JP7438845B2 - In-plane magnetized film, in-plane magnetized film multilayer structure, hard bias layer, and magnetoresistive element - Google Patents

Description

The present invention relates to an in-plane magnetized film, an in-plane magnetized film multilayer structure, a hard bias layer, and a magnetoresistive element. Pt-oxide that can achieve magnetic performance of 2.00 memu/cm ² or more without performing film formation by heating the substrate (hereinafter sometimes referred to as heating film formation). a Pt-based in-plane magnetized film, a Pt-oxide-based in-plane magnetized film multilayer structure, a hard bias layer having the in-plane magnetized film or the in-plane magnetized film multilayer structure, and the hard bias layer. This invention relates to a magnetoresistive element. The Pt-oxide-based in-plane magnetization film and the Pt-oxide-based in-plane magnetization film multilayer structure can be used for a hard bias layer of a magnetoresistive element.

If the hard bias layer has a coercive force Hc of 2.00 kOe or more and a residual magnetization Mrt per unit area of 2.00 memu/cm ² or more, it will be more effective than the hard bias layer of the current magnetoresistive element. It is thought that they have coercive force and residual magnetization of the same level or higher.

Note that in this application, the hard bias layer refers to a thin film magnet that applies a bias magnetic field to a magnetic layer that exhibits a magnetoresistive effect (hereinafter sometimes referred to as a free magnetic layer).

Further, in this application, metal Co may be simply described as Co, metal Pt may be simply described as Pt, and metal Ru may be simply described as Ru. Further, other metal elements may also be described in the same manner.

Further, in the present application, boron (B) is included in the category of metal elements.

Magnetic sensors are currently used in many fields, and one type of magnetic sensor that is commonly used is a magnetoresistive element.

A magnetoresistive element has a magnetic layer (free magnetic layer) that exhibits a magnetoresistive effect, and a hard bias layer that applies a bias magnetic field to the magnetic layer (free magnetic layer). , it is required to be able to stably apply a magnetic field of a predetermined magnitude or more to the free magnetic layer.

Therefore, the hard bias layer is required to have high coercive force and residual magnetization.

However, the coercive force of the hard bias layer of the current magnetoresistive element is about 2 kOe (for example, FIG. 7 of Patent Document 1), and it is desired to realize a coercive force higher than this.

Further, it is desired that the residual magnetization per unit area is about 2 memu/cm ² or more (for example, paragraph 0007 of Patent Document 2).

As a technique that may be able to cope with these problems, there is, for example, a technique described in Patent Document 3. The technology described in Patent Document 3 includes a seed layer (Ta layer) provided between a sensor stack (a stack including a free magnetic layer) and a hard bias layer; A composite seed layer (including a metal layer with a cubic (111) crystal structure or a hexagonal close-packed (001) crystal structure) orients the magnetic material so that its easy axis points in the longitudinal direction, and increases the coercive force of the hard bias layer. This is a method that attempts to improve the However, it does not satisfy the above-mentioned magnetic properties desired for a hard bias layer. Furthermore, in this method, it is necessary to increase the thickness of the seed layer provided between the sensor stack and the hard bias layer in order to improve the coercive force. Therefore, this structure also has the problem that the magnetic field applied to the free magnetic layer in the sensor stack becomes weak.

Further, Patent Document 4 describes the use of FePt as a magnetic material used for a hard bias layer, a FePt hard bias layer having a Pt or Fe seed layer, and a capping layer of Pt or Fe. 4 proposes a structure in which Pt or Fe in the seed layer and capping layer and FePt in the hard bias layer mix with each other during annealing at an annealing temperature of approximately 250 to 350°C. . However, in the heating process required to form this hard bias layer, it is necessary to consider the influence on other films already stacked, and this heating process is a process that should be avoided as much as possible.

Patent Document 5 shows that the annealing temperature is optimized and it is possible to lower the annealing temperature to about 200°C, and the coercive force of the hard bias layer is 3.5 kOe or more. However, the residual magnetization per unit area is about 1.2 memu/cm ² , which does not satisfy the above-mentioned magnetic properties desired for a hard bias layer.

Patent Document 6 describes a magnetic recording medium for longitudinal recording, the magnetic layer of which includes ferromagnetic crystal grains having a hexagonal close-packed structure and surrounding non-magnetic grain boundaries mainly made of oxides. However, there is no case where such a granular structure has been used for a hard bias layer of a magnetoresistive element. Furthermore, the technology described in Patent Document 6 aims to reduce the signal-to-noise ratio, which is a problem of magnetic recording media, and multilayers the magnetic layers by using a non-magnetic layer between the magnetic layers. The upper and lower magnetic layers have antiferromagnetic coupling, and the structure is not suitable for improving the coercive force of the magnetic layer.

Japanese Patent Application Publication No. 2008-283016 Special Publication No. 2008-547150 JP2011-008907A US Patent Application Publication No. 2009/027493A1 Japanese Patent Application Publication No. 2012-216275 Japanese Patent Application Publication No. 2003-178423

When considering application to actual magnetoresistive elements, it is preferable to make the sensor stack (laminate with a free magnetic layer) and hard bias layer as thin as possible, and do not perform thermal deposition. It is preferable.

In order to satisfy this condition and obtain a hard bias layer that exceeds the coercive force (about 2 kOe) and residual magnetization per unit area (about 2 memu/cm ² ) of the hard bias layer of the current magnetoresistive element, The inventor believes that it is necessary to search for elements and compounds different from those used in the current hard bias layer, and also hopes to apply oxides to Pt-based in-plane magnetization films. The inventor thought that this might be promising. Furthermore, when forming a Pt-oxide-based in-plane magnetized film, the Pt-oxide-based in-plane magnetized film is formed on a base film, but since the surface of the base film is uneven, The present inventor believes that by appropriately utilizing the unevenness, it may be possible to form a Pt-oxide-based in-plane magnetized film while minimizing the magnetic interaction between Pt magnetic crystal grains. Ta.

The present invention has been made in view of these points, and has magnetic performance such that the coercive force Hc is 2.00 kOe or more and the residual magnetization Mrt per unit area is 2.00 memu/cm ² or more. It is an object of the present invention to provide an in-plane magnetized film and an in-plane magnetized film multilayer structure that can be achieved without performing thermal film formation, and also to provide an in-plane magnetized film or an in-plane magnetized film multilayer structure that can be achieved without heating. It is also a supplementary object to provide a hard bias layer comprising the hard bias layer, and a magnetoresistive element comprising the hard bias layer.

The present invention solves the above problems using the following in-plane magnetized film, in-plane magnetized film multilayer structure, hard bias layer, and magnetoresistive element.

That is, the first aspect of the in-plane magnetized film according to the present invention is an in-plane magnetized film that is formed on a base film and used as a hard bias layer of a magnetoresistive element, and is made of metal Pt and oxides. and has a thickness of 20 nm or more and 80 nm or less, and contains metal Pt of 20 at% or more and 55 at% or less with respect to the total metal component of the in-plane magnetized film, and the in-plane magnetization is removed from the base film. The in-plane magnetized film is characterized in that the slope of the change in the amount of Pt in the boundary region where the film changes is 8 (1/nm) or more.

Here, regarding the in-plane magnetized film according to the present invention and members such as the base film that are present accompanying it, the wording that refers to the vertical direction means that the base film on which the in-plane magnetized film is laminated is at the lowest position. The meaning and content shall be interpreted based on the state in which the base film is arranged horizontally.

In addition, "the slope of the transition of the amount of Pt in the boundary region transitioning from the base film to the in-plane magnetized film" is the same as "(E) of the Ru base film and the CoPt in-plane magnetized film directly above it" in the [Example] column. It is calculated by the method described in "Analysis of Pt amount transition in cross section in film thickness direction (Examples 2, 6, 9 to 12, Comparative Examples 1, 3, 4)". The same applies to similar descriptions in other parts of this application.

A second aspect of the in-plane magnetized film according to the present invention is an in-plane magnetized film that is formed on a base film and used as a hard bias layer of a magnetoresistive element, and contains metal Pt and an oxide. and contains 20 at% or more of metal Pt and 55 at% or less of the total metal component, and contains a lower magnetic layer provided on the base film, metal Pt and the oxide, an upper magnetic layer containing 20 at% or more and 55 at% or less of metal Pt with respect to the total metal component, and provided on the lower magnetic layer, and the lower magnetic layer has a thickness of 0. The thickness of the in-plane magnetized film including the lower magnetic layer and the upper magnetic layer is 20 nm or more and 80 nm or less, and the lower magnetic layer is thicker than the upper magnetic layer. The in-plane magnetized film having a large content of the oxide and comprising the lower magnetic layer and the upper magnetic layer has a coercive force of 2.00 kOe or more and a residual magnetization per unit area of 2.0 kOe or more. The present invention is an in-plane magnetization film characterized by having an in-plane magnetization of .00 memu/cm ² or more.

The lower magnetic layer may contain the oxide at 25 vol% or more and 35 vol% or less, and the upper magnetic layer may contain the oxide at 5 vol% or more and 15 vol% or less.

The in-plane magnetization film may contain metal Co at 45 at% or more and 80 at% or less based on the total metal components.

The in-plane magnetization film may contain boron from 0.5 at% to 3.5 at% of the total metal components.

The oxide may include at least one of oxides of Ti, Si, W, B, Mo, Ta, and Nb.

A first aspect of the in-plane magnetized film multilayer structure according to the present invention is an in-plane magnetized film multilayer structure that is formed on a base film and used as a hard bias layer of a magnetoresistive element, and has a plurality of planes. It has an internally magnetized film and a nonmagnetic intermediate layer, and the nonmagnetic intermediate layer is arranged between the in-plane magnetized films and is adjacent to each other with the nonmagnetic intermediate layer in between. The in-plane magnetized films are ferromagnetically coupled to each other, and the in-plane magnetized film contains metal Pt and an oxide. Pt containing 20 at% or more and 55 at% or less, the total thickness of the plurality of in-plane magnetized films is 30 nm or more, and a boundary region transitioning from the base film to the in-plane magnetized film directly above the base film. This is a multilayer structure of in-plane magnetized films characterized by a gradient of quantity transition of 8 (1/nm) or more.

A second aspect of the in-plane magnetized film multilayer structure according to the present invention is an in-plane magnetized film multilayer structure that is formed on a base film and used as a hard bias layer of a magnetoresistive element, and has a plurality of planes. It has an internally magnetized film and a nonmagnetic intermediate layer, and the nonmagnetic intermediate layer is arranged between the in-plane magnetized films and is adjacent to each other with the nonmagnetic intermediate layer in between. The in-plane magnetized films are ferromagnetically coupled to each other, and the in-plane magnetized film contains metal Pt and an oxide. 20 at% or more and 55 at% or less, the slope of the transition of Pt amount in the boundary region transitioning from the base film to the in-plane magnetized film directly above the base film is 8 (1/nm) or more; The magnetized film multilayer structure is an in-plane magnetized film multilayer structure characterized by a coercive force of 2.00 kOe or more and a residual magnetization per unit area of 2.00 memu/cm ² or more.

In this application, the nonmagnetic intermediate layer refers to a nonmagnetic layer disposed between in-plane magnetized films.

In this application, ferromagnetic coupling is based on exchange interaction that occurs when the spins of adjacent magnetic layers (here, the in-plane magnetized films) are parallel (in the same direction) with a nonmagnetic intermediate layer in between. It is a combination.

Furthermore, in this application, the "residual magnetization per unit area" of an in-plane magnetized film is the value obtained by multiplying the residual magnetization per unit volume of the in-plane magnetized film by the thickness of the in-plane magnetized film. Yes, "residual magnetization per unit area" of an in-plane magnetized film multilayer structure is the residual magnetization per unit volume of the in-plane magnetized film included in the in-plane magnetized film multilayer structure. It is the value multiplied by the total value of the thickness of the in-plane magnetized films included in .

Preferably, the nonmagnetic intermediate layer is made of Ru or a Ru alloy.

The thickness of the nonmagnetic intermediate layer is typically 0.3 nm or more and 3 nm or less.

The standard thickness of each layer of the in-plane magnetized film is 5 nm or more and 30 nm or less.

The hard bias layer according to the present invention is a hard bias layer characterized by having the above-described in-plane magnetized film or the above-described in-plane magnetized film multilayer structure.

