JP2005079482A - Method for manufacturing replacement spring magnet - Google Patents

Abstract

[PROBLEMS] To prevent peeling of a film after film formation and after heat treatment, and can be used for a small motor, a dental magnetic attachment, etc. in addition to a magnetic recording medium. It aims to provide a replacement spring magnet.
A A1 iron crystal structure - disordered phase consisting of platinum, L1 ₀ iron crystal structure - Upon disordered phase consisting of platinum to produce an exchange-spring magnet having dispersed by sputtering, as the substrate Sputtering is performed using glass or pure iron at a power of 20 to 300 W in a gas atmosphere of Ar: H ₂ of 95: 5 to 100: 0 and a gas pressure of 0.1 to 100 mTorr.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing an exchange spring magnet, and more particularly, to a technique for manufacturing an exchange spring magnet that can prevent film peeling after film formation and heat treatment and can be made thick.

  An exchange spring magnet has, for example, a structure in which a hard magnetic regular phase having a low saturation magnetic flux density and a high coercive force is dispersed in a soft magnetic irregular phase having a high saturation magnetic flux density and a small coercive force. Since it has both a high saturation magnetic flux density and a high coercive force which are characteristics of both the regular phase and the regular phase, it is expected as a next-generation permanent magnet.

As such an exchange spring magnet, a Co / Pt system having a particularly high magnetization characteristic in a regular phase single layer region, an anisotropy of about 5 × 10 ⁷ erg / cm ³ , and a coercive force of 10 kOe or more. And Fe / Pt-based thin films. For example, various studies have been made on Co / Pt-based thin films for the purpose of application to high-density recording media due to the above characteristics (see Non-Patent Document 1).

Further, to prepare a Co / Pt-based thin film having a thickness of 10mm or 25 mm, to promote the grain growth by heat treatment, in the process of transformation in ordered phase L1 ₀ crystal structure from the disordered phase A1 crystal structure, a change in magnetic properties Has been reported (see Non-Patent Document 2). Here, the A1 crystal structure and L1 ₀ crystal structure refers to a crystal structure at struckturbericht display.

JOUNAL OF APPLIED PYSICS, VOLUME 86, NUMBER 8 (1999) “On the relationship of high coercivity and L10 ordered phase in CoPt and FePt thin film” Physica B 327 (2003) 190-193 “The CoPt system: a natural exchange spring”

  However, when an exchange spring magnet is produced using the technique described in Patent Document 1 or 2, only a film having a thickness of about 10 to 25 nm can be obtained. For this reason, the thin film obtained by the technique described in each of the above patent documents can be applied to a magnetic recording medium having a relatively small thickness, but cannot be applied to a small motor having a relatively large thickness. .

  The present invention has been made in view of the above circumstances, and can be used for small motors, dental magnetic attachments, and the like in addition to magnetic recording media while preventing film peeling after film formation and heat treatment. An object of the present invention is to provide an exchange spring magnet having a thickness of about several μm, which is larger than the conventional one.

  The inventors of the present invention have earnestly researched an exchange spring magnet that can prevent film peeling after film formation and heat treatment, and that can achieve a relatively thick film. As a result, the present inventors have found that the use of glass or pure iron for the substrate in sputtering during film formation can prevent film peeling after film formation and heat treatment. In addition, it has been found that the film thickness can be increased by optimizing the deposition rate during sputtering. The present invention has been made based on such findings.

Method of manufacturing a replacement spring magnet of the present invention, iron A1 crystal structure - disordered phase consisting of platinum, L1 ₀ Iron crystal structure - by sputtering the exchange-spring magnet ordered phase consisting of platinum is dispersed In manufacturing, glass or pure iron is used as a substrate, Ar: H ₂ is 95: 5 to 100: 0, and gas pressure is 0.1 to 100 mTorr. Sputtering is performed with an input power of 20 to 300 W. It is characterized by doing. Here, pure iron means high-purity iron in which the total amount of carbon and other impurities is 0.02% or less.

