Magnetic material film, magnetic-material-film-equipped member, actuator, and sensor

Abstract

[Problem] To provide: a highly magnetized magnetic material film having a thickness of several tens to several hundreds of microns; a magnetic-material-film-equipped member having the magnetic material film; an actuator; and a sensor. [Solution] A magnetic material film 10 includes a main magnetic material layer 20 having at least one or more crystal particles, and the concentration (T / (R+T)) of a transition metal element (T) with respect to the total (R+T) of a rare earth element (R) and the transition metal element (T) in at least one or more crystal particles 22 changes along the thickness direction of the main magnetic material layer 20.

Description

Magnetic film, member with magnetic film, actuator, and sensor

[0001] The present disclosure relates to a magnetic film, a member with a magnetic film, an actuator, and a sensor.

[0002] As various electronic devices continue to become more compact, the development of small devices such as micromotors and microactuators for use in these devices is progressing. The size and performance of these devices are greatly influenced by the dimensions and magnetic properties of the permanent magnets used in the devices. However, conventional high-performance magnets are sintered magnets and bonded magnets. Although sintered magnets have very high magnetic properties, their surface layer deteriorates during processing, making it difficult to process them into shapes with thicknesses of 200 μm or less, which are required for small device applications, while maintaining their properties.

[0003] On the other hand, high-performance permanent magnets that can be formed by sputtering have also been developed, but due to the low film formation rate, it has been difficult to manufacture magnets with thicknesses of 10 μm or more. As a result, it has been difficult to realize high-performance permanent magnet films with thicknesses of around 100 to 200 μm, and from the perspective of miniaturizing devices and improving performance, there has been a demand for magnets with dimensions in this range.

[0004] Patent Document 1 discloses a magnet film in which a hard magnetic material containing SmCo5 is formed to a thickness of 1 to 200 μm on the main surface of a yoke portion containing a soft magnetic material.

[0005] However, the amount of magnetic flux that can be generated from a magnet depends heavily on its volume, so the smaller and thinner the magnet, the less magnetic flux it can generate. On the other hand, the amount of magnetic flux also depends on the magnetization of the magnet. To increase the amount of magnetic flux while still being compact, magnets with high magnetization are needed.

[0006] International Publication No. 2022 / 045260

[0007] The present disclosure has been made in consideration of the above-described circumstances, and its purpose is to provide a magnetic film having a high magnetization in a magnetic film having a thickness of several tens to several hundreds of microns, and a magnetic film-coated member, actuator, and sensor having the magnetic film.

[0008] In order to achieve the above object, a magnetic film according to one aspect of the present disclosure is a magnetic film having rare earth elements essentially containing Sm or Nd, and transition metal elements containing Co or Fe, wherein the magnetic film is a hard magnetic material, and the magnetic film has a main magnetic layer having at least one crystal grain, the concentration (T / (R+T)) of the transition metal element (T) relative to the sum (R+T) of the rare earth element (R) and the transition metal element (T) in the at least one crystal grain varies along the thickness direction of the main magnetic layer, and a first concentration of the transition metal element at a surface side end of the at least one crystal grain close to the surface of the magnetic film differs by a predetermined percentage or more from a second concentration of the transition metal element at a back side end of the at least one crystal grain close to the back side opposite the surface of the magnetic film.

[0009] In a magnetic film according to one aspect of the present disclosure, the concentration of a transition metal element, such as Co, is gradient along the film thickness direction, which allows a magnetic film to be formed that contains more transition metal elements than in the stoichiometric composition while maintaining the crystal structure. This allows for increased magnetization and maintains high coercivity.

[0010] The first concentration may be lower than the second concentration by a predetermined percentage or more. In this case, the concentration of the transition metal element becomes lower on the surface side of the magnetic film, and the concentration of the rare earth element becomes relatively higher, which makes it easier to suppress magnetization reversal from the surface side of the magnetic film, and therefore tends to further improve the coercive force.

[0011] The first concentration may be higher than the second concentration by a predetermined percentage or more. In this case, the concentration of the transition metal element becomes higher on the surface side of the magnetic film, which tends to further improve magnetization and corrosion resistance.

[0012] Preferably, the predetermined ratio is 0.1% or more. For example, a difference in concentration of 0.1% or more tends to increase the effect of improving magnetization.

[0013] The main magnetic layer is made of SmCo5, Sm2Co 17 , SmFe 12 , NdFe 12 , SmFe17 The magnetic film may further contain nitrogen element.

[0014] The magnetic film may further include a sub-magnetic layer in contact with the main magnetic layer. The atomic ratio of the rare earth element contained in the sub-magnetic layer may be different from that of the rare earth element contained in the main magnetic layer. For example, when the rare earth element is represented by R and the transition metal element is represented by T, the main magnetic layer may be composed of RT5, and the sub-magnetic layer may be composed of, for example, Sm2Co. 17 R2T etc. 17 Alternatively, it may be made of R2T7 such as Sm2Co7.

[0015] The thickness of the main magnetic layer is preferably 10 μm or more, and may be 20 μm or more, 30 μm or more, 50 μm or more, or 10 to 300 μm.

[0016] A magnetic film-attached member according to one aspect of the present disclosure includes any one of the magnetic films described above and a base member having a magnetic film formed on its surface. The sub-magnetic layer may be laminated between the base member and the main magnetic layer, and may be, for example, SmCo. 17 R2T etc. 17 The sub-magnetic layer may be formed on the surface of the main magnetic layer facing away from the base member, and in that case may be formed of R2T7 such as Sm2Co7. The sub-magnetic layer may be formed between the base member and the main magnetic layer, and on the surface of the main magnetic layer facing away from the base member.

[0017] A magnetic film-attached member according to one aspect of the present disclosure includes any one of the magnetic films described above and a base member having a magnetic film formed on its back surface. The surface of the base member may contain the same transition metal element as the transition metal element contained in the main magnetic layer. This configuration makes it easier to further increase the concentration gradient between the first concentration and the second concentration. This makes it easier to manufacture a magnetic film having a higher concentration of the transition metal element closer to the base member.

[0018] An actuator according to an aspect of the present disclosure includes any one of the magnetic films described above.

[0019] A sensor according to an aspect of the present disclosure includes any one of the magnetic films described above.

