JP2016207680A - Thin film magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film magnet having a large maximum energy by suppressing decrease of coercive force, while having a large magnetization.SOLUTION: A thin film magnet is constituted of a first layer composed of Fe or an alloy of Fe and Co, a second layer composed of FeZ, and a third layer containing rear earth, formed on a substrate. Here, the Z in the second layer is Mo or Ta, the element ratio is 0.05<x<0.95, and the second layer is located between the first layer and third layer. The thin film magnet includes one or more first layer, one or more second layer and one or more third layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a thin film magnet applied to a small motor, a magnetic sensor, an actuator, and the like, and a manufacturing method thereof.

Magnet performance is represented by the maximum energy product. High magnet performance, i.e., in order to obtain a high maximum energy product, it is necessary to increase the residual magnetization M _r and coercivity H _c.

In recent years, a soft magnetic phase with high magnetization is used to obtain high remanent magnetization, and a hard magnetic phase with high crystal magnetic anisotropy is used to obtain high coercivity, and both are magnetically coupled by exchange interaction. Attention has been focused on nanocomposite magnets combined in this way.

The potential of the nanocomposite magnet is described in Non-Patent Document 1, and it is calculated that a maximum energy product of 100 MGOe or more may be obtained depending on the combination of the soft magnetic phase and the hard magnetic phase.

The coercive force of the nanocomposite magnet is manifested by the magnetization of the hard magnetic phase fixing the direction of magnetization of the soft magnetic phase and preventing the magnetization reversal of the soft magnetic phase. In order to obtain a sufficient coercive force, there is a microstructure in which the hard magnetic phase and the soft magnetic phase have magnetic coupling at the contact interface, and the thickness of the soft magnetic phase is controlled to be equal to or less than the domain wall width of the hard magnetic phase. is necessary. The domain wall width of a ferromagnetic material is generally several nanometers to several tens of nanometers. Therefore, it is considered that the sputtered thin film method in which nano-level size control is relatively easy is an effective means for producing a nanocomposite magnet. Thin film magnets are expected to be applied to small motors, magnetic sensors, actuators, and the like.

In Patent Documents 1 and 2, a nanocomposite magnet is manufactured with a multilayer thin film structure in which R-TM-B as a hard magnetic phase and Fe or FeCo as a soft magnetic phase are alternately laminated. However, in the laminated structure in which the hard magnetic phase and the soft magnetic phase are directly joined as described above, the high coercive force of the hard magnetic phase cannot be fully utilized, and the maximum energy product is not sufficiently improved.

Physical Review B48 (1993) p15812 JP-A-9-237714 JP-A-9-266113

The present invention provides a nanocomposite thin film magnet having a high maximum energy product by providing a good balance between magnetization and coercive force.

In the present invention, in order to suppress the propagation of magnetization reversal generated from the soft magnetic layer, the exchange coupling between the hard magnetic layer and the soft magnetic layer is not broken between the hard magnetic layer and the soft magnetic layer, and the function of the pinning site is An intermediate layer is introduced.

The present invention is characterized in that an Fe _x Z _1-x (0.05 <x <0.95) layer exists between the hard magnetic layer and the soft magnetic layer. Here, Z is Mo or Ta. By adopting a configuration of Fe _x Z _1-x (0.05 <x <0.95) in which the magnetic element Fe and the nonmagnetic element Z coexist, the exchange coupling between the first layer and the third layer is broken. In addition, it is possible to obtain the function of a pinning site that inhibits domain wall movement. Moreover, Z is difficult to dissolve in rare earth elements. For this reason, a function of suppressing the mutual diffusion of the hard magnetic layer containing the rare earth element and the soft magnetic layer is also expected. By adopting such a configuration, it is possible to have a high energy product as compared with a conventional nanocomposite magnet. The existence of a layer having a magnetic element and a non-magnetic element between a soft magnetic layer having high magnetization and a hard magnetic layer having high magnetic anisotropy prevents the exchange coupling between the soft magnetic layer and the hard magnetic layer from being broken. In addition, the inventors have found that the magnetization reversal generated from the soft magnetic layer can be prevented from propagating to the hard magnetic layer, and have reached the present invention.

Between the first layer which is a soft magnetic layer and the third layer which is hard magnetic, there is a second layer made of Fe _x Z _1-x . This structure can prevent the magnetization reversal generated from the first layer from propagating to the third layer. The value of x is in the range of 0.05 <x <0.95. When x ≦ 0.05, the exchange coupling between the first layer and the third layer is broken, and the behavior of the first layer magnetization reversal in a low magnetic field cannot be suppressed, so a high maximum energy product cannot be obtained. . When 0.95 ≦ x, the magnetization reversal generated in the first layer cannot be suppressed from propagating to the third layer, so that the coercive force is lowered and a high maximum energy product cannot be obtained.

In order to obtain a high maximum energy product, a material having high magnetization is suitable for the first layer, and Fe or Fe—Co alloy having high magnetization at room temperature is used.

The third layer is preferably made of a material having a high magnetocrystalline anisotropy so that the thin film magnet has a high coercive force, and is a magnetic material containing rare earth. Preferably, 5 to 30 at% R (R is at least one of rare earth elements including Y), 0 to 20 at% X (one or two of each element of B, C, Si, Ge, P, S) R-TM-X, more preferably 5 kOe or more, comprising a rare-earth magnetic layer comprising TM or the remainder TM (which is Fe or a part of Fe substituted with Co, or Co). A magnetic layer having a coercive force of.

