magnetic layer main body 12B, and from the viewpoint of the above, the more preferable range of the content ratio of Co in the magnetic layer main body 12B is preferably 55 atomic% or more and 80 atomic% or less, and more preferably 65 atomic% or more and 75 atomic% or less with respect to the total of the metal components of the initial magnetic layer 12A.
As described above, pt has a function of reducing the magnetic moment of an alloy by alloying with Co in a predetermined composition range, and has an effect of adjusting the magnetic strength of a magnetic crystal grain. On the other hand, the magnetic layer main body 12B of the in-plane magnetization film 12 obtained by sputtering has a function of increasing the magnetocrystalline anisotropy constant Ku of the CoPt alloy crystal grains (magnetic crystal grains) in the magnetic layer main body 12B of the in-plane magnetization film 12 and increasing the coercive force of the magnetic layer main body 12B.
From the viewpoint of increasing the coercive force of the magnetic layer main body portion 12B and the viewpoint of adjusting the magnetic strength of the CoPt alloy crystal grains (magnetic crystal grains) in the magnetic layer main body portion 12B, the magnetic layer main body portion 12B contains Pt of 18 atomic% or more and 56 atomic% or less with respect to the total of the metal components of the magnetic layer main body portion 12B, and from the viewpoint of the above, the more preferable range of the content ratio of Pt in the magnetic layer main body portion 12B is preferably 20 atomic% or more and 45 atomic% or less, and more preferably 25 atomic% or more and 35 atomic% or less with respect to the total of the metal components of the magnetic layer main body portion 12B.
The magnetic layer main body portion 12B of the in-plane magnetization film 12 of embodiment 1 contains an oxide as a non-magnetic grain boundary material. In the magnetic layer main body 12B, the CoPt alloy magnetic grains are separated from each other by the oxide that is a non-magnetic grain boundary material, and a grain structure is formed. That is, the grain structure of the magnetic layer main body 12B is composed of CoPt alloy grains and grain boundaries surrounding the grains, which are composed of an oxide as a non-magnetic grain boundary material.
When the content of the oxide as the nonmagnetic grain boundary material in the magnetic layer main body portion 12B is increased, it is easy to reliably separate the magnetic crystal grains from each other and to make the magnetic crystal grains independent from each other, and therefore, from this point of view, the content of the oxide as the nonmagnetic grain boundary material contained in the magnetic layer main body portion 12B of the in-plane magnetization film 12 of embodiment 1 is set to 2.0% by volume or more, preferably 3.0% by volume or more, and more preferably 4.0% by volume or more, relative to the entire volume of the magnetic layer main body portion 12B.
However, if the content of the oxide as the nonmagnetic grain boundary material in the magnetic layer main body portion 12B is too large, the oxide as the nonmagnetic grain boundary material may be mixed into the CoPt alloy crystal grains (magnetic crystal grains) to adversely affect the crystallinity of the CoPt alloy crystal grains (magnetic crystal grains), and the proportion of the structure other than hcp in the CoPt alloy crystal grains (magnetic crystal grains) may be increased. From this point of view, the content of the oxide as the non-magnetic grain boundary material contained in the magnetic layer main body portion 12B of the in-plane magnetization film 12 according to embodiment 1 is set to 31.0% by volume or less, preferably 15.0% by volume or less, and more preferably 10.0% by volume or less, based on the entire volume of the magnetic layer main body portion 12B.
Therefore, in embodiment 1, the content of the oxide as the nonmagnetic grain boundary material in the magnetic layer main body portion 12B is set to 2.0% by volume or more and 31.0% by volume or less with respect to the entire volume of the magnetic layer main body portion 12B, and the content of the oxide as the nonmagnetic grain boundary material contained in the magnetic layer main body portion 12B is preferably set to 3.0% by volume or more and 15.0% by volume or less, more preferably set to 4.0% by volume or more and 10.0% by volume or less.
In addition, when boron oxide is contained as the oxide as the nonmagnetic grain boundary material in the magnetic layer main body portion 12B, the coercive force Hc of the magnetic layer main body portion 12B becomes large, and the coercive force Hc of the in-plane magnetization film 12 becomes large, so that boron oxide is preferably contained as the oxide.
In the current in-plane magnetization film, since an elemental element such as Cr, W, ta, B is used as a grain boundary material for separating the CoPt alloy grains (magnetic grains) from each other, it is considered that the grain boundary material is solid-solved to some extent in the CoPt alloy. Therefore, it is considered that the crystallinity of the CoPt alloy crystal grains (magnetic crystal grains) of the present in-plane magnetization film is adversely affected and saturation magnetization and remanence are reduced, and that the coercive force Hc and remanence values of the present in-plane magnetization film are adversely affected.
On the other hand, in the magnetic layer main body portion 12B of the in-plane magnetization film 12 according to embodiment 1, since the grain boundary material is an oxide, the grain boundary material is less likely to be solid-dissolved in the CoPt alloy than in the case where the grain boundary material is a simple element such as Cr, W, ta, B. Therefore, the saturation magnetization and remanence of the magnetic layer main body portion 12B of the in-plane magnetization film 12 of embodiment 1 become large, and the coercive force Hc and remanence of the in-plane magnetization film 12 of embodiment 1 become large.
(1-5) thickness of in-plane magnetization film 12 (initial magnetic layer 12A and magnetic layer main body 12B)
As described above, the "remanence per unit area" of the in-plane magnetization film is a value obtained by multiplying the remanence per unit volume of the in-plane magnetization film by the thickness of the in-plane magnetization film, and therefore, if the thickness of the in-plane magnetization film is thinned, there is a tendency that the remanence Mrt per unit area is reduced. In addition, if the thickness of the in-plane magnetization film is increased, the coercive force Hc of the in-plane magnetization film tends to decrease due to the shape magnetic anisotropy effect. These are applicable to both the initial magnetic layer 12A and the magnetic layer main body 12B.
The thickness of the initial magnetic layer 12A is, as described above, normally 1nm to 32nm, and from the viewpoint of greatly satisfying both the coercive force Hc and the remanence Mrt per unit area, the thickness of the initial magnetic layer 12A is preferably 2nm to 30nm, more preferably 8nm to 20 nm.
The thickness of the magnetic layer main body 12B is normally 15nm to 80nm, and from the viewpoint of greatly satisfying both the coercive force Hc and the remanence Mrt per unit area, the thickness of the magnetic layer main body 12B is preferably 20nm to 60nm, more preferably 25nm to 50 nm.
(1-6) substrate layer
As described above, in the related art, as the underlayer of the co—pt based in-plane magnetization film, a nonmagnetic underlayer (Cr, ti, cr alloy, ti alloy, etc.) that promotes in-plane orientation of the c-axis of the CoPt alloy of hcp structure is used (paragraph 0028 of patent document 2 described in the column of [ prior art document ]). As described above, in other conventional techniques, the coercive force Hc of the co—pt based in-plane magnetization film is increased by forming the nonmagnetic Ru underlayer by setting the air pressure at the time of film formation to a high air pressure and forming the co—pt based in-plane magnetization film on the nonmagnetic Ru underlayer having a thickness of up to about 15nm or more (paragraph 0016 and non-patent document 1 of patent document 3 described in the column of [ prior art document ]). However, in these techniques, since the nonmagnetic under layer is used, even if the in-plane magnetization film is formed as the hard bias layer by using these techniques, the distance between the magnetoresistive element portion and the hard bias layer is set to a distance corresponding to the thickness of the nonmagnetic under layer, and the magnetic field applied to the magnetoresistive element portion by the hard bias layer is reduced.
On the other hand, in the in-plane magnetization film 12 and the hard bias layer 14 composed of the in-plane magnetization film 12 of embodiment 1, the initial magnetic layer 12A, which is a part of the in-plane magnetization film 12 (hard bias layer 14), is directly formed on the insulating layer 70 without using a nonmagnetic underlayer for improving the magnetic characteristics of the formed in-plane magnetization film. That is, the insulating layer 70 serves as a base layer of the in-plane magnetization film 12 (hard bias layer 14). Therefore, in the hard bias layer 14 constituted by the in-plane magnetization film 12 of embodiment 1, the distance between the magnetoresistive element portion and the free magnetic layer 60 is short, and the decrease in the magnetic field applied to the free magnetic layer 60 is suppressed. In addition, it is demonstrated in [ example ] described later that even if the in-plane magnetization film 12 according to embodiment 1 is directly formed on the insulating layer 70, a favorable coercivity Hc can be obtained by using a predetermined initial magnetic layer 12A.
In addition, it was also demonstrated in [ example ] described later that the in-plane magnetization film 12 of embodiment 1 can obtain a favorable coercivity Hc even when the surface roughness of the insulating layer 70 serving as a base is extremely small to 0.1nm or more and 1.5nm or less. In general, when the surface roughness of a nonmagnetic underlayer serving as a base is large to some extent during formation, the magnetic segregation of the co—pt alloy crystal grains is promoted, and the coercive force Hc tends to be increased.
In addition, since the surface roughness of the insulating layer 70 that becomes the base at the time of formation is extremely small to 0.1nm or more and 1.5nm or less, the in-plane magnetization film 12 of embodiment 1 can also have an effect of reducing the irregularities on the surface of the formed in-plane magnetization film 12. If the irregularities on the surface of the formed in-plane magnetization film 12 are reduced, the work for producing the magnetoresistance effect element 10 is reduced, and the subsequent steps are easy to perform.
In the in-plane magnetization film 12 of embodiment 1, the above-described operational effects (the reason that the excellent coercive force Hc can be obtained even if the in-plane magnetization film 12 of embodiment 1 is directly formed on the insulating layer 70 having a surface roughness of at least 0.1nm and at most 1.5 nm) can be obtained is that the in-plane magnetization film 12 is configured to be divided into the initial magnetic layer 12A and the magnetic layer main body 12B, and the nonmagnetic grain boundary material of the initial magnetic layer 12A is configured to contain at least one of Zn oxide and Ta oxide, which is demonstrated in [ examples ] described later. However, the theoretical reason why the above-described operational effects can be obtained by constituting the nonmagnetic grain boundary material of the initial magnetic layer 12A so as to contain at least one of Zn oxide and Ta oxide is not clear at present.