[0020] FIG. 1 is a schematic cross-sectional view of a magnetic film according to an embodiment of the present disclosure. FIG. 2A is a cross-sectional view showing a portion of a manufacturing process for the magnetic film shown in FIG. 1. FIG. 2B is a cross-sectional view showing a subsequent step in the manufacturing process for the magnetic film shown in FIG. 2A. FIG. 2C is a cross-sectional view showing a subsequent step in the manufacturing process for the magnetic film shown in FIG. 2B. FIG. 2D is a schematic cross-sectional view of a magnetic film according to another embodiment of the present disclosure. FIG. 3A is a schematic cross-sectional view of an example of a motor having the magnetic film shown in FIG. 1. FIG. 3B is a schematic cross-sectional view of an example of a linear actuator having the magnetic film shown in FIG. 1. FIG. 3C is a schematic cross-sectional view of an example of a sensor having the magnetic film shown in FIG. 1. FIG. 4 is a cross-sectional SEM image of a magnetic film according to an example of the present disclosure. FIG. 5 is a graph showing the concentration distribution of transition metal elements at measurement points along line V in the thickness direction of the crystal grain shown in FIG. 4. FIG. 6 is an STEM image of the vicinity of the grain boundary in part VI shown in FIG. 4. FIG. 7 is a graph showing the concentration distribution of rare earth elements at measurement points along a virtual line substantially perpendicular to the grain boundary shown in FIG. 6. Fig. 8A is a cross-sectional SEM image of a magnetic film formed on the surface of a base member having a concave curved surface. Fig. 8B is a cross-sectional SEM image of a magnetic film formed on the surface of a base member having a convex curved surface. Fig. 9 is a graph showing the concentration distribution of transition metal elements at measurement points along a line in the thickness direction in a crystal grain in a magnetic film according to an embodiment of the present disclosure.

[0021] The following description will be given based on the embodiments.

[0022] 1, the magnetic film 10 according to this embodiment is a hard magnetic material and is formed on the surface of a substrate 1 serving as a base member. The magnetic film 10 has at least a main magnetic layer 20 and may have sub-magnetic layers 30a and 30b as necessary. The sub-magnetic layer 30a is formed by laminating it between the substrate 1 and the main magnetic layer 20, and another sub-magnetic layer 30b is formed by laminating it on the surface of the main magnetic layer 20 located on the side opposite the substrate 1. In the magnetic film 10 according to this embodiment, the main magnetic layer 20 mainly constitutes the permanent magnet film (hard magnetic film).

[0023] The magnetic film 10, which includes at least the main magnetic layer 20, is a magnetic film containing rare earth elements R essentially containing Sm or Nd, transition metal elements T containing Co or Fe, and optionally containing nitrogen. The rare earth elements R may be Sc, Y, or lanthanides. The transition metal elements T do not include rare earth elements. The transition metal elements T may also be iron-group elements. In addition to rare earth elements and transition metal elements, the magnetic film 10 may also contain, for example, Li, K, Cl, Mo, Ta, Nb, Ti, Cr, or Ni. The main magnetic layer 20 and the optional sub-magnetic layers 30a and 30b preferably contain the same elements, but may have different compositions.

[0024] When the rare earth element is represented by R and the transition metal element is represented by T, the main magnetic layer 20 has the following properties: RT5, RT 17 , R.T. 12 , R2T 17 For example, the main magnetic layer 20 may contain either SmCo5, Sm2Co 17 , SmFe 12 , NdFe 12 , SmFe 17 Preferably, the sub-magnetic layers 30a and 30b are made of either SmCo or N3. Preferably, the atomic ratio of the rare earth element (R) contained in each of the sub-magnetic layers 30a and 30b is different from the atomic ratio of the rare earth element contained in the main magnetic layer 20. For example, if the main magnetic layer 20 is made of SmCo, the sub-magnetic layer 30a should have a composition (for example, SmCo) lower than the content of the rare earth element (R / (R+T)) contained in the main magnetic layer 20. 17 ), and the sub-magnetic layer 30b is preferably composed of a composition (e.g., Sm2Co7) with a higher rare earth element content than the main magnetic layer 20. When the sub-magnetic layers 30a and 30b are present, a large concentration gradient is likely to be formed in the magnetic film 10. Furthermore, it is preferable that the surface of the base member contains the same transition metal element as the transition metal element contained in the main magnetic layer 20.

[0025] Preferably, no intervening layer made of a non-magnetic material, such as an oxide layer, resin layer, or adhesive layer, thicker than 0.5 to 4 nm in resolution observable with a scanning electron microscope (SEM) is present between the substrate 1 and the sub-magnetic layer 30a, between the sub-magnetic layer 30a and the main magnetic layer 20, or between the main magnetic layer 20 and the sub-magnetic layer 30b. However, an intervening layer thinner than 0.5 to 4 nm in resolution may be present. Also, a protective layer made of a non-magnetic material, such as an oxide layer, resin layer, or adhesive layer, may be formed on the surface of the sub-magnetic layer 30b, or on the surface of the main magnetic layer 20 if the sub-magnetic layer 30b is not present.

[0026] The thickness of the protective layer is not particularly limited, but is preferably thin from the viewpoint of maximizing the magnetic flux from the main magnetic layer 20 toward the surface of the magnetic film 10. The lower limit of the thickness of the main magnetic layer 20 is preferably 10 μm or more, 20 μm or more, 30 μm or more, or 50 μm or more from the viewpoint of further improving the surface magnetic flux density. The upper limit of the thickness may be preferably 350 μm or less, 300 μm or less, or 200 μm or less from the viewpoint of miniaturizing a device incorporating the magnetic film 10.

[0027] The thickness of each of the sub-magnetic layers 30a and 30b is preferably smaller than the thickness of the main magnetic layer 20. For example, the thickness of the sub-magnetic layer 30a may be ½, ¼, or ⅛ of the thickness of the main magnetic layer 20. The thickness of the sub-magnetic layer 30b may be ½, ⅓, or ¼ of the thickness of the sub-magnetic layer 30a. The thicknesses of these layers 20, 30a, and 30b can be measured as an average of multiple measurement points in the cross-sectional SEM image shown in FIG. 4, for example.

[0028] In the following description, the main magnetic layer 20 contains SmCo as a main phase, and the sub-magnetic layer 30a contains SmCo. 17 as a main phase, and the sub-magnetic layer 30b contains Sm2Co7 as a main phase.

[0029] SmCo5 has a CaCu5-type crystal structure and is an intermetallic compound of Sm and Co. The ratio of Sm atoms to Co atoms in SmCo5 may deviate from the stoichiometric ratio. For example, when various elements are added to improve magnetic properties, the ratio of Sm atoms to Co atoms in SmCo5 may not necessarily be the stoichiometric ratio. Therefore, as long as SmCo5 has a CaCu5-type crystal structure, the ratio of Sm atoms to Co atoms may deviate from the stoichiometric ratio.

[0030] In this specification, "as the main phase" refers to the phase with the largest area ratio in a cross section substantially perpendicular to the surface of the magnetic film 10. For example, the main magnetic layer 20 may have a phase different from SmCo5, such as another crystalline phase and a grain boundary phase. The proportion of SmCo5 in the SmCo5 film may be, for example, 70 mass % or more, 80 mass % or more, 90 mass % or more, or 95 mass % or more. An example of a different phase is an Sm-rich phase having a higher Sm content than SmCo5.