A magnetoresistive element according to the present invention is a magnetoresistive element characterized by having the hard bias layer.

According to the present invention, magnetic performance such as a coercive force Hc of 2.00 kOe or more and a residual magnetization Mrt per unit area of 2.00 memu/cm ² or more can be achieved without thermal film formation. an in-plane magnetized film, an in-plane magnetized film multilayer structure, a hard bias layer having the in-plane magnetized film or the in-plane magnetized film multilayer structure, and a magnetoresistive effect including the hard bias layer. element can be provided.

FIG. 2 is a cross-sectional view schematically showing a state in which the in-plane magnetized film 10 according to the first embodiment of the present invention is applied to a hard bias layer 14 of a magnetoresistive element 12. An enlarged cross-sectional view schematically depicting the in-plane magnetized film 10 together with the base film 40 FIG. 3 is a diagram schematically showing the initial stage of formation of the lower magnetic layer 10A of the in-plane magnetized film 10. FIG. 3 is a diagram schematically showing a stage where the formation of the lower magnetic layer 10A of the in-plane magnetized film 10 has been completed. FIG. 3 is a diagram schematically showing a stage where the formation of the entire upper magnetic layer 10B of the in-plane magnetized film 10 has been completed, and the formation of the entire in-plane magnetized film 10 has been completed. FIG. 3 is a cross-sectional view schematically showing a state in which an in-plane magnetized film multilayer structure 20 according to a second embodiment of the present invention is applied to a hard bias layer 28 of a magnetoresistive element 26. FIG. 3 is a perspective view schematically showing the shape of a thinned sample 60 after being subjected to a thinning process. An example of an observed image obtained by imaging using a scanning transmission electron microscope (observed image of Reference Example 6). Results of line analysis (elemental analysis) performed in the thickness direction (along the black line in FIG. 8) of the in-plane magnetized film of Reference Example 6. FIG. 3 is a perspective view schematically showing the shape of a thinned sample 80 after being subjected to thinning treatment. An example of an observed image obtained by imaging using a scanning transmission electron microscope (observed image of Example 9). Results of line analysis (elemental analysis) performed in the thickness direction (along the black line in FIG. 11) of the in-plane magnetized film of Example 9. An image showing the results of "element mapping for Pt" performed on the square area 200. A graph showing the transition of the amount of Pt in the film thickness direction for Example 9 (vertical axis: normalized amount of Pt, horizontal axis: scanning position). An observation image obtained by imaging a square area 200 using a scanning transmission electron microscope.

(1) First Embodiment (1-1) Overview FIG. 1 shows a state in which an in-plane magnetized film 10 according to a first embodiment of the present invention is applied to a hard bias layer 14 of a magnetoresistive element 12. FIG. 2 is a schematic cross-sectional view. FIG. 2 is an enlarged cross-sectional view schematically depicting the in-plane magnetized film 10 together with the base film 40. Note that in FIG. 1, the description of the base film 40 is omitted.

Here, the configuration shown in FIG. 1 will be explained with a tunnel type magnetoresistive element in mind as the magnetoresistive element 12. However, the in-plane magnetized film 10 according to the first embodiment has a tunnel type magnetoresistive effect. The present invention is not limited to application to the hard bias layer of an element, and can also be applied to, for example, a hard bias layer of a giant magnetoresistive element or an anisotropic magnetoresistive element.

The magnetoresistive element 12 (here, tunnel type magnetoresistive element) consists of two ferromagnetic layers (free magnetic layer 16, pinned layer 54) separated by a very thin non-magnetic tunnel barrier layer (hereinafter referred to as barrier layer 54). 52). The pinned layer 52 has its magnetization direction fixed by being fixed by exchange coupling with an adjacent antiferromagnetic layer (not shown). The free magnetic layer 16 can freely rotate its magnetization direction with respect to the magnetization direction of the pinned layer 52 in the presence of an external magnetic field. When the free magnetic layer 16 is rotated relative to the magnetization direction of the pinned layer 52 by an external magnetic field, the electrical resistance changes, and by detecting this change in electrical resistance, the external magnetic field can be detected.

The hard bias layer 14 has the role of applying a bias magnetic field to the free magnetic layer 16 to stabilize the magnetization direction axis of the free magnetic layer 16. The insulating layer 50 is made of an electrically insulating material, and the sensor current flowing vertically through the sensor stack (free magnetic layer 16, barrier layer 54, pinned layer 52) It has the role of suppressing the flow from being shunted to the hard bias layers 14 on both sides of the barrier layer 54 and pinned layer 52).

As shown in FIG. 1, the in-plane magnetized film 10 according to the first embodiment can be used as a hard bias layer 14 of a magnetoresistive element 12, and a bias magnetic field is applied to a free magnetic layer 16 that exhibits a magnetoresistive effect. can be added.

The in-plane magnetization film 10 according to the first embodiment is a CoPt-oxide-based in-plane magnetization film, which contains metal Co, metal Pt, and an oxide, and has a hard bias of the current magnetoresistive element. It is a single-layer in-plane magnetized film having a coercive force equivalent to or higher than the coercive force of the layer (coercive force of 2.00 kOe or more) and residual magnetization per unit area (2.00 memu/cm ² or more). However, as shown in FIG. 2, among the parts of the in-plane magnetized film 10, a part near the base film 40 (hereinafter sometimes referred to as the lower magnetic layer 10A) is a part of the base film 40 that is located above the base film 40. 40 (hereinafter sometimes referred to as the upper magnetic layer 10B), the oxide content is higher than that in the portion far from the upper magnetic layer 10B. This will be explained in detail in ``Distribution of oxides in the thickness direction and their effects.''

In the first embodiment, the hard bias layer 14 is composed only of the in-plane magnetized film 10 (the lower magnetic layer 10A and the upper magnetic layer 10B) according to the first embodiment.

(1-2) Constituent Components of In-plane Magnetized Film 10 As described above, the in-plane magnetized film 10 according to the first embodiment contains Co and Pt as metal components, and also contains an oxide.

Metallic Co and metal Pt become constituent components of magnetic crystal grains (fine magnets) in an in-plane magnetized film formed by sputtering.

Co is a ferromagnetic metal element and plays a central role in the formation of magnetic crystal grains (microscopic magnets) in the in-plane magnetized film. Aspects of increasing the magnetocrystalline anisotropy constant Ku of CoPt alloy crystal grains (magnetic crystal grains) in an in-plane magnetized film obtained by sputtering and CoPt alloy crystal grains (magnetic crystal grains) in the obtained in-plane magnetized film From the viewpoint of maintaining magnetism, the content ratio of Co in the in-plane magnetized film according to this embodiment is set to 45 at % or more and 80 at % or less with respect to the total metal component in the in-plane magnetized film. Further, from the same point of view, the content ratio of Co in the in-plane magnetized film according to the first embodiment is 45 at% or more and 70 at% or less with respect to the total metal component in the in-plane magnetized film. It is preferably 45 at% or more and 60 at% or less.

Pt has a function of reducing the magnetic moment of the alloy by alloying with Co in a predetermined composition range, and has a role of adjusting the magnetic strength of magnetic crystal grains. On the other hand, it has the function of increasing the coercive force of the in-plane magnetized film by increasing the crystal magnetic anisotropy constant Ku of the CoPt alloy crystal grains (magnetic crystal grains) in the in-plane magnetized film obtained by sputtering. From the viewpoint of increasing the coercive force of the in-plane magnetized film and adjusting the magnetism of the CoPt alloy crystal grains (magnetic crystal grains) in the obtained in-plane magnetized film, the in-plane magnetized film according to the first embodiment The content ratio of Pt in the in-plane magnetized film is set to 20 at% or more and 55 at% or less with respect to the total metal components in the in-plane magnetized film. Further, from the same point of view, the content ratio of Pt in the in-plane magnetized film according to the first embodiment is 30 at% or more and 55 at% or less with respect to the total metal component in the in-plane magnetized film. It is preferably 40 at% or more and 55 at% or less.

Further, as a metal component of the in-plane magnetized film 10 according to the first embodiment, boron B may be included in addition to Co and Pt from 0.5 at% to 3.5 at%. By containing boron B of 0.5 at % or more and 3.5 at % or less, there is an effect of further improving the coercive force Hc of the in-plane magnetized film 10.

The oxide contained in the in-plane magnetization film 10 according to the first embodiment includes at least one of oxides of Ti, Si, W, B, Mo, Ta, and Nb. In the in-plane magnetized film 10, the CoPt alloy magnetic crystal grains are partitioned from each other by the above-mentioned nonmagnetic material made of oxide, forming a granular structure. That is, this granular structure consists of CoPt alloy crystal grains and the crystal grain boundaries of the oxide surrounding the CoPt alloy crystal grains.

Therefore, it is preferable to increase the content of oxide in the in-plane magnetized film 10 because it becomes easier to partition the magnetic crystal grains and make the magnetic crystal grains independent from each other. From this point of view, the content of oxides contained in the in-plane magnetized film 10 according to the first embodiment (the average value of the content of oxides in the entire in-plane magnetized film 10) should be set to 6 vol% or more. is standard, and from the same point of view, the content of oxides contained in the in-plane magnetized film 10 according to the first embodiment (the average value of the content of oxides in the entire in-plane magnetized film 10) ) is preferably 7 vol% or more, more preferably 8 vol% or more.

However, if the content of oxides in the in-plane magnetized film 10 (the average value of the oxide content in the entire in-plane magnetized film 10) becomes too large, the oxides will be absorbed into the CoPt alloy crystal grains (magnetic crystal grains). There is a possibility that the proportion of structures other than hcp in the CoPt alloy crystal grains (magnetic crystal grains) will increase due to the adverse effect on the crystallinity of the CoPt alloy crystal grains (magnetic crystal grains). From this point of view, the content of oxides contained in the in-plane magnetized film 10 according to the first embodiment (the average value of the content of oxides in the entire in-plane magnetized film 10) should be set to 32 vol% or less. is standard, and from the same point of view, the content of oxides contained in the in-plane magnetized film 10 according to the first embodiment is preferably 25 vol% or less, and preferably 20 vol% or less. It is more preferable.

Therefore, in the first embodiment, the content of oxides contained in the in-plane magnetized film 10 (the average value of the content of oxides in the entire in-plane magnetized film 10) is set to 6 vol% or more and 32 vol% or less. The content of oxides contained in the in-plane magnetized film 10 according to the first embodiment (the average value of the oxide content in the entire in-plane magnetized film 10) is It is preferably 7 vol% or more and 25 vol% or less, and more preferably 8 vol% or more and 20 vol% or less.

Furthermore, if WO ₃ or MoO ₃ is included as an oxide, the coercive force Hc of the in-plane magnetized film 10 increases, so it is preferable to include WO ₃ or MoO ₃ as an oxide.

In addition, in the current in-plane magnetization film, single elements such as Cr, W, Ta, and B are used as grain boundary materials that partition CoPt alloy crystal grains (magnetic crystal grains), so the grain boundary materials are It is thought that a certain degree of solid solution is formed in the CoPt alloy. For this reason, it is thought that the CoPt alloy crystal grains (magnetic crystal grains) of the current in-plane magnetized film are adversely affected by crystallinity and have reduced saturation magnetization and residual magnetization, and the current in-plane magnetized film is It is considered that the values of coercive force Hc and residual magnetization are adversely affected.

On the other hand, in the in-plane magnetized film 10 according to the first embodiment, since the grain boundary material is an oxide, the grain boundary The material is difficult to form a solid solution in the CoPt alloy. Therefore, the saturation magnetization and residual magnetization of the CoPt alloy crystal grains (magnetic crystal grains) in the in-plane magnetized film 10 according to the first embodiment become large, and the in-plane magnetized film 10 according to the first embodiment The coercive force Hc and residual magnetization of will increase.

(1-3) Thickness of the in-plane magnetized film 10 When the thickness of the in-plane magnetized film 10 is made thinner, the residual magnetization Mrt per unit area tends to become smaller. As the thickness increases, the coercive force Hc tends to decrease, so from the viewpoint of achieving both, the thickness of the in-plane magnetized film 10 (the combined thickness of the lower magnetic layer 10A and the upper magnetic layer 10B) should be 20 nm or more. It is standard to set it to 80 nm or less.

