JP4991981B2 - Manufacturing method of nano granular soft magnetic film - Google Patents

Description

The invention of this application relates to a method for producing a nano granular soft magnetic film . More specifically, the invention of this application relates to a method for producing a nanogranular soft magnetic film having an amplified anisotropic magnetic field prevailing with a high electrical resistivity and being usable in an ultrahigh frequency region of about 10 GHz. is there.

  Soft magnetic materials having excellent response to magnetic fields are indispensable materials for various electric and electronic devices such as transformers, choke coils, and electromagnetic wave absorbing materials. These soft magnetic materials always have a resonance frequency peculiar to the material, and the soft magnetic characteristics are lost above this resonance frequency. With the rapid increase in speed of communication equipment and computers, an increase in the resonance frequency of soft magnetic materials has become a very large social demand. In order to increase the resonance frequency of the soft magnetic material, it is effective to increase the saturation magnetization, increase the electrical resistance, and improve the anisotropic magnetic field by imparting uniaxial anisotropy.

  By the way, a nanogranular magnetic film having a structure in which ferromagnetic particles (granule) having an average particle diameter of nanometer order are embedded in a matrix (matrix) made of oxide or nitride is known. Among these, we have already found that samples with a relatively large volume fraction of ferromagnetic particles have magnetic coupling due to contact between the ferromagnetic particles, averaged magnetic anisotropy, and soft magnetic properties. (Patent Document 1, Patent Document 2, Non-Patent Document 1 to Non-Patent Document 7).

This nanogranular soft magnetic film has a very large electrical resistivity of 10 ³ μΩcm or more,
In addition, it is possible to apply an anisotropic magnetic field Hk that is approximately five times larger than the maximum value of the anisotropic magnetic field that can be applied to the soft magnetic alloy material. As a result, the resonance frequency reaches the GHz region, which is an extremely useful material as a soft magnetic film that can be used in the high frequency region.
JP-A-10-189322 JP 2002-158486 A S. Ohnuma, H. Fujimori, S. Furukawa, S. Mitani and T. Matsumoto, J. Alloy and Compounds, 222, p.167 (1995) S. Ohnuma, H. Fujimori, S. Mitani and T. Matsumoto, J. Appl. Phys., 79, p.5130 (1996) S. Ohnuma and T. Masumoto, Scripta. Mater., 44, p.1309 (2001) S. Ohnuma, S. Mitani, H. Fujimori, T. Matsumoto, J. Magn. Soc. Jpm., 19, p.425 (1995) S. Ohnuma, N. Kobayashi, T. Matsumoto, S. Mitani and H. Fujimori, J. Magn. Soc. Jpm., 23, p.240 (1999) K. Hono and M. Ohnuma, book chapter of "Magnetic Nanostructure" edited by HS Nalwa, ASP, p.327 (2002) Masato Onuma, The Japan Society for the Promotion of Science, 147th Committee Material, 81st Workshop, p.11, (2003)

However, the operating frequency of electrical and electronic equipment in the recent advanced information society has been increasing steadily, and among the existing high-frequency soft magnetic materials, even for nanogranular soft magnetic materials with high electrical resistivity and high resonance frequency, There is a strong demand for the development of information that can meet social demands for higher information density and faster processing.

  The invention of this application has been made in view of such a state of the art, has a high electrical resistivity and an amplified anisotropic magnetic field, and can be used in an ultrahigh frequency region of about 10 GHz. It is an object of the present invention to provide a nanogranular soft magnetic film and a method for producing the same.

In order to solve the above problems, the invention of this application is firstly based on a (Co, Fe)-(Ni, Pd, Pt) -Si-O system containing at least one of Fe and Co as a main constituent. A method for producing a nanogranular soft magnetic film, in which ferromagnetic particles having an average particle size of 10 nm or less are embedded in a parent phase made of an oxide ceramic, and after film formation , 0 Provided is a method for producing a nanogranular soft magnetic film characterized in that an anisotropic magnetic field is amplified by heat treatment in a state where a strong magnetic field of 1 T or more is applied in the in-plane direction.