[0031] The [00L] crystal orientation of SmCo5 is oriented in the thickness direction of the main magnetic layer 20, i.e., in a direction approximately perpendicular to the film surface. L is any natural number. L indicates the same direction in all cases. L is, for example, 2. The [00L] crystal orientation of SmCo5 in the thickness direction of the main magnetic layer 20 means that the orientation degree is 50% or more. This orientation degree is based on the vector-corrected Lotgering method and indicates the ratio of the sum of the diffraction peaks based on the [00L] crystal orientation component to the sum of the diffraction peaks based on the crystal planes (hkl) of SmCo5. The orientation degree is preferably 90% or more, and more preferably 95% or more, because this further improves the surface magnetic flux density of the magnetic film 10. SmCo5 has a high Curie point of 700°C or higher, thereby providing excellent thermal stability.

[0032] Sm2Co 17 is Th2Zn 17 It has a crystalline structure of the type SmCo and is an intermetallic compound of Sm and Co. 17 The ratio of Sm atoms to Co atoms in SmCo may deviate from the stoichiometric ratio. 17The ratio of Sm atoms to Co atoms in SmCo may not necessarily be the stoichiometric ratio if various elements are added to improve magnetic properties, for example. 17 is Th2Zn 17 As long as the crystal structure is of this type, the ratio of Sm atoms to Co atoms may deviate from the stoichiometric ratio.

[0033] The sub-magnetic layer 30a is made of Sm2Co 17 The SmCo alloy may have different phases, such as other crystalline phases and grain boundary phases. 17 SmCo in the membrane 17 The proportion of may be, for example, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0034] The ratio of Sm atoms to Co atoms in the sub-magnetic layer 30b may be 0.28 or more and 0.51 or less. The sub-magnetic layer 30b may be SmCo, SmCo, or SmCo. The sub-magnetic layer 30b may have multiple crystalline phases and grain boundary phases.

[0035] In addition, the main magnetic layer 20 is made of SmFe 17 When N3 is contained as the main phase, Sm2Fe 17 N is Th2Zn 17 It has the following crystal structure and is a compound of Sm, Fe, and N. SmFe 17 The ratio of Sm atoms to Fe atoms to N atoms in N3 may deviate from the stoichiometric ratio. 17 When various elements are added to improve magnetic properties, the ratio of Sm atoms, Fe atoms, and N atoms in N3 may not necessarily be the stoichiometric ratio because the added elements replace Sm and Fe. 17 N3 is Th2Zn 17 As long as the crystal structure is of this type, the ratio of Sm atoms to Fe atoms to N atoms may deviate from the stoichiometric ratio.

[0036] Crystal Grains 22 In this embodiment, as shown in FIG. 1 , the main magnetic layer 20 has a plurality of crystal grains 22. The crystal grains 22 in this embodiment preferably have at least one columnar grain 22a, and may also have non-columnar grains 22b. The columnar grains 22a are classified into penetrating grains 22a1 and non-penetrating grains 22a2. The non-columnar grains 22b are classified into penetrating grains 22b1 and non-penetrating grains 22b2.

[0037] The main magnetic layer 20 of this embodiment may be crystal grains 22 in which columnar grains 22a account for the majority, or may be crystal grains 22 in which non-columnar grains 22b account for the majority. Crystal grains 22 in which columnar grains 22a account for the majority are defined as those in which, in a cross-sectional SEM image of an observation field in which 100 or more crystal grains 22 are observed, 50% or more, preferably 60% or more of the grains are columnar grains 22a. Crystal grains 22 in which non-columnar grains 22b account for the majority are defined as those in which, in a cross-sectional SEM image of an observation field in which 100 or more crystal grains 22 are observed, 50% or more, preferably 60% or more of the grains are non-columnar grains 22b.

[0038] In the following description, the crystal grains 22 will be mainly described as being mostly composed of columnar grains 22a.

[0039] The columnar grains 22a are observed, for example, in a cross-sectional SEM image as shown in Fig. 4, and are defined as crystal grains in which a first length Lc along the thickness direction of the main magnetic layer 20 shown in Fig. 1 is longer than a second length La along a direction substantially perpendicular to the thickness direction. Among the columnar grains 22a, crystal grains that penetrate from the lower surface to the upper surface along the thickness direction of the main magnetic layer 20 are defined as penetrating grains 22a1, and columnar grains 22a that do not penetrate are defined as non-penetrating grains 22a2.

[0040] 1 , crystal grains whose first length Lc along the thickness direction of the main magnetic layer 20 is equal to or shorter than a second length La along a direction substantially perpendicular to the thickness direction are defined as non-columnar grains 22b. Among the non-columnar grains 22b, crystal grains that penetrate from the lower surface to the upper surface along the thickness direction of the main magnetic layer 20 are defined as penetrating grains 22b1, and non-penetrating non-columnar grains 22b are defined as non-penetrating grains 22b2.

[0041] In this embodiment, in a cross-sectional SEM image of the magnetic film 10, for example, the first average value Lc1 of the first lengths Lc of the crystal grains 22 along the thickness direction of the main magnetic layer 20 within an observation range where 100 or more crystal grains 22 are observed is 10 μm or greater. Furthermore, the ratio (Lc1 / La2) of the first average value Lc1 to the second average value La2 of the second lengths La of the crystal grains 22 observed within the same observation range is not particularly limited, but is preferably, for example, 0.5 or greater, 1.1 or greater, or 2.0 or greater. In other words, when Lc1 / La2 is greater than a predetermined value, the ratio of grain length in the thickness direction increases, which is thought to enhance the effect of reducing the demagnetizing field. As a result, the coercivity of the magnetic film 10 can be increased.

[0042] 1, the main magnetic layer 20 has grain boundaries 23 between the columnar grains 22a or between the columnar grains 22a and the non-columnar grains 22b. The thickness of the grain boundaries 23 is not particularly limited, but is, for example, 10 nm or less, preferably 0.5 to 10.0 nm, or preferably 2.0 to 7.0 nm, as shown in FIG.

[0043] 7, the decrease rate, which indicates the rate at which the atomic ratio of the rare earth element (e.g., Sm) at the grain boundary 23 decreases relative to the atomic ratio of the rare earth element inside the crystal grain 22a, is 3% or more. That is, (amount of R inside the grain - amount of R at the grain boundary) / (amount of R inside the grain) is preferably 3% or more, and also preferably 3% to 80% or 3% to 70%. The inside of the crystal grain 22a refers to a location 50 nm or more away from the grain boundary 23 in a direction substantially perpendicular to the longitudinal direction of the grain boundary 23.