(1-4) Base film As the base film 40 (see FIG. 2) used when forming the in-plane magnetized film 10 according to the first embodiment, magnetic particles (CoPt alloy particles) of the in-plane magnetized film 10 and A base film made of metal Ru or Ru alloy having the same crystal structure (hexagonal close-packed structure hcp) is suitable. The surface of the base film 40 is uneven, with convex portions 40A and concave portions 40B formed therein.

In order to orderly orient the magnetic crystal grains (CoPt alloy particles) in the laminated in-plane magnetized film 10 in the plane, when a Ru base film or Ru alloy base film is used as the base film 40, the Ru base film or Ru alloy base film is It is preferable that many (10.0) planes or (11.0) planes are arranged on the surface.

Note that the base film used when forming the in-plane magnetized film according to the present invention is not limited to the Ru base film or the Ru alloy base film, and the CoPt magnetic crystal grains of the obtained in-plane magnetized film are Any underlying film can be used as long as it can orient the CoPt magnetic crystal grains and promote magnetic separation of the CoPt magnetic crystal grains.

(1-5) Oxide distribution in the thickness direction of the in-plane magnetized film 10 and its effects As described above, the lower magnetic layer 10A, which is a part of the in-plane magnetized film 10 near the base film 40, (see FIG. 2) has a higher oxide content than the upper magnetic layer 10B (see FIG. 2), which is a portion above it and farther from the base film 40. In the following description, the Ru base film 42 made of metal Ru is used as the base film 40, and the lower magnetic layer 10A of the in-plane magnetized film 10 is formed with a high oxide content (Co-20Pt)-30vol. The following description assumes that a (Co-20Pt)-10vol _{% WO3} target with a low oxide content is used to form the upper magnetic layer 10B of the in-plane magnetized film 10.

In order to increase the oxide content in the lower magnetic layer 10A of the in-plane magnetized film 10 and decrease the oxide content in the upper magnetic layer 10B, first, when producing the in-plane magnetized film 10, the oxide content is After forming the lower magnetic layer 10A with a predetermined thickness using a sputtering target (Co-20Pt)-30vol%WO ₃ with a large oxide content, a sputtering target (Co-20Pt)-10vol%WO ₃ with a small oxide content is used. Then, the upper magnetic layer 10B is formed until the required thickness is reached.

The process of forming the in-plane magnetized film 10 at this time is schematically shown in FIGS. 3 to 5. FIG. 3 is a diagram schematically showing the initial stage of formation of the lower magnetic layer 10A of the in-plane magnetized film 10, and FIG. 4 is a diagram schematically showing the stage when the formation of the lower magnetic layer 10A of the in-plane magnetized film 10 has been completed. 5 is a diagram schematically showing a stage when the entire upper magnetic layer 10B of the in-plane magnetized film 10 has been formed, and the entire in-plane magnetized film 10 has been formed.

When sputtering is performed using a CoPt-WO ₃ sputtering target to form a CoPt-WO ₃ in-plane magnetized film on the Ru base film 42 made of metal Ru, the CoPt alloy, which is the metal component, is attached to the Ru base film 42. The CoPt alloy phase 46 is preferentially precipitated in the convex portions 42A, and the oxide component WO ₃ is precipitated in the concave portions 42B of the Ru base film 42 to form an oxide (WO ₃ ) phase 48. Therefore, an oxide (WO ₃ ) phase 48 is arranged between the convex portions 42A of the Ru base film 42 (concave portions 42B of the Ru base film 42), and the CoPt alloy magnetic crystal grains are magnetically separated from each other. It turns out. In order to fill the recesses 42B of the Ru base film 42 with oxide (WO ₃ ), a large amount of oxide (WO ₃ ) is required. A (Co-20Pt)-30vol%WO ₃ target with a large amount of WO ₃ is used to form 10A. By doing this, in the in-plane magnetized film 10, the recesses 42B of the Ru base film 42 and the spaces between the CoPt alloy magnetic crystal grains are filled with oxide, almost no metal exists, and the CoPt alloy magnetic crystal grains are filled with oxide. Magnetic separation between the two is promoted.

The thickness of the lower magnetic layer 10A with a high oxide content is typically 0.2 nm or more, and should be 0.5 nm or more, from the viewpoint of filling the recesses 42B of the Ru base film 42 with oxides. is preferable, and more preferably 1 nm or more. However, if the thickness of the lower magnetic layer 10A with a high oxide content is made thicker than necessary, the proportion of magnetic crystal grains in the in-plane magnetized film 10 will decrease. , since the coercive force Hc may be affected in the direction in which it decreases, it is standard that the thickness of the lower magnetic layer 10A is 8 nm or less, preferably 7 nm or less, and 5 nm or less. is more preferable.

Therefore, the thickness of the lower magnetic layer 10A with a high oxide content is typically 0.2 nm or more and 8 nm or less, preferably 0.5 nm or more and 7 nm or less, and 1 nm or more and 5 nm or less. It is more preferable.

CoPt alloy, which is a metal component, precipitates preferentially in the convex portions 42A of the Ru base film 42 to form a CoPt alloy phase 46, and WO ₃ , which is an oxide component, precipitates in the concave portions 42B of the Ru base film 42 and is oxidized. The reason why the material (WO ₃ ) phase 48 is formed is that when viewed from the sputtered particles 44 flying onto the Ru base film 42, the recesses 42B of the Ru base film 42 become shadows. This is because the Ru base film 42 is easily solidified, and therefore the oxide is deposited in the recess 42B of the Ru base film 42.

The thickness of the upper magnetic layer 10B with a low oxide content is set so that the total thickness (that is, the thickness of the in-plane magnetized film 10) with the lower magnetic layer 10A with a high oxide content is 20 nm or more and 80 nm or less. It is standard to set it to .

In the lower magnetic layer 10A, the CoPt alloy phase 46 and the oxide (WO ₃ ) phase 48 are separated and formed by the mechanism described above, so that the upper magnetic layer 10B formed on the lower magnetic layer 10A Also, the CoPt alloy phase 46 and the oxide (WO ₃ ) phase 48 are likely to be formed separately, and even in the formation of the upper magnetic layer 10B with a small oxide content, the CoPt alloy phase 46 and the oxide (WO ₃ ) phase 48 are easily formed separately. ) It is likely to be formed separately from phase 48.

As explained above, in forming the lower magnetic layer 10A of the in-plane magnetized film 10 according to the first embodiment, a (Co-20Pt)-30vol%WO ₃ target with a large amount of WO ₃ is used. Therefore, in the in-plane magnetized film 10, oxide components rather than metal components tend to predominately accumulate between CoPt alloy crystal grains (magnetic crystal grains), and oxide components tend to accumulate between CoPt alloy magnetic crystal grains. A physical (WO ₃ ) phase 48 is formed, and there is almost no metal between the CoPt alloy magnetic crystal grains, and the magnetic interaction between the CoPt alloy crystal grains (magnetic crystal grains) is weakened. Therefore, the coercive force Hc can be improved.

The fact that there is almost no metal between the CoPt alloy magnetic crystal grains in the in-plane magnetized film according to the present invention is explained in "(E) Ru base film and the CoPt surface immediately above it" in [Example] described later. This is demonstrated in "Analysis of Pt amount transition in the cross section of the internally magnetized film in the film thickness direction (Examples 2, 6, 9 to 12, Comparative Examples 1, 3, and 4)".

(1-6) Method of forming in-plane magnetized film 10 The in-plane magnetized film 10 according to the first embodiment has a large amount of oxide (WO ₃ ) on the Ru base film 42 (Co-20Pt)- Sputtering is performed using a 30vol%WO ₃ sputtering target to form the lower magnetic layer 10A with a predetermined thickness, and then (Co-20Pt)-10vol%WO ₃ sputtering with a small amount of oxide (WO ₃ ) is performed. Sputtering is performed using a target to form an upper magnetic layer 10B on the lower magnetic layer 10A. Note that heating is not necessary in this film formation process, and the in-plane magnetized film 10 according to the first embodiment can be formed by film formation at room temperature.

(2) Second Embodiment FIG. 6 schematically shows a state in which an in-plane magnetized film multilayer structure 20 according to a second embodiment of the present invention is applied to a hard bias layer 28 of a magnetoresistive element 26. FIG.

The in-plane magnetized film multilayer structure 20 according to the second embodiment will be described below, including the constituent components of the in-plane magnetized film 10, the thickness of the in-plane magnetized film 10, and the materials used when forming the in-plane magnetized film 10 The distribution of oxides in the thickness direction of the base film 40 and the in-plane magnetized film 10, their effects, and the method for forming the in-plane magnetized film 10 have already been explained in "(1) First Embodiment". Therefore, the explanation will be omitted.

As shown in FIG. 6, the in-plane magnetized film multilayer structure 20 according to the second embodiment of the present invention includes a non-magnetic intermediate layer 22 on the in-plane magnetized film 10 according to the first embodiment, and the non-magnetic The structure is such that an additional in-plane magnetized film 24 having the same composition as the upper magnetic layer 10B of the in-plane magnetized film 10 is stacked on the intermediate layer 22. In FIG. 6, only one layer of the additional in-plane magnetized film 24 is stacked, but a plurality of layers of the additional in-plane magnetized film 24 may be stacked with the nonmagnetic intermediate layer 22 interposed therebetween.

In the in-plane magnetized film multilayer structure 20, the thickness of the in-plane magnetized film 10 and the thickness of the additional in-plane magnetized film 24 are typically 5 nm or more and 30 nm or less. The thickness of the additional in-plane magnetized film 24 is preferably from 5 nm to 15 nm, more preferably from 10 nm to 15 nm, from the viewpoint of increasing the coercive force Hc. Further, the total thickness of the in-plane magnetized film 10 and the additional in-plane magnetized film 24 is typically set to 20 nm or more from the viewpoint of making the residual magnetization Mrt per unit area 2.00 meum/cm ² or more. Regarding the upper limit of the total thickness of the in-plane magnetized film 10 and the additional in-plane magnetized film 24, as will be described later, adjacent in-plane magnetized films 10 separated by the interposition of the non-magnetic intermediate layer 22 The additional in-plane magnetized film 24 performs ferromagnetic coupling, and adjacent additional in-plane magnetized films 24 separated by the intervening non-magnetic intermediate layer 22 perform ferromagnetic coupling, so that the additional in-plane magnetized film 10 and the additional in-plane magnetized film 10 Even if the total thickness of the in-plane magnetized film 24 increases, the coercive force Hc does not theoretically decrease, and there is no upper limit. In fact, it has been confirmed by Examples described below that the coercive force Hc is 2.00 kOe or more when the total thickness of the in-plane magnetized film 10 and the additional in-plane magnetized film 24 is up to 60 nm.

The in-plane magnetized film multilayer structure 20 according to the second embodiment can be used as the hard bias layer 28 of the magnetoresistive element 26, and can apply a bias magnetic field to the free magnetic layer 16 that exhibits the magnetoresistive effect. .

The non-magnetic intermediate layer 22 is interposed between the in-plane magnetized film 10 and the additional in-plane magnetized film 24 and between the additional in-plane magnetized films 24 to separate the in-plane magnetized film 10 and the additional in-plane magnetized film 24. It also has the role of separating the additional in-plane magnetized films 24 from each other to form a multilayer in-plane magnetized film. By interposing the nonmagnetic intermediate layer 22 and forming a multilayer in-plane magnetized film, it is possible to further improve the coercive force Hc while maintaining the value of residual magnetization Mrt per unit area.

The in-plane magnetized film 10 and the additional in-plane magnetized film 24, which are separated by the interposition of the nonmagnetic intermediate layer 22, and the additional in-plane magnetized films 24 are arranged so that their spins are parallel (in the same direction). By arranging them in this way, the in-plane magnetized film 10 and the additional in-plane magnetized film 24, which are separated by the interposition of the non-magnetic intermediate layer 22, and the additional in-plane magnetized films 24 are ferromagnetically coupled. The in-plane magnetized film multilayer structure 20 can improve the coercive force Hc while maintaining the value of residual magnetization Mrt per unit area, and can exhibit a good coercive force Hc.