(1-7) sputtering target
The sputtering target used for forming the initial magnetic layer 12A of the in-plane magnetization film 12 according to embodiment 1 by room temperature film formation contains metal Co, metal Pt, and a non-magnetic grain boundary material, and contains 60 to 82 at% of metal Co, 18 to 40 at% of metal Pt, and 6 to 30 at% of the non-magnetic grain boundary material, and at least one of Zn oxide and Ta oxide, based on the total metal components of the sputtering target. As described in [ example ] below, the actual composition (composition obtained by composition analysis) of the produced CoPt-oxide-based in-plane magnetization film is deviated from the composition of the sputtering target used for producing the CoPt-oxide-based in-plane magnetization film, and therefore, the composition ranges of the elements contained in the sputtering target are not identical to the composition ranges of the elements contained in the initial magnetic layer 12A of the in-plane magnetization film 12 of embodiment 1.
(1-8) method for Forming initial magnetic layer 12A
The initial magnetic layer 12A of the in-plane magnetization film 12 of embodiment 1 is formed by sputtering using the sputtering target described in the above "(1-7) sputtering target", and forming a film on the insulating layer 70. The initial magnetic layer 12A is formed at room temperature without heating. The in-plane magnetization film 12 of embodiment 1 can be formed by film formation at room temperature without heating even in sputtering when the magnetic layer main body 12B is formed.
As described in the above "(1-6) underlayer", in the formation of the in-plane magnetization film 12 of embodiment 1, the initial magnetic layer 12A is directly formed by sputtering on the insulating layer 70, and the magnetic layer main body 12B is formed by sputtering on the initial magnetic layer 12A, instead of using a nonmagnetic underlayer for improving the magnetic characteristics of the formed in-plane magnetization film 12, thereby forming the in-plane magnetization film 12.
(2) Embodiment 2
Fig. 3 is a cross-sectional view schematically showing the magnetoresistance effect element 20, the in-plane magnetization film multilayer structure 22, and the hard bias layer 24 according to embodiment 2 of the present invention, and is a cross-sectional view schematically showing a state in which the in-plane magnetization film multilayer structure 22 according to embodiment 2 of the present invention is applied to the hard bias layer 24 of the magnetoresistance effect element 20.
The in-plane magnetization film multilayer structure 22 of embodiment 2 will be described below, but the same components as those of embodiment 1 will be denoted by the same reference numerals in principle, and description thereof will be omitted.
As shown in fig. 3, the in-plane magnetization film multilayer structure 22 according to embodiment 2 of the present invention is formed as follows: an initial magnetic layer 22A is formed on the insulating layer 70, a nonmagnetic initial intermediate layer 22C is formed on the initial magnetic layer 22A, and a magnetic layer main body 22B is formed on the nonmagnetic initial intermediate layer 22C. Here, the components and thicknesses of the initial magnetic layer 22A and the magnetic layer main body 22B are the same as those of the initial magnetic layer 12A and the magnetic layer main body 12B of the in-plane magnetization film 12 of embodiment 1, and therefore, description thereof is omitted in principle.
The in-plane magnetization film multilayer structure 22 according to embodiment 2 can be used as the hard bias layer 24 of the magnetoresistance effect element 20, and can apply a bias magnetic field to the free magnetic layer 60 that exhibits the magnetoresistance effect.
The nonmagnetic initial intermediate layer 22C is formed into a multilayer structure by separating the initial magnetic layer 22A and the magnetic layer main body 22B in the thickness direction, and has a function of further increasing the coercive force Hc while maintaining the value of the residual magnetism Mrt per unit area by reducing the thickness of a single layer of the magnetic layer while maintaining the total thickness of the magnetic layers.
The initial magnetic layer 22A and the magnetic layer main body 22B separated by the nonmagnetic initial intermediate layer 22C are arranged so that the spins are parallel (in the same direction). With this arrangement, since the initial magnetic layer 22A and the magnetic layer main body 22B separated by sandwiching the nonmagnetic initial intermediate layer 22C are ferromagnetically coupled, the in-plane magnetization film multilayer structure 22 can increase the coercive force Hc while maintaining the value of the remanence Mrt per unit area, and can exhibit a favorable coercive force Hc.
From the standpoint of not impairing the crystal structure of the CoPt alloy magnetic crystal grains, the metal used in the nonmagnetic initial intermediate layer 22C is set to be the same as the crystal structure (hexagonal closest packed structure hcp) of the CoPt alloy magnetic crystal grains. Specifically, as the nonmagnetic initial intermediate layer 22C, metallic Ru or a Ru alloy having the same crystal structure (hexagonal closest packed structure hcp) as that of the CoPt alloy magnetic crystal grains in the initial magnetic layer 22A and the magnetic layer main body portion 22B can be suitably used.
Specifically, for example, cr, pt, and Co may be used as the additive element when the metal used in the nonmagnetic initial interlayer 22C is a Ru alloy, and the range of the addition amount of these metals may be set to a range where the Ru alloy has a hexagonal closest packed structure hcp.
As a result of arc melting to prepare a bulk sample of Ru alloy and peak analysis by X-ray diffraction by an X-ray diffraction apparatus (XRD: smartLab manufactured by Co., ltd.), it was confirmed that the hexagonal closest packed structure hcp and RuCr were present when the Cr addition amount was 50 atomic% in the RuCr alloy 2 In the case of using a RuCr alloy for the nonmagnetic initial intermediate layer 22C, the amount of Cr added is suitably set to less than 50 at%, preferably less than 40 at%, more preferably less than 30 at%. In addition, in the RuPt alloy, the addition amount of Pt is 15 atomsIn% by weight, since a mixed phase of the hexagonal closest packed structure hcp and the face centered cubic structure fcc derived from Pt was confirmed, when the RuPt alloy was used for the nonmagnetic initial intermediate layer 22C, the addition amount of Pt was suitably set to less than 15 atomic%, preferably less than 12.5 atomic%, and more preferably less than 10 atomic%. In addition, although the hexagonal closest-packed structure hcp is formed in the RuCo alloy regardless of the addition amount of Co, the addition amount of Co is set to less than 40 atomic%, preferably less than 30 atomic%, more preferably less than 20 atomic%, because the alloy becomes a magnetic body if 40 atomic% or more of Co is added.
With respect to the thickness of the nonmagnetic initial intermediate layer 22C, if the thickness of the nonmagnetic initial intermediate layer 22C is too small, the above-described function may not be exhibited (the function of separating the nonmagnetic initial intermediate layer 22C into the initial magnetic layer 22A and the magnetic layer main body 22B in the thickness direction and forming a plurality of layers, and further increasing the coercive force Hc while maintaining the value of the residual magnetism Mrt per unit area by reducing the thickness of the single layer of the magnetic layer while maintaining the total thickness of the magnetic layers), and therefore the thickness of the nonmagnetic initial intermediate layer 22C is normally 0.3nm or more, preferably 0.5nm or more, and more preferably 0.7nm or more.
On the other hand, the smaller the thickness of the nonmagnetic initial intermediate layer 22C, the closer the distance between the magnetic layer main body 22B and the free magnetic layer 60, and the reduction in the magnetic field applied to the free magnetic layer 60 by the hard bias layer 24 composed of the in-plane magnetization film multilayer structure 22 is suppressed, and therefore, the thickness of the nonmagnetic initial intermediate layer 22C is normally 2nm or less, preferably 1.5nm or less, and more preferably 1.2nm or less.
Therefore, the thickness of the nonmagnetic initial intermediate layer 22C is normally 0.3nm to 2nm, preferably 0.5nm to 1.5nm, more preferably 0.7nm to 1.2 nm.
(3) Embodiment 3
Fig. 4 is a cross-sectional view schematically showing the magnetoresistance effect element 30, the in-plane magnetization film multilayer structure 32, and the hard bias layer 34 according to embodiment 3 of the present invention, and is a cross-sectional view schematically showing a state in which the in-plane magnetization film multilayer structure 32 according to embodiment 3 of the present invention is applied to the hard bias layer 34 of the magnetoresistance effect element 30.
Hereinafter, the in-plane magnetization film multilayer structure 32 of embodiment 3 will be described, but the same components as those of embodiment 1 will be denoted by the same reference numerals in principle, and description thereof will be omitted.
As shown in fig. 4, the in-plane magnetization film multilayer structure 32 according to embodiment 3 of the present invention is formed as follows: an initial magnetic layer 32A is formed on the insulating layer 70, a 1 st magnetic layer main body portion 32B is formed on the initial magnetic layer 32A, a non-magnetic intermediate layer 32D is formed on the 1 st magnetic layer main body portion 32B, a 2 nd magnetic layer main body portion 32C is formed on the non-magnetic intermediate layer 32D, and the in-plane magnetization film multilayer structure 32 according to embodiment 3 of the present invention has a structure in which the magnetic layer main body portion is separated into the 1 st magnetic layer main body portion 32B and the 2 nd magnetic layer main body portion 32C by the non-magnetic intermediate layer 32D. Here, the constituent components and thicknesses of the initial magnetic layer 32A are the same as those of the initial magnetic layer 12A of the in-plane magnetization film 12 of embodiment 1, and therefore, description thereof is omitted in principle. The constituent components of the 1 st magnetic layer main body portion 32B and the 2 nd magnetic layer main body portion 32C are the same as the constituent components of the magnetic layer main body portion 12B of the in-plane magnetization film 12 of embodiment 1, and therefore, the description is omitted in principle.
The in-plane magnetization film multilayer structure 32 according to embodiment 3 can be used as the hard bias layer 34 of the magnetoresistance effect element 30, and can apply a bias magnetic field to the free magnetic layer 60 that exhibits the magnetoresistance effect.
The nonmagnetic intermediate layer 32D separates the magnetic layer main body portion in the thickness direction into the 1 st magnetic layer main body portion 32B and the 2 nd magnetic layer main body portion 32C, and is a layer having an effect of further improving the coercive force Hc by reducing the thickness of a single layer of the magnetic layer while maintaining the total thickness of the magnetic layers, and thereby maintaining the value of the residual magnetism Mrt per unit area.
The 1 st magnetic layer main body portion 32B and the 2 nd magnetic layer main body portion 32C separated by sandwiching the nonmagnetic intermediate layer 32D are arranged in a spin-parallel (same direction) manner. With this arrangement, since the 1 st magnetic layer main body portion 32B and the 2 nd magnetic layer main body portion 32C separated by sandwiching the nonmagnetic intermediate layer 32D are ferromagnetically coupled, the in-plane magnetization film multilayer structure 32 can increase the coercive force Hc while maintaining the value of the remanence Mrt per unit area, and can exhibit a favorable coercive force Hc.