[0044] It is thought that the change in composition of the grain boundary 23 probably causes the grain boundary to become amorphous or a microcrystalline structure containing amorphous, resulting in a gap in the anisotropy field. In other words, it is thought that the grain boundary with a small amount of rare earth elements such as Sm pins the motion of the domain wall between adjacent crystal grains 22, preventing the propagation of magnetization reversal, thereby further improving the coercive force.

[0045] In this embodiment, for any of the crystal grains 22 constituting the main magnetic layer 20, for example, the penetrating grain 22a1, the distribution of the concentration (T / (R+T)) of the transition metal element (T) relative to the sum (R+T) of the rare earth element (R) and the transition metal element (T) along the imaginary line V in FIG. 4 changes along the thickness direction, for example, as shown in FIG.

[0046] That is, the first concentration (T1 / (R1+T1)) of the transition metal element at the surface side end 24 of the crystal grain 22a1 close to the surface of the magnetic film 10 is lower by a predetermined percentage (preferably 0.1%) or more than the second concentration (T2 / (R2+T2)) of the transition metal element at the back side end 25 of the crystal grain 22a1 close to the back side (base member side) located opposite the surface of the magnetic film 10.

[0047] Method for Manufacturing the Magnetic Film Next, a method for manufacturing the magnetic film 10 will be described.

[0048] First, a substrate 1 is prepared as a base member. The substrate 1 is not particularly limited, but in order to form the magnetic film 10 on the surface of the substrate 1, at least the surface of the substrate 1 contains the same transition metal element as the transition metal element contained in the main magnetic layer 20. Examples of materials for the substrate 1 include Co, Fe, Ni, Mo, Ta, Nb, FeCo, CoCr, and CoCrMo. For example, if the transition metal element contained in the main magnetic layer 20 is Co or Fe, the surface of the substrate 1 preferably has a Co layer or an Fe layer. Alternatively, the substrate 1 may be a Co substrate or an Fe substrate.

[0049] When a Co substrate is used as the substrate 1, it is preferably a metal Co plate, and the purity of Co in the Co substrate may be 99% by mass or more, or may be 99.998% by mass or more. Another base material may be present below the Co substrate. The thickness of the Co substrate is not particularly limited and can be appropriately selected depending on the application, but may be, for example, 0.01 to 2 mm.

[0050] Next, a detailed description will be given of a method for manufacturing the magnetic film 10 on the surface of the substrate 1. As an example, a description will be given of a case where a Co substrate is used as the substrate 1. First, as shown in FIG. 2A, the substrate 1 made of a Co substrate is prepared.

[0051] Surface 1α of substrate 1 is preferably roughened. For example, the arithmetic mean surface roughness Ra (e.g., JIS B 0601) of the surface of substrate 1 is preferably 0.5 μm or more, more preferably 5.1 μm or more. The upper limit of the arithmetic mean surface roughness Ra of the substrate is not particularly limited, but may be, for example, 50 μm or less, or 29 μm or less. Surface roughness can be measured by known methods. The surface roughness of substrate 1 can be controlled by known methods, such as surface processing methods using sandpaper, sandblasting, barrel polishing, electrolytic polishing, and a combination of photolithography and etching (e.g., wet etching, dry etching, microblasting) to form a desired pattern (e.g., a checkerboard pattern). When sandpaper processing is performed, it is preferable to perform the polishing in a random direction.

[0052] 2B, a SmCo film 10a is formed on the surface of the substrate 1. The SmCo film 10a is preferably produced by, for example, a molten salt immersion method or a method based on the molten salt immersion method. First, the substrate 1 and a reaction solution containing an Sm source and a molten salt are prepared.

[0053] When preparing a reaction solution, a predetermined inorganic salt is first dehydrated by drying. Examples of inorganic salts include KCl (potassium chloride), LiCl (lithium chloride), and NaCl (sodium chloride). One type of inorganic salt may be used, or two or more types of inorganic salts may be used in combination. The dehydrated inorganic salt is heated to a predetermined temperature to melt the inorganic salt (molten salt). The temperature at which the inorganic salt is melted may be determined appropriately depending on the type of inorganic salt used, but is preferably 400°C or higher, more preferably 500°C or higher, and even more preferably 600°C or higher.

[0054] A Sm source is added to the molten salt (molten inorganic salt) to obtain a reaction solution. Examples of the Sm source include metallic Sm and Sm alloys. One type of Sm source may be used, or two or more types of Sm sources may be used. When the total number of moles of the Sm source and the number of moles of the inorganic salt in the reaction solution is taken as 100 mol %, the proportion of the Sm source in the reaction solution is preferably, for example, 0.2 mol % to 6 mol %.

[0055] Next, the reaction solution is brought into contact with the surface of the substrate 1, and the Sm source in the molten salt is reactively diffused onto the surface of the substrate 1, thereby forming a magnetic coating containing Sm on the surface of the substrate 1. This process is referred to as the reactive diffusion process.

[0056] In the reaction-diffusion process, a plate-shaped Co substrate (substrate 1) is immersed in a reaction solution at a predetermined temperature for a predetermined time, and a magnetic coating containing Sm is formed on both sides of the substrate 1. However, if the substrate 1 is immersed directly in the reaction solution, a magnetic coating containing Sm will be formed in areas where a magnetic coating is not required, resulting in a decrease in yield. Therefore, the areas where a magnetic coating is not required may be covered with an inert film to suppress reaction-diffusion.

[0057] For example, it is preferable to form a mask of a high-melting-point material in the unnecessary region. Examples of the high-melting-point material include W, Ta, Nb, Mo, and alloys containing at least one of these elements. The high-melting-point material mask may be formed, for example, by a vapor deposition method. After forming the high-melting-point material mask on the outer peripheral surface and end surface, the substrate 1 is immersed in a reaction solution, whereby the Sm source reacts and diffuses only in the necessary region of the substrate 1, and a magnetic coating containing Sm can be formed.

[0058] In the reaction-diffusion step, the temperature of the reaction solution is maintained at a temperature at which the inorganic salt can remain molten. From the viewpoint of efficiently forming a magnetic coating, the temperature of the reaction solution is preferably 500°C or higher and 900°C or lower, and more preferably 650°C or higher and 800°C or lower. The reaction time may be appropriately set depending on the reaction temperature and the proportion of the Sm source in the reaction solution so that a magnetic coating of the desired thickness can be formed. For example, the reaction time may be 1 hour or higher and 60 hours or lower.

[0059] In this embodiment, the concentration of Sm (an example of a rare earth element) in the reaction solution is not constant between the start and end of the reaction during the reaction-diffusion step, but is controlled so that the Sm concentration at the end of the reaction is 0.5 mol / L or more higher than the start of the reaction. Specifically, the Sm concentration at the start of the reaction may be 0.5 mol / L and the Sm concentration at the end may be 1.5 mol / L. For example, by gradually adding an Sm source to the reaction solution, the Sm concentration in the reaction solution is increased and the concentration distribution of the transition metal element T in the magnetic film is adjusted. The Sm source may be added continuously, intermittently, or all at once.