The metal used for the non-magnetic intermediate layer 22 is a metal having the same crystal structure as the CoPt alloy magnetic crystal grains (hexagonal close-packed structure hcp) from the viewpoint of not damaging the crystal structure of the CoPt alloy magnetic crystal grains. Specifically, as the non-magnetic intermediate layer 22, metal Ru or Ru alloy having the same crystal structure (hexagonal close-packed structure hcp) as the crystal structure of the CoPt alloy magnetic crystal grains in the in-plane magnetized film 10 is preferably used. Can be used.

When the metal used for the non-magnetic intermediate layer 22 is a Ru alloy, specifically, for example, Cr, Pt, and Co can be used as additive elements. It is preferable to set the range to a close-packed structure hcp.

A bulk sample of Ru alloy was prepared by arc melting, and X-ray diffraction peak analysis was performed using an X-ray diffraction device (XRD: SmartLab, manufactured by Rigaku Corporation). At 50 at%, a mixed phase of hexagonal close-packed structure hcp and _RuCr2 was confirmed, so when using RuCr alloy for the non-magnetic intermediate layer 22, it is appropriate that the amount of Cr added be less than 50 at%. , is preferably less than 40 at%, more preferably less than 30 at%. Furthermore, in the RuPt alloy, when the amount of Pt added was 15 at%, a mixed phase of a hexagonal close-packed structure hcp and a face-centered cubic structure derived from Pt was confirmed. When used, the amount of Pt added is suitably less than 15 at%, preferably less than 12.5 at%, and more preferably less than 10 at%. In addition, RuCo alloys form a hexagonal close-packed structure hcp regardless of the amount of Co added, but if 40 at% or more of Co is added, it becomes a magnetic material, so it is recommended that the amount of Co added be less than 40 at%. It is suitable and preferably less than 30 at%, more preferably less than 20 at%.

Further, the standard thickness of the nonmagnetic intermediate layer 22 is 0.3 nm or more and 3 nm or less.

Examples, comparative examples, and reference examples for supporting the present invention will be described below.

In (A) below, the thickness of the lower magnetic layer of the CoPt-WO ₃ in-plane magnetization film (when the composition ratio of the metal components Co and Pt is Co:Pt=76.6:23.4) In (B) below, the lower magnetic layer of CoPt-WO ₃ in-plane magnetization film (composition ratio of metal components Co and Pt is Co:Pt = 48.0:52.0) In (C) below, an additional in-plane magnetized CoPt-WO ₃ film is stacked on top of the CoPt-WO ₃ in-plane magnetized film via a Ru nonmagnetic intermediate layer. We are investigating the effects of multilayer structure of multilayered in-plane magnetized films.

In addition, in (D) below, the actual composition of the produced CoPt-WO ₃ in-plane magnetized film (composition obtained by composition analysis) and the sputtering target used for producing the CoPt-WO ₃ in-plane magnetized film are shown. In order to confirm the degree of deviation between the composition and the composition, the CoPt--WO ₃ in-plane magnetized films of Reference Examples 1 to 8 were taken up and subjected to composition analysis. As a result, it was found that a discrepancy occurred between the composition of the produced in-plane magnetized film and the composition of the sputtering target used to produce the in-plane magnetized film.

The compositions of the CoPt-WO ₃ in-plane magnetized films in the examples and comparative examples described in (A) to (C) below were determined in (D) below with respect to the composition of the sputtering target used for fabrication. It was calculated by performing calculations to correct the compositional deviation.

In addition, in (E) below, we analyze the transition of Pt amount in the cross section in the film thickness direction of the Ru base film and the CoPt in-plane magnetized film immediately above it, and analyze the boundary area where the Ru base film changes to the CoPt in-plane magnetized film. The slope k (1/nm) of the Pt amount transition was calculated.

<(A) Study on the thickness of the lower magnetic layer (Co:Pt=76.6:23.4) of CoPt-WO ₃ in-plane magnetization film (Examples 1 to 8, Comparative Examples 1 and 2)>
In Examples 1 to 8 and Comparative Examples 1 and 2, among the parts of the CoPt-WO _{3 in-plane magnetized film produced using the (Co-20Pt)-WO 3 sputtering} target, the lower magnetic layer with a high oxide content Experimental data were obtained by varying the thickness of the material. In the produced CoPt-WO ₃ in-plane magnetization film, the WO ₃ content in the lower magnetic layer is 31.1 vol%, and the WO ₃ content in the upper magnetic layer is 10.4 vol%.

In Examples 1 to 6, the thickness of the lower magnetic layer was varied from 0.5 nm to 3 nm in 0.5 nm increments, and in Examples 7 and 8, the thickness of the lower magnetic layer was 5 nm and 7 nm. In Comparative Examples 1 and 2, the thickness of the lower magnetic layer was 0 nm and 10 nm. In any of Examples 1 to 8 and Comparative Examples 1 and 2, the thickness of the in-plane magnetized film (the combined thickness of the lower magnetic layer and the upper magnetic layer) is 30 nm.

This will be explained in detail below.

First, a Ru base film was formed on a Si substrate to a thickness of 60 nm by sputtering using ES-3100W manufactured by Eiko Engineering Co., Ltd. Note that the sputtering equipment used for sputtering in the Examples and Comparative Examples of the present application was used for forming any of the films (Ru underlayer, lower magnetic layer and upper magnetic layer of the in-plane magnetized film, Ru nonmagnetic intermediate layer, additional surface ES-3100W manufactured by Eiko Engineering Co., Ltd. was also used for forming the internally magnetized film, but the name of the apparatus will be omitted below.

In Examples 1 to 8 and Comparative Example 2, a (Co-20Pt)-30vol%WO ₃ sputtering target was placed on the Ru base film so that the lower magnetic layer of the CoPt in-plane magnetization film had a predetermined thickness. An upper magnetic layer of a CoPt in-plane magnetized film is formed on the formed lower magnetic layer by a sputtering method using a (Co-20Pt)-10vol%WO ₃ sputtering target to reduce the thickness of the in-plane magnetized film. It was formed by sputtering so that the thickness (the combined thickness of the lower magnetic layer and the upper magnetic layer) was 30 nm. In Comparative Example 1, a CoPt in-plane magnetization film was sputtered on the Ru base film to a thickness of 30 nm using a (Co-20Pt)-10vol%WO ₃ sputtering target without providing a lower magnetic layer. Formed by law.

In these film-forming processes (the film-forming process of the Ru base film and the lower and upper magnetic layers of the in-plane magnetized film), the substrate was not heated, and film formation was performed at room temperature.

The hysteresis loops of the produced in-plane magnetized films of Examples 1 to 8 and Comparative Examples 1 and 2 were measured using a vibrating magnetometer (VSM: TM-VSM211483-HGC type manufactured by Tamagawa Seisakusho Co., Ltd.) (hereinafter referred to as a vibrating magnetometer). ). The coercive force Hc (kOe) and residual magnetization Mr (memu/cm ³ ) were read from the measured hysteresis loop. Then, the read residual magnetization Mr (memu/cm ³ ) is multiplied by the total thickness of the manufactured CoPt in-plane magnetized film, and the residual magnetization Mr per unit area of the manufactured CoPt-oxide-based in-plane magnetized film is calculated. (memu/cm ² ) was calculated.

In addition, in Examples 2 and 6 and Comparative Example 1, "Analysis of Pt content transition in the film thickness direction cross section of the Ru base film and the CoPt in-plane magnetized film immediately above it" described in (E) below was performed, The "inclination k (1/nm) of the graph showing the transition of the amount of Pt" in the boundary region where the Ru base film changes to the CoPt in-plane magnetization film was determined.

The results of Examples 1 to 8 and Comparative Examples 1 and 2 are shown in Table 1 below.

As can be seen from Table 1, the in-plane magnetized films of Examples 2 and 6 are in-plane magnetized films with a thickness of 30 nm containing metal Co, metal Pt, and oxide, and the metal components (Co, Pt ) is within the scope of the present invention from the viewpoint that the content of Pt is 20 at% or more and 55 at% or less with respect to the total of Magnetic performance including coercive force Hc of 2.00 kOe or more and residual magnetization Mrt per unit area of 2.00 memu/cm ^{2 or} more is achieved by room temperature film formation without substrate heating. .

In the in-plane magnetized films of Examples 2 and 6, the slope of the transition of the amount of Pt in the boundary region where the transition from the base film to the in-plane magnetized film changes is 8 (1/nm) or more, and the CoPt magnetization in the region near the base film is It is estimated that there is almost no amount of metal (Co, Pt) present between the crystal grains. Therefore, it is presumed that the magnetic separation between the CoPt magnetic crystal grains is sufficient, and the in-plane magnetized films of Examples 2 and 6 have a large coercive force Hc of 4.86 kOe and 4.87 kOe. It is thought that it has become.

In addition, the in-plane magnetized films of Examples 1 to 8 are in-plane magnetized films with a thickness of 30 nm that contain metal Co, metal Pt, and oxide, and A lower magnetic layer containing Pt and an oxide, containing 20 at% or more and 55 at% or less of metal Pt with respect to the total metal component, and a lower magnetic layer provided on the base film, and a lower magnetic layer containing metal Pt and the oxide. an upper magnetic layer provided on the lower magnetic layer, containing metal Pt of 20 at% or more and 55 at% or less with respect to the total metal component, and the upper magnetic layer is more oxidized than the upper magnetic layer. The thickness of the lower magnetic layer containing a large amount of carbon is 0.2 nm or more and 8 nm or less, the coercive force Hc is 2.00 kOe or more, and the residual magnetization Mrt per unit area is 2.00 memu/cm ² or more. This magnetic performance is included in the scope of the present invention from the viewpoint that it is achieved by film formation at room temperature without heating the substrate.

On the other hand, it is an in-plane magnetized film with a thickness of 30 nm containing metal Co, metal Pt, and oxide, and the Pt content is 23.3 at% with respect to the total metal components (Co, Pt). The slope of the Pt content transition in the boundary region where the transition from the base film to the in-plane magnetized film is less than 8 (1/nm), and the oxide content in the thickness direction of the in-plane magnetized film is 10.4 vol%. The in-plane magnetized film of Comparative Example 1, which is constant and not included in the scope of the present invention, has a coercive force Hc of 4.64 kOe, and the in-plane magnetized film of Examples 1 to 8, which is included in the scope of the present invention, has a coercive force Hc of 4.64 kOe. It is inferior to the coercive force Hc (4.75 to 4.87 kOe) of In the in-plane magnetized film of Comparative Example 1, the slope of the Pt amount transition in the boundary region where the transition from the base film to the in-plane magnetized film changes is less than 8 (1/nm), and the slope is 8 (1/nm) or more. It is smaller than the in-plane magnetized films of Examples 2 and 6, and the amount of metal (Co, Pt) present between the CoPt magnetic crystal grains is large in the region near the base film. It is thought that the reason for the decrease in the coercive force Hc is that the magnetic separation between the two is insufficient.

Further, the in-plane magnetization film has a thickness of 30 nm and contains metal Co, metal Pt, and oxide, and the content of Pt is 20 at% or more and 55 at% or less with respect to the total of the metal components (Co, Pt). However, the in-plane magnetization film of Comparative Example 2, which has a lower magnetic layer with a high oxide content of 31.1 vol% and is as thick as 10 nm and is not included in the scope of the present invention, has a coercive force Hc of 3.85 kOe. This is significantly inferior to the coercive force Hc (4.75 to 4.87 kOe) of the in-plane magnetized films of Examples 1 to 8. This is thought to be due to the fact that when the thickness of the lower magnetic layer with a high oxide content of 31.1 vol% becomes too thick (10 nm), the proportion of magnetic crystal grains in the in-plane magnetized film becomes relatively small. .

<(B) Study on the thickness of the lower magnetic layer (Co:Pt=48.0:52.0) of CoPt-WO ₃ in-plane magnetization film (Examples 9 and 10, Comparative Example 3)>
In Examples 9 and 10 and Comparative Example 3, among the parts of the CoPt-WO ₃ in-plane magnetized film produced using a (Co-45Pt)-WO ₃ sputtering target, the thickness of the lower magnetic layer with a high oxide content was Experimental data were obtained by varying the In the produced CoPt-WO ₃ in-plane magnetization film, the WO ₃ content in the lower magnetic layer is 30.9 vol%, and the WO ₃ content in the upper magnetic layer is 10.3 vol%.