The second aspect of the present invention is that in the first invention, after the heat treatment is performed at a heating rate of 20 ° C./min or less to a temperature between 100 ° C. and 500 ° C., the temperature is increased from 0.1 hour. Provided is a method for producing a nanogranular soft magnetic film, which is performed by holding for 5 hours and then cooling at a cooling rate of 20 ° C./min or less.

According to a third aspect of the present invention, there is provided a method for producing a nanogranular soft magnetic film according to the first or second invention, wherein the magnetic field is applied in the range of 0.1T to 10T by an electromagnet or a superconducting magnet. To do.

According to a fourth aspect of the nanogranular soft magnetic film according to any one of the first to third inventions, the Ni group element is added to the ferromagnetic particles in an amount of 5 atomic% to 30 atomic%. A manufacturing method is provided.

  The nanogranular soft magnetic film of the invention of this application has a high electrical resistivity and an amplified anisotropic magnetic field, and can be used in an ultrahigh frequency region of about 10 GHz.

  In addition, the method for producing a nano granular soft magnetic film of the invention of this application is that the nano granular soft magnetic film is subjected to a heat treatment in a strong magnetic field of 0.1 T or more by an electromagnet or a superconducting magnet, thereby differentiating with a high electrical resistivity. A nano granular soft magnetic film having a isotropic magnetic field can be provided, and an ultrahigh frequency high magnetic permeability soft magnetic material having a very high electric resistance and a giant anisotropic magnetic field can be obtained.

  Hereinafter, the invention of this application will be described in detail.

Giving uniaxial magnetic anisotropy by heat treatment in a magnetic field is used as an established technique in the production process of soft magnetic materials. Usually, a relatively low magnetic field that saturates the magnetization of the target soft magnetic material (in other words, just aligns the magnetic domains) is sufficient for this effect, and an anisotropic magnetic field that can be applied even if a higher magnetic field is applied is It is said that it will not increase. This is because, in soft magnetic materials known so far, induction of uniaxial magnetic anisotropy by heat treatment in a magnetic field is caused by a huge internal magnetic field (also known as molecular magnetic field) of several hundred T that is spontaneously present in a magnetic domain. ) Is the driving force. That is, the magnetic interaction of magnetic atom pairs (pseudo-dipole interaction) is affected by a strong internal magnetic field during heat treatment, and the magnetic atom pairs rearrange in the direction of the internal magnetic field. That's why.

  However, the inventors of this application have conducted extensive research on the magnetic anisotropy of nanogranular soft magnetic materials, and as a result, compared with nanogranular soft magnetic materials, in a strong magnetic field (over 0.1 T) exceeding the saturation magnetic field. It has been found that when heat treatment is performed, a large uniaxial magnetic anisotropy is induced, thereby increasing the anisotropy magnetic field, and thus extremely effective in increasing the frequency of soft magnetic properties.

  Such knowledge could not be anticipated by heat treatment in the magnetic field of existing alloy soft magnetic materials and weak magnetic field heat treatment of granular soft magnetic materials, and presented a new concept regarding the origin of anisotropic magnetic fields in granular soft magnetic materials. And succeeded in producing a new material called an extremely high electric resistance / giant anisotropic magnetic field material. This was also revealed for the first time by using heat treatment in a strong magnetic field. Such a phenomenon is considered to be related to the use of a nano granular structure as a soft magnetic material. At present, the mechanism is not yet elucidated, but it is fully expected that nanogranular soft magnetic materials have a new mechanism of induced magnetic anisotropy. In other words, in the nano-granular structure, the magnetization almost approaches saturation in a normal weak magnetic field, but it is not sufficient, and the magnetic moment of the magnetic atoms present at the boundary between nanomagnetic particles is unsaturated in the weak magnetic field, and they are subjected to a strong magnetic field. It is thought that it will approach saturation for the first time. It is presumed that such magnetic atoms undergo rearrangement by heat treatment under a strong magnetic field, and eventually a large magnetic anisotropy was induced.