[0060] The magnetic film formed on the surface of the substrate 1 in the reaction diffusion process is Sm2Co 17The SmCo layer and the SmCo5 layer are precursors. Specifically, the magnetic coating after the reaction-diffusion process preferably contains SmCo, SmCo, SmCo, SmCo, SmCo, SmCo, and Sm as the main phase, and particularly preferably SmCo. SmCo is an intermetallic compound of Sm and Co having an MgCu crystal structure. As long as the main phase SmCo has an MgCu crystal structure, the ratio of Sm atoms to Co atoms in SmCo may deviate slightly from the stoichiometric ratio. For example, when an additive element is added to improve magnetic properties, the ratio of Sm atoms to Co atoms may deviate slightly from the stoichiometric ratio.

[0061] In addition to the main phase, the magnetic coating may contain a heterophase, such as an Sm-rich phase having a higher Sm ratio than SmCo2, and a grain boundary phase. The SmCo2 content in the magnetic coating may be 50 wt% or more, preferably 70 wt% or more, and more preferably 90 wt% or more.

[0062] After the reaction-diffusion step, the substrate 1 on which the magnetic film is formed may be washed with an organic solvent such as ethanol or pure water.

[0063] Next, the substrate 1 on which the magnetic film containing SmCo2 has been formed is heated at a predetermined temperature for a predetermined time (heating step). In this heating step, the reaction between SmCo2 and Co on the surface of the substrate 1 further progresses, and SmCo is released from the surface of the substrate 1 made of Co and the magnetic film 10a made of the SmCo2 layer, as shown in Figure 2C. 17 The sub-magnetic layer 30a is formed from a layer of SmCo5, and the main magnetic layer 20 is formed from a layer of SmCo5. The sub-magnetic layer 30b is also formed on the surface of the main magnetic layer 20.

[0064] The temperature rise rate in the heating step is not particularly limited, and is preferably, for example, 1°C / min or more and 20°C / min or less. The holding temperature (ultimate temperature) is preferably 800°C or more and 1200°C or less, more preferably 850°C or more and 1150°C or less, and even more preferably 900°C or more and 1100°C or less. The holding time at the holding temperature is preferably, for example, 2 hours or more and 48 hours or less. Furthermore, the temperature drop rate during cooling after heating is preferably 5°C / min or more, more preferably 10°C / min or more, and even more preferably 20°C / min or more.

[0065] The atmosphere for the heating step is not particularly limited, but in order to suppress oxidation of the SmCo5 layer, an inert gas atmosphere is preferable. Examples of the inert gas that can be used include Ar gas and N2 gas.

[0066] In this embodiment, after the heating step, the temperature may be lowered to a predetermined temperature and then maintained at that temperature for a predetermined time (low-temperature annealing step). This low-temperature annealing step may cause Co elements to diffuse from the Co in the substrate 1 through the grain boundaries of the SmCo crystals and modulate the two-particle grain boundaries between the SmCo crystal grains. In other words, it is believed that an amorphous phase richer in transition metal (Co) than the main phase crystal grains 22, or a mixed phase of an amorphous phase and a microcrystalline phase, may be more likely to form at the two-particle grain boundaries 23.

[0067] The holding temperature in the low-temperature annealing step is preferably 550°C or higher and 700°C or lower, and more preferably 550°C or higher and 600°C or lower. The holding time in the low-temperature annealing step is preferably, for example, 2 hours or higher and 8 hours or lower. In particular, annealing at 600°C or lower does not cause coarsening of the crystal grains 22 of the main phase, such as the SmCo5 phase, or decomposition of the main phase, but causes diffusion of the element (Co) of the substrate 1 through the two-grain grain boundary 23, which is thought to result in the formation of amorphous two-grain grain boundaries 23 with a thickness of several nanometers. Note that two-grain grain boundaries are formed even when low-temperature annealing is not performed.

[0068] The multilayered magnetic film 10 can be manufactured through the above-mentioned steps (reaction diffusion step, heating step, and low-temperature annealing step). 17 A multilayer structure is obtained by forming a SmCo layer and a SmCo layer in that order on the surface of the substrate 1. When a mask made of a high-melting point material is formed on the surface of the substrate 1, the mask may be removed after the heating step, or the mask may be left in place.

[0069] Furthermore, when an Fe substrate is used as the substrate 1, a magnetic film can be manufactured using the same procedure. When an Fe substrate is used as the substrate 1, it is preferably a metal Fe plate, and the Fe purity in the Fe substrate may be 99% by mass or more, or even 99.998% by mass or more. Another substrate may be present below the Fe substrate. The thickness of the Fe substrate is not particularly limited and can be appropriately selected depending on the application, but can be, for example, 0.01 to 2 mm. Then, by immersing the Fe substrate in the reaction solution described above using the molten salt immersion method, a SmFe2 film can be formed on the surface of the Fe substrate 1.

[0070] The magnetic film formed on the surface of the substrate 1 in the reaction diffusion process is SmFe. 17 It is a precursor of the N3 layer. Specifically, the magnetic coating after the reaction diffusion process preferably contains Sm2Fe7, SmFe3, SmFe2, Sm5Fe2, Sm3Fe, or Sm as the main phase, and particularly preferably SmFe2 as the main phase. SmFe2 is an intermetallic compound of Sm and Fe having an MgCu2-type crystal structure. As long as the main phase SmFe2 has an MgCu2-type crystal structure, the ratio of Sm atoms to Fe atoms in SmFe2 may be slightly deviated from the stoichiometric ratio. For example, when an additive element is added to improve magnetic properties, the ratio of Sm atoms to Fe atoms may be slightly deviated from the stoichiometric ratio.

[0071] By performing heat treatment in an Ar atmosphere in the heating step, Fe elements are diffused from the Fe substrate toward the SmFe2 magnetic film, and the SmFe2 magnetic film is transformed into Sm2Fe. 17 It can be changed into a magnetic film.

[0072] Furthermore, after the heating step and before the low-temperature annealing step, the magnetic film may be nitrided by heating it in a nitrogen atmosphere. Examples of nitrogen atmospheres include ammonia, a mixed gas of ammonia and hydrogen, nitrogen, or a mixed gas of nitrogen and hydrogen. When ammonia is used, the sample can be nitrided in a short time. The flow rate of the gas may be appropriately selected depending on the type of gas and the amount of sample, but may be 10 mL / min or more, 50 mL / min or more, or 200 mL / min or more. The heating temperature is preferably 300°C or more and 600°C or less, and the heating time is preferably 1 to 60 hours. SmFe 17 By nitriding the magnetic film under the above conditions, Sm2Fe with high magnetic properties is obtained. 17 A N3 magnetic film can be obtained.