In Examples 9 and 10, the thickness of the lower magnetic layer was 1 nm and 3 nm. In Comparative Example 3, the thickness of the lower magnetic layer was 0 nm. In each of Examples 9 and 10 and Comparative Example 3, the thickness of the in-plane magnetized film (the combined thickness of the lower magnetic layer and the upper magnetic layer) is 30 nm.

This will be explained in detail below.

First, a Ru base film was formed on a Si substrate to a thickness of 60 nm by sputtering.

In Examples 9 and 10, the lower magnetic layer of the CoPt in-plane magnetization film was sputtered onto the Ru base film to a predetermined thickness using a (Co-45Pt)-30vol%WO ₃ sputtering target. An upper magnetic layer of a CoPt in-plane magnetized film was formed on the lower magnetic layer formed by using a (Co-45Pt)-10vol%WO ₃ sputtering target to reduce the thickness of the in-plane magnetized film (lower magnetic layer). It was formed by sputtering so that the combined thickness of the magnetic layer and the upper magnetic layer was 30 nm. In Comparative Example 3, a CoPt in-plane magnetization film was sputtered on the Ru base film to a thickness of 30 nm using a (Co-45Pt)-10vol%WO ₃ sputtering target without providing a lower magnetic layer. Formed by law.

In these film-forming processes (the film-forming process of the Ru base film and the lower and upper magnetic layers of the in-plane magnetized film), the substrate was not heated, and film formation was performed at room temperature.

The hysteresis loops of the produced in-plane magnetized films of Examples 9 and 10 and Comparative Example 3 were measured using a vibrating magnetometer. The coercive force Hc (kOe) and residual magnetization Mr (memu/cm ³ ) were read from the measured hysteresis loop. Then, the read residual magnetization Mr (memu/cm ³ ) is multiplied by the total thickness of the manufactured CoPt in-plane magnetized film, and the residual magnetization Mr per unit area of the manufactured CoPt-oxide-based in-plane magnetized film is calculated. (memu/cm ² ) was calculated.

In addition, we performed the "Analysis of the Pt content transition in the film thickness direction cross section of the Ru base film and the CoPt in-plane magnetized film directly above it" described in (E) below, and the transition from the Ru base film to the CoPt in-plane magnetized film was performed. The "inclination k (1/nm) of the graph showing the transition of the amount of Pt" in the boundary region was determined.

The results of Examples 9 and 10 and Comparative Example 3 are shown in Table 2 below.

As can be seen from Table 2, the in-plane magnetized films of Examples 9 and 10 are in-plane magnetized films with a thickness of 30 nm containing metal Co, metal Pt, and oxide, and the metal components (Co, Pt ) is 20 at% or more and 55 at% or less, and the slope of the Pt content transition in the boundary region transitioning from the base film to the in-plane magnetized film is 8 (1/nm) or more, Room-temperature film formation without substrate heating, which is within the scope of the present invention, has magnetic performance such that the coercive force Hc is 2.00 kOe or more and the residual magnetization Mrt per unit area is 2.00 memu/cm ² or more. This has been realized.

The in-plane magnetized films of Examples 9 and 10 have a slope of 8 (1/nm) or more in the Pt amount transition in the boundary region where the base film changes to the in-plane magnetized film, and the CoPt magnetization in the region near the base film is It is estimated that there is almost no amount of metal (Co, Pt) present between the crystal grains. Therefore, it is presumed that the magnetic separation between the CoPt magnetic crystal grains is sufficient, and the in-plane magnetized films of Examples 9 and 10 have a large coercive force Hc of 5.39 kOe. Conceivable.

In addition, the in-plane magnetized films of Examples 9 and 10 are in-plane magnetized films with a thickness of 30 nm that contain metal Co, metal Pt, and oxide, and A lower magnetic layer containing Pt and an oxide, containing 20 at% or more and 55 at% or less of metal Pt with respect to the total metal component, and a lower magnetic layer provided on the base film, and a lower magnetic layer containing metal Pt and the oxide. an upper magnetic layer provided on the lower magnetic layer, containing metal Pt of 20 at% or more and 55 at% or less with respect to the total metal component, and the upper magnetic layer is more oxidized than the upper magnetic layer. The thickness of the lower magnetic layer containing a large amount of carbon is 0.2 nm or more and 8 nm or less, the coercive force Hc is 2.00 kOe or more, and the residual magnetization Mrt per unit area is 2.00 memu/cm ² or more. The scope of the present invention also falls within the scope of the present invention from the viewpoint that this magnetic performance is achieved by film formation at room temperature without heating the substrate.

On the other hand, it is an in-plane magnetized film with a thickness of 30 nm containing metal Co, metal Pt, and oxide, and the Pt content is 51.8 at% with respect to the total metal components (Co, Pt). The in-plane magnetized film of Comparative Example 3, which has a constant oxide content of 10.3 vol% in the thickness direction of the in-plane magnetized film and is not included in the scope of the present invention, has a coercive force Hc of 5.31 kOe. This is inferior to the coercive force Hc (5.39 kOe) of the in-plane magnetized films of Examples 9 and 10, which are included in the scope of the present invention. In the in-plane magnetized film of Comparative Example 3, the slope of the Pt amount transition in the boundary region where it changes from the base film to the in-plane magnetized film is less than 8 (1/nm), and the slope is 8 (1/nm) or more. It is smaller than the in-plane magnetized films of Examples 9 and 10, and the amount of metal (Co, Pt) existing between the CoPt magnetic crystal grains is large in the region near the base film. It is thought that the reason for the decrease in the coercive force Hc is that the magnetic separation between the two is insufficient.

<(C) Study on the effect of providing a lower magnetic layer in a CoPt-WO ₃ in-plane magnetized film multilayer structure (Examples 11 and 12, Comparative Example 4)>
The in-plane magnetized film multilayer structure formed in Example 11 had a 15-nm-thick CoPt-WO ₃ in-plane magnetized film ((Co-52.0Pt)-30.9vol%WO ₃ lower magnetic layer with a thickness of 1 nm; (Co-51.8Pt)-10.3vol%WO ₃ (with a thickness of 14 nm), a Ru nonmagnetic intermediate layer with a thickness of 2 nm is formed, and on the Ru nonmagnetic intermediate layer, A 15 nm thick (Co-51.8Pt)-10.3 vol% WO ₃ in-plane magnetization film with an oxide content of 10.3 vol% is stacked, and then a 2 nm thick Ru nonmagnetic intermediate layer and an oxidized (Co-51.8Pt)-10.3vol% WO ₃ in-plane magnetized films with a thickness of 15 nm and a CoPt-WO 3 in-plane magnetized film with a content of 10.3 vol% are stacked, and the total thickness of the CoPt-WO ₃ in-plane magnetized films becomes 60 nm. Repeatedly stacking a 2 nm thick Ru nonmagnetic intermediate layer and a 15 nm thick (Co-51.8Pt)-10.3 vol% WO ₃ in-plane magnetized film with an oxide content of 10.3 vol% until CoPt -WO ₃ It has a multilayer structure with in-plane magnetization films stacked in four layers.

The in-plane magnetized film multilayer structure formed in Example 12 had a 15-nm-thick CoPt-WO ₃ in-plane magnetized film ((Co-52.0Pt)-30.9vol%WO ₃ lower magnetic layer with a thickness of 3 nm; (Co-51.8Pt)-10.3vol%WO ₃ (with a thickness of 12 nm), a Ru non-magnetic intermediate layer with a thickness of 2 nm is formed, and on the Ru non-magnetic intermediate layer, A 15 nm thick (Co-51.8Pt)-10.3 vol% WO ₃ in-plane magnetization film with an oxide content of 10.3 vol% is stacked, and then a 2 nm thick Ru nonmagnetic intermediate layer and an oxidized (Co-51.8Pt)-10.3vol% WO ₃ in-plane magnetized films with a thickness of 15 nm and a CoPt-WO 3 in-plane magnetized film with a content of 10.3 vol% are stacked, and the total thickness of the CoPt-WO ₃ in-plane magnetized films becomes 60 nm. Repeatedly stacking a 2 nm thick Ru nonmagnetic intermediate layer and a 15 nm thick (Co-51.8Pt)-10.3 vol% WO ₃ in-plane magnetized film with an oxide content of 10.3 vol% until CoPt -WO ₃ It has a multilayer structure with in-plane magnetization films stacked in four layers.

The multilayer structure of the in-plane magnetized film formed in Comparative Example 4 consists of forming a 2-nm-thick Ru nonmagnetic intermediate layer on a 15-nm-thick (Co-51.8Pt)-10.3vol%WO ₃ in-plane magnetized film. On the Ru nonmagnetic intermediate layer, a 15 nm thick (Co-51.8Pt)-10.3 vol% WO ₃ in-plane magnetized film with an oxide content of 10.3 vol% was stacked, and further on top of that, A 2 nm thick Ru nonmagnetic intermediate layer and a 15 nm thick (Co-51.8Pt)-10.3 vol% WO ₃ in-plane magnetized film with an oxide content of 10.3 vol % are stacked, and a CoPt-WO ₃ in-plane magnetization film is stacked. A 2 nm thick Ru non-magnetic interlayer and a 15 nm thick (Co-51.8Pt)-10.3 vol% WO ₃ with an oxide content of 10.3 vol% until the total thickness of the magnetized film is 60 nm. It has an in-plane magnetized film multilayer structure in which four layers of CoPt-WO ₃ in-plane magnetized films are stacked by repeating stacking of in-plane magnetized films. In this way, in Comparative Example 4, unlike Examples 11 and 12, in the first layer of CoPt-WO ₃ in-plane magnetization film provided on the Ru base film, the lower magnetic layer with a high oxide content was first formed. An upper magnetic layer having a low oxide content is not formed after the formation of the upper magnetic layer.

This will be explained in detail below.

First, a Ru base film was formed on a Si substrate to a thickness of 60 nm by sputtering.

In Example 11, a (Co-52.0Pt)-30.9vol%WO ₃ in-plane magnetized film (lower magnetic layer) was formed to a thickness of 1 nm on the formed Ru base film by sputtering. On top of that, a (Co-51.8Pt)-10.3vol%WO ₃ in-plane magnetized film (upper magnetic layer) was formed to a thickness of 14 nm by sputtering, and the CoPt-WO ₃ film with a thickness of 15 nm was formed. A Ru nonmagnetic intermediate layer is formed to a thickness of 2 nm on the in-plane magnetized film by a sputtering method (using a Ru 100 at% sputtering target), and sputtering is performed on the formed Ru nonmagnetic intermediate layer with a thickness of 2 nm. A 15 nm thick (Co-51.8Pt)-10.3 vol%WO ₃ in-plane magnetized film was formed by sputtering, and on top of that a 2 nm thick Ru non-magnetic intermediate layer and an oxide content of 10 nm were formed. (Co-51.8Pt)-10.3vol%WO ₃ in-plane magnetized films with a thickness of 15 nm and .3 vol% were stacked by sputtering until the total thickness of the CoPt-WO ₃ in-plane magnetized films reached 60 nm. Repeatedly stacking a 2 nm thick Ru nonmagnetic intermediate layer and a 15 nm thick (Co-51.8Pt)-10.3 vol% WO ₃ in-plane magnetized film with an oxide content of 10.3 vol% by sputtering method, A multilayer structure of in-plane magnetized films was formed by stacking four layers of CoPt-WO ₃ in-plane magnetized films.

In Example 12, a (Co-52.0Pt)-30.9vol%WO ₃ in-plane magnetized film (lower magnetic layer) was formed to a thickness of 3 nm on the formed Ru base film by sputtering. A (Co-51.8Pt)-10.3vol%WO ₃ in-plane magnetized film (upper magnetic layer) was formed on top of the 12 nm thick (Co-51.8Pt)-10.3vol%WO 3 in-plane magnetization film (upper magnetic layer) using a sputtering method, and a 15-nm thick CoPt-WO ₃ in-plane magnetized film was formed on the top by sputtering. A Ru nonmagnetic intermediate layer is formed to a thickness of 2 nm on the magnetized film by sputtering (using a 100 at% Ru sputtering target), and then a 2 nm thick Ru nonmagnetic intermediate layer is formed by sputtering on the formed 2 nm thick Ru nonmagnetic intermediate layer. A 15 nm thick (Co-51.8Pt)-10.3 vol% WO ₃ in-plane magnetized film was formed by sputtering, and on top of that a 2 nm thick Ru nonmagnetic intermediate layer and an oxide content of 10.3 vol. (Co-51.8Pt)-10.3vol%WO ₃ in-plane magnetized films with a thickness of 15 nm were stacked by sputtering until the total thickness of the CoPt-WO ₃ in-plane magnetized films reached 60 nm. _CoPt- A multilayer structure of in-plane magnetized films was formed by stacking four WO ₃ in-plane magnetized films.