In the present invention, in order to obtain high magnetization, one or more first layers are necessary. At the same time, in order to fix the magnetization of the first layer, a third layer which is the same number or more hard magnetic phases as the first layer is also necessary. Between the first layer and the third layer, a second layer that prevents the magnetization reversal generated from the first layer from propagating to the third layer is necessary. It is preferable that the number of layers is the same as or more than that of the first layer in the same manner as the above layer.

The soft magnetic first layer has a thickness of 50 nm or less because the direction of magnetization of the first layer is fixed by exchange coupling with the third layer and is difficult to reverse. Is preferably 10 nm or less. Further, in order to obtain a high maximum energy product, the ratio of the first layer having high magnetization needs to be high, and the thickness of the first layer is 0.5 nm or more.

The thickness of the second layer is 2 nm or less so as not to weaken the exchange coupling between the first layer and the third layer. If it is thicker than this, the magnetization direction of the first layer cannot be fixed. In order to effectively prevent propagation of magnetization reversal generated from the first layer, the thickness of the second layer is set to 0.1 nm or more. If it is thinner than this, pinning is insufficient and propagation of magnetization reversal cannot be prevented.

The thickness of the third layer is set to 1000 nm or less in order to increase the ratio of the first layer having high magnetization and obtain a high maximum energy product. If it is thicker than this, the proportion of the first layer decreases, and high magnetization cannot be obtained. In order to maintain the coercive force, the thickness of the third layer is set to 1 nm or more. If it is thinner than this, sufficient coercive force cannot be obtained due to thermal disturbance.

The presence of Fe _x Z _1-x between a ferromagnetic material containing rare earth and Fe or an alloy of Fe and Co allows the ferromagnetic material containing rare earth and an alloy of Fe or Fe and Co to be exchange coupled. , by suppressing the decrease in H _c by magnetization reversal occurring alloy of Fe or Fe and Co, it is possible to obtain a nanocomposite film magnet having a good balance of the magnetization and the coercive force.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment of the present invention is not limited to the embodiments described later, and various modifications can be made within the scope of the technical idea.

[Basic structure]
First, a basic layer structure common to the thin film magnets according to the respective embodiments will be described with reference to FIG. Each embodiment described later includes this structure.

The first layer is a layer made of Fe or an alloy of Fe and Co, the second layer is made of Fe _x Z _1-x , and the third layer is a layer made of a ferromagnetic containing a rare earth element, The M layer is composed of one or more of Mo, Cr, Ti, W, Ta, FeMn, NiO, FeO, CoO, Co—Pt, and Fe—Pt.

The thin film magnet shown in FIG. 1 has a laminated structure in which an M layer, a third layer, a second layer, a first layer, a second layer, and a third layer are formed in this order from the surface of the substrate. .

In this structure, the second layer is formed between the soft magnetic first layer and the hard magnetic third layer, and the magnetization reversal generated from the soft magnetic layer propagates to the hard magnetic layer. The structure which suppresses is taken.

The first layer is preferably a material having a higher magnetization at room temperature than the third layer. Fe or Fe—Co alloy.

The second layer is expressed as Fe _x Z _1-x , and the value of x is in the range of 0.05 <x <0.95. The value of x is more preferably in the range of 0.45 <x <0.55. When x ≦ 0.05, the exchange coupling between the first layer and the third layer is broken, and the behavior of the first layer magnetization reversal in a low magnetic field cannot be suppressed, so a high maximum energy product cannot be obtained. . When 0.95 ≦ x, the magnetization reversal generated in the first layer cannot be suppressed from propagating to the third layer, so that the coercive force is lowered and a high maximum energy product cannot be obtained.

The third layer is 5 to 30 at% R (R is at least one kind of rare earth elements including Y), and 0 to 20 at% X (B, C, Si, Ge, P, and 1 of each element) R-TM-X, which is a magnetic layer containing a rare earth composed of a seed or consisting of two or more elements), the balance TM (TM is Fe or a part of Fe substituted with Co, or Co), preferably It is a magnetic layer having a coercive force of 5 kOe or more.

Between the soft magnetic first layer and the hard magnetic third layer, there is a second layer represented by Fe _x Z _1-x . Without this second layer, the magnetization reversal generated from the first layer propagates to the third layer, a good coercive force cannot be obtained, and a high maximum energy product cannot be obtained.

The thickness of the first layer is 0.5 to 50 nm. When the thickness is smaller than this, the effect of increasing the magnetization is not sufficiently obtained as compared with the third single layer. When the thickness is larger than this thickness, the exchange interaction is insufficient and the coercive force is lowered. The thickness of the second layer is 0.1 to 2 nm. If it is larger than this thickness, the first layer may not be sufficiently subjected to exchange coupling, and if it is smaller than this thickness, the effect of pinning the domain wall is not sufficiently obtained. The third layer has a thickness of 1 nm to 1000 nm. If it is larger than this thickness, the effect of increasing magnetization cannot be obtained sufficiently, and if it is smaller than this thickness, sufficient coercive force cannot be obtained due to thermal disturbance. As the proportion of the first layer in the total thin film volume increases, the magnetization increases and the coercive force decreases. When the proportion of the third layer increases, the coercive force value approaches that of the third single layer, and it is difficult to obtain an increase in magnetization.