[0073] The above-described method for manufacturing the magnetic film 10 can be applied not only to the flat substrate 1 but also to the case where the magnetic film 10 is formed on the surface of a base member having various curved surfaces, for example, and can also be applied to the case where the magnetic film 10 is formed on the inner surface of a cylindrical base member.

[0074] Summary of this embodiment In the magnetic film 10 according to this embodiment, the penetrating grains 22a1 of the crystal grains 22 constituting the main magnetic layer 20 have a gradient in the concentration of transition metals such as Co along the film thickness direction. This makes it possible to realize a magnetic film 10 that contains more transition metal than in the stoichiometric composition while maintaining the crystal structure. This allows the magnetization of the magnetic film 10 to be increased. Furthermore, the coercive force can also be maintained at a high level.

[0075] Furthermore, in the magnetic film 10 according to this embodiment, the first concentration (T1 / (R1+T1)) of the transition metal element at the surface-side end 24 of the penetrating particle 22a1 near the surface of the magnetic film 10 is lower by a predetermined percentage (preferably 0.1%) than the second concentration (T2 / (R2+T2)) of the transition metal element at the back-side end 25 of the penetrating particle 22a1 near the back surface (base member side) opposite the surface of the magnetic film 10. In this case, the concentration of the transition metal element T is lower on the surface side of the magnetic film 10, and the concentration of the rare earth element is relatively higher. Since magnetization reversal of the magnetic film 10 occurs from the surface, as in a sintered magnet, increasing the concentration of the rare earth element on the surface of the magnetic film 10 makes it less likely for magnetization reversal to occur, further improving the coercive force. Furthermore, increasing the concentration of the rare earth element on the surface of the magnetic film 10 makes it easier for the concentration of the transition metal element to be higher at the back surface-side end of the magnetic film 10, thereby further improving magnetization.

[0076] Furthermore, in this embodiment, it is preferable that at least one columnar grain 22a, whose first length Lc along the thickness direction of the main magnetic layer 20 is longer than its second length La along a direction substantially perpendicular to the thickness direction, is present within the observation range of the SEM cross section. Furthermore, the first average length (Lc1) of the crystal grains 22 along the thickness direction is 10 μm or more. More preferably, within the observation range of the SEM cross section in which 100 or more crystal grains 22 are observed, the columnar grains 22a are observed in ⅕ or more, ⅔ or more, or ½ or more.

[0077] That is, in the magnetic film 10 of this embodiment, the crystal grains 22 are elongated in the direction of the easy axis of crystalline magnetization. This minimizes the influence of magnetostatic interactions when the magnetization of adjacent grains 22 reverses. As a result, it is possible to reduce the local demagnetizing field, thereby increasing the coercive force of the magnetic film 10. In summary, the crystal grains 22 being long in the thickness direction reduce the local demagnetizing field, improving the coercive force of the magnet (magnetic film). Note that, while crystal grains 22a that are long in the thickness direction are known in sputtered films, it is difficult to manufacture sputtered films of 10 μm or more.

[0078] Furthermore, in this embodiment, the columnar particles 22a have penetrating particles 22a1 whose first length Lc is equal to the thickness of the main magnetic layer 20. The main magnetic layer 20 has penetrating particles 22a1 whose particle length in the thickness direction is the longest, which increases the effect of reducing the demagnetizing field in the magnetic film 10. As a result, the coercive force of the magnetic film 10 is further improved.

[0079] Furthermore, in this embodiment, the magnetic film 10 is magnetized to function as a magnet film, and the surface magnetic flux density of the magnet film is preferably 5 mT or more, more preferably 7 mT or more, and even more preferably 10 mT or more. The surface magnetic flux density of the magnet film can be measured by contacting a Hall element probe with the surface of the magnetic film 10 functioning as a magnet film, tracing the film surface, and converting the output voltage into magnetic flux density.

[0080] In this embodiment, the sub-magnetic layer 30a or the substrate 1 can also function as a yoke for the main magnetic layer 20, which functions as a magnet film. In other words, the surface magnetic flux density of the magnetic film 10 can be improved.

[0081] The present disclosure is not limited to the above-described embodiments, and various modifications can be made within the scope of the present disclosure.

[0082] For example, in an embodiment different from the above-described embodiment, a Co coating is formed on the surface of a base member that does not contain transition metal elements and is used as the substrate 1. Examples of the base member include a Mo plate. The method for forming the Co coating is not particularly limited, but may be electrolytic plating. After forming a SmCo coating on the surface of the substrate 1 by molten salt immersion or a method based on the molten salt immersion method, a Co coating is formed on the surface of the SmCo coating by, for example, electrolytic plating. During the reaction time of the reaction-diffusion step, the concentration of Sm (an example of a rare earth element) in the reaction solution is not constant between the start and end of the reaction. The Sm concentration at the end of the reaction is controlled to be 0.5 mol / L or more lower than the start of the reaction. Subsequently, by heating at a predetermined temperature for a predetermined time, Co diffuses from the surface Co coating into the SmCo coating, forming the magnetic film 10.

[0083] In this embodiment, in the crystal grains 22 of the main magnetic layer 20, a first concentration (T1 / (R1+T1)) of the transition metal element at a surface-side end 24 of the crystal grain 22 close to the surface of the magnetic film 10 is higher by a predetermined percentage (preferably 0.1%) or more than a second concentration (T2 / (R2+T2)) of the transition metal element at a back-side end 25 of the crystal grain 22 close to the back surface opposite the surface of the magnetic film 10. In this embodiment, the concentration of the transition metal element is higher on the surface side of the magnetic film 10, further improving magnetization and corrosion resistance.

[0084] Furthermore, the surface shape of the substrate (magnetic film-coated member) 1 having the magnetic film 10 according to the above-described embodiment on its surface is not limited to the planar shape shown in FIG. 1 . For example, as shown in FIG. 8A , the magnetic film 10 may be formed on the surface of a substrate 1a having a concavely curved surface, or on the surface of a substrate 1b having a convexly curved surface. In either case, it is possible to form a main magnetic layer 20 having elongated columnar grains 22a in the film thickness direction, which is substantially perpendicular to the concave or convex curved surface. That is, it is possible to form a main magnetic layer 20 having elongated columnar grains 22a in the direction substantially perpendicular to the tangent to the curved surface of the substrate 1.

[0085] The magnetic film 10 according to this embodiment may be magnetized to form a magnet film 10A and used in an actuator. For example, it may be formed on the surface of a rotor 1A of a motor 40A shown in FIG. 3A. The magnet film 10A may be disposed so as to face a coil 42A at a predetermined distance.