In Comparative Example 4, a (Co-51.8Pt)-10.3vol%WO ₃ in-plane magnetized film was formed to a thickness of 15 nm on the formed Ru base film by a sputtering method, and then a sputtering method ( A Ru non-magnetic intermediate layer is formed to a thickness of 2 nm using a sputtering target containing 100 at% Ru (using a sputtering target of 100 at% Ru), and a 15 nm-thick (Co-51.8 Co-51.8 A Pt)-10.3 vol% WO ₃ in-plane magnetization film was formed by sputtering, and on top of that, a 2 nm thick Ru nonmagnetic intermediate layer and a 15 nm thick (Pt)-10.3 vol% WO 3 film with an oxide content of 10.3 vol% A _{2 nm} thick Ru non-magnetic intermediate layer and A 15 nm thick (Co-51.8Pt)-10.3vol% WO ₃ in-plane magnetized film with an oxide content of 10.3 vol% was repeatedly stacked by a sputtering method to form 4 CoPt-WO ₃ in-plane magnetized films. A multilayer structure of in-plane magnetized films was formed by stacking layers. In this way, in Comparative Example 4, unlike Examples 11 and 12, in the first layer of CoPt-WO ₃ in-plane magnetization film provided on the Ru base film, the lower magnetic layer with a high oxide content was first formed. The upper magnetic layer with low oxide content is not formed after the formation of (Co-51.8Pt)-10.3vol%WO _{3 .} It is an in-plane magnetized film.

In the film-forming processes of Examples 11 and 12 and Comparative Example 4 (the film-forming process of the Ru base film, CoPt in-plane magnetized film, and Ru nonmagnetic intermediate layer), the substrate was not heated, and the film was formed at room temperature. went.

The hysteresis loops of the CoPt in-plane magnetized film multilayer structures of Examples 11 and 12 and Comparative Example 4 were measured using a vibrating magnetometer. The coercive force Hc (kOe) and residual magnetization Mr (memu/cm ³ ) were read from the measured hysteresis loop. Then, the read residual magnetization Mr (memu/cm ³ ) is multiplied by the total thickness of the formed CoPt in-plane magnetized film, and the residual magnetization Mr per unit area of the CoPt-oxide-based in-plane magnetized film produced is calculated. (memu/cm ² ) was calculated.

In addition, we performed the "Analysis of the Pt content transition in the film thickness direction cross section of the Ru base film and the CoPt in-plane magnetized film directly above it" described in (E) below, and the transition from the Ru base film to the CoPt in-plane magnetized film was performed. The "inclination k (1/nm) of the graph showing the transition of the amount of Pt" in the boundary region was determined.

The results of Examples 11 and 12 and Comparative Example 4 are shown in Table 3 below.

As can be seen from Table 3, in the first layer of CoPt-WO ₃ in-plane magnetization film provided on the Ru base film, the lower magnetic layer (Co-52.0Pt)-30.9vol%WO with a high oxide content is first formed. In the in-plane magnetized film multilayer structure of Examples 11 and 12, in which the upper magnetic layer (Co-51.8Pt)-10.3vol%WO ₃ with a low oxide content is formed after forming ₃ , the first layer is In the CoPt--WO ₃ in-plane magnetized film, the coercive force Hc is approximately 2% larger than that of the in-plane magnetized film multilayer structure formed in Comparative Example 4 in which the oxide content is constant in the thickness direction.

In the in-plane magnetized film multilayer structure of Examples 11 and 12, in the first layer CoPt-WO ₃ in-plane magnetized film, the lower magnetic layer (Co-52.0Pt)-30.9vol%WO with a high oxide content was first formed. After forming ₃ , the upper magnetic layer (Co-51.8Pt)-10.3vol%WO ₃ with low oxide content is formed, so the amount of Pt in the boundary region where the underlying film changes to the in-plane magnetized film decreases. The slope of the transition is 8 (1/nm) or more, and the amount of metal (Co, Pt) existing between the CoPt magnetic crystal grains is decreasing in the region near the base film, and the amount of metal (Co, Pt) existing between the CoPt magnetic crystal grains is decreasing. It is thought that sufficient magnetic separation was achieved, which is why the coercive force Hc became large.

On the other hand, in Comparative Example 4, in which the oxide content is constant in the thickness direction even in the first layer of CoPt-WO ₃ in-plane magnetized film, the change in Pt content in the boundary region where the base film changes to the in-plane magnetized film is The slope is 7.54 (1/nm), which is less than 8 (1/nm), which is smaller than that of the in-plane magnetized films of Examples 11 and 12, which have a slope of 8 or more. The amount of metal (Co, Pt) present between the magnetic crystal grains was large, and the magnetic separation between the CoPt magnetic crystal grains was insufficient, so the coercive force Hc of Comparative Example 4 was lower than that of the example. It is considered that the coercive force Hc of Nos. 11 and 12 is smaller than that of Nos. 11 and 12.

<(D) Composition analysis of in-plane magnetized film (Reference Examples 1 to 8)>
Compositional analysis of the in-plane magnetized films of Reference Examples 1 to 8 was performed to determine the actual composition of the produced CoPt-WO ₃ in-plane magnetized films (composition obtained by composition analysis) and the CoPt-WO ₃ in-plane magnetization. The degree of deviation from the composition of the sputtering target used for film production was confirmed. Hereinafter, the procedure of the compositional analysis method performed on the in-plane magnetized film of Reference Example 6 will be outlined, and then the contents of each procedure will be specifically explained.

[Summary of the procedure] Perform line analysis for compositional analysis in the thickness direction of the in-plane magnetized film, and select locations where the composition has little variation from the locations where the line analysis is performed in the cross-section in the thickness direction of the in-plane magnetized film (Procedure 1-4). Then, an auxiliary line is drawn left and right in the in-plane direction of the in-plane magnetized film where the composition analysis is performed so as to include any measurement point included in a location where the composition has little variation, and for a linear region of 100 nm on the auxiliary line, Perform line analysis for compositional analysis (Step 5). Then, for each detected element, the average value of the detection intensities for the 167 measurement points is calculated to determine the composition of the in-plane magnetized film (Step 6). The contents of steps 1 to 6 will be explained in detail below.

[Step 1] Cut the in-plane magnetized film to be subjected to composition analysis in two parallel planes in a direction perpendicular to the in-plane direction (thickness direction of the in-plane magnetized film), and cut the obtained two parallel planes. The thinning process is performed by the FIB method (μ-sampling method) until the distance between the cut surfaces becomes about 30 nm. The shape of the exfoliated sample 60 after this exfoliating process is schematically shown in FIG. As shown in FIG. 7, the shape of the exfoliated sample 60 is approximately a rectangular parallelepiped. The distance between the two parallel cut planes is about 30 nm, and the length of one side in the in-plane direction of the rectangular parallelepiped thinned sample 60 is about 30 nm, but the lengths of the other two sides are: As long as observation using a scanning transmission electron microscope is possible, it may be determined as appropriate.

[Step 2] The cut surface of the thin sectioned sample 60 obtained in Step 1 (the cut surface in the thickness direction of the in-plane magnetized film) can be observed with a length of 100 nm up to 2 cm (up to 200,000 times magnification) (possible) Take an image using a scanning transmission electron microscope to obtain an observation image. The observation image obtained is rectangular, but the line where the top surface of the in-plane magnetized film to be observed intersects with the cut plane (the cut plane in the thickness direction of the in-plane magnetized film) is the longitudinal axis of the rectangular observation image. Take an image in the same direction. An example of the obtained observed image (observed image of Reference Example 6) is shown in FIG. H-9500 manufactured by Hitachi High-Technologies Corporation was used to obtain an observation image of the in-plane magnetized film.

[Step 3] From the observation image obtained in Step 2, select an arbitrary point included in the in-plane magnetized film (indicated by a black circle 62 in FIG. 8), and from that point, select a position 10 nm left and right in the longitudinal direction of the observation image. A point is attached to each (indicated by a white circle 64 in FIG. 8). Then, line analysis for elemental analysis is performed in the thickness direction of the in-plane magnetized film passing through the point indicated by the black circle 62, and elemental analysis is performed in the thickness direction of the in-plane magnetized film passing through the point indicated by the white circle 64. Line analysis was performed to determine the thickness of the in-plane magnetized film for three straight lines (one straight line in the thickness direction passing through the black circle 62 and two straight lines in the thickness direction passing through the white circle 64). Line analysis (scanning from top to bottom) for elemental analysis is performed in the horizontal direction. When performing line analysis for this elemental analysis, the scanning range of the three straight lines is, in principle, the entire range in the thickness direction of the in-plane magnetized film (if the target of compositional analysis is a multilayer structure of in-plane magnetized films) It is necessary to select one black circle point 62 and two white circle points 64 so that .

In the compositional analysis of the in-plane magnetized film, energy dispersive X-ray analysis (EDX) was employed as the elemental analysis method, and JEM-ARM200F manufactured by JEOL Ltd. was used as the elemental analyzer. The specific analysis conditions were as follows. That is, the X-ray detector was a Si drift detector, the X-ray extraction angle was 21.9°, the solid angle was approximately 0.98 sr, a generally appropriate spectroscopic crystal was used depending on each element, and the measurement time was 1. seconds/point, the scanning point interval was 0.6 nm, and the irradiation beam diameter was approximately 0.2 nmφ. Hereinafter, the conditions described in this paragraph may be referred to as "analysis conditions for procedure 3."

Figure 9 shows the results of line analysis (elemental analysis) conducted along the black line (line in the thickness direction of the in-plane magnetized film passing through the point of black circle 62) in Figure 8 (observation image of Reference Example 6). . In FIG. 9, the vertical axis represents the detection intensity for each element, and the horizontal axis represents the scanning position. Each element shown in the legend in FIG. 9 is an element for which sufficient detection intensity was confirmed. In the case of this reference example 6, the elements for which sufficient detection intensity was confirmed are Co, Pt, W, O, and Ru. Met. Further, in the composition analysis of Reference Example 6, the Kα1 line was selected for the detection of Co and O, and the Lα1 line was selected for the detection of Pt, Ru, and W. In addition, each detection intensity was corrected by subtracting the detection intensity in a blank measurement measured in advance. The final end (lowest end) of the line analysis in FIG. 8 is the Si substrate. Theoretically, nothing other than Si and O due to surface oxidation is detected at this location. Therefore, detection values other than Si and O detected at this location are considered to be unavoidable detection error values in the device, so only when the detection intensity shows a value greater than this value does it indicate the presence of the element in question. I took it as a thing.

Reference Example 6 uses a sputtering target with a composition of (Co-45Pt)-30 vol% WO ₃ and a 1 nm-thick lower magnetic layer with a composition of (Co-52.0Pt)-30.9 vol% WO ₃ . Immediately above, a 29 nm thick upper magnetic layer with a composition of (Co-51.8Pt)-10.3 vol% WO ₃ was formed using a sputtering target with a composition of (Co-45Pt)-10 vol% WO ₃ . went. Further, a 10 nm thick Ta layer was provided as the uppermost layer for the purpose of preventing oxidation of the in-plane magnetization film, and a 100 at % Ta sputtering target was used to form this layer.

As can be seen from the line analysis results shown in Figure 9, Co, Pt, W, and O were mainly found in the in-plane magnetization film, Ru was mainly found in the base film, and Ta was mainly found in the antioxidation layer. It was done. At the interface of each layer in contact with the in-plane magnetized film, a state in which the elements of the vertically adjacent layers are diffused into each other due to the sputtering heat during film formation is partially confirmed. Looking at the distribution of major elements, it was confirmed that the film was formed roughly as designed.