As the substrate, various metals, glass, silicon, ceramics and the like can be selected and used. However, it may be necessary to perform processing at a high temperature in order to obtain a desired crystal structure. Therefore, it is desirable to select a material having a high melting point. The underlayer and the M layer that becomes the CAP phase are layers made of at least one or more of Mo, Cr, Ti, W, Ta, FeMn, NiO, FeO, CoO, Co—Pt, and Fe—Pt. is there. The thickness of the M layer is preferably 5 nm to 100 nm so that even if an alloy or compound is formed at the interface by mutual diffusion with the adjacent hard magnetic layer or soft magnetic layer, its function is not impaired sufficiently. 5 to 20 nm.

Hereinafter, preferred examples of the production method of the present invention will be described. Examples of the manufacturing method of the magnetic alloy thin film include a vacuum deposition method, a sputtering method, and a molecular beam epitaxy method. Among these, an example of a manufacturing method by the sputtering method will be described.

First, a target material is prepared as a material. As the target material, an Fe target or an Fe / Co target is prepared as the target of the first layer. A target of Fe, Z (Mo or Ta) is prepared as a target of the second layer. Here, since Nd ₂ Fe ₁₄ B is used as an example of the hard magnetic phase, Nd, Fe, and B targets are used as the third layer target. It is possible to perform sputtering at a desired ratio using a single element target material using an apparatus having a sputtering mechanism equal to or more than the number of targets to be used. As the target of each layer, an alloy target material having a desired composition can be prepared and used, or a combination of an alloy target material and a single element target can be sputtered at a desired ratio. Similarly, when other elements such as Zr, Ti, Bi, Sn, Ga, Nb, Ta, Si, V, Ag, and Ge are to be contained as appropriate, sputtering can be performed at a desired ratio. On the other hand, since it is desirable to reduce impurity elements such as O, N, and C as much as possible, the impurity content in the target material is also reduced as much as possible.

The target material oxidizes from the surface during storage. In particular, when a rare earth target material such as Nd is used, the oxidation rate is fast. Therefore, before using these target materials, it is necessary to perform sputtering sufficiently to bring out a clean surface of the target material.

As the base material on which the film is formed by sputtering, various metals, glass, silicon, ceramics and the like can be selected and used. However, in order to obtain a desired crystal structure, it is desirable to use a material having a high melting point in order to perform a treatment at a high temperature. In addition to the resistance in high temperature processing, the adhesion to the laminated film may be insufficient, and as a countermeasure against this, it is usually performed to improve the adhesion by providing a base film. A protective film can be provided on the laminated film to prevent oxidation.

Since it is desirable that a film forming apparatus that performs sputtering reduces impurity elements such as O, N, and C as much as possible, the vacuum chamber is exhausted to 10 ⁻⁶ Pa or less, more preferably 10 ⁻⁸ Pa or less. It is desirable. In order to maintain a high vacuum state, it is desirable to have a base material introduction chamber connected to the film formation chamber. In addition, before the target material is used, it is necessary to perform sputtering sufficiently to bring out a clean surface of the target material. Therefore, the film forming apparatus is a shield that can be operated in a vacuum state between the base material and the target material. It is desirable to have a mechanism. The sputtering method is preferably a magnetron sputtering method that enables sputtering in a lower Ar atmosphere for the purpose of reducing impurity elements as much as possible. Here, since the target material containing Fe and Co greatly reduces the leakage magnetic flux of magnetron sputtering and makes sputtering difficult, it is necessary to select the thickness of the target material appropriately. As the power source for sputtering, either DC or RF can be used, and can be appropriately selected depending on the target material.

A laminated structure of the first layer, the second layer, and the third layer can be obtained using the target material and the base material described above. The first layer can be laminated, for example, by sputtering an Fe target material. The second layer can be laminated by sputtering Fe, Z (Mo or Ta) at a desired ratio. The third layer can be laminated, for example, by sputtering Nd, Fe, B at a desired ratio. By repeating these, a desired laminated structure can be obtained. In addition, the laminated structure can be manufactured by performing sputtering of different target materials in a separate chamber by transferring the substrate in a film forming apparatus.

It is necessary to stack one or more first layers, and in order to fix the magnetization of the first layer, it is also necessary to stack a third layer that is the same number or more hard magnetic phase as the first layer. It is. A second layer is required between the first layer and the third layer.

The thickness of the first layer is from the end of the surface where only Fe exists, the thickness of the second layer is the end to the end of the surface where Fe and Z coexist, and the thickness of the third layer is Is from end to end of the surface where Nd and FeB coexist.

The thicknesses of the first layer, the second layer, and the third layer in the laminated structure can be set to any thickness and composition by adjusting the sputtering power and time. Here, in order to adjust the thickness and composition, it is necessary to confirm the film formation rate in advance. The film formation rate is generally measured by measuring a film formed with a predetermined power and a predetermined time with a contact-type step meter. It is also possible to use a crystal oscillator thickness meter or the like in the film forming apparatus.