The thicknesses of the 1 st magnetic layer main body portion 32B and the 2 nd magnetic layer main body portion 32C may be in terms of total thickness, and the total thickness of the 1 st magnetic layer main body portion 32B and the 2 nd magnetic layer main body portion 32C is preferably in the range of from 15nm to 80nm, more preferably in the range of from 25nm to 50nm, from the viewpoint of greatly satisfying both the coercive force Hc and the remanence Mrt per unit area.
From the standpoint of not impairing the crystal structure of the CoPt alloy magnetic crystal grains, the metal used in the nonmagnetic intermediate layer 32D is set to be the same as the crystal structure (hexagonal closest packed structure hcp) of the CoPt alloy magnetic crystal grains. Specifically, as the nonmagnetic intermediate layer 32D, metallic Ru or a Ru alloy having the same crystal structure (hexagonal closest packed structure hcp) as that of the CoPt alloy magnetic crystal grains in the in-plane magnetization film 12 can be suitably used.
Specifically, for example, cr, pt, and Co may be used as the additive element when the metal used in the nonmagnetic intermediate layer 32D is a Ru alloy, and the range of the addition amount of these metals may be set to a range where the Ru alloy has a hexagonal closest packed structure hcp.
As a result of arc melting to prepare a bulk sample of Ru alloy and peak analysis by X-ray diffraction apparatus (XRD: smartLab manufactured by Co., ltd.), when the addition amount of Cr in RuCr alloy was 50 atomic%, it was confirmed that the hexagonal closest packed structure hcp and RuCr were present 2 In the case where a RuCr alloy is used for the nonmagnetic intermediate layer 32D, therefore, the addition amount of Cr is suitably set to less than 50 at%, preferably less than 40 at%, more preferably less than 30 at%. In addition, when the addition amount of Pt in the RuPt alloy was 15 atomic%, it was confirmed that the hexagonal closest packed structure hcp and the face-centered cubic structure fcc derived from Pt were present In the case of using RuPt alloy for the nonmagnetic intermediate layer 32D, therefore, it is appropriate to set the addition amount of Pt to less than 15 at%, preferably to less than 12.5 at%, more preferably to less than 10 at%. In addition, although the RuCo alloy forms a hexagonal closest-packed structure hcp regardless of the amount of Co added, the addition of Co is suitably set to less than 40 atomic%, preferably less than 30 atomic%, and more preferably less than 20 atomic%, because it becomes a magnetic body when Co is added at 40 atomic% or more.
With respect to the thickness of the nonmagnetic intermediate layer 32D, if the thickness of the nonmagnetic intermediate layer 32D is too small, the above-described function may not be exhibited (the separation of the magnetic layer main body portion in the thickness direction into the 1 st magnetic layer main body portion 32B and the 2 nd magnetic layer main body portion 32C is performed in multiple layers, and the function of further increasing the coercive force Hc while maintaining the value of the residual magnetism Mrt per unit area by reducing the thickness of a single layer of the magnetic layer while maintaining the total thickness of the magnetic layers) is possible, and therefore, the thickness of the nonmagnetic intermediate layer 32D is normally 0.3nm or more, preferably 0.5nm or more, and more preferably 0.7nm or more.
On the other hand, the smaller the thickness of the nonmagnetic intermediate layer 32D, the larger the proportion of the in-plane magnetization film (the initial magnetic layer 32A and the magnetic layer main body portions 32B, 32C) in the in-plane magnetization film multilayer structure 32, and the larger the magnetic field applied to the free magnetic layer 60 by the hard bias layer 34 constituted by the in-plane magnetization film multilayer structure 32, and therefore, the thickness of the nonmagnetic intermediate layer 32D is normally 2nm or less, preferably 1.5nm or less, and more preferably 1.2nm or less.
Therefore, the thickness of the nonmagnetic intermediate layer 32D is normally 0.3nm or more and 2nm or less, preferably 0.5nm or more and 1.5nm or less, and more preferably 0.7nm or more and 1.2nm or less.
(4) Embodiment 4
Fig. 5 is a sectional view schematically showing the magnetoresistance effect element 40, the in-plane magnetization film multilayer structure 42, and the hard bias layer 44 according to embodiment 4 of the present invention, and is a sectional view schematically showing a state in which the in-plane magnetization film multilayer structure 42 according to embodiment 4 of the present invention is applied to the hard bias layer 44 of the magnetoresistance effect element 40.
The in-plane magnetization film multilayer structure 42 of embodiment 4 will be described below, but the same components as those of embodiment 1 will be denoted by the same reference numerals in principle, and description thereof will be omitted.
As shown in fig. 5, the in-plane magnetization film multilayer structure 42 according to embodiment 4 of the present invention is formed as follows: an initial magnetic layer 42A is formed on the insulating layer 70, a non-magnetic initial intermediate layer 42D is formed on the initial magnetic layer 42A, a 1 st magnetic layer main body portion 42B is formed on the non-magnetic initial intermediate layer 42D, a non-magnetic intermediate layer 42E is formed on the 1 st magnetic layer main body portion 42B, a 2 nd magnetic layer main body portion 42C is formed on the non-magnetic intermediate layer 42E, the initial magnetic layer 42A is separated from the magnetic layer main body portions 42B, 42C by the non-magnetic initial intermediate layer 42D, and the in-plane magnetization film multilayer structure 42 according to the 4 th embodiment of the present invention has a structure in which the magnetic layer main body portion is separated into the 1 st magnetic layer main body portion 42B and the 2 nd magnetic layer main body portion 42C by the non-magnetic intermediate layer 42E. Here, the constituent components and thicknesses of the initial magnetic layer 42A and the 1 st and 2 nd magnetic layer main portions 42B and 42C are the same as those of the initial magnetic layer 32A and the 1 st and 2 nd magnetic layer main portions 32B and 32C of the in-plane magnetization film multilayer structure 32 according to embodiment 3, respectively, and therefore, the description thereof is omitted in principle.
The in-plane magnetization film multilayer structure 42 according to embodiment 4 can be used as the hard bias layer 44 of the magnetoresistance effect element 40, and can apply a bias magnetic field to the free magnetic layer 60 that exhibits the magnetoresistance effect.
The nonmagnetic initial intermediate layer 42D is a layer which separates the initial magnetic layer 42A and the 1 st magnetic layer main body portion 42B in the thickness direction and is multilayered, and has an effect of further increasing the coercive force Hc while maintaining the value of the remanence Mrt per unit area by reducing the thickness of a single layer of the magnetic layer while maintaining the total thickness of the magnetic layers.
The initial magnetic layer 42A and the 1 st magnetic layer main body 42B separated by the nonmagnetic initial intermediate layer 42D are arranged so as to be spin-parallel (in the same direction). With this arrangement, since the initial magnetic layer 42A and the 1 st magnetic layer main body portion 42B separated by sandwiching the nonmagnetic initial intermediate layer 42D are ferromagnetically coupled, the in-plane magnetization film multilayer structure 42 can increase the coercive force Hc while maintaining the value of the remanence Mrt per unit area, and can exhibit a favorable coercive force Hc.
The metal used for the nonmagnetic initial intermediate layer 42D is the same as the metal used for the nonmagnetic initial intermediate layer 22C of the in-plane magnetization film multilayer structure 22 according to embodiment 2, and the thickness of the nonmagnetic initial intermediate layer 42D is the same as the thickness of the nonmagnetic initial intermediate layer 22C of the in-plane magnetization film multilayer structure 22 according to embodiment 2.
The nonmagnetic intermediate layer 42E separates the magnetic layer main body portion in the thickness direction into the 1 st magnetic layer main body portion 42B and the 2 nd magnetic layer main body portion 42C, and is a layer having an effect of further increasing the coercive force Hc while maintaining the value of the residual magnetism Mrt per unit area by reducing the thickness of a single layer of the magnetic layer while maintaining the total thickness of the magnetic layers.
The 1 st magnetic layer main body portion 42B and the 2 nd magnetic layer main body portion 42C separated by sandwiching the nonmagnetic intermediate layer 42E are arranged in a spin-parallel (same direction) manner. With this arrangement, since the 1 st magnetic layer main body portion 42B and the 2 nd magnetic layer main body portion 42C separated by sandwiching the nonmagnetic intermediate layer 42E are ferromagnetically coupled, the in-plane magnetization film multilayer structure 42 can increase the coercive force Hc while maintaining the value of the remanence Mrt per unit area, and can exhibit a favorable coercive force Hc.
The metal used for the nonmagnetic intermediate layer 42E is the same as the metal used for the nonmagnetic intermediate layer 32D of the in-plane magnetization film multilayer structure 32 according to embodiment 3, and the thickness of the nonmagnetic intermediate layer 42E is the same as the thickness of the nonmagnetic intermediate layer 32D of the in-plane magnetization film multilayer structure 32 according to embodiment 3.
Examples
Hereinafter, examples, comparative examples and reference examples for proving the present invention will be described.
In the following (A), the CoPt-nonmagnetic oxide is in an in-plane magnetization film single-layer structureThe influence of the kind of the non-magnetic grain boundary oxide in the initial magnetic layer of the in-plane magnetization film on the coercive force Hc and the remanence Mrt per unit area was studied; in the following (B), the in-plane magnetization film multilayer structure of the CoPt-nonmagnetic oxide (initial magnetic layer: coPt-ZnO in-plane magnetization film, magnetic layer main body: coPt-B) 2 O 3 In-plane magnetization film) the influence of the thickness of the initial magnetic layer of the in-plane magnetization film on the coercive force Hc and the remanence Mrt per unit area was studied; in the following (C), the in-plane magnetization film multilayer structure of the CoPt-nonmagnetic oxide (initial magnetic layer: coPt-ZnO in-plane magnetization film, magnetic layer main body: coPt-B) 2 O 3 In-plane magnetization film) the influence of the oxide (ZnO) content (volume fraction) in the initial magnetic layer of the in-plane magnetization film on the coercive force Hc and the remanence Mrt per unit area was studied; in the following (D), the in-plane magnetization film multilayer structure of the CoPt-nonmagnetic oxide (initial magnetic layer: coPt-ZnO in-plane magnetization film, magnetic layer main body: coPt-B) 2 O 3 In-plane magnetization film) the influence of the composition ratio of Co and Pt, which are metal components in the initial magnetic layer of the in-plane magnetization film, on the coercive force Hc and the remanence Mrt per unit area was studied; in the following (E), the in-plane magnetization film multilayer structure of the CoPt-nonmagnetic oxide (initial magnetic layer: coPt in-plane magnetization film, magnetic layer main body portion: coPt-B) 2 O 3 In-plane magnetization film) is Ta as a non-magnetic grain boundary material of the initial magnetic layer of the in-plane magnetization film 2 O 5 The influence of coercive force Hc and residual magnetism Mrt per unit area is studied; in the following (F), the in-plane magnetization film multilayer structure of the CoPt-nonmagnetic oxide (initial magnetic layer: coPt-ZnO in-plane magnetization film, magnetic layer main body: coPt-B) 2 O 3 In-plane magnetization film) was examined as to the influence of coercive force Hc and remanence Mrt per unit area by adding Fe as a metal component in the initial magnetic layer of the in-plane magnetization film.