The nanogranular soft magnetic film of the invention of this application has a form in which ferromagnetic particles having an average particle size of 10 nm or less and containing at least one of Fe or Co as a main constituent are embedded in a matrix made of oxide ceramics. None, heat treatment while applying a strong magnetic field in the in-plane direction with an anisotropic magnetic field of 0.1 T or more is 1.2 to 4 times the anisotropic magnetic field of the soft magnetic film immediately after film formation It is amplified. Such a nanogranular soft magnetic film can be manufactured by the method described above.

  In the nanogranular soft magnetic film, the composition of the ferromagnetic particles containing at least one of Fe or Co as a main constituent is preferably 60 atom% to 90 atom% in order to exhibit excellent soft magnetic properties.

  The average particle size of the ferromagnetic particles is 10 nm or less. When the average particle size is larger than 10 nm, the coercive force is increased and the soft magnetic material is lost. Further, the lower limit of the average particle diameter is about 2 nm which becomes superparamagnetic.

  The anisotropic magnetic field Hk of the nanogranular soft magnetic film is 1.2 to 4 times, more preferably 2 to 4 times the value of the anisotropic magnetic field of the nanogranular soft magnetic film immediately after film formation in a weak magnetic field. Can be amplified. The amplification factor of the anisotropic magnetic field Hk depends on the value of the anisotropic magnetic field of the nano-granular soft magnetic film immediately after film formation in a weak magnetic field. It will be extremely effective.

The electrical resistivity of the nanogranular soft magnetic film is 200 μΩcm or more, more preferably 500 μΩcm or more. The upper limit of the electrical resistivity is about 10 ⁴ μΩcm from the threshold value that changes from metal conduction to tunnel conduction. If the electrical specific resistance is as described above, it can greatly contribute to the use in the ultra-high frequency region, similar to the amplified anisotropic magnetic field Hk.

  The film thickness of the nanogranular soft magnetic film is appropriately set according to the application and the like, but is usually 0.1 μm to 5 μm.

  A typical example of the nanogranular soft magnetic film is shown below.

Co-Pd-Si-O, Co-Ni-So-O, Co-Al-O, Co-Pt-Al-O, Co-Zr-O, Co-Al-N, Co -Mg-F system -Fe-Al-O system, Fe-BN system, Fe-Zr-O system -Co-Fe-Mg-F system, Co-Fe-Al-O system, Co-Fe-RE -H system, Co-Fe-RE-O system; provided that RE is a rare earth element.

  Next, a method for producing a nano granular soft magnetic film according to the invention of this application will be described.

In the method for producing a nanogranular soft magnetic film according to the invention of this application, ferromagnetic particles having an average particle size of 10 nm or less, the main component of which is at least one of Fe or Co, are embedded in a parent phase made of oxide ceramics. A nano-granular soft magnetic film having a form is prepared, and then heat treatment is performed in a state of applying a magnetic field in an in-plane direction of 0.1 T or more in a vacuum.

  Further, 5 atomic% to 30 atomic% of Ni group elements, that is, Ni, Pd, and Pt may be added to the ferromagnetic particles in the nano granular soft magnetic film. This provides a method for producing a nanogranular soft magnetic film that satisfies the conditions of claim 1 in a wider composition range.

  First, a method for producing a nanogranular soft magnetic film before heat treatment in a strong magnetic field in the invention of this application will be described.

As a film forming method in this case, for example, a sputtering method can be used. It is desirable to apply a weak magnetic field of about 50 Oe to 500 Oe with a permanent magnet in the in-plane direction of the magnetic film in order to impart uniaxial magnetic anisotropy to the produced nano granular soft magnetic film during sputtering film formation. Sputter film formation is preferably performed in a vacuum of about 0.1 Pa to 1 × 10 ⁻⁴ Pa.

  In the manufacturing method of the invention of this application, a heat treatment in a strong magnetic field is performed on the nanogranular soft magnetic film formed in a weak magnetic field as described above.

  In this case, an electromagnet or a superconducting magnet is used and a magnetic field of 0.1 T or more is applied. If the strength of the applied magnetic field is too weak, the anisotropic magnetic field Hk will not be sufficiently amplified. The upper limit of the strength of the applied magnetic field is about 10 T from the upper limit of the steady magnetic field that can be easily generated.