In such a production method of the exchange spring magnet, the film forming rate is set to 0.5 to 5 μm / hour, and the temperature rising rate is 10 to 1000 ° C./min and the heat treatment temperature is 200 to 700 ° C. after the film forming. It is desirable to perform heat treatment for a time of 0 to 10 minutes and an atmospheric pressure of 1 × 10 ⁻² Torr or less. The holding time is more preferably 0 minutes.

  According to the present invention, by using glass or pure iron for the substrate during sputtering, it is possible to prevent peeling after the thin film having a single composition of Fe / Pt and after the heat treatment are formed. A film can be formed relatively thick by optimizing the speed. Further, according to the present invention, by heat-treating the Fe / Pt disordered phase produced by sputtering, a part thereof is transformed into an Fe / Pt ordered phase, and the Fe / Pt ordered phase of the hard magnetic phase An exchange spring magnet having both the Fe / Pt irregular phase of the soft magnetic phase can be obtained.

Hereinafter, preferred embodiments of the present invention will be described in detail.
[Sputtering]
Method of manufacturing a replacement spring magnet of the present invention, iron A1 crystal structure - disordered phase consisting of platinum, L1 ₀ iron crystal structure - sputtering an exchange spring magnet ordered phase consisting of platinum are dispersed, and It is a method of manufacturing by heat treatment. Hereinafter, the reasons for limiting the substrate, gas atmosphere, gas pressure, input power, and film formation rate when performing sputtering will be described in detail.

  When performing sputtering, conventionally, glass, pure iron, tantalum, copper, silicon, tungsten, polyimide, iron-based compounds, and the like have been used as substrates. Among these, in the present invention, glass or pure iron is particularly used. By using glass or pure iron as the substrate, peeling of the film after film formation and after heat treatment can be prevented.

The gas atmosphere in the sputtering (gas composition), Ar: _{H 2} 95: 5 to 100: 0 can be in the range of, Ar: an _{H 2} 100: 0 and it is preferable to. By setting Ar: H ₂ in the above range, it is possible to prevent the nonmagnetic substance from remaining inside the film, and to realize excellent magnetic characteristics of the exchange spring magnet.

  The gas pressure during sputtering can be in the range of 0.1 to 100 mTorr, and is preferably 20 mTorr. By setting the gas pressure within the above range, film formation can be easily performed.

  The input power during sputtering can be in the range of 20 to 300 W, preferably 200 W. By setting the input power within the above range, film formation can be easily performed.

  The film formation rate during sputtering can be in the range of 0.5 to 5 μm / hour, and is preferably 1.7 μm / hour. By setting the film formation rate within the above range, film formation can be easily performed, and the film thickness can be set to 300 μm at the maximum.

[Heat treatment method]
In a more preferable method for manufacturing an exchange spring magnet according to the present invention, after the film formation by sputtering described above, a heat treatment is performed in which a heating rate, a heat treatment temperature, a holding time, and an atmospheric pressure are defined. Below, the reason for limitation of each of these conditions is demonstrated in detail.

  The heating rate during the heat treatment can be in the range of 10 to 1000 ° C./min, and preferably 250 ° C./min. By setting the heating rate to 10 ° C./min or more, it is possible to prevent the crystal grain size of the exchange spring magnet from becoming coarse, and it is possible to leave an irregular phase in the regular phase. On the other hand, when the rate of temperature rise is 1000 ° C./min or less, transformation from the irregular phase to the regular phase can be sufficiently realized.

  The heat treatment temperature during the heat treatment can be in the range of 200 to 700 ° C, and preferably in the range of 400 to 600 ° C. By setting the heat treatment temperature to 200 ° C. or higher, the transformation from the irregular phase to the regular phase can be sufficiently realized. On the other hand, by setting the heat treatment temperature to 700 ° C. or lower, the irregular phase can remain in the ordered phase.

  The holding time during the heat treatment can be in the range of 0 to 10 minutes, preferably 0 minutes. By setting the holding time in the above range, not only the coercive force of the exchange spring magnet but also the residual magnetization can be increased.