[Procedure 4] From the results of the line analysis performed in Step 3 (line analysis performed for elemental analysis in the thickness direction of the in-plane magnetized film), select points where measurement points with little variation in composition gather. A gathering point of measurement points with little variation in composition is a gathering point of measurement points satisfying the following conditions a to c.

Condition a) It is a measurement point for any one of the three straight line analyzes performed in step 3, and the measurement point has a total detection intensity of Co and Pt exceeding 300 counts.

Condition b) The sum of the detected intensities of Co and Pt at the relevant measurement point is counted as When the sum of the detection intensities of Co and Pt at point ) is taken as Y count,
Y/X-1<0.05
to satisfy.

Condition c) Five or more consecutive measurement points satisfying conditions a and b.

Since the gathering point of the measurement points satisfying the conditions a to c is five or more consecutive measurement points, it becomes a linear region of 0.6 nm×4=2.4 nm or more. Therefore, the gathering point of the measurement points satisfying the conditions a to c is a linear region where at least one of Co and Pt is stably detected in a range of 2.4 nm or more.

[Step 5] Select any one measurement point from the set of measurement points selected in step 4 and use it as a reference point for compositional analysis of the in-plane magnetized film (indicated by a double white circle 66 in FIG. 8). . Then, auxiliary lines (black broken lines 68 in FIG. 8) are drawn left and right in the in-plane direction of the in-plane magnetized film for which compositional analysis is to be performed (the longitudinal direction of the observed image in FIG. 8) so as to include the reference point. A compositional analysis is performed on a 100 nm linear region on the line (indicated by a white broken line 70 in FIG. 8) under the same analysis conditions as in step 3. The white broken line 70, which is the target area for compositional analysis, is the area where the line analysis in the thickness direction is performed (10 nm or more with respect to the white line 64A in FIG. The distance between the two points was set so that they were separated from each other (indicated by the white line 72 with arrows at both ends in FIG. , analysis results at a total of 167 measurement points are obtained.

[Step 6] For each detected element, calculate the average value of the detection intensity (number of counts) for the 167 measurement points. The ratio of the average values of the detection intensities (number of counts) of each detected element becomes the composition ratio of each element in the in-plane magnetized film.

Note that in EDX analysis, it is inevitable that fluorescent X-rays from light elements such as oxygen (O) are absorbed by fluorescent X-rays from heavy elements such as platinum (Pt). In the inner magnetization film, light elements such as oxygen (O) and heavy elements such as platinum (Pt) coexist. Therefore, regarding oxygen (O), it is assumed that all the metals that exist as oxides (W in Reference Example 6) are in an appropriately oxidized state (WO ₃ in Reference Example 6). The composition of

The compositions of the sputtering targets used to fabricate the in-plane magnetized films of Reference Examples 1 to 8 and the results of composition analysis for the in-plane magnetized films of Reference Examples 1 to 8 are shown in Table 4 below.

As shown in Table 4, there is a discrepancy between the composition of the sputtering target and the composition of the in-plane magnetized film produced using the sputtering target. ) The compositions of the CoPt--WO ₃ in-plane magnetized films in the Examples and Comparative Examples described in 1.) were determined.

In FIG. 8, the circles and straight lines indicated by the symbols 62, 64, 64A, 66, 68, 70, and 72 are added for convenience to explain the method of composition analysis, and are not used in actual measurements. It does not necessarily correspond to the location where it was performed.

<(E) Analysis of Pt amount transition in the film thickness direction cross section of the Ru base film and the CoPt in-plane magnetized film directly above it (Examples 2, 6, 9 to 12, Comparative Examples 1, 3, 4)>
In Examples 2, 6, 9 to 12, and Comparative Examples 1, 3, and 4, changes in the amount of Pt in the cross section in the film thickness direction of the Ru base film and the CoPt in-plane magnetized film immediately above it were analyzed. Below, after an overview of the steps of the analysis method used, the content of each step will be specifically explained. Here, explanation will be given based on the analysis results in Example 9.

[Summary of the procedure] Perform line analysis for compositional analysis in the thickness direction of the in-plane magnetized film, and select locations where the composition has little variation from the locations where the line analysis is performed in the cross-section in the thickness direction of the in-plane magnetized film (Procedure 1-4). Then, auxiliary lines are drawn left and right in the in-plane direction of the in-plane magnetized film so as to include arbitrary measurement points included in locations where the composition has little variation. Then, a square region (100 nm long x 100 nm wide) including the auxiliary line and a portion where the amount of Pt in the Ru base film is 0 is set (step 5). Element mapping for Pt is performed for the set square area (100 nm long x 100 nm wide) (step 6). Then, from the elemental mapping results for Pt, the average Pt amount per 1 nm in the vertical direction (film thickness direction) was calculated, and the transition of the Pt amount from the Ru base film to the CoPt in-plane magnetized film was graphed (vertical). Axis: standardized detected amount of Pt, horizontal axis: distance in the vertical direction (film thickness direction) (Step 7). From the graph obtained in step 7, the slope k (1/nm) of the transition of the amount of Pt in the boundary region where the Ru base film changes to the CoPt in-plane magnetization film is calculated (step 8).

If the amount of Pt is small in the concave and convex portions of the surface of the Ru base film, which is the boundary region between the Ru base film and the CoPt in-plane magnetized film (the amount of Pt present in the concavities on the surface of the Ru base film is small), the amount of Pt in the longitudinal direction (film thickness The amount of Pt detected every 1 nm in the direction) suddenly increases in the boundary region where the Ru base film changes to the CoPt in-plane magnetized film (the slope k of the graph showing the change in the amount of Pt increases). In other words, in the boundary region where the Ru underlayer changes to the CoPt in-plane magnetized film, the slope k (1/nm) of the graph showing the change in the amount of Pt is large, which means that the Pt in the recesses on the surface of the Ru underlayer is large. This means that the amount of CoPt alloy magnetic crystal grains in the CoPt in-plane magnetized film formed on the Ru base film is weak. It acts in the direction of increasing the coercive force Hc of the magnetized film.

The contents of steps 1 to 8 will be explained in detail below.

[Step 1] Cut the in-plane magnetized film to be subjected to composition analysis in two parallel planes in a direction perpendicular to the in-plane direction (thickness direction of the in-plane magnetized film), and cut the obtained two parallel planes. The thinning process is performed by the FIB method (μ-sampling method) until the distance between the cut surfaces becomes about 30 nm. The shape of the exfoliated sample 80 after this exfoliating process is schematically shown in FIG. As shown in FIG. 10, the shape of the exfoliated sample 80 is approximately a rectangular parallelepiped. The distance between the two parallel cut planes is about 30 nm, and the length of one side in the in-plane direction of the rectangular parallelepiped thinned sample 80 is about 30 nm, but the lengths of the other two sides are: As long as observation using a scanning transmission electron microscope is possible, it may be determined as appropriate.

[Procedure 2] The cut surface (cut surface in the thickness direction of the in-plane magnetized film) of the thinned sample 80 obtained in Step 1 can be observed with a length of 100 nm magnified to 2 cm (magnified observation up to 200,000 times). (possible) Take an image using a scanning transmission electron microscope to obtain an observation image. The observation image obtained is rectangular, but the line where the top surface of the in-plane magnetized film to be observed intersects the cut plane (the cut plane in the thickness direction of the in-plane magnetized film) is the longitudinal axis of the rectangular observation image. Take an image in the same direction. An example of the obtained observed image (observed image of Example 9) is shown in FIG. To obtain an observation image of the in-plane magnetized film, H-9500 manufactured by Hitachi High-Technologies Corporation was used.

[Step 3] From the observation image obtained in Step 2, select an arbitrary point included in the in-plane magnetized film (indicated by a black circle 82 in FIG. 11), and from that point, select a position 10 nm left and right in the longitudinal direction of the observation image. A point is attached to each (indicated by a white circle 84 in FIG. 11). Then, line analysis for elemental analysis is performed in the thickness direction of the in-plane magnetized film passing through the point indicated by the black circle 82, and elemental analysis is performed in the thickness direction of the in-plane magnetized film passing through the point indicated by the white circle 84. Line analysis for analysis was performed to determine the thickness of the in-plane magnetized film for three straight lines (one straight line in the thickness direction passing through the point of black circle 82 and two straight lines in the thickness direction passing through the point of white circle 84). Line analysis (scanning from top to bottom) for elemental analysis is performed in the horizontal direction. When performing line analysis for this elemental analysis, the scanning range of the three straight lines is, in principle, the entire range in the thickness direction of the in-plane magnetized film (if the target of compositional analysis is a multilayer structure of in-plane magnetized films) It is necessary to select one black circle 82 point and two white circles 84 points so that the total range from the top layer in-plane magnetization film to the bottom layer in-plane magnetization film can be obtained. .

In the compositional analysis of the in-plane magnetized film, energy dispersive X-ray analysis (EDX) was employed as the elemental analysis method, and JEM-ARM200F manufactured by JEOL Ltd. was used as the elemental analyzer. The specific analysis conditions were as follows. That is, the X-ray detector was a Si drift detector, the X-ray extraction angle was 21.9°, the solid angle was approximately 0.98 sr, a generally appropriate spectroscopic crystal was used depending on each element, and the measurement time was 1. seconds/point, the scanning point interval was 0.6 nm, and the irradiation beam diameter was approximately 0.2 nmφ. Hereinafter, the conditions described in this paragraph may be referred to as "analysis conditions for procedure 3."

FIG. 12 shows the results of line analysis (elemental analysis) conducted along the black line (line in the thickness direction of the in-plane magnetized film passing through the point of black circle 82) in FIG. 11 (observation image of Example 9). . In FIG. 12, the vertical axis represents the detection intensity for each element, and the horizontal axis represents the scanning position. Each element shown in the legend in FIG. 12 is an element for which sufficient detection intensity was confirmed. In the case of Example 9, the elements for which sufficient detection intensity was confirmed were Co, Pt, W, O, and Ru. Met. Furthermore, in the composition analysis of Example 9, the Kα1 line was selected for the detection of Co and O, and the Lα1 line was selected for the detection of Pt, Ru, and W. In addition, each detection intensity was corrected by subtracting the detection intensity in a blank measurement measured in advance. The final end (lowest end) of the line analysis in FIG. 11 is the Si substrate. Theoretically, nothing other than Si and O due to surface oxidation is detected at this location. Therefore, detection values other than Si and O detected at this location are considered to be unavoidable detection error values in the device, so only when the detection intensity shows a value greater than this value does it indicate the presence of the element in question. I took it as a thing.

In Example 9, a sputtering target having a composition of (Co-45Pt)-30 vol% WO ₃ was used, and a 1 nm thick lower magnetic layer having a composition of (Co-52.0Pt)-30.9 vol% WO ₃ was provided. Directly above it, a 29 nm thick upper magnetic layer having a composition of (Co-51.8Pt)-10.3 vol% WO ₃ is formed using a sputtering target having a composition of (Co-45Pt)-10 vol% WO ₃ I did it. Furthermore, a 10 nm thick Ta layer was provided as the top layer for the purpose of preventing oxidation of the in-plane magnetization film. A 100 at % Ta sputtering target was used to form this Ta layer.

As can be seen from the line analysis results shown in FIG. 12, Co, Pt, W, and O were mainly found in the in-plane magnetized film. Looking at the distribution of each major element in the in-plane magnetized film, it was confirmed that the film was formed roughly as designed.

[Procedure 4] From the results of the line analysis performed in Step 3 (line analysis performed for elemental analysis in the thickness direction of the in-plane magnetized film), select points where measurement points with little variation in composition gather. A gathering point of measurement points with little variation in composition is a gathering point of measurement points satisfying the following conditions a to c.

Condition a) It is a measurement point for any one of the three straight line analyzes performed in step 3, and the measurement point has a total detection intensity of Co and Pt exceeding 300 counts.

Condition b) The sum of the detected intensities of Co and Pt at the relevant measurement point is counted as When the sum of the detection intensities of Co and Pt at point ) is taken as Y count,
Y/X-1<0.05
to satisfy.

Condition c) There must be 5 or more consecutive measurement points that satisfy conditions a and b.