The heat treatment is performed in a vacuum, and the degree of vacuum is preferably about 0.1 Pa to 1 × 10 ⁻⁴ Pa.

Further, in the heat treatment, the heating rate is preferably 20 ° C./min or less. If the heating rate is too high, temperature control at the lower limit of the heat treatment temperature becomes difficult. The lower limit of the heating rate is about 1 ° C./min due to the lower limit capable of stably maintaining a constant heating rate. The heat treatment temperature is preferably between 100 ° C. and 500 ° C. If the heat treatment temperature is too high, the granular structure becomes coarse, and if the heat treatment temperature is too low, the domain wall becomes difficult to move. The heating time (holding time) is preferably 0.1 to 5 hours. When the heating time is out of the above range, the anisotropic magnetic field Hk is not sufficiently amplified. The cooling rate is preferably 20 ° C./min or less. If the cooling rate is too fast, it becomes difficult to fix the domain wall. The lower limit of the cooling rate is about 1 ° C./min due to the effect on the effective heat treatment time.

  As a substrate used for film formation, a glass substrate, a semiconductor substrate such as Si or Ge, or the like can be used.

  Next, examples of the invention of this application will be described. Of course, the invention of this application is not limited to the following examples, and it goes without saying that various aspects are possible in detail.

<Nano-granular soft magnetic thin film with weak magnetic field>
Sample 1
Under the following conditions, a Co—Pd—Si—O nanogranular soft magnetic thin film was formed into a weak magnetic field.

Manufacturing method: RF magnetron sputtering method Substrate: Corning 7059 quartz glass Vacuum degree: 0.67 Pa
Magnetic field: 100 Oe (applied in the in-plane direction of the magnetic film by a permanent magnet)
Target: Composite target with Pd chip on Co-Si alloy Power: 200W
Oxygen partial pressure: 2 sccm
The composition of the obtained nanogranular soft magnetic film was Co ₅₆ Pd ₁₃ Si ₈ O ₂₃ , the anisotropic magnetic field Hk was 300 Oe, and the film thickness was 2.5 μm.

Sample 2
In the production of Sample 1, a Co-Pd-Si-O nanogranular soft magnetic thin film was formed in a weak magnetic field in the same manner except that the number of Pd chips on the target on Co-Si and the oxygen partial pressure were changed. It was.

The composition of the obtained nanogranular soft magnetic film was Co ₅₅ Pd ₆ Si ₈ O ₃₁ , the anisotropic magnetic field Hk was 50 Oe, and the film thickness was 2.1 μm.

[Example 1]
The nano-granular soft magnetic film of Sample 1 formed in the weak magnetic field was subjected to a heat treatment under the following conditions, and Example 1 was obtained.

Magnetic field strength: 1T to 10T (applying a magnetic field in the in-plane direction of the soft magnetic film with an electromagnet)
Degree of vacuum: 0.4 Pa
Heating rate: 2 ° C / min
Heat treatment temperature: 200 ° C
Holding time: 1 hour Cooling rate: 2 ° C / min
The electrical resistivity of the nanogranular soft magnetic film of Example 1 was 1.5 × 10 ³ μΩm, the saturation magnetic flux density Bs was 9.5 kG, and the coercive force Hc was 9 Oe. The magnetic field dependence of the anisotropic magnetic field Hk is shown in FIG. Further, FIG. 2A shows the magnetization curve of the nanogranular soft magnetic film when the magnetic field is 10T.

[Example 2]
In Example 1, heat treatment was performed in the same manner except that Sample 2 was used instead of Sample 1, and Example 2 was obtained.

The electrical resistivity of the nanogranular soft magnetic film of Example 2 was 9.6 × 10 ⁴ μΩm, the saturation magnetic flux density Bs was 7 kG, and the coercive force Hc was 3.5 Oe. The magnetic field dependence of the anisotropic magnetic field Hk is shown in FIG. Further, FIG. 2B shows the magnetization curve of the nanogranular soft magnetic film when the magnetic field is 10T.