The atmospheric pressure during the heat treatment can be, for example, 1 × 10 ⁻² Torr or less in an Ar gas atmosphere or a mixed gas atmosphere of Ar gas and H ₂ gas. By setting the atmospheric pressure within the above range, the exchange spring magnet can be prevented from being oxidized.

  As described above, in the method for manufacturing the exchange spring magnet of the present invention, the substrate during sputtering, the gas atmosphere, the gas pressure, the input power, the film formation rate, the temperature increase rate during the subsequent heat treatment, and the heat treatment temperature. Further, by limiting the holding time and the atmospheric pressure, it is possible to prevent the thin film from peeling off during film formation and heat treatment, and to obtain an exchange spring magnet with a thick film. Of the above-mentioned limitations, the substrate and gas pressure during sputtering are particularly important. However, with regard to other limitations, film formation cannot be performed smoothly if it deviates from the preferred range.

Next, the exchange spring magnet obtained by the manufacturing method of the present invention will be described. After the sputtering is completed, the above-described heat treatment is performed to transform the disordered phase (soft magnetic phase) partially into the ordered phase (hard magnetic phase), and the ordered phase is dispersed in the disordered phase. FIG. 1 is a schematic view of the exchange spring magnet (Fe / Pe system) obtained in this way, and a large number of regular phases are dispersed in an irregular phase having a thickness of several nm to several μm. Disordered phase, in struckturbericht display a L1 ₀ crystal structure, ordered phase is A1 crystal structure. By such a combination of different crystal structures, the thin film can have both high saturation magnetic flux density and high coercive force, which are both irregular and ordered phase characteristics.

Hereinafter, the present invention will be described more specifically with reference to examples.
[Investigation of substrate, gas atmosphere (gas composition), gas pressure, and input power during sputtering]
Under the conditions of the substrate, gas composition, gas pressure, and input power shown in Table 1, the film formation time is 60 minutes (conditions for obtaining a thin film with a thickness of about 1.7 μm) using RF sputtering. Film formation was performed, and each thin film of Production Examples 1 to 18 was obtained. About each thin film of these manufacture examples 1-18, the film-forming state, the peeling state, and the nonmagnetic phase mixed state were investigated. The results are also shown in Table 1. In Table 1, “film formation”, “peeling”, and “non-magnetic phase mixture” were all evaluated by ○ or ×. Specifically, for “film formation”, whether or not a film was formed on the substrate was visually determined. If the film was made, it was rated as ◯, and if not, it was marked as x. For “peeling”, it was determined whether or not the film formed by visual observation was peeled off. If it was not peeled off, it was marked as ◯, and if it was peeled off, it was marked as x. Furthermore, regarding “nonmagnetic phase mixture”, the state of mixture of nonmagnetic phases such as oxides was determined by quantitative analysis. When oxygen was not detected, it was marked as ◯, and when oxygen was detected, it was marked as x.

  According to Table 1, with respect to production examples 1, 2, 8, 11 to 13, 16, and 17 that satisfy all the conditions of claim 1 of the present invention with respect to the substrate, gas composition, gas pressure, and input power, It can be seen that good results were obtained for all of “film formation”, “peeling” and “nonmagnetic phase mixture”.

  On the other hand, in Production Examples 3 to 7 using a material other than glass and pure iron for the substrate, it can be seen that good results for “peeling” are not obtained. In addition, it can be seen that in Production Example 9 in which the gas composition is outside the scope of claim 1 of the present invention, a nonmagnetic phase is mixed. Furthermore, it can be seen that in the production examples 10, 14, 15, and 18 in which the gas pressure or the input power is outside the scope of claim 1 of the present invention, good results for “film formation” are not obtained.