Since a deviation occurs between the actual composition (composition obtained by composition analysis) of the fabricated CoPt-nonmagnetic oxide based in-plane magnetization film and the composition of the sputtering target used for the fabrication of the CoPt-nonmagnetic oxide based in-plane magnetization film, the actual composition is obtained by composition analysis for a plurality of points in the fabricated CoPt-nonmagnetic oxide based in-plane magnetization film, and based on the result, calculation for correcting the deviation in composition is performed in all examples, comparative examples, and reference examples described below, and the corrected composition is taken as the composition of each in-plane magnetization film of all examples, comparative examples, and reference examples.
In the composition analysis of the in-plane magnetization film, energy dispersive X-ray analysis (EDX) was used as an element analysis method, and emaxeveltion manufactured by horiba ltd was used as an element analysis device. However, boron (B) is a light element having a smaller atomic number than oxygen (O), and therefore cannot be detected by EDX analysis, and thus B in the in-plane magnetization film 2 O 3 The exact value of the content of (c) is not clear at this stage. Therefore, although B is contained in the compositions of the in-plane magnetization films of examples, comparative examples and reference examples described below 2 O 3 B in the target composition is described in the value of the content of (C) 2 O 3 But may deviate from the actual value.
The composition of the CoPt-nonmagnetic oxide based in-plane magnetization films in examples, comparative examples, and reference examples described in (a) to (F) below were calculated by performing calculation to correct the composition deviation with respect to the composition of the sputtering target used in the production. However, for B 2 O 3 As described above, B in the target composition is described 2 O 3 Is a value of the content of (2).
(A) influence of the type of nonmagnetic oxide in the initial magnetic layer of the in-plane magnetization film in the in-plane magnetization film monolayer structure of CoPt-nonmagnetic oxide on coercive force Hc and remanence Mrt per unit area (reference examples 1 to 8)
In reference examples 1 to 8, experimental data were obtained by variously changing the type of nonmagnetic grain boundary oxide having a single-layer structure of an in-plane magnetization film of a CoPt nonmagnetic oxide formed on a silicon substrate. The non-magnetic grain boundary oxides used in reference examples 1 to 8 were Al in the order from reference example 1 to reference example 8 2 O 3 、B 2 O 3 、Ga 2 O 3 、MgO、MnO、Nb 2 O 5 、Ta 2 O 5 ZnO. The formed CoPt-nonmagnetic oxide in-plane magnetization films were all single layers, with no nonmagnetic intermediate layer provided.
The silicon substrate used had its surface subjected to an oxidation treatment of about 100nm, and the surface was silicon oxide SiOx as an insulating layer. The surface of the silicon substrate used was mirror-finished, and the surface roughness Ra (arithmetic average roughness) of the silicon substrate was 0.1nm. That is, the surface roughness Ra (arithmetic average roughness) of the silicon oxide SiOx (silicon oxide SiOx as an insulating layer of the surface of the silicon substrate) which becomes the base layer of the in-plane magnetization film was 0.1nm. Hereinafter, the silicon substrate to be used will be referred to as a surface oxidation-treated silicon substrate.
The CoPt-nonmagnetic oxide in-plane magnetization film single-layer structures of reference examples 1 to 8, in which oxide types were different, were formed on a surface-oxidized silicon substrate by a sputtering method using ES-3100W manufactured by commercial product of commercial product コ by d. The film formation was performed at room temperature without heating the substrate during the film formation. In examples, comparative examples and reference examples of the present application, sputtering apparatuses used in sputtering for sample preparation were ES-3100W manufactured by Fahrenheit, purpura, inc. コ, and the description of the apparatus names is omitted below.
Specifically, as described below, production of a sample for research of the type of the nonmagnetic grain boundary oxide in the initial magnetic layer and acquisition of experimental data were performed.
In reference example 1, (Co-25 Pt) -10% by volume of Al was used 2 O 3 A sputtering target comprising a surface-oxidized silicon substrate, namely, an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, namely, an insulating layer serving as a base layer, wherein a sputtering method is used to form a silicon oxide film having a thickness of 15nm (Co-26.12 Pt) -5.11 vol.% Al 2 O 3 An in-plane magnetization film single-layer structure; in reference example 2, (Co-25 Pt) -10% by volume of B was used 2 O 3 Sputtering target, oxygen on surfaceOn the chemically treated silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, an insulating layer serving as a base layer, a film having a thickness of 15nm (Co-26.12 Pt) to 10% by volume of B was formed by sputtering 2 O 3 An in-plane magnetization film single-layer structure; in reference example 3, (Co-25 Pt) -10% by volume Ga is used 2 O 3 A sputtering target comprising a surface-oxidized silicon substrate, namely, a very smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, namely, an insulating layer serving as a base layer, wherein a sputtering method is used to form a silicon oxide film having a thickness of 15nm (Co-26.12 Pt) -4.89 vol% Ga 2 O 3 An in-plane magnetization film single-layer structure; in reference example 4, a single-layer structure of (Co-26.12 Pt) -4.28 vol% MgO in-plane magnetization film having a thickness of 15nm was formed on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, an insulating layer serving as a base layer, by a sputtering method using a (Co-25 Pt) -10 vol% MgO sputtering target; in reference example 5, a single-layer structure of (Co-26.12 Pt) -4.72 vol% MnO in-plane magnetization film having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, an insulating layer serving as a base layer, using a (Co-25 Pt) -10 vol% MnO sputtering target; in reference example 6, (Co-25 Pt) -10% by volume Nb was used 2 O 5 A sputtering target comprising a surface-oxidized silicon substrate, namely, an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, namely, an insulating layer serving as a base layer, wherein a sputtering method is used to form a film having a thickness of 15nm (Co-26.12 Pt) -4.57 vol.% Nb 2 O 5 An in-plane magnetization film single-layer structure; in reference example 7, (Co-25 Pt) -10% by volume Ta was used 2 O 5 A sputtering target comprising a surface-oxidized silicon substrate, namely, an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, namely, an insulating layer serving as a base layer, wherein (Co-26.12 Pt) -4.32% by volume Ta having a thickness of 15nm is formed by a sputtering method 2 O 5 An in-plane magnetization film single-layer structure; in reference example 8, (Co-25 Pt) -10 volumes were usedThe% ZnO sputtering target was formed as a single-layer structure of a (Co-26.12 Pt) -4.44 vol% ZnO in-plane magnetization film having a thickness of 15nm by a sputtering method on a surface oxidation-treated silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a base layer.
On the in-plane magnetization film single-layer structures of reference examples 1 to 8 formed as described above, carbon cap layers were formed by sputtering, respectively, to prepare samples for magnetic property measurement.
In each of the above-described film forming processes in reference examples 1 to 8, the substrate was not heated, and film formation was performed at room temperature.
Hysteresis loops of the single-layer structures of the in-plane magnetization films (initial magnetic layers) of reference examples 1 to 8 were measured by a vibrating magnetometer (VSM: TM-VSM211483-HGC type manufactured by Yuchuan Co., ltd.) (hereinafter referred to as vibrating magnetometer). Reading coercive force Hc (kOe) and remanence Mr (memu/cm) from a measured hysteresis loop 3 ) Saturated magnetization Ms (memu/cm) 3 ). Then, the read remanence Mr (memu/cm 3 ) Multiplying the thickness of the CoPt in-plane magnetization film (initial magnetic layer) to calculate the remanence (memu/cm) per unit area of the single-layer structure of the in-plane magnetization film (initial magnetic layer) 2 ) The read saturation magnetization Ms (memu/cm 3 ) Multiplying the thickness of the CoPt in-plane magnetization film (initial magnetic layer) to calculate the saturation magnetization Mst (memu/cm) per unit area of the single-layer structure of the in-plane magnetization film (initial magnetic layer) 2 )。
The experimental results of reference examples 1 to 8 are shown in table 1 below. In addition, for the experimental results of reference examples 1 to 8, a bar graph having the type of nonmagnetic grain boundary oxide as the horizontal axis and the coercive force Hc (kOe) as the vertical axis is shown in fig. 6.
Further, the CoPt in-plane magnetization film (initial magnetic layer) of reference example 8 having a composition of (Co-26.12 Pt) -4.44 vol% ZnO was observed for its vertical cross section (cross section of the CoPt in-plane magnetization film in a direction orthogonal to the in-plane direction) by a scanning transmission electron microscope (H-9500 manufactured by hitachi, inc.), and an observation image (cross-sectional TEM photograph) was taken. An observation image (cross-sectional TEM photograph) thereof is shown in fig. 7.
TABLE 1
As can be seen from Table 1 and FIG. 6, ta is used 2 O 5 The coercive forces Hc of reference example 7 of the nonmagnetic grain boundary oxide as the in-plane magnetization film (initial magnetic layer) and reference example 8 of the nonmagnetic grain boundary oxide using ZnO as the in-plane magnetization film (initial magnetic layer) were 2.09kOe and 3.13kOe, respectively, and exceeded 2.00kOe, and the coercive forces Hc were remarkably good as compared with reference examples 1 to 6 using other nonmagnetic grain boundary oxides.