[0086] Alternatively, the magnetic film 10 according to this embodiment may be magnetized to become a magnet film 10B, and may be formed, for example, on an actuator substrate 1B of a linear actuator 40B shown in FIG. 3B so as to face a coil 42B at a predetermined distance.

[0087] Alternatively, the magnetic film 10 according to this embodiment may be magnetized to become a magnet film 10C and formed, for example, on a detection substrate 1C of a position sensor 40C shown in FIG. 3C so as to face a magnetic sensor 42C at a predetermined distance.

[0088] The present disclosure will be described below based on more detailed examples, but the present disclosure is not limited to these examples.

[0089] Example 1 (Preparation of Substrate) A plurality of flat Co substrates (20×20×1 mm) were prepared as base members.

[0090] (Reaction-Diffusion Process) LiCl was dried and dehydrated. The dehydrated LiCl was heated to 700°C in a metal Mo container using an external heater and melted. Sm metal powder was added to the molten LiCl as an Sm source. The Sm source was added so that the molar ratio of LiCl to Sm was LiCl:Sm = 100.0:1.25. Next, a substrate was immersed in the molten LiCl. The substrate had been washed with acetone in advance. The reaction-diffusion temperature was 700°C, and the reaction-diffusion time was 9 hours. A laminate in which a SmCo2 film was formed on the substrate was obtained by the reaction-diffusion process.

[0091] In the reaction-diffusion step, the Sm concentration in the molten salt was changed so that the Sm concentration in the molten salt was 0.5 mol / L at the start of the reaction and 1.5 mol / L at the end of the reaction. Specifically, the same amount of Sm metal powder was added to the molten salt every hour to gradually change the Sm concentration in the molten salt.

[0092] (Heating Step) The obtained laminate was heated to 1050° C. The temperature increase rate was 0.15° C. / sec. The laminate was then heated at a holding temperature of 1050° C. for 24 hours. The heating step was performed in an Ar gas atmosphere.

[0093] (Low-temperature annealing step) The laminate was cooled to 600°C and then held for 3 hours to perform low-temperature annealing. The temperature drop rate was 20°C / sec, and the atmosphere was Ar gas. The laminate was then cooled without applying a magnetic field to obtain a flat SmCo-based magnet. The temperature drop rate after the low-temperature annealing was 20°C / sec. Using SEM-EDS (Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry, manufactured by OXFORD, product name EX-370 X-MAX50), the structure of the obtained SmCo-based magnet was determined to be SmCo on a Co substrate. 17It was confirmed that the SmCo5 film, the Sm2Co7 film and the SmCo5 film were formed in this order.

[0094] (Magnetic film thickness measurement)

[0095] The resulting SmCo-based magnet film was coated with resin. A portion of the resin was polished to expose the cross section of the SmCo-based magnet film. The exposed cross section was observed using a scanning electron microscope (manufactured by Hitachi High-Tech Corporation, product name SU5000), and the thickness of the main magnetic layer 20 made of SmCo was measured as the film thickness of the magnetic film. The observation magnification was adjusted so that the front and back surfaces of the film being measured were within the field of view. In Example 1, the film thickness of the main magnetic layer 20 was confirmed to be 55±5 μm.

[0096] (Cross-section observation) To visualize the cross section of the magnetic film in the film thickness direction, SEM images were taken from a surface polished approximately parallel to the film thickness direction of the magnetic film, with a field of view of 1 mm or more along the surface direction. The observation magnification was 500x. A portion of the cross-section SEM photograph of Example 1 in Table 1 is shown in Figure 4.

[0097] (Composition Analysis of Crystal Grains) The composition of the crystal grains was analyzed using an EPMA (Electron Probe Micro Analyzer) for the same cross section as in the SEM image.

[0098] Specifically, as shown in FIG. 4 , composition analysis was performed using EPMA at measurement intervals of 8 μm along the imaginary line V of the crystal grain 22 a to obtain the concentration distribution of Co as a transition metal element. The results are shown in FIG. 5 . Furthermore, for the crystal grain 22 a, a first concentration (T1 / (R1+T1)) was determined at the front-side end 24, which is the ratio of Co (atomic number) to the sum of Co as a transition metal element and Sm as a rare earth element (total atomic number). Furthermore, for the same crystal grain 22 a, a second concentration (T2 / (R2+T2)) was determined at the back-side end 25, which is the ratio of Co (atomic number) to the sum of Co as a transition metal element and Sm as a rare earth element (total atomic number).

[0099] The concentration measurement point of the front side end 24 was a position 4 μm inward along the film thickness direction from the front side end of the crystal grain 22, and the concentration measurement point of the back side end 25 was a position 4 μm inward along the film thickness direction from the back side end of the crystal grain 22. Note that the front side end means the end of the crystal grain 22 closest to the front side of the magnetic film 10, and the back side end means the end of the crystal grain 22 closest to the back side of the magnetic film 10.

[0100] Furthermore, the rate at which the first concentration changed compared to the second concentration was calculated as a percentage (Δ(T / (R+T)), and the average of three columnar crystal particles 22a whose entire peripheries were observed in the SEM image is shown in Table 1. In Table 1, a minus sign indicates that the first concentration decreased compared to the second concentration. Taking measurement error into consideration, when the absolute value of Δ(T / (R+T)) was 0.10% or more, it was determined that the difference was equal to or greater than a predetermined rate.

[0101] (Compositional Analysis of Grain Boundaries) A ​​portion of the sample containing grain boundaries, such as portion VI in FIG. 4, was processed using a focused ion beam (FIB) to obtain a thin section with a thickness of 100 nm. Compositional analysis of the crystal grains and grain boundary phases was performed on the thin section using scanning transmission electron microscope-energy dispersive X-ray spectroscopy (STEM-EDS).

[0102] Specifically, as shown in Fig. 6, composition analysis was performed by STEM-EDS from one crystal grain to the other crystal grain, approximately perpendicularly across the grain boundary phase, with measurement intervals of 5 nm, with one of the measurement points located on the two-particle grain boundary, to obtain the rare earth element (Sm) concentration at the two-particle grain boundary. The composition analysis results near the two-particle grain boundary are shown in Fig. 7.

[0103] (Magnetic Properties) The substrate (Co base material) and the sub-magnetic layer were removed by polishing, leaving only the main magnetic layer, and then a pulse magnetic field of 6 T was applied to magnetize the magnetic film, and the remanence and coercivity HcJ were measured using a vibrating sample magnetometer (VSM). The results are shown in Table 1.

[0104]

[0105] Comparative Example 1 A magnetic film was prepared and similar measurements were carried out in the same manner as in Example 1, except that the Sm concentration in the molten salt was controlled to be constant at 1.0 mol / L from the beginning to the end of the reaction in the reaction-diffusion step. The results are shown in Table 1.