[Examination of heat-up rate of heat treatment after sputtering, heat treatment temperature and atmospheric pressure]
Next, the thin film of Production Example 1 was subjected to the heat treatment shown in Table 2 to obtain the thin films of Production Examples 19 to 25. About each thin film of these manufacture examples 19-25, the residual state of the irregular phase, the presence or absence of ordering, and the oxidation condition were investigated. The results are also shown in Table 2. In Table 2, “remaining irregular phase”, “regularization”, and “oxidation” were all evaluated as ○ or ×. Specifically, the “remaining irregular phase” was judged by thermomagnetic properties, and it was evaluated as “◯” when the irregular phase remained, and “X” when it did not remain. In addition, “regularization” was judged by thermomagnetic properties, and “◯” was given if part or all of the irregular phase was regularized, and “X” was given if it was not regularized. Further, regarding “oxidation”, the state of formation of oxides and the like was determined by quantitative analysis, and “O” was determined when oxygen was not detected, and “X” was detected when oxygen was detected.

  According to Table 2, with respect to the production examples 19 and 24 that satisfy all the conditions of claim 3 of the present invention with respect to the heating rate, the heat treatment temperature, and the atmospheric pressure, It can be seen that good results have been obtained for all of the “oxidation”.

  On the other hand, with respect to Production Examples 20 and 21 in which the temperature rise is outside the scope of claim 3 of the present invention, good results regarding “remaining irregular phase” or “ordering” are not obtained. I understand. This is because the heating rate is too small in Production Example 20 and the heating rate is too high in Production Example 21. In addition, it can be seen that in the production examples 22 and 23 in which the heat treatment temperature is outside the range of claim 3 of the present invention, good results are not obtained with respect to “ordering” or “remaining irregular phase”. This is because the heat treatment temperature is too low in Production Example 22 and the heat treatment temperature is too high in Production Example 23. Furthermore, it can be seen that in the case of Production Example 25 in which the pressure atmosphere is outside the scope of claim 3 of the present invention, good results for “oxidation” are not obtained.

[Examination of retention time dependence and orientation of magnetic properties (coercivity and remanent magnetization), confirmation of exchange interaction and confirmation of magnetic phase]
A ULVAC SBR-1104E was used as a sputtering apparatus, and an Fe / Pt film was formed by RF sputtering to produce a thin film. At this time, glass was used for the substrate, the gas atmosphere was 100% Ar, the gas pressure was 2.0 × 10 ⁻² Torr, and the film formation time was 60 minutes. Next, the thin film was heat-treated using an infrared heating furnace. At this time, the heating rate was 250 ° C./min, the heat treatment temperature was 500 ° C., the atmospheric pressure was 3.0 × 10 ⁻⁵ Torr, and the holding time was 0 to 60 minutes. In addition, the heating pattern at the time of heat processing is shown in FIG. With respect to the thin film obtained as described above, the investigation results regarding the retention time dependence, orientation, exchange interaction, and magnetic phase of magnetic properties (coercivity and remanent magnetization) will be described in detail below with reference to FIGS. explain.

  FIG. 3 is a graph showing the retention time dependence of magnetic properties (coercivity and remanent magnetization). According to FIG. 3, it can be seen that the remanent magnetization is the largest at a retention time of 0 minutes, about 1.05 T, and the coercive force is as high as 510 kA / m. When there is no exchange interaction and no orientation, the theoretical value of the remanent magnetization of the Fe / Pt system ordered alloy is 0.7T. The result of FIG. 3 exceeds the value, and it can be seen that the exchange interaction is expressed.

  FIG. 4 is a diagram showing the relationship (magnetization curve) between the magnetization and the magnetic field in the vertical direction and in-plane direction of the thin film. According to the figure, since there is no significant difference between the in-plane direction and the perpendicular direction in the shape of this magnetization curve, the value of remanent magnetization is not increased due to the effect of in-plane orientation. I understand that. Therefore, it can be said that the improvement of the remanent magnetization is due to the exchange interaction.

  Next, the exchange interaction was evaluated by the springback rate. Here, as shown in FIG. 5A, the springback rate is defined as M when the demagnetizing field is removed after applying the demagnetizing field from H = 0 (Mr) to Hm. In this case, the value is defined by M / Mr × 100 (%). This value increases when exchange interaction works.