During sputtering, the substrate is heated at 200 to 700 ° C. for crystallization. On the other hand, during sputtering, the substrate can be crystallized by keeping the substrate at room temperature and performing heat treatment at 200 to 1100 ° C. after film formation. In this case, each film after film formation is usually made of fine crystals or amorphous having a thickness of about several tens of nanometers, and crystals grow by heat treatment. The heat treatment is preferably performed in a vacuum or an inert gas in order to reduce oxidation and nitridation as much as possible. For the same purpose, it is more preferable that the heat treatment mechanism and the film forming apparatus can be transported in a vacuum. The heat treatment time is desirably a short time, and a range of 1 minute to 1 hour is sufficient. Further, heating and heat treatment during film formation can be performed in any combination.

Here, the first layer, the second layer, and the third layer are crystallized by sputtering energy and substrate heating energy. Sputtering energy is lost as soon as the sputtered particles adhere to the substrate and the crystals are formed. On the other hand, the substrate heating energy is continuously supplied at the time of film formation, but the diffusion of the first layer, the second layer, and the third layer hardly progresses at the heat energy of 200 to 700 ° C. The structure is maintained. Even when crystallization is performed by heat treatment after low-temperature film formation, fine crystal grain growth proceeds by thermal energy of 200 to 1100 ° C., but diffusion of the first layer, the second layer, and the third layer substantially proceeds. Without being stacked, the laminated structure is maintained.

A structural example of the thin film magnet according to Example 1 will be described. The composition of the first layer is Fe, the composition of the second layer is Fe _0.5 Mo _0.5 , and the third layer is Nd—Fe—B. The substrate is a Si substrate with a thermal oxide film. The thin film is formed using a sputtering apparatus having Mo, Fe, Nd, B, and Co. By using this apparatus, a laminated structure can be formed without exposure to the atmosphere. Therefore, a multilayer structure can be formed without forming an oxide between the layers. Thereby, the laminated structure shown in FIG. 1 is produced.

(Embodiment 1) First, the inside of the sputtering apparatus is evacuated to 5 × 10 ⁻⁴ Pa or less, and the thermally oxidized Si substrate is heated to 650 ° C. Thereafter, Ar gas was introduced, and a pressure of 1 Pa was applied to the Mo target to form a 20 nm Mo layer on the high temperature substrate. The input power was 100 W, preliminary sputtering was performed for 3 minutes with the shutter attached between the substrate and the target closed, and after removing oxides and the like on the target surface, the shutter was opened to form a Mo layer. . The film formation rate is 0.14 nm / sec. Thereafter, the substrate temperature was lowered to 550 ° C., and then an Nd—Fe—B layer was formed. An Nd—Fe—B layer having a thickness of 50 nm was formed on the Nd, Fe, and B targets with an input power of 56 W, 110 W, and 101 W, respectively. Preliminary sputtering was performed for 3 minutes with the shutter attached between the substrate and the target closed to remove oxides and the like on the target surface, and then the shutter was opened to form an Nd—Fe—B layer. The film formation rate is 0.12 nm / sec. Here, the composition of Nd—Fe—B is Nd ₁₅ Fe ₇₅ B ₁₀ (at%). Thereafter, the substrate temperature was lowered to 200 ° C., and then a Fe _0.5 Mo _0.5 layer was formed. A Fe _0.5 Mo _0.5 layer was formed to a thickness of 1 nm on the Fe and Mo targets with an input power of 52 W and 36 W, respectively. The film formation rate is 0.10 nm / sec. Thereafter, an Fe layer was formed. An input power of 100 W was set to the Fe target, and an Fe layer was formed to 6 nm. The film formation rate is 0.12 nm / sec. Thereafter, a 1 nm film was formed under the same conditions as those obtained by laminating the Fe _0.5 Mo _0.5 layer on the Nd—Fe—B layer. Thereafter, the substrate temperature was raised to 550 ° C., and an Nd—Fe—B layer was formed to a thickness of 50 nm under the same conditions. Thereafter, the substrate temperature was lowered to 200 ° C., and Mo was deposited to a thickness of 10 nm under the same conditions to prevent oxidation of the thin film.

The film thickness is a value calculated from the film formation rate. The magnetic properties of each sample were measured by applying a magnetic field of ± 33 kOe in a direction perpendicular to the film surface using a vibrating sample magnetometer (VSM). All measurements were performed at 23 ° ± 1 °. The measured data was subjected to mirror correction using the magnetization curve of the Ni thin film, and then subjected to addition / subtraction processing using the magnetization curve of only the substrate to calculate the magnetization behavior of only the deposited thin film. The magnetization was calculated by setting the density of the thin film to 7.5 g / cc.

(Example 2) A Mo layer and an Nd-Fe-B layer were formed on a thermally oxidized Si substrate under the same conditions as in Example 1, and then the temperature was lowered to 200 ° C to form an Fe _0.9 Mo _0.1 layer. Was deposited to 1 nm. Input powers to the Fe and Mo targets are 84 W and 24 W, respectively. Next, after forming a 6 nm thick Fe layer under the same conditions as in Example 1, a 1 nm thick Fe _0.9 Mo _0.1 layer was formed under the same conditions as described above. Thereafter, an Nd—Fe—B layer and an Mo layer were formed on the Fe _x Mo _1-x layer in the same manner as in the conditions formed in Example 1. That is, compared with Example 1, the value of x of the second layer Fe _x Mo _1-x is different.