The good coercive force Hc of reference example 7 and reference example 8 is an epoch-making result of an experiment in which an in-plane magnetization film (initial magnetic layer) was directly formed on an extremely smooth silicon oxide layer (surface oxidation treatment layer of a surface oxidation treated silicon substrate, i.e., an insulating layer serving as a underlayer) having a surface roughness Ra (arithmetic average roughness) of 0.1 nm. As shown in the sectional TEM photograph of fig. 7, the initial magnetic layer of (Co-26.12 Pt) -4.44 vol% ZnO of reference example 8 was formed directly on an extremely smooth silicon oxide layer (surface oxidation-treated layer of the surface oxidation-treated silicon substrate, i.e., insulating layer that becomes the underlayer) having a surface roughness Ra (arithmetic average roughness) of 0.1nm, but Co-26.12Pt alloy particles were formed in a clearly separated columnar shape. For (Co-26.12 Pt) -4.32% by volume Ta of reference example 7 2 O 5 Although the perpendicular cross section of the initial magnetic layer of reference example 7 was not observed by an electron microscope at this stage, the coercive force Hc (2.09 kOe) of reference example 7 was more than 2.00kOe but less than the coercive force Hc (3.13 kOe) of reference example 8, and therefore, it was considered that the initial magnetic layer of reference example 7 was not formed in a clearly separated columnar shape as the initial magnetic layer of reference example 8. The initial magnetic layers of reference examples 1 to 6 were not observed in the vertical cross section by an electron microscope at this stage, but the coercive force Hc of reference examples 1 to 6 was 0.14kOe to 1.21kOe, and good coercive force Hc was not obtained, and therefore, the initial magnetic layers of reference examples 1 to 6 were observedIn the reactive layer, as has been known in the prior art, it is considered that almost no CoPt alloy particles are formed in a columnar shape on a silicon oxide layer (surface oxidation treatment layer of a surface oxidation treatment silicon substrate, i.e., an insulating layer serving as a base layer) which is amorphous, and the magnetic separation between the CoPt alloy particles is deteriorated.
As described above, in the related art, as the underlayer of the co—pt based in-plane magnetization film, a nonmagnetic underlayer (Cr, ti, cr alloy, ti alloy, etc.) that promotes in-plane orientation of the c-axis of the CoPt alloy of hcp structure is used (paragraph 0028 of patent document 2 described in the column of [ prior art document ]). As described above, in other conventional techniques, the nonmagnetic Ru underlayer is formed by setting the air pressure at a high pressure at the time of film formation, and the co—pt-based in-plane magnetization film is formed on the nonmagnetic Ru underlayer having a thickness of up to about 15nm or more, so that the coercive force Hc of the co—pt-based in-plane magnetization film is improved (paragraph 0016 and non-patent document 1 of patent document 3 described in the column of [ prior art document ]). In the prior art, it is impossible to obtain a good coercive force Hc and the like by directly forming an in-plane magnetization film on an extremely smooth silicon oxide layer (surface oxidation treatment layer of a surface oxidation treated silicon substrate, i.e., an insulating layer serving as a base layer) having a surface roughness Ra (arithmetic average roughness) of 0.1 nm.
According to the experimental results of coercive force Hc of reference examples 7 and 8, in the present invention, as the nonmagnetic grain boundary oxide of the in-plane magnetization film (initial magnetic layer) directly formed on the substrate of the extremely smooth silicon oxide layer (surface oxidation treatment layer of the surface oxidation treated silicon substrate, i.e., insulating layer which becomes the underlayer) having a surface roughness Ra (arithmetic average roughness) of 0.1nm, the nonmagnetic grain boundary oxide containing at least one of Zn oxide and Ta oxide was used.
In the following studies (B) to (D) and (F), the in-plane magnetization film of reference example 8 (in-plane magnetization film using ZnO as a nonmagnetic grain boundary oxide) that gave the best results was used as the initial magnetic layer.
As shown in the cross-sectional TEM photograph of FIG. 7, the initial magnetic layer of (Co-26.12 Pt) -4.44 vol% ZnO of reference example 8 wasThe Co-26.12Pt alloy particles have a particle structure formed in a clearly separated columnar shape, and (Co-26.12 Pt) -10% by volume of B as a main body of the magnetic layer used in the following researches (B) to (F) are considered 2 O 3 Since the in-plane magnetization film has the same grain structure, it is considered that the findings of experimental data concerning the content of the nonmagnetic grain boundary material (oxide) and the composition of the metal components (Co, pt, fe) in the copt—zno in-plane magnetization film (initial magnetic layer) can be used for the study of the numerical range of the content of the nonmagnetic grain boundary material (oxide) in the magnetic layer main body portion and the study of the numerical range of the composition of the metal components (Co, pt, fe).
The term "B" refers to a multilayer structure of an in-plane magnetization film of a CoPt-nonmagnetic oxide (initial magnetic layer: coPt-ZnO in-plane magnetization film, magnetic layer main body is CoPt-B) 2 O 3 In-plane magnetization film) on the influence of the thickness of the initial magnetic layer of the in-plane magnetization film on the coercive force Hc and the remanence Mrt per unit area (examples 1 to 6, comparative example 1) >
In examples 1 to 6, on the surface oxidation-treated silicon substrate, that is, on the extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on the insulating layer serving as the underlayer, the (Co-26.12 Pt) -4.44 vol% ZnO in-plane magnetization film serving as the initial magnetic layer was formed by sputtering using the (Co-25 Pt) -10 vol% ZnO sputtering target so that the thickness became 2nm (example 1), 5nm (example 2), 10nm (example 3), 15nm (example 4), 20nm (example 5), 30nm (example 6).
Then, a Ru nonmagnetic initial intermediate layer having a thickness of 1nm was formed by sputtering on the formed (Co-26.12 Pt) -4.44 vol% ZnO in-plane magnetization film (initial magnetic layer), and a (Co-26.12 Pt) -10 vol% B as a 1 st magnetic layer main body having a thickness of 15nm was formed by sputtering on the formed Ru nonmagnetic initial intermediate layer having a thickness of 1nm 2 O 3 An in-plane magnetization film comprising (Co-26.12 Pt) 10 vol.% B as a main body of the 1 st magnetic layer formed at a thickness of 15nm 2 O 3 On the in-plane magnetized film, a Ru nonmagnetic intermediate layer having a thickness of 1nm was formed by sputtering, and the Ru nonmagnetic intermediate layer having a thickness of 1nm was formedOn the intermediate layer, (Co-26.12 Pt) -10% by volume of B as a main body portion of the 2 nd magnetic layer was formed by sputtering to a thickness of 15nm 2 O 3 An in-plane magnetization film, thereby forming an in-plane magnetization film multilayer structure.
In comparative example 1, no (Co-26.12 Pt) -4.44 vol% ZnO in-plane magnetization film was formed as an initial magnetic layer on a surface-oxidized silicon substrate, and (Co-26.12 Pt) -10 vol% B as a main body portion of the 1 st magnetic layer was formed by a sputtering method on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer as a underlayer 2 O 3 An in-plane magnetization film comprising (Co-26.12 Pt) 10 vol.% B as a main body of the 1 st magnetic layer formed at a thickness of 15nm 2 O 3 A Ru nonmagnetic intermediate layer having a thickness of 1nm was formed on the in-plane magnetization film by a sputtering method, and a (Co-26.12 Pt) -10 vol% B as a main body portion of the 2 nd magnetic layer having a thickness of 15nm was formed on the formed Ru nonmagnetic intermediate layer having a thickness of 1nm by a sputtering method 2 O 3 An in-plane magnetization film, thereby forming an in-plane magnetization film multilayer structure.
On the in-plane magnetization film multilayer structures of examples 1 to 6 and comparative example 1 formed as described above, carbon cap layers were formed by sputtering, respectively, to prepare samples for magnetic property measurement.
In each of the above-described film forming processes in examples 1 to 6 and comparative example 1, the substrate was not heated, and film formation was performed at room temperature.
Hysteresis loops of the in-plane magnetization film multilayer structures of examples 1 to 6 produced were measured by a vibrating magnetometer. Reading coercive force Hc (kOe) and remanence Mr (memu/cm) from a measured hysteresis loop 3 ) Saturated magnetization Ms (memu/cm) 3 ). Then, the read remanence Mr (memu/cm 3 ) Multiplying the total thickness of the CoPt in-plane magnetization films to calculate the remanence (memu/cm) per unit area of the multilayer structure of the in-plane magnetization film 2 ) The read saturation magnetization Ms (memu/cm 3 ) Multiplying the total thickness of the CoPt in-plane magnetization films to calculate the in-plane magnetization filmSaturation magnetization per unit area Mst (memu/cm) of multilayer structure 2 )。
The experimental results of examples 1 to 6 and comparative example 1 are shown in table 2 below. Fig. 8 shows graphs of the experimental results of examples 1 to 6 and comparative example 1, in which the thickness of the initial magnetic layer of the in-plane magnetization film is shown on the horizontal axis and the coercivity Hc (kOe) is shown on the vertical axis.
TABLE 2
As is clear from table 2 and fig. 8, when ZnO is used as the initial magnetic layer of the nonmagnetic oxide grain boundary material, the coercive force Hc is 3.15kOe and maximum when the thickness is 15nm (example 4), but on the other hand, when ZnO is used as the initial magnetic layer of the nonmagnetic oxide grain boundary material, the thickness is as thick as 20nm (example 5) and 30nm (example 6) when the thickness is thicker than 15nm, the coercive force Hc is reduced. Therefore, the initial magnetic layer using ZnO as the nonmagnetic oxide grain boundary material is used only to a limited extent from the surface of the surface-oxidized silicon substrate (for example, within about 30nm from the surface of the surface-oxidized silicon substrate), and it is considered that the use B, which has been conventionally used as an in-plane magnetization film, is preferable as the magnetic layer main body 2 O 3 In-plane magnetization film (CoPt-B) as non-magnetic oxide grain boundary material 2 O 3 )。
As is clear from the results shown in Table 2 and FIG. 8, the multilayer structure of the in-plane magnetization film exhibited good magnetic characteristics (coercive force Hc of 2.00kOe or more, residual magnetism per unit area of 2.00memu/cm 2 The thickness of the initial magnetic layer is preferably 2nm to 30nm, more preferably 8nm to 20nm, from the viewpoint of the coercivity Hc and the remanence Mrt per unit area being both greatly balanced.