Since the gathering point of the measurement points satisfying the conditions a to c is five or more consecutive measurement points, it becomes a linear region of 0.6 nm×4=2.4 nm or more. Therefore, the gathering point of the measurement points satisfying the conditions a to c is a linear region where at least one of Co and Pt is stably detected in a range of 2.4 nm or more.

Furthermore, through the above measurements, the position of the CoPt in-plane magnetized film in FIG. 11, which is a cross section in the film thickness direction, can be specified, and at the same time, the base film of the CoPt in-plane magnetized film is a base film whose main element is Ru. You can also confirm that there is.

[Step 5] In FIG. 11, a square region 200 of 100 nm in length and 100 nm in width is defined as a region for performing elemental mapping for Pt.

The horizontal position of the square region 200 is selected to be a range that is 10 nm or more away from both the white line 84A where the line analysis was performed in the vertical direction and the location where the composition analysis was performed in (D) above. A white line 90 with arrows at both ends in FIG. 11 indicates the distance between the square region 200 and the white line 84A, and this distance needs to be 10 nm or more.

The vertical position of the square area 200 is determined by an auxiliary line in the in-plane direction passing through the double white circle 86 (in FIG. (indicated by a black broken line 88), and a region where Pt is not detected in the Ru base film (hereinafter sometimes referred to as a region with zero Pt content).

The area with zero Pt content can be determined using the line analysis result in Step 4. Specifically, the "detected amount of Pt in the area within the Ru base film" can be determined by the "detected amount of Pt in the CoPt in-plane magnetized film". It refers to the "site within the Ru base film" where the value divided by the "maximum value of the amount" is less than 0.01.

[Step 6] The same conditions as the analysis conditions of Step 3 were used, except that the number of captured pixels was 256 x 256, the measurement time was 1 second/point, and the scanning point interval was 1 nm, as determined in Step 5. Pt is detected in the square region 200, and element mapping for Pt is performed. FIG. 13 shows an image showing the results of "elemental mapping for Pt" performed on the square region 200.

[Step 7] From the results of "elemental mapping for Pt" obtained in step 6, calculate the average Pt amount per 1 nm in the longitudinal direction (film thickness direction), and calculate the Pt content from the Ru base film to the CoPt in-plane magnetized film. Obtain a graph showing the amount over time.

Specifically, the average amount of Pt per 1 nm in the vertical direction (film thickness direction) is the average value of the detected amount of Pt in the horizontal direction (in-plane direction) with respect to 1 nm in the vertical direction (film thickness direction). The length of the region in the horizontal direction (in-plane direction) used in calculating the average amount of Pt per 1 nm in the vertical direction (film thickness direction) is 100 nm or more. The obtained average Pt amount per 1 nm in the longitudinal direction (thickness direction) is divided by the "maximum detected amount of Pt in the CoPt in-plane magnetized film" to standardize it. The amount of Pt is hereinafter referred to as the "normalized amount of Pt"). FIG. 14 is a graph (vertical axis: normalized Pt amount, horizontal axis: scanning position) showing the transition of the Pt amount in the film thickness direction for Example 9. The scanning position X indicated by the arrow in FIG. 14 corresponds to the position Y of the white broken line 92, which is the region with zero Pt content in the Ru base film, in FIG. 15 showing the cross section in the film thickness direction of the in-plane magnetized film of Example 9. do.

[Step 8] In Figure 14, when the "normalized Pt amount" is 2%, it is considered the lower limit of Pt detection, and the first plot where the "normalized Pt amount" exceeds 2% is From the scanning position (nm) corresponding to position P (2%) to the scanning position (nm) corresponding to position P (80%) of the first plot where the "normalized Pt amount" exceeds 80% The slope k (1/nm) of the graph showing the transition of the Pt amount is obtained by linearly approximating the data regarding the "normalized Pt amount" in , using the least squares method.

If the amount of Pt is small in the concave and convex portions of the surface of the Ru base film, which is the boundary region between the Ru base film and the CoPt in-plane magnetized film (the amount of Pt present in the concavities on the surface of the Ru base film is small), The amount of Pt rapidly increases in the boundary region where the Ru base film changes to the CoPt in-plane magnetization film (the slope k (1/nm) of the graph showing the change in the amount of Pt increases). This is because CoPt alloy magnetic crystal grains are deposited on the protrusions of the Ru base film, and a large amount of Pt is present in the region above the tips of the protrusions of the Ru base film.

In the boundary region where the Ru base film changes to the CoPt in-plane magnetized film, the slope k (1/nm) of the graph showing the change in the amount of Pt is large, which means that the amount of Pt present in the recesses on the surface of the Ru base film is large. This means that the magnetic coupling between the CoPt alloy magnetic crystal grains in the CoPt in-plane magnetized film formed on the Ru base film is weak, and the coercive force of the CoPt in-plane magnetized film is weak. It acts in the direction of increasing Hc.

Note that in FIG. 11, the circles and straight lines indicated by the symbols 82, 84, 84A, 86, 88, 90, and 200 are added for convenience to explain the method of composition analysis, and are not used in actual measurements. It does not necessarily correspond to the location where it was performed.

The in-plane magnetized film, the in-plane magnetized film multilayer structure, the hard bias layer, and the magnetoresistive element according to the present invention have a coercive force Hc of 2.00 kOe or more and a residual magnetization Mrt per unit area of 2.00 memu. A magnetic performance of /cm ² or higher can be achieved without thermal film formation, and has industrial applicability.

DESCRIPTION OF SYMBOLS 10... In-plane magnetized film 10A... Lower magnetic layer 10B... Upper magnetic layer 12, 26... Magnetoresistive element 14, 28... Hard bias layer 16... Free magnetic layer 20... In-plane magnetized film multilayer structure 22... Nonmagnetic intermediate layer 24... Additional in-plane magnetized film 40... Base film 40A, 42A... Convex portion 40B, 42B... Concave part 42... Ru base film 44... Sputtered particles 46... CoPt alloy phase 48... Oxide (WO ₃ ) phase 50... Insulating layer 52 ... Pinned layer 54 ... Barrier layer 60 ... Thinned sample 62 ... Black circle (any point included in the in-plane magnetized film)
64... White circle (point located 10 nm left and right in the longitudinal direction of the observed image from black circle 62)
64A...White line 66...Double white circle (reference point for compositional analysis of in-plane magnetized film)
68... Black broken line (auxiliary line drawn from the double white circle 66 (reference point) in the longitudinal direction of the observed image)
70... White broken line (100 nm straight line area on black broken line 68 (auxiliary line))
72...White line with arrows at both ends (indicates a distance of 10 nm or more from white line 64A)
80... Thinned sample 82... Black circle (any point included in the in-plane magnetized film)
84... White circle (point located 10 nm left and right in the longitudinal direction of the observed image from black circle 82)
84A...White line 86...Double white circle (reference point for compositional analysis of in-plane magnetized film)
88... Black broken line (auxiliary line drawn from double white circle 86 (reference point) in the longitudinal direction of the observed image)
90...White line with arrows at both ends 92...White broken line 200...Square area

Claims (13)

An in-plane magnetized film formed on a base film having an uneven surface and used as a hard bias layer of a magnetoresistive element,
It contains metal Pt and an oxide, and has a thickness of 20 nm or more and 80 nm or less,
Containing metal Pt of 20 at% or more and 55 at% or less with respect to the total metal component of the in-plane magnetized film,
The distance from the bottom of the concave part of the unevenness of the base film to the top of the convex part of the unevenness is 0.2 nm or more and 1 nm or less,
Pt is not included in the convex portions of the unevenness of the base film,
The slope of the transition of the amount of Pt in the boundary region transitioning from the base film to the in-plane magnetized film is 8 (1/nm) or more,
The in-plane magnetized film has a coercive force of 2.00 kOe or more and a residual magnetization per unit area of 2.00 memu/cm ² or more . An in-plane magnetized film formed on a base film and used as a hard bias layer of a magnetoresistive element,
a lower magnetic layer containing metal Pt and an oxide, containing 20 at% or more and 55 at% or less of metal Pt with respect to the total metal component, and provided on the base film;
an upper magnetic layer containing metal Pt and the oxide, containing 20 at% or more and 55 at% or less of metal Pt with respect to the total metal component, and provided on the lower magnetic layer;
It is equipped with
The thickness of the lower magnetic layer is 0.2 nm or more and 8 nm or less, and the thickness of the in-plane magnetized film comprising the lower magnetic layer and the upper magnetic layer is 20 nm or more and 80 nm or less,
The lower magnetic layer has a higher content of the oxide than the upper magnetic layer,
The in-plane magnetized film comprising the lower magnetic layer and the upper magnetic layer has a coercive force of 2.00 kOe or more and a residual magnetization per unit area of 2.00 memu/cm ² or more. An in-plane magnetized film characterized by: The in-plane magnetized film according to claim 2, wherein the lower magnetic layer contains the oxide at 25 vol% or more and 35 vol% or less, and the upper magnetic layer contains the oxide at 5 vol% or more and 15 vol% or less. . 4. The in-plane magnetized film according to claim 1, wherein the in-plane magnetized film contains metal Co at 45 at% or more and 80 at% or less based on the total metal components. The in-plane magnetization film according to any one of claims 1 to 4, wherein the in-plane magnetization film contains boron from 0.5 at% to 3.5 at% based on the total metal components. film. 6. The in-plane magnetized film according to claim 1, wherein the oxide contains at least one of oxides of Ti, Si, W, B, Mo, Ta, and Nb. An in-plane magnetized film multilayer structure formed on a base film having an uneven surface and used as a hard bias layer of a magnetoresistive element,
a plurality of in-plane magnetized films;
a non-magnetic intermediate layer;
It has
The non-magnetic intermediate layer is disposed between the in-plane magnetized films, and the in-plane magnetized films adjacent to each other with the non-magnetic intermediate layer in between are ferromagnetically coupled to each other,
The in-plane magnetized film is
Contains metal Pt and an oxide,
Containing metal Pt from 20 at% to 55 at% with respect to the total metal component of the in-plane magnetized film,
The total thickness of the plurality of in-plane magnetized films is 30 nm or more,
The distance from the bottom of the concave part of the unevenness of the base film to the top of the convex part of the unevenness is 0.2 nm or more and 1 nm or less,
Pt is not included in the convex portions of the unevenness of the base film,
The slope of the transition of the amount of Pt in the boundary region transitioning from the base film to the in-plane magnetized film directly above the base film is 8 (1/nm) or more,
The in-plane magnetized film multilayer structure has a coercive force of 2.00 kOe or more and a residual magnetization per unit area of 2.00 memu/cm ² or more . An in-plane magnetized film multilayer structure formed on a base film having an uneven surface and used as a hard bias layer of a magnetoresistive element,
a plurality of in-plane magnetized films;
a non-magnetic intermediate layer;
It has
The non-magnetic intermediate layer is disposed between the in-plane magnetized films, and the in-plane magnetized films adjacent to each other with the non-magnetic intermediate layer in between are ferromagnetically coupled to each other,
The in-plane magnetized film is
Contains metal Pt and an oxide,
Containing metal Pt from 20 at% to 55 at% with respect to the total metal component of the in-plane magnetized film,
The distance from the bottom of the concave part of the unevenness of the base film to the top of the convex part of the unevenness is 0.2 nm or more and 1 nm or less,
Pt is not included in the convex portions of the unevenness of the base film,
The slope of the transition of the amount of Pt in the boundary region transitioning from the base film to the in-plane magnetized film directly above the base film is 8 (1/nm) or more,
The in-plane magnetized film multilayer structure has a coercive force of 2.00 kOe or more and a residual magnetization per unit area of 2.00 memu/cm ² or more. 9. The in-plane magnetized film multilayer structure according to claim 7, wherein the nonmagnetic intermediate layer is made of Ru or Ru alloy. The in-plane magnetized film multilayer structure according to any one of claims 7 to 9, wherein the thickness of the nonmagnetic intermediate layer is 0.3 nm or more and 3 nm or less. The in-plane magnetized film multilayer structure according to any one of claims 7 to 10, wherein the thickness of each layer of the in-plane magnetized film is 5 nm or more and 30 nm or less. A hard bias layer comprising the in-plane magnetized film according to any one of claims 1 to 6, or the in-plane magnetized film multilayer structure according to any one of claims 7 to 11. A magnetoresistive element comprising the hard bias layer according to claim 12.

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