(Example 3) An Mo layer and an Nd-Fe-B layer were formed on a thermally oxidized Si substrate under the same conditions as in Example 1, and then the temperature was lowered to 200 ° C to form an Fe _0.7 Mo _0.3 layer. Was deposited to 1 nm. The input power to the Fe and Mo targets is 68W and 32W, respectively. Next, after forming a 6 nm thick Fe layer under the same conditions as in Example 1, a 1 nm thick Fe _0.9 Mo _0.1 layer was formed under the same conditions as described above. Thereafter, an Nd—Fe—B layer and an Mo layer were formed on the Fe _x Mo _1-x layer in the same manner as in the conditions formed in Example 1. That is, compared with Example 1, the value of x of the second layer Fe _x Mo _1-x is different.

(Example 4) A Mo layer and an Nd-Fe-B layer were formed on a thermally oxidized Si substrate under the same conditions as in Example 1, and then the temperature was lowered to 200 ° C to form an Fe _0.3 Mo _0.7 layer. Was deposited to 1 nm. Input powers to the Fe and Mo targets are 45 W and 60 W, respectively. Next, after forming a 6 nm thick Fe layer under the same conditions as in Example 1, a 1 nm thick Fe _0.9 Mo _0.1 layer was formed under the same conditions as described above. Thereafter, an Nd—Fe—B layer and an Mo layer were formed on the Fe _x Mo _1-x layer in the same manner as in the conditions formed in Example 1. That is, compared with Example 1, the value of x of the second layer Fe _x Mo _1-x is different.

(Example 5) A Mo layer and an Nd-Fe-B layer were formed on a thermally oxidized Si substrate under the same conditions as in Example 1, and then the temperature was lowered to 200 ° C to obtain an Fe _0.1 Mo _0.9 layer. Was deposited to 1 nm. The input power to the Fe and Mo targets is 39 W and 85 W, respectively. Next, after forming a 6 nm thick Fe layer under the same conditions as in Example 1, a 1 nm thick Fe _0.1 Mo _0.9 layer was formed under the same conditions as described above. Thereafter, an Nd—Fe—B layer and an Mo layer were formed on the Fe _x Mo _1-x layer in the same manner as in the conditions formed in Example 1. That is, compared with Example 1, the value of x of the second layer Fe _x Mo _1-x is different.

(Example 6) A Mo layer, a Nd-Fe-B layer, and a Fe _0.5 Mo _0.5 layer were formed on the thermally oxidized Si substrate under the same conditions as in Example 1. Then, 8 nm of Fe was deposited on the Fe target with an input power of 100 W. The film formation rate is 0.12 nm / sec. Thereafter, an Fe _0.5 Mo _0.5 layer, an Nd—Fe—B layer, and an Mo layer were sequentially laminated to obtain a thin film magnet. That is, the thickness of the Fe layer (first layer) is different from that in Example 1.

(Example 7) A Mo layer, a Nd-Fe-B layer, and a Fe _0.9 Mo _0.1 layer were formed on the thermally oxidized Si substrate under the same conditions as in Example 2. Then, 8 nm of Fe was deposited on the Fe target with an input power of 100 W. The film formation rate is 0.12 nm / sec. Thereafter, an Fe _0.9 Mo _0.1 layer, an Nd—Fe—B layer, and an Mo layer were sequentially laminated to obtain a thin film magnet. That is, the thickness of the Fe layer (first layer) is different from that in Example 2.

(Example 8) A Mo layer, a Nd-Fe-B layer, and a Fe _0.7 Mo _0.3 layer were formed on the thermally oxidized Si substrate under the same conditions as in Example 3. Then, 8 nm of Fe was deposited on the Fe target with an input power of 100 W. The film formation rate is 0.12 nm / sec. Thereafter, an Fe _0.7 Mo _0.3 layer, an Nd—Fe—B layer, and an Mo layer were sequentially laminated to obtain a thin film magnet. That is, the thickness of the Fe layer (first layer) is different from that in Example 3.

Mo layer under the same conditions as Example 9 Example 4 to thermally oxidized Si substrate, Nd-Fe-B _layer, was deposited Fe 0.3 _{Mo 0.7} layers. Then, 8 nm of Fe was deposited on the Fe target with an input power of 100 W. The film formation rate is 0.12 nm / sec. Thereafter, an Fe _0.3 Mo _0.7 layer, an Nd—Fe—B layer, and an Mo layer were sequentially laminated to obtain a thin film magnet. That is, the thickness of the Fe layer (first layer) is different from that in Example 4.

(Example 10) Mo layer under the same conditions as in Example 5 to thermally oxidized Si substrate, Nd-Fe-B _layer, was deposited Fe 0.1 _{Mo 0.9} layers. Then, 8 nm of Fe was deposited on the Fe target with an input power of 100 W. The film formation rate is 0.12 nm / sec. Thereafter, an Fe _0.1 Mo _0.9 layer, an Nd—Fe—B layer, and an Mo layer were sequentially laminated to obtain a thin film magnet. That is, the thickness of the Fe layer (first layer) is different from that in Example 5.