In comparative example 1, no initial magnetic layer using ZnO as a non-magnetic oxide grain boundary material was provided, and the silicon substrate was subjected to surface oxidation treatmentUse of B for junction formation 2 O 3 In-plane magnetization film (CoPt-B) as non-magnetic oxide grain boundary material 2 O 3 ) Are not included in the scope of the present invention. In comparative example 1, although the coercive force Hc was 2.48kOe and exceeded 2.00kOe, the remanence Mrt per unit area was 1.83memu/cm 2 As a result, the residual magnetic flux Mrt per unit area was less than 2.00memu/cm 2 。
The term "C" refers to a multilayer structure of an in-plane magnetization film of a CoPt-nonmagnetic oxide (initial magnetic layer: coPt-ZnO in-plane magnetization film, magnetic layer main body: coPt-B) 2 O 3 In-plane magnetization film) the influence of the oxide (ZnO) content (volume fraction) in the initial magnetic layer of the in-plane magnetization film on the coercive force Hc and the remanence Mrt per unit area (examples 4, 7 to 15, comparative examples 2, 3) >
In examples 4, 7 to 15 and comparative examples 2 and 3, an initial magnetic layer having a thickness of 15nm including CoPt was formed by a sputtering method on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, with the ZnO content varying from 0% by volume to 30.10% by volume.
Specifically, in comparative example 2, a Co-25Pt sputtering target containing no nonmagnetic oxide grain boundary material was used, and a Co-26.12Pt initial magnetic layer having a thickness of 15nm was formed by a sputtering method on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer; in comparative example 3, a (Co-25 Pt) -4 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, using a (Co-25 Pt) -4 vol% ZnO sputtering target; in example 7, a (Co-25 Pt) -6 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, using a (Co-25 Pt) -6 vol% ZnO sputtering target; in example 8, a (Co-25 Pt) -8 vol% ZnO sputtering target was used to form a (Co-26.12 Pt) -3.25 vol% ZnO initial magnetic layer having a thickness of 15nm by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer; in example 4, a (Co-25 Pt) -10 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, using a (Co-25 Pt) -10 vol% ZnO sputtering target; in example 9, a (Co-25 Pt) -12 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, using a (Co-25 Pt) -12 vol% ZnO sputtering target; in example 10, a (Co-25 Pt) -14 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, using a (Co-25 Pt) -14 vol% ZnO sputtering target; in example 11, a (Co-25 Pt) -16 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, using a (Co-25 Pt) -16 vol% ZnO sputtering target; in example 12, a (Co-25 Pt) -18 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, using a (Co-25 Pt) -18 vol% ZnO sputtering target; in example 13, a (Co-25 Pt) -20 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, using a (Co-25 Pt) -20 vol% ZnO sputtering target; in example 14, a (Co-25 Pt) -25 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, using a (Co-25 Pt) -25 vol% ZnO sputtering target; in example 15, a (Co-25 Pt) -30% by volume ZnO sputtering target was used to form a 15nm thick (Co-26.12 Pt) -30.10% by volume ZnO initial magnetic layer by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer.
Then, a Ru nonmagnetic initial intermediate layer having a thickness of 1nm was formed on the initial magnetic layer formed by sputtering, and (Co-26.12 Pt) -10% by volume of B, which was a main body portion of the 1 st magnetic layer, having a thickness of 15nm was formed on the Ru nonmagnetic initial intermediate layer having a thickness of 1nm by sputtering 2 O 3 An in-plane magnetization film comprising (Co-26.12 Pt) 10 vol.% B as a main body of the 1 st magnetic layer formed at a thickness of 15nm 2 O 3 A Ru nonmagnetic intermediate layer having a thickness of 1nm was formed on the in-plane magnetization film by a sputtering method, and a (Co-26.12 Pt) -10 vol% B as a main body portion of the 2 nd magnetic layer having a thickness of 15nm was formed on the formed Ru nonmagnetic intermediate layer having a thickness of 1nm by a sputtering method 2 O 3 An in-plane magnetization film, thereby forming an in-plane magnetization film multilayer structure.
Samples for measuring magnetic characteristics were prepared by forming carbon cap layers on the in-plane magnetization film multilayer structures of examples 4, 7 to 15 and comparative examples 2 and 3 formed as described above, respectively, by sputtering.
In each of the above-described film formation processes in examples 4, 7 to 15 and comparative examples 2 and 3, the substrate was not heated, and the film formation was performed at room temperature.
In-plane magnetized films of examples 4, 7 to 15 and comparative examples 2 and 3 produced by vibration magnetometer measurement Hysteresis loops of a multilayer structure. Reading coercive force Hc (kOe) and remanence Mr (memu/cm) from a measured hysteresis loop 3 ) Saturated magnetization Ms (memu/cm) 3 ). Then, the read remanence Mr (memu/cm 3 ) Multiplying the total thickness of the CoPt in-plane magnetization films to calculate the remanence (memu/cm) per unit area of the multilayer structure of the in-plane magnetization film 2 ) The read saturation magnetization Ms (memu/cm 3 ) Multiplying the total thickness of the CoPt in-plane magnetization films to calculate the saturation magnetization Mst (memu/cm) per unit area of the multilayer structure 2 )。
The experimental results of examples 4, 7 to 15 and comparative examples 2 and 3 are shown in table 3 below. In addition, the experimental results of examples 4, 7 to 15 and comparative examples 2 and 3 are shown in fig. 9, in which the ZnO content in the initial magnetic layer of the in-plane magnetization film is shown on the horizontal axis and the coercive force Hc (kOe) is shown on the vertical axis.
TABLE 3
As is clear from table 3 and fig. 9, when the ZnO content in the initial magnetic layer using ZnO as the non-magnetic oxide grain boundary material is 5.89% by volume (example 9), the coercive force Hc is 3.25kOe, and the coercive force Hc is maximum, and if the ZnO content in the initial magnetic layer using ZnO as the non-magnetic oxide grain boundary material is more than 5.89% by volume, the larger the ZnO content in the initial magnetic layer, the smaller the magnitude of the coercive force Hc. However, even if the content of ZnO in the initial magnetic layer is as large as 30.10 vol%, the coercive force Hc is 2.10kOe, and the coercive force Hc is maintained at 2.00kOe or more. In contrast to the coercivity Hc of comparative example 3, in which the ZnO content in the initial magnetic layer was 1.60% by volume, being 0.84kOe, the coercivity Hc of example 7, in which the ZnO content in the initial magnetic layer was 2.30% by volume, was rapidly increased to 2.97kOe, and it was found that the coercivity Hc of the in-plane magnetization film multilayer structure rapidly increased if the ZnO content in the initial magnetic layer was changed from 1.60% by volume to 2.30% by volume.
From tables 3 andas is clear from the results shown in FIG. 9, the multilayer structure of the in-plane magnetization film exhibits excellent magnetic characteristics (coercive force Hc of 2.00kOe or more, remanence per unit area of 2.00 memu/cm) 2 The ZnO content in the initial magnetic layer may be set to 2.0% by volume or more and 31.0% by volume or less with respect to the entire volume of the initial magnetic layer, and is preferably set to 3.0% by volume or more and 15.0% by volume or less, more preferably set to 04.0% by volume or more and 10.0% by volume or less, from the viewpoint of greatly satisfying both the coercive force Hc and the residual magnetism Mrt per unit area.
The content of ZnO in the initial magnetic layer was 0% by volume and 1.60% by volume, respectively, and the content of ZnO in the initial magnetic layer was less than 2.0% by volume, and in comparative examples 2 and 3 outside the scope of the present invention, the coercive force was as small as 0.41kOe and 0.84kOe, respectively, and was less than 2.00kOe, respectively.
The residual magnetism Mrt per unit area exceeded 3.00memu/cm in examples 4, 7 to 15 and comparative examples 2 and 3 2 Good results were obtained.
A multilayer structure of an in-plane magnetization film of a CoPt-nonmagnetic oxide (initial magnetic layer: coPt-ZnO in-plane magnetization film, magnetic layer main body: coPt-B) 2 O 3 In-plane magnetization film) the influence of the composition ratio of Co and Pt, which are metal components in the initial magnetic layer of the in-plane magnetization film, on the coercive force Hc and the remanence Mrt per unit area (examples 4, 16 to 19, comparative examples 4 and 5)
In examples 4, 16 to 19 and comparative examples 4 and 5, on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, an insulating layer serving as a underlayer, the composition of Co and Pt, which are metal components of an initial magnetic layer, was changed, and an initial magnetic layer (copt—zno) having a thickness of 15nm using ZnO as a non-magnetic oxide grain boundary material was formed by a sputtering method. Specifically, experimental data were obtained by changing Co from 83.97 to 31.04 at% and Pt from 16.03 to 68.96 at% relative to the total of Co and Pt, which are metal components of the initial magnetic layer.
In comparative example 4, a (Co-16.03 Pt) -4.44 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, an insulating layer serving as a underlayer, using a (Co-15 Pt) -10 vol% ZnO sputtering target; in example 16, a (Co-20.13 Pt) -4.44 vol% ZnO initial magnetic layer having a thickness of 15nm was formed on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, an insulating layer serving as a underlayer, by a sputtering method using a (Co-20 Pt) -10 vol% ZnO sputtering target; in example 4, a (Co-25 Pt) -10 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, using a (Co-25 Pt) -10 vol% ZnO sputtering target; in example 17, a (Co-30 Pt) -10 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, on an insulating layer serving as a underlayer, using a (Co-30 Pt) -10 vol% ZnO sputtering target; in example 18, a (Co-43.77 Pt) -4.44% by volume initial magnetic layer of ZnO having a thickness of 15nm was formed on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, an insulating layer serving as a underlayer, by sputtering using a (Co-35 Pt) -10% by volume ZnO sputtering target; in example 19, a (Co-55.42 Pt) -4.44% by volume initial magnetic layer of ZnO having a thickness of 15nm was formed on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, an insulating layer serving as a underlayer, by sputtering using a (Co-40 Pt) -10% by volume ZnO sputtering target; in comparative example 5, a (Co-68.96 Pt) -4.44% by volume ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, an insulating layer serving as a underlayer, using a (Co-45 Pt) -10% by volume ZnO sputtering target.
Then, a Ru nonmagnetic initial intermediate layer having a thickness of 1nm was formed on the initial magnetic layer formed by sputtering, and (Co-26.12 Pt) -10% by volume of B, which was a main body portion of the 1 st magnetic layer, having a thickness of 15nm was formed on the Ru nonmagnetic initial intermediate layer having a thickness of 1nm by sputtering 2 O 3 An in-plane magnetization film comprising (Co-26.12 Pt) 10 vol.% B as a main body of the 1 st magnetic layer formed at a thickness of 15nm 2 O 3 A Ru nonmagnetic intermediate layer having a thickness of 1nm was formed on the in-plane magnetization film by a sputtering method, and a (Co-26.12 Pt) -10 vol% B as a main body portion of the 2 nd magnetic layer having a thickness of 15nm was formed on the formed Ru nonmagnetic intermediate layer having a thickness of 1nm by a sputtering method 2 O 3 An in-plane magnetization film, thereby forming an in-plane magnetization film multilayer structure.