[0106] Evaluation 1 From the results in Table 1, it was found that Example 1, in which Δ[T / (R+T)] fell within the predetermined range, was superior to Comparative Example 1 in magnetization and coercivity.

[0107] Example 2 (Preparation of Substrate) A plurality of flat Mo substrates (20×20×1 mm) were prepared as base members.

[0108] (First electrolytic plating step) The acid-washed Mo substrate was immersed in a Co plating bath to form a Co film on the surface of the Mo substrate under the plating conditions of a temperature of 650° C., a current of 0.5 A, and a plating time of 5 minutes.

[0109] (Reaction-diffusion step) In the reaction-diffusion step, the Sm concentration in the molten salt was changed so that the Sm concentration in the molten salt was 1.5 mol / L at the start of the reaction and 0.5 mol / L at the end of the reaction. Specifically, the same amount of LiCl powder was added to the molten salt every hour to gradually change the Sm concentration in the molten salt. Otherwise, the reaction-diffusion step was performed in the same manner as in Example 1.

[0110] (Second Electrolytic Plating Step) A Co film was formed on the surface under the same conditions as in the first electrolytic plating step described above, except that the plating time was set to 15 minutes.

[0111] (Heating Step and Low-Temperature Annealing Step) The obtained laminate was subjected to a heating step and a low-temperature annealing step in the same manner as in Example 1 to form a magnetic film.

[0112] In Example 2, the sub-magnetic layer and the substrate located on the surface side were removed by polishing to leave only the main magnetic layer, and then the magnetization and coercivity were measured in the same manner as in Example 1. The results are shown in Table 2.

[0113]

[0114] (Corrosion Resistance) The magnetic films were subjected to a saturated pressure cooker test (PCT) to evaluate their corrosion resistance. In the PCT, the magnetic films of Example 2 and Comparative Example 2 were left in an environment of 0.2 MPa, a temperature of 120°C, and a humidity of 100% RH for 1000 hours. The weight loss of the magnetic films after 1000 hours was measured.

[0115] Comparative Example 2 A magnetic film was prepared and similar measurements were carried out in the same manner as in Example 2, except that the Sm concentration in the molten salt was controlled to be constant at 1.0 mol / L from the beginning to the end of the reaction in the reaction-diffusion step. The results are shown in Table 2.

[0116] Evaluation 2: From the results in Table 1, it was found that Example 2, in which Δ[T / (R+T)] satisfies the predetermined range, exhibited superior magnetization and coercive force compared to Comparative Example 2. Furthermore, the weight loss of the magnetic film of Example 2 was smaller than that of Comparative Example 2, confirming that Example 2 had superior corrosion resistance.

[0117] Example 3: A magnetic film was prepared in the same manner as in Example 1, and measurements were performed in the same manner, except that the base member was changed to an Fe substrate (20 × 20 × 1 mm), the Sm concentration in the molten salt at the start and end of the reaction in the reaction-diffusion process, the reaction-diffusion temperature, and the reaction-diffusion time were changed to 1.5 mol / L, 3.5 mol / L, 750°C, and 12 hours, respectively, and the magnetic film was nitrided by heat-treating it in a nitrogen atmosphere at 500°C for 60 hours before the low-temperature annealing process. The results are shown in Table 3. The results of the composition analysis using EPMA are shown in Figure 9. The EPMA measurement interval was changed to 4 μm depending on the obtained film thickness (44 ± 4 μm).

[0118] The structure of the obtained SmFe magnet is SmFe on an Fe substrate. 17 The N3 phase was formed.

[0119] A magnetic film was prepared and measured in the same manner as in Example 3, except that the Sm concentration in the molten salt was controlled to be constant at 2.5 mol / L from the beginning to the end of the reaction in the reaction diffusion step. The results are shown in Table 3.

[0120]

[0121] Evaluation 3 From the results in Table 3, it was found that even in the case of SmFe-based magnets, Example 3, in which Δ[T / (R+T)] fell within the predetermined range, had superior magnetization and coercive force compared to Comparative Example 3.

[0122] REFERENCE SIGNS LIST 1, 1a, 1b... substrate (base member) 1α... surface 1A... motor rotor (base member) 1B... actuator substrate (base member) 1C... detection substrate (base member) 10... magnetic film 10A, 10B, 10C... magnet film 20... main magnetic layer 22... crystal grain 22a... columnar grain 22a1... penetrating grain 22a2... non-penetrating grain 22b... non-columnar grain 23... grain boundary 24... surface side end 25... back side end 30a, 30b... sub-magnetic layer 40A... motor

Claims

1. A magnetic film having rare earth elements essentially including Sm or Nd, and transition metal elements including Co or Fe, wherein the magnetic film is a hard magnetic material, the magnetic film has a main magnetic layer having at least one crystal grain, the concentration of the transition metal element relative to the total of the rare earth element and the transition metal element in the at least one crystal grain varies along the thickness direction of the main magnetic layer, and a first concentration of the transition metal element at a surface side end of the at least one crystal grain near the surface of the magnetic film differs by a predetermined percentage or more from a second concentration of the transition metal element at a back side end of the at least one crystal grain near the back side opposite the surface of the magnetic film.

2. The magnetic film according to claim 1, wherein said first concentration is lower than said second concentration by a predetermined percentage or more.

3. The magnetic film according to claim 1, wherein said first concentration is higher than said second concentration by a predetermined percentage or more.

4. The magnetic film according to claim 1, wherein said predetermined ratio is 0.1% or more.

5. When the rare earth element is represented by R and the transition metal element is represented by T, the main magnetic layer has a structure of RT5, RT2T 17 , R.T. 12 , R2T 17 2. The magnetic film according to claim 1, comprising either one of:

6. The main magnetic layer is made of SmCo5, Sm2Co 17 , SmFe 12 , NdFe 12 , SmFe 17 2. The magnetic film according to claim 1, comprising either one of:

7. The magnetic film according to claim 1, further comprising a sub-magnetic layer in contact with said main magnetic layer.

8. The magnetic film according to claim 7, wherein the atomic ratio of the rare earth element contained in the sub-magnetic layer is different from the atomic ratio of the rare earth element contained in the main magnetic layer.

9. The magnetic film according to claim 1, further comprising a nitrogen element.

10. The magnetic film according to any one of claims 1 to 9, wherein the main magnetic layer has a thickness of 10 to 300 µm.

11. A magnetic film-attached member comprising the magnetic film according to any one of claims 1 to 9 and a base member on which the magnetic film is attached.

12. The member with a magnetic film according to claim 11, wherein the surface of said base member contains the same transition metal element as that contained in said main magnetic layer.

13. An actuator comprising a magnetic film according to any one of claims 1 to 9.

14. A sensor comprising a magnetic film according to any one of claims 1 to 9.

Images