(Example 11) A Mo layer was laminated on a thermally oxidized Si substrate under the same conditions as in Example 1. Thereafter, the substrate temperature was lowered to 550 ° C., and then an Nd—Fe—B layer was formed. An Nd—Fe—B layer having a thickness of 10 nm was formed on the Nd, Fe, and B targets with an input power of 56 W, 110 W, and 101 W, respectively. Preliminary sputtering was performed for 3 minutes with the shutter attached between the substrate and the target closed to remove oxides and the like on the target surface, and then the shutter was opened to form an Nd—Fe—B layer. The film formation rate is 0.12 nm / sec. Here, the film composition of Nd—Fe—B is Nd ₁₅ Fe ₇₅ B ₁₀ (at%). Thereafter, an Fe _0.5 Mo _0.5 layer was formed under the same conditions as in Example 1. Thereafter, an input power of 100 W was set to the Fe target, and an Fe layer was formed to 1 nm. The film formation rate is 0.12 nm / sec. Then, after laminating an Fe _0.5 Mo _0.5 layer under the same conditions as in Example 1, the substrate temperature was raised to 550 ° C., and an Nd—Fe—B layer was formed to a thickness of 10 nm under the same conditions. Thereafter, the substrate temperature was lowered to 200 ° C., and a Mo layer was formed to a thickness of 10 nm under the same conditions in order to prevent oxidation of the thin film. That is, compared with Example 1, the thickness of the first layer and the thickness of the third layer are different.

(Example 12) A Mo layer was laminated on the thermally oxidized Si substrate under the same conditions as in Example 1. Thereafter, the substrate temperature was lowered to 550 ° C., and then an Nd—Fe—B layer was formed. An Nd—Fe—B layer having a thickness of 200 nm was formed on the Nd, Fe, and B targets with an input power of 56 W, 110 W, and 101 W, respectively. Preliminary sputtering was performed for 3 minutes with the shutter attached between the substrate and the target closed to remove oxides and the like on the target surface, and then the shutter was opened to form an Nd—Fe—B layer. The film formation rate is 0.12 nm / sec. Here, the film composition of Nd—Fe—B is Nd ₁₅ Fe ₇₅ B ₁₀ (at%). Thereafter, an Fe _0.5 Mo _0.5 layer was formed under the same conditions as in Example 1. Thereafter, an input power of 100 W was set for the Fe target, and an Fe layer was formed to a thickness of 20 nm. The film formation rate is 0.12 nm / sec. Then, after laminating an Fe _0.5 Mo _0.5 layer under the same conditions as in Example 1, the substrate temperature was raised to 550 ° C., and an Nd—Fe—B layer was formed to a thickness of 10 nm under the same conditions. Thereafter, the substrate temperature was lowered to 200 ° C., and a Mo layer was formed to a thickness of 200 nm under the same conditions in order to prevent oxidation of the thin film. That is, compared with Example 1, the thickness of the first layer and the thickness of the third layer are different.

(Example 13) A Mo layer was laminated on the thermally oxidized Si substrate under the same conditions as in Example 1. Thereafter, the substrate temperature was lowered to 550 ° C., and then an Nd—Fe—B layer was formed. An Nd—Fe—B layer having a thickness of 500 nm was formed on the Nd, Fe, and B targets with an input power of 56 W, 110 W, and 101 W, respectively. Preliminary sputtering was performed for 3 minutes with the shutter attached between the substrate and the target closed to remove oxides and the like on the target surface, and then the shutter was opened to form an Nd—Fe—B layer. The film formation rate is 0.12 nm / sec. Here, the film composition of Nd—Fe—B is Nd ₁₅ Fe ₇₅ B ₁₀ (at%). Thereafter, an Fe _0.5 Mo _0.5 layer was formed under the same conditions as in Example 1. Thereafter, an input power of 100 W was set for the Fe target, and an Fe layer was formed to a thickness of 50 nm. The film formation rate is 0.12 nm / sec. Then, after laminating an Fe _0.5 Mo _0.5 layer under the same conditions as in Example 1, the substrate temperature was raised to 550 ° C., and an Nd—Fe—B layer was formed to a thickness of 500 nm under the same conditions. Thereafter, the substrate temperature was lowered to 200 ° C., and a Mo layer was formed to a thickness of 10 nm under the same conditions in order to prevent oxidation of the thin film. That is, compared with Example 1, the thickness of the first layer and the thickness of the third layer are different.

(Example 14) A Mo layer was laminated on a thermally oxidized Si substrate under the same conditions as in Example 1. Thereafter, the substrate temperature was lowered to 550 ° C., and then an Nd—Fe—B layer was formed. An Nd—Fe—B layer having a thickness of 1000 nm was formed on the Nd, Fe, and B targets with an input power of 56 W, 110 W, and 101 W, respectively. Preliminary sputtering was performed for 3 minutes with the shutter attached between the substrate and the target closed to remove oxides and the like on the target surface, and then the shutter was opened to form an Nd—Fe—B layer. The film formation rate is 0.12 nm / sec. Here, the film composition of Nd—Fe—B is Nd ₁₅ Fe ₇₅ B ₁₀ (at%). Thereafter, an Fe _0.5 Mo _0.5 layer was formed under the same conditions as in Example 1. Thereafter, an input power of 100 W was set for the Fe target, and an Fe layer was formed to a thickness of 50 nm. The film formation rate is 0.12 nm / sec. Then, after laminating an Fe _0.5 Mo _0.5 layer under the same conditions as in Example 1, the substrate temperature was raised to 550 ° C., and an Nd—Fe—B layer was formed to a thickness of 1000 nm under the same conditions. Thereafter, the substrate temperature was lowered to 200 ° C., and a Mo layer was formed to a thickness of 10 nm under the same conditions in order to prevent oxidation of the thin film. That is, the thickness of the third layer is different from that in Example 13.