  FIG. 5B is a graph showing the relationship between the springback rate and the ratio of the reversal magnetic field to the coercive force. According to the figure, the thin film of the present invention has a higher springback rate than that of the Fe / Pt ordered alloy, so that the ordered phase (hard magnetism) and the irregular phase (soft magnetism) It can be determined that exchange interaction is working between them, and it can be said that an exchange spring magnet is obtained.

  Furthermore, the magnetic phase was analyzed by thermomagnetic properties. FIG. 6 is a graph showing the relationship between magnetic moment and temperature, where (a) is an irregular phase (soft magnetic phase) thin film, (b) is an ordered phase (hard magnetic phase) thin film, and (c). Shows the result for the thin film of the present invention in which a regular phase and an irregular phase are mixed. According to these figures, the graph FIG. 6C for the thin film of the present invention has peaks close to the graph FIG. 6A of the disordered phase alone and the graph FIG. 6B of the ordered phase alone, respectively. Therefore, it can be said that it has a magnetically multiphase structure.

[Comparison of film thickness between the Fe / Pt exchange spring magnet of the present invention and a conventional exchange spring magnet using platinum]
The thicknesses of the exchange spring magnets obtained by the production method of the present invention, that is, the Fe / Pt thin films of Production Examples 1, 2, 8, 11 to 13, 16, and 17 described in Example 1, are all 1.7 μm. It was about. In contrast, the Co / Pt-based thin film (fct structure) and the Fe / Pt-based thin film (fct structure) obtained by the manufacturing method of Patent Document 1 both have a film thickness of 10 nm. The film thicknesses of the Co / Pt-based thin film (fct structure) and Co / Pt-based thin film (fcc structure) obtained in the above were 10 nm and 25 nm, respectively. Therefore, according to the manufacturing method of the present invention, it can be said that the film thickness can be increased as compared with the conventional method.

  According to the present invention, it is possible to provide an exchange spring magnet that can prevent film peeling after film formation and heat treatment, and that can be made thicker. Therefore, the manufacturing method of the exchange spring magnet of the present invention requires a high saturation magnetic flux density and a high coercive force, and a film thickness of about several μm is required. Motor, magnetic sensor, rotation sensor, acceleration sensor, torque sensor , As well as the manufacture of dental magnetic attachments and the like.

It is a schematic diagram of the exchange spring magnet (Fe / Pe system) of this invention. It is a graph which shows the heating pattern at the time of heat processing. It is a graph which shows the retention time dependence of a magnetic characteristic (coercive force and residual magnetization). It is a figure which shows the relationship (magnetization curve) of the magnetization and magnetic field about the perpendicular direction and in-plane direction of a thin film. (A) is a figure which shows the relationship between the magnetization and magnetic field which were used in order to define a springback rate, (b) is a graph which shows the relationship between a springback rate and the ratio of the reversal magnetic field with respect to a coercive force. is there. It is a graph which shows the relationship between magnetic moment and temperature, (a) is a thin film of an irregular phase (soft magnetic phase), (b) is a thin film of an ordered phase (hard magnetic phase), and (c) is an ordered phase. The result about the thin film of this invention in which an irregular phase is mixed is shown.

Claims (4)

Iron A1 crystal structure - disordered phase consisting of platinum, L1 ₀ Iron crystal structure - a method of ordered phase consisting of platinum to produce an exchange-spring magnet having dispersed by sputtering,
Using glass or pure iron as a substrate, Ar: _{H 2} is 95: 5 to 100: 0, and at a gas atmosphere of gas pressure 0.1～100MTorr, characterized by performing the sputtering power applied 20~300W A method for manufacturing an exchange spring magnet.   The method for producing an exchange spring magnet according to claim 1, wherein the film formation rate is 0.5 to 5 μm / hour. The heat treatment is performed after the film formation at a heating rate of 10 to 1000 ° C./min, a heat treatment temperature of 200 to 700 ° C., a holding time of 0 to 10 minutes, and an atmospheric pressure of 1 × 10 ⁻² Torr or less. Or the manufacturing method of the exchange spring magnet of 2.   The method for manufacturing an exchange spring magnet according to claim 3, wherein the holding time is 0 minute.

Images