[Comparative Example 1]
In Example 1, heat treatment was performed in the same manner except that no magnetic field was applied, and Comparative Example 1 was obtained.

The electrical resistivity of the nanogranular soft magnetic film of Comparative Example 1 was 1.5 × 10 ³ μΩm, the saturation magnetic flux density Bs was 9.5 kG, and the coercive force Hc was 9 Oe. The anisotropic magnetic field Hk was 300 Oe. The magnetization curve of the nanogranular soft magnetic film of Comparative Example 1 is shown in FIG.

[Comparative Example 2]
In Example 2, heat treatment was performed in the same manner except that no magnetic field was applied, and Comparative Example 2 was obtained.

The electrical resistivity of the nanogranular soft magnetic film of Comparative Example 2 was 9.6 × 10 ⁴ μΩm, the saturation magnetic flux density Bs was 7 kG, and the coercive force Hc was 3.5 Oe. The anisotropic magnetic field Hk was 50 Oe. The magnetization curve of the nanogranular soft magnetic film of Comparative Example 2 is shown in FIG.

  From FIG. 1 and a comparison between FIG. 2 and FIG. 3, an increase in the anisotropic magnetic field Hk due to the application of a strong magnetic field is clearly observed. As described above, the nano-granular soft magnetic film showing a large anisotropic magnetic field Hk of 200 Oe or more (about 300 Oe) in the state of film formation in a weak magnetic field and the anisotropic magnetic field of 100 Oe or less (about 50 Oe) in the state of film formation in a weak magnetic field. In any of the nanogranular soft magnetic films showing Hk, an increase in the anisotropic magnetic field Hk was observed due to the application of a strong magnetic field. In particular, in a sample showing an anisotropic magnetic field Hk of 100 Oe or less (50 Oe) in the state of film formation in a weak magnetic field, the magnitude of the anisotropic magnetic field Hk is 3 as compared with the initial value (value after film formation in the weak magnetic field). Doubled and the increase amount was over 100 Oe.

  Therefore, it can be seen that by using the method of the invention of this application, an increase in the anisotropic magnetic field Hk can be achieved in a nanogranular soft magnetic film exhibiting a large electrical resistivity, particularly in a film having a large electrical resistivity. Since both the large electrical resistivity and the large anisotropic magnetic field Hk have the effect of increasing the resonance frequency, the method of the invention of this application is used as a method for developing a soft magnetic material that can be applied up to several tens of GHz. Is possible.

(A) is a figure which shows the magnetic field strength dependence of the anisotropic magnetic field Hk of Example 1, (b) is a figure which shows the magnetic field strength dependence of the anisotropic magnetic field Hk of Example 2. FIG. (A) is a figure which shows the magnetization curve of Example 1, (b) is a figure which shows the magnetization curve of Example 2. FIG. (A) is a figure which shows the magnetization curve of the comparative example 1, (b) is a figure which shows the magnetization curve of the comparative example 2.

Claims (4)

A method for producing a (Co, Fe)-(Ni, Pd, Pt) -Si-O-based nanogranular soft magnetic film having at least one of Fe and Co as a main component, wherein the average particle size is 10 nm or less The ferromagnetic particles are embedded in a matrix of oxide ceramics, and after film formation , heat treatment is performed in a vacuum with a strong magnetic field of 1 T or more applied in the in-plane direction. Method for amplifying an anisotropic magnetic field from 1.2 times to 4 times by the method   The temperature of the heat treatment is raised to a temperature between 100 ° C. and 500 ° C. at a heating rate of 20 ° C./min or less, then held at that temperature for 0.1 to 5 hours, and then a cooling rate of 20 ° C./min or less. The method for producing a nanogranular soft magnetic film according to claim 1, wherein the method is performed by cooling at a temperature.   3. The method for producing a nanogranular soft magnetic film according to claim 1, wherein the magnetic field is applied by an electromagnet or a superconducting magnet in the range of 1T to 10T. The method for producing a nanogranular soft magnetic film according to any one of claims 1 to 3, wherein a Ni group element is added to the ferromagnetic particles in an amount of 5 atomic percent to 30 atomic percent.

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