(Example 15) A Mo layer and an Nd-Fe-B layer were formed on a thermally oxidized Si substrate under the same conditions as in Example 1, and then the temperature was lowered to 200 ° C to form an Fe _0.5 Mo _0.5 layer. Was deposited to 2 nm. The input power to the Fe and Mo targets is 52W and 36W, respectively. Next, after forming a 6 nm thick Fe layer under the same conditions as in Example 1, a 2 nm thick Fe _0.5 Mo _0.5 layer was formed under the same conditions as described above. Thereafter, an Nd—Fe—B layer and an Mo layer were formed on the Fe _x Mo _1-x layer in the same manner as in the conditions formed in Example 1. That is, the thickness of the second layer is different from that in Example 1.

(Example 16) A Mo layer and an Nd-Fe-B layer were formed on a thermally oxidized Si substrate under the same conditions as in Example 1, and then the temperature was lowered to 200 ° C to obtain an Fe _0.5 Mo _0.5 layer. Was deposited to 1.5 nm. The input power to the Fe and Mo targets is 52W and 36W, respectively. Next, after forming a 6 nm thick Fe layer under the same conditions as in Example 1, a 1.5 nm thick Fe _0.5 Mo _0.5 layer was formed under the same conditions as described above. Thereafter, an Nd—Fe—B layer and an Mo layer were formed on the Fe _x Mo _1-x layer in the same manner as in the conditions formed in Example 1. That is, the thickness of the second layer is different from that in Example 1.

(Example 17) A Mo layer and an Nd-Fe-B layer were formed on a thermally oxidized Si substrate under the same conditions as in Example 1, and then the temperature was lowered to 200 ° C to obtain an Fe _0.5 Mo _0.5 layer. Was deposited to 0.5 nm. The input power to the Fe and Mo targets is 52W and 36W, respectively. Next, after forming an Fe layer with a thickness of 6 nm under the same conditions as in Example 1, an Fe _0.5 Mo _0.5 layer was formed with a thickness of 0.5 nm under the same conditions as described above. Thereafter, an Nd—Fe—B layer and an Mo layer were formed on the Fe _x Mo _1-x layer in the same manner as in the conditions formed in Example 1. That is, the thickness of the second layer is different from that in Example 1.

(Example 18) A Mo layer and an Nd-Fe-B layer were formed on a thermally oxidized Si substrate under the same conditions as in Example 1, and then the temperature was lowered to 200 ° C to form an Fe _0.5 Mo _0.5 layer. Was deposited to a thickness of 0.1 nm. The input power to the Fe and Mo targets is 52W and 36W, respectively. Next, after forming an Fe layer with a thickness of 6 nm under the same conditions as in Example 1, an Fe _0.5 Mo _0.5 layer was formed with a thickness of 0.1 nm under the same conditions as described above. Thereafter, an Nd—Fe—B layer and an Mo layer were formed on the Fe _x Mo _1-x layer in the same manner as in the conditions formed in Example 1. That is, the thickness of the second layer is different from that in Example 1.

(Example 19) A Mo layer, Nd-Fe-B layer, and Fe _0.5 Mo _0.5 layer were formed on a thermally oxidized Si substrate under the same conditions as in Example 1. Thereafter, an Fe _0.5 Co _0.5 layer was formed to a thickness of 6 nm with an input power of 60 W on the Fe target and 40 W on the Co target. The film formation rate is 0.12 nm / sec. Thereafter, an Fe _0.5 Mo _0.5 layer, an Nd—Fe—B layer, and an Mo layer were sequentially laminated to obtain a thin film magnet. That is, the composition of the first layer is different from that in Example 1.

(Example 20) A Mo layer, a Nd-Fe-B layer, and a Fe _0.5 Mo _0.5 layer were formed on the thermally oxidized Si substrate under the same conditions as in Example 1. Thereafter, an Fe _0.7 Co _0.3 layer was formed to a thickness of 6 nm with an input power of ₇₀ W for the Fe target and 30 W for the Co target. The film formation rate is 0.12 nm / sec. Thereafter, an Fe _0.7 Mo _0.3 layer, an Nd—Fe—B layer, and an Mo layer were sequentially laminated to obtain a thin film magnet. That is, the composition of the first layer is different from that in Example 1.

(Example 21) A Mo layer, an Nd-Fe-B layer, and an Fe _0.5 Mo _0.5 layer were formed on the thermally oxidized Si substrate under the same conditions as in Example 1. Thereafter, a Fe _0.3 Co _0.7 layer was formed to a thickness of 6 nm with an input power of 45 W on the Fe target and 65 W on the Co target. The film formation rate is 0.12 nm / sec. Thereafter, an Fe _0.3 Mo _0.7 layer, an Nd—Fe—B layer, and an Mo layer were sequentially laminated to obtain a thin film magnet. That is, the composition of the first layer is different from that in Example 1.