Samples for measuring magnetic characteristics were prepared by forming carbon cap layers on the in-plane magnetization film multilayer structures of examples 4, 16 to 19 and comparative examples 4 and 5 formed as described above, respectively, by sputtering.
In each of the above-described film formation processes in examples 4, 16 to 19 and comparative examples 4 and 5, the substrate was not heated, and the film formation was performed at room temperature.
Hysteresis loops of the in-plane magnetization film multilayer structures of examples 4, 16 to 19 and comparative examples 4 and 5 produced were measured by a vibrating magnetometer. From the hysteresis loop measured, the coercive force Hc (kOe) and residual magnetism Mr (memu/cm) were read 3 ) Saturated magnetization Ms (memu/cm) 3 ). Then, the read remanence Mr (memu/cm 3 ) Multiplying the total thickness of the CoPt in-plane magnetization films to calculate the remanence (memu/cm) per unit area of the multilayer structure of the in-plane magnetization film 2 ) The read saturation magnetization Ms (memu/cm 3 ) Multiplying the total thickness of the CoPt in-plane magnetization films to calculate the saturation magnetization Mst (memu/cm) per unit area of the multilayer structure 2 )。
The experimental results of examples 4, 16 to 19 and comparative examples 4 and 5 are shown in table 4 below. Fig. 10 is a graph showing the initial magnetic layer, in which the horizontal axis represents the Pt content (atomic%) relative to the total of Co and Pt, which are metal components, and the vertical axis represents the coercive force Hc (kOe).
TABLE 4
As is clear from Table 4 and FIG. 10, examples 4 and 16 to 19, which were included in the scope of the present invention, having a coercive force Hc of 2.00kOe or more and a residual magnetic Mrt per unit area of 2.00 mu/cm, were obtained by forming films at room temperature, in which the film was not heated by a substrate, in which the total Co content of the metal components (Co, pt) in the initial magnetic layer (in-plane magnetization film) of CoPt-ZnO was 44 at% or more and 82 at% or less, the Pt content was 18 at% or more and 56 at% or less, the volume ratio of ZnO to the entire in-plane magnetization film of CoPt-ZnO was 4.44 vol%, and the thickness was 15nm 2 The magnetic properties described above.
As is clear from the results shown in Table 4 and FIG. 10, the multilayer structure of the in-plane magnetization film exhibited excellent magnetic characteristics (coercive force Hc of 2.00kOe or more, residual magnetism per unit area of 2.00 memu/cm) 2 The above) is preferable that the Pt content in the initial magnetic layer is set to 18 atomic% or more and 56 atomic% or less relative to the total of the metal components of the initial magnetic layer, and is preferably 20 atomic% or more and 45 atomic% or less, more preferably 25 atomic% or more and 35 atomic% or less relative to the total of the metal components of the initial magnetic layer, from the viewpoint of greatly satisfying both the coercive force Hc and the remanence Mrt per unit area. The Co content in the initial magnetic layer is such that the in-plane magnetization film multilayer structure exhibits excellent magnetic characteristics (coercive force Hc of 2.00kOe or more, remanence per unit area of 2.00 memu/cm) 2 The above) is preferable from the standpoint of greatly satisfying both the coercive force Hc and the remanence Mrt per unit area, since the content of Co in the initial magnetic layer is set to 44 at% or more and 82 at% or less relative to the total of the metal components of the initial magnetic layer The content is selected from 55 at% to 80 at%, more preferably from 65 at% to 75 at%.
On the other hand, in comparative example 4, in which the content of Co was 83.97 at% and the content of Pt was 16.03 at% relative to the total of the metal components (Co and Pt) of the CoPt-ZnO initial magnetic layer (in-plane magnetization film), the coercive force Hc was 1.68kOe and the coercive force Hc was less than 2.00kOe, which was not included in the scope of the present invention. In comparative example 5, in which the Co content was 31.04 at% and the Pt content was 68.96 at% based on the total of the metal components (Co and Pt) of the CoPt-ZnO initial magnetic layer (in-plane magnetization film), the coercive force Hc was 1.55kOe and was less than 2.00kOe, and the residual magnetism Mrt per unit area was 1.79memu/cm 2 A residual magnetic Mrt per unit area of less than 2.00memu/cm 2 。
The term "E" refers to a multilayer structure of an in-plane magnetization film of a CoPt-nonmagnetic oxide (initial magnetic layer: coPt in-plane magnetization film, magnetic layer main body: coPt-B) 2 O 3 In-plane magnetization film) is Ta as a non-magnetic grain boundary material of the initial magnetic layer of the in-plane magnetization film 2 O 5 Investigation of the Effect of coercivity Hc and remanence Mrt per unit area (examples 4, 20) >
In example 20, the non-magnetic grain boundary material was formed by sputtering to be Ta 2 O 5 The initial magnetic layer of (2) was prepared as a sample for measuring magnetic properties, and experimental data were obtained.
Specifically, (Co-25 Pt) -10% by volume Ta was used 2 O 5 A sputtering target comprising a surface-oxidized silicon substrate, namely, an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, namely, an insulating layer serving as a base layer, wherein (Co-26.12 Pt) -4.32% by volume Ta having a thickness of 15nm is formed by a sputtering method 2 O 5 An initial magnetic layer.
Then, a Ru nonmagnetic initial intermediate layer having a thickness of 1nm was formed on the initial magnetic layer formed by sputtering, and a Ru nonmagnetic initial intermediate layer having a thickness of 1nm was formed on the initial magnetic layer formed by sputtering to form a layer having a thickness of 15nm as a 1 st magnetic layer main body (Co-26.12 Pt) -10 vol% B 2 O 3 An in-plane magnetization film comprising (Co-26.12 Pt) 10 vol.% B as a main body of the 1 st magnetic layer formed at a thickness of 15nm 2 O 3 A Ru nonmagnetic intermediate layer having a thickness of 1nm was formed on the in-plane magnetization film by a sputtering method, and a (Co-26.12 Pt) -10 vol% B as a main body portion of the 2 nd magnetic layer having a thickness of 15nm was formed on the formed Ru nonmagnetic intermediate layer having a thickness of 1nm by a sputtering method 2 O 3 An in-plane magnetization film, thereby forming an in-plane magnetization film multilayer structure.
A sample for measuring magnetic characteristics was prepared by forming a cap layer of carbon on the in-plane magnetization film multilayer structure of example 20 formed as described above by sputtering.
In each of the above film forming processes in example 20, the substrate was not heated, and the film was formed at room temperature.
Hysteresis loops of the in-plane magnetization film multilayer structure of example 20 thus fabricated were measured by a vibrating magnetometer. Reading coercive force Hc (kOe) and remanence Mr (memu/cm) from a measured hysteresis loop 3 ) Saturated magnetization Ms (memu/cm) 3 ). Then, the read remanence Mr (memu/cm 3 ) Multiplying the total thickness of the CoPt in-plane magnetization films to calculate the remanence (memu/cm) per unit area of the multilayer structure of the in-plane magnetization film 2 ) The read saturation magnetization Ms (memu/cm 3 ) Multiplying the total thickness of the CoPt in-plane magnetization films to calculate the saturation magnetization Mst (memu/cm) per unit area of the multilayer structure 2 )。
The experimental results of example 20 are shown in table 5 below together with the experimental results of example 4.
TABLE 5
As is clear from Table 5, the non-magnetic grain boundary material of the initial magnetic layer was Ta 2 O 5 In example 20 (2), a coercive force Hc of 3.01kOe and a remanence Mrt per unit area of 3.01kOe were also obtained3.16memu/cm 2 Is not limited to the above-mentioned materials. However, in example 4 in which the nonmagnetic grain boundary material of the initial magnetic layer was ZnO, both the coercive force Hc and the remanence Mrt per unit area were Ta compared with the nonmagnetic grain boundary material of the initial magnetic layer 2 O 5 Example 20 of (2) is better, although only slightly better.
The term "F" refers to a multilayer structure of an in-plane magnetization film of a CoPt-nonmagnetic oxide (initial magnetic layer: coPt-ZnO in-plane magnetization film, magnetic layer main body: coPt-B) 2 O 3 In-plane magnetization film) was supplemented with Fe as a study of the influence of the metal component in the initial magnetic layer of the in-plane magnetization film on the coercive force Hc and the remanence Mrt per unit area (examples 4, 21) >
In example 21, a CoPtFe-ZnO initial magnetic layer was formed by a sputtering method, and a sample for measuring magnetic characteristics was prepared, and experimental data was obtained.
Specifically, a (Co-26.11 Pt-0.78 Fe) -4.44 vol% ZnO initial magnetic layer having a thickness of 15nm was formed by sputtering on a surface-oxidized silicon substrate, that is, on an extremely smooth silicon oxide layer having a surface roughness Ra (arithmetic average roughness) of 0.1nm, that is, an insulating layer serving as a underlayer, using a (Co-25 Pt-1 Fe) -10 vol% ZnO sputtering target.
Then, a Ru nonmagnetic initial intermediate layer having a thickness of 1nm was formed on the initial magnetic layer formed by sputtering, and (Co-26.12 Pt) -10% by volume of B, which was a main body portion of the 1 st magnetic layer, having a thickness of 15nm was formed on the Ru nonmagnetic initial intermediate layer having a thickness of 1nm by sputtering 2 O 3 An in-plane magnetization film comprising (Co-26.12 Pt) 10 vol.% B as a main body of the 1 st magnetic layer formed at a thickness of 15nm 2 O 3 A Ru nonmagnetic intermediate layer having a thickness of 1nm was formed on the in-plane magnetization film by a sputtering method, and a (Co-26.12 Pt) -10 vol% B as a main body portion of the 2 nd magnetic layer having a thickness of 15nm was formed on the formed Ru nonmagnetic intermediate layer having a thickness of 1nm by a sputtering method 2 O 3 An in-plane magnetization film, thereby forming an in-plane magnetization film multilayer structure.
A sample for measuring magnetic characteristics was prepared by forming a cap layer of carbon on the in-plane magnetization film multilayer structure of example 21 formed as described above by sputtering.
In each of the above film forming processes in example 21, the substrate was not heated, and the film was formed at room temperature.