(Example 22) A Mo layer and an Nd-Fe-B layer were formed on a thermally oxidized Si substrate under the same conditions as in Example 1, and then the temperature was lowered to 200 ° C to form an Fe _0.5 Ta _0.5 layer. Was deposited to 1 nm. The input power to the Fe and Ta targets is 88W and 32W, respectively. Next, after forming a 6 nm thick Fe layer under the same conditions as in Example 1, a 1 nm thick Fe _0.5 Ta _0.5 layer was formed under the same conditions as described above. Thereafter, an Nd—Fe—B layer and an Mo layer were formed on the Fe _x Ta _1-x layer in the same manner as in the conditions formed in Example 1. That is, compared with Example 1, the element of Z in the second layer Fe _x Z _1-x is Ta.

Table 1 shows the layer configurations and magnetic characteristics of Examples 1 to 22 and Table 2 shows Comparative Examples 1 to 13 in a table. Comparative Example 1 is a hard magnetic Nd—Fe—B thin film, Comparative Example 2 is a thin film when the x value of the second layer Fe _x Mo _1-x is 0, and Comparative Example 3 is a second layer. Thin film when x value of Fe _x Mo _1-x is 0.97, Comparative Example 4 is thin film when x value of second layer Fe _x Mo _1-x is 0.03, comparative example 5 is a thin film when the value of x of the second layer Fe _x Mo _1-x is 1, and the second layer is a thin film that does not exist between the first layer and the third layer. Comparative Example 6 is a thin film with a first layer thickness of 100 nm compared to Example 13, Comparative Example 7 is a thin film with a first layer of 100 nm compared to Example 1, and Comparative Example 8 is a comparative example. Compared to Example 1, the first layer is a 0.3 nm thin film. In Comparative Example 9, the second layer is a 4 nm thin film compared to Example 1, and in Comparative Example 10, the second layer is a 0.05 nm thin film compared to Example 1. In Comparative Example 11, the third layer is a thin film having a thickness of 1100 nm as compared with Example 1, and in Comparative Example 12, the third layer is a thin film having a thickness of 0.5 nm as compared with Example 1. Comparative Example 13 is a thin film in which the lamination procedure is different from that in Example 1, and the first layer is laminated between the second layer and the third layer.

The thin film of Example 1 has the largest maximum energy product (BH) _max . In Comparative Example 1, M _s is small and (BH) _max is low compared to Examples 1 to 22. This is because the first layer having a high magnetization exists in the embodiment. Examples 1 to 22, as compared with Comparative Example 1, _{H c} is reduced. This is because the first layer, which is soft magnetic, reduces the anisotropy of the entire thin film magnet. In Comparative Example 2 and Comparative Example 3, the second layer breaks the exchange coupling between the first layer and the third layer, and (BH) _max is lower than that of the example. In Comparative Example 4, since the value of x is small, the effect of the second layer that suppresses the propagation of magnetization reversal generated from the first layer is small, the coercive force is low, and high (BH) _max cannot be obtained. It was. Since Comparative Example 5 does not have the second layer, there is no mechanism for suppressing the propagation of magnetization reversal generated from the first layer. Therefore, a high (BH) _max was not obtained. In Comparative Examples 6 and 7, the thickness of the first layer was large, the magnetization reversal of the first layer could not be suppressed, and a high (BH) _max could not be obtained. In Comparative Example 8, the thickness of the first layer was small, and the effect of improving the magnetization was not obtained. In Comparative Example 9, the second layer was thick, and the exchange coupling between the first layer and the third layer was broken, and (BH) _max was lower than that of the example. In Comparative Example 10, the second layer was thin, the effect of the second layer suppressing the propagation of magnetization reversal generated from the first layer was small, the coercive force was low, and high (BH) _max was not obtained. . In Comparative Example 11, since the third layer was thick, the ratio of the first layer was reduced, and the effect of improving the magnetization was not obtained. In Comparative Example 12, the third layer was thin, the coercive force was reduced due to thermal disturbance, and (BH) _max was lowered. In Comparative Example 13, since the second layer does not exist between the first layer and the third layer, propagation of magnetization reversal generated from the first layer cannot be suppressed, and (BH) _max is low. became.

Examples 1 to 22 show higher (BH) _max than the Nd—Fe—B thin film of Comparative Example 1, indicating the effect of the nanocomposite magnet.

FIG. 2 shows magnetic hysteresis curves of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 5. In Example 1, compared to Comparative Example 1, M _s and M _r are high, and a higher maximum energy product can be obtained. On the other hand, in Comparative Example 2 in which there is no Fe element in the second layer as in Comparative Example 2, Nd—Fe—B as the third layer and Fe as the first layer are not exchange-coupled, and the magnetic hysteresis is It has been divided into two stages. In Comparative Example 3, since there is no second layer, magnetization reversal cannot be suppressed, and high M _r and H _c are not obtained. That is, a high (BH) _max can be obtained by adopting the structure as in the above embodiment.

Sectional view of an embodiment of the present invention Demagnetization curves of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 5

Claims (1)

At least a substrate, a first layer made of Fe or an alloy of Fe and Co formed on the substrate, and a second layer made of Fe _x Z _1-x (where Z is Mo or Ta) ), A third layer containing a rare earth element, the first layer is a soft magnetic layer, the third layer is a hard magnetic layer, and x is 0.05 <x <0.95, The second layer exists between the first layer and the third layer, one or more of the first layers, one or more of the second layers, and one or more of the third layers. A thickness of the first layer is not less than 0.5 nm and not more than 50 nm, a thickness of the second layer is not less than 0.1 nm and not more than 2 nm, A thin film magnet having a thickness of the third layer of 1 nm or more and 1000 nm or less.

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