Hysteresis loops of the in-plane magnetization film multilayer structure of example 21 produced were measured by a vibrating magnetometer. From the hysteresis loop measured, the coercive force Hc (kOe) and residual magnetism Mr (memu/cm) were read 3 ) Saturated magnetization Ms (memu/cm) 3 ). Then, the read remanence Mr (memu/cm 3 ) Multiplying the total thickness of the CoPt in-plane magnetization films to calculate the remanence (memu/cm) per unit area of the multilayer structure of the in-plane magnetization film 2 ) The read saturation magnetization Ms (memu/cm 3 ) Multiplying the total thickness of the CoPt in-plane magnetization films to calculate the saturation magnetization Mst (memu/cm) per unit area of the multilayer structure 2 )。
The experimental results of example 21 are shown in table 6 below together with the experimental results of examples 4 and 20.
TABLE 6
As is clear from Table 6, in example 21 in which the initial magnetic layer of the in-plane magnetization film had metal components of Co, pt and Fe, the coercive force Hc was 2.98kOe and 2.00kOe or more, and the remanence Mrt per unit area was 3.31memu/cm 2 And 2.00memu/cm 2 As described above, good magnetic characteristics can also be obtained.
Industrial applicability
The in-plane magnetization film and the in-plane magnetization film multilayer structure of the present invention can realize a coercive force Hc of 2.00kOe or more and a remanence Mrt of 2.00memu/cm per unit area without performing a heating film formation 2 The magnetic properties described above are industrially applicable. In addition, the hard bias layer of the present invention has the in-plane magnetization film or the in-plane magnetization film multilayer structure of the present invention, has good magnetic properties, and has the capability of producing Industrial applicability. The magnetoresistance effect element of the present invention has the hard bias layer of the present invention having excellent magnetic properties, and is industrially applicable. Further, the sputtering target of the present invention can be used to form an initial magnetic layer of the in-plane magnetization film of the present invention having excellent magnetic properties by film formation at room temperature, and is industrially applicable.
Symbol description
10. 20, 30, 40, 200, … magneto-resistance effect element
12. 204 … in-plane magnetized film
Initial magnetic layers 12A, 22A, 32A, 42A and …
12B, 22B … magnetic layer main body portion
14. 24, 34, 44, 206, … hard bias layer
22. 32, 42 … in-plane magnetized film multilayer structure
22C, 42D … non-magnetic initial interlayer
32B, 42B … first magnetic layer main body portion
32C, 42C … 2 nd magnetic layer main body portion
32D, 42E … nonmagnetic intermediate layer
50 … magnetic shielding layer
52 … seed layer
54 … antiferromagnetic layer
56 … pinning layer
58 … Barrier layer
60 … free magnetic layer
62 … cap layer
70 … insulating layer
202 … Ru base layer
Claims (21)
1. An in-plane magnetization film used as a hard bias layer of a magneto-resistance effect element, characterized in that,
the device comprises:
an initial magnetic layer containing metal Co, metal Pt and a nonmagnetic grain boundary material and having a thickness of 1nm to 32nm, wherein the metal Co is contained in an amount of 44 to 82 at% inclusive, the metal Pt is contained in an amount of 18 to 56 at% inclusive, and the nonmagnetic grain boundary material is contained in an amount of 2.0 to 31.0 at% inclusive, based on the total volume of the metal components; and
A magnetic layer main body portion formed on the initial magnetic layer and containing a metal Co, a metal Pt and a non-magnetic oxide, wherein the metal Co is contained in an amount of 44 to 82 at% inclusive, the metal Pt is contained in an amount of 18 to 56 at% inclusive, the non-magnetic oxide is contained in an amount of 2.0 to 31.0 at% inclusive,
the non-magnetic grain boundary material of the initial magnetic layer contains at least one of Zn oxide and Ta oxide.
2. The in-plane magnetization film according to claim 1, wherein the initial magnetic layer further contains metal Fe, and contains metal Co and metal Fe in a total amount of 44 at% to 82 at% and metal Pt in an amount of 18 at% to 56 at% with respect to the total of metal components.
3. The in-plane magnetization film according to claim 1, wherein the nonmagnetic oxide of the magnetic layer main body portion contains boron oxide.
4. The in-plane magnetization film according to any one of claims 1 to 3, wherein the initial magnetic layer is formed on a base layer having a surface roughness of 0.1nm or more and 1.5nm or less.
5. The in-plane magnetization film according to claim 4, wherein the base layer is an insulating layer.
6. An in-plane magnetization film multilayer structure used as a hard bias layer of a magneto-resistance effect element, characterized in that,
the device comprises:
an initial magnetic layer containing metal Co, metal Pt and a nonmagnetic grain boundary material and having a thickness of 1nm to 32nm, wherein the metal Co is contained in an amount of 44 to 82 at% inclusive, the metal Pt is contained in an amount of 18 to 56 at% inclusive, and the nonmagnetic grain boundary material is contained in an amount of 2.0 to 31.0 at% inclusive, based on the total volume of the metal components;
a non-magnetic initial intermediate layer formed on the initial magnetic layer; and
a magnetic layer main body portion formed on the nonmagnetic initial intermediate layer and containing a metal Co, a metal Pt and a nonmagnetic oxide, wherein the metal Co is contained in an amount of 44 to 82 at% inclusive, the metal Pt is contained in an amount of 18 to 56 at% inclusive, the nonmagnetic oxide is contained in an amount of 2.0 to 31.0 at% inclusive,
The non-magnetic grain boundary material of the initial magnetic layer contains at least one of Zn oxide and Ta oxide.
7. An in-plane magnetization film multilayer structure used as a hard bias layer of a magneto-resistance effect element, characterized in that,
comprises an initial magnetic layer, two or more magnetic layer main body parts, and a non-magnetic intermediate layer,
the initial magnetic layer contains metal Co, metal Pt and a non-magnetic grain boundary material, contains 44 to 82 at% of metal Co, 18 to 56 at% of metal Pt, and 2.0 to 31.0 at% of non-magnetic grain boundary material based on the total volume, the initial magnetic layer has a thickness of 1 to 32nm,
the two or more magnetic layer main bodies each contain metal Co, metal Pt and a nonmagnetic oxide, 44 to 82 at% of metal Co, 18 to 56 at% of metal Pt, and 2.0 to 31.0 at% of nonmagnetic oxide based on the total volume of the metal components,
The lowermost magnetic layer body of the two or more magnetic layer body portions is formed on the initial magnetic layer,
the nonmagnetic intermediate layer is disposed between the magnetic layer main body portions, and the magnetic layer main body portions adjacent to each other across the nonmagnetic intermediate layer are ferromagnetically coupled to each other,
the non-magnetic grain boundary material of the initial magnetic layer contains at least one of Zn oxide and Ta oxide.
8. An in-plane magnetization film multilayer structure used as a hard bias layer of a magneto-resistance effect element, characterized in that,
comprises an initial magnetic layer, a non-magnetic initial intermediate layer formed on the initial magnetic layer, two or more magnetic layer main body parts, and a non-magnetic intermediate layer,
the initial magnetic layer contains metal Co, metal Pt and a non-magnetic grain boundary material, contains 44 to 82 at% of metal Co, 18 to 56 at% of metal Pt, and 2.0 to 31.0 at% of non-magnetic grain boundary material based on the total volume, the initial magnetic layer has a thickness of 1 to 32nm,
The two or more magnetic layer main bodies each contain metal Co, metal Pt and a nonmagnetic oxide, 44 to 82 at% of metal Co, 18 to 56 at% of metal Pt, and 2.0 to 31.0 at% of nonmagnetic oxide based on the total volume of the metal components,
the lowermost magnetic layer body of the two or more magnetic layer body portions is formed on the non-magnetic initial intermediate layer,
the nonmagnetic intermediate layer is disposed between the magnetic layer main body portions, and the magnetic layer main body portions adjacent to each other across the nonmagnetic intermediate layer are ferromagnetically coupled to each other,
the non-magnetic grain boundary material of the initial magnetic layer contains at least one of Zn oxide and Ta oxide.
9. The in-plane magnetization film multilayer structure according to claim 6 or 8, wherein the nonmagnetic initial intermediate layer is composed of Ru or a Ru alloy.
10. The in-plane magnetization film multilayer structure according to claim 6 or 8, wherein a thickness of the nonmagnetic initial intermediate layer is 0.3nm or more and 2nm or less.
11. The in-plane magnetization film multilayer structure according to claim 7 or 8, wherein the nonmagnetic intermediate layer is composed of Ru or a Ru alloy.
12. The in-plane magnetization film multilayer structure according to claim 7 or 8, wherein a thickness of the nonmagnetic intermediate layer is 0.3nm or more and 2nm or less.
13. The multilayer structure of an in-plane magnetization film according to any one of claims 6 to 8, wherein the initial magnetic layer further contains metallic Fe, and contains metallic Co and metallic Fe in a total amount of 44 atomic% to 82 atomic% and metallic Pt in an amount of 18 atomic% to 56 atomic% with respect to a total amount of metallic components.
14. The in-plane magnetization film multilayer structure according to any one of claims 6 to 8, wherein the nonmagnetic oxide of the magnetic layer main body portion contains boron oxide.
15. The in-plane magnetization film multilayer structure according to any one of claims 6 to 8, wherein the initial magnetic layer is formed on a base layer having a surface roughness of 0.1nm or more and 1.5nm or less.
16. The in-plane magnetization film multilayer structure according to claim 15, wherein the base layer is an insulating layer.
17. A hard bias layer having the in-plane magnetization film according to claim 5.
18. A hard bias layer having the in-plane magnetization film multilayer structure according to claim 16.
19. A magnetoresistance effect element having the hard bias layer according to claim 17.
20. A magnetoresistance effect element having the hard bias layer according to claim 18.
21. A sputtering target for forming an in-plane magnetized film used as at least a part of a hard bias layer of a magneto-resistance effect element by room temperature film formation, characterized in that,
contains metal Co, metal Pt and non-magnetic grain boundary material,
a metal Co of 60 to 82 at% inclusive and a metal Pt of 18 to 40 at% inclusive, based on the total metal components of the sputtering target,
the non-magnetic grain boundary material is contained in an amount of 6 to 30% by volume based on the entire sputtering target,
the non-magnetic grain boundary material contains at least one of Zn oxide and Ta oxide.
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| JP2022138492A JP2024034320A (en) | 2022-08-31 | 2022-08-31 | In-plane magnetized film, in-plane magnetized film multilayer structure, hard bias layer, magnetoresistive element, and sputtering target |
| JP2022-138492 | 2022-08-31 |
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