JP3297023B2 - Magnet powder, sintered magnet, manufacturing method thereof, bonded magnet, motor and magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet material having hexagonal ferrite, particularly a hexagonal M-type ferrite, which is suitably used as a permanent magnet material for an automobile motor or the like, and a method for producing the same.

[0002]

2. Description of the Related Art Magnet plumbite type (M type) hexagonal Sr ferrite or Ba ferrite is mainly used as an oxide permanent magnet material, and these sintered magnets and bonded magnets are manufactured. ing.

[0003] Of the magnet properties, particularly important are the residual magnetic flux density (Br) and the intrinsic coercive force (HcJ).

[0004] Br is determined by the density of the magnet and its degree of orientation,
It is determined by the saturation magnetization (4πIs) determined by the crystal structure, and is expressed by Br = 4πIs × degree of orientation × density. The 4πIs of M-type Sr ferrite and Ba ferrite is about 4.65 kG. Density and degree of orientation,
Even in the case of the sintered magnet that can obtain the highest value, 98
% Is the limit. Therefore, Br of these magnets
Is limited to about 4.46 kG, and high B of 4.5 kG or more
Obtaining r has heretofore been virtually impossible.

The present inventors have disclosed in Japanese Patent Application Laid-Open No. Hei 9-115715 that by adding an appropriate amount of, for example, La and Zn to M-type ferrite, 4πIs can be increased up to about 200G.
It has been found that Br can be increased to 4.5 kG or more. However, in this case, since the anisotropic magnetic field ( _HA ) described later decreases, it was difficult to simultaneously obtain Br of 4.5 kG or more and HcJ of 3.5 kOe or more.

HcJ is the anisotropic magnetic field ｛H_A(= 2K₁/ I
s) The product of｝ and the single domain particle ratio (fc) (H_A× fc)
Is proportional to Where K₁Is the crystal magnetic anisotropy constant
It is a constant determined by the crystal structure like Is. M type B
For a ferrite, K₁= 3.3 × 10⁶erg / cm^ThreeIn
In the case of M-type Sr ferrite, K₁= 3.5 × 10⁶er
g / cm ^ThreeIt is. Thus, M-type Sr ferrite has the largest
K₁Is known to have₁No more improvement
It was difficult to do.

On the other hand, when the ferrite particles are in a single magnetic domain state, it is necessary to rotate the magnetization against the anisotropic magnetic field in order to reverse the magnetization, and thus the maximum HcJ is expected. In order to convert the ferrite particles into single domain particles, it is necessary that the size of the ferrite particles be equal to or less than the critical diameter (dc) described below.

Dc = 2 (k · Tc · K ₁ / a) ^1/2 / Is ²

Here, k is the Boltzmann constant, Tc is the Curie temperature, and a is the distance between iron ions. In the case of M-type Sr ferrite, dc is about 1 μm. For example, when manufacturing a sintered magnet, it is necessary to control the crystal grain size of the sintered body to 1 μm or less. Conventionally, it has been difficult to realize such fine crystal grains at the same time as high density and high degree of orientation for obtaining high Br. However, the present inventors have disclosed in Japanese Patent Application Laid-Open No. 6-53064 a new method. A manufacturing method was proposed, and it was shown that high characteristics could not be obtained. However, also in this method, when Br is 4.4 kG, H
The cJ was about 4.0 kOe, and it was difficult to maintain a high Br of 4.4 kG or more and simultaneously obtain a high HcJ of 4.5 kOe or more.

Further, in order to control the crystal grain size of the sintered body to 1 μm or less, it is necessary to reduce the grain size in the forming step to preferably 0.5 μm or less in consideration of the grain growth in the sintering step. is there. When such fine particles are used, there is a problem that productivity generally decreases due to an increase in molding time and cracks during molding. For this reason, it has been very difficult to achieve both high characteristics and high productivity.

On the other hand, in order to obtain a high HcJ, Al ₂ O ₃
It has been conventionally known that the addition of Cr ₂ O ₃ is effective. In this case, since Al ³⁺ and Cr ³⁺ have the effect of replacing Fe ³⁺ having an “upward” spin in the M-type structure to increase _HA and suppress grain growth, it is 4.5 kOe or more. High HcJ is obtained. However, the sintering density tends to decrease as Is decreases, so that the Br decreases significantly. For this reason, only about 4.2 kG Br was obtained at the maximum with a composition in which HcJ was 4.5 kOe.

Incidentally, the temperature dependency of HcJ of the conventional anisotropic M-type ferrite sintered magnet is about +13 Oe / ° C., and the temperature coefficient is a relatively large value of about +0.3 to + 0.5% / ° C. Was. For this reason, HcJ was greatly reduced on the low temperature side, and there was a case where demagnetization occurred. In order to prevent this demagnetization, it is necessary to set HcJ at room temperature to a large value, for example, about 5 kOe, so that it was practically impossible to obtain high Br at the same time. The temperature dependency of HcJ of M-type ferrite powder is better than that of sintered magnets, but it is still at least about + 80e / ° C and the temperature coefficient is + 0.15% / ° C or more, further improving the temperature characteristics. It was difficult to do. Ferrite magnets are often used in motors and the like used in various parts of automobiles because they have excellent environmental resistance and are inexpensive. Automobiles are sometimes used in cold or extremely hot environments, and motors are also required to operate stably in such harsh environments. However, the conventional ferrite magnet has a problem that the coercive force is significantly deteriorated in a low-temperature environment as described above.

Further, even if these characteristics are satisfied, if the squareness (Hk / HcJ) in the demagnetization curve is low, (BH) max becomes low and the change with time becomes large. There is.

On the other hand, in the production process using an aqueous solvent, if the high degree of orientation obtained by using an organic solvent system can be obtained, the production becomes easy, which is advantageous not only in terms of productivity but also in terms of environment. And there is no need for equipment to prevent contamination.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to increase the saturation magnetization and magnetic anisotropy of an M-type ferrite at the same time, thereby achieving a high residual magnetic flux density which cannot be achieved by a conventional M-type ferrite magnet. Ferrite magnet with excellent coercive force and temperature characteristics of coercive force, especially excellent magnetic characteristics with little decrease in coercive force even at low temperatures, and excellent squareness of demagnetization curve And a method for producing the same.

Another object of the present invention is to provide a ferrite magnet capable of obtaining high characteristics even when the content of expensive Co is reduced, and a method of manufacturing the same.

It is another object of the present invention to provide a method for producing a ferrite magnet having a degree of orientation comparable to that of a solvent system even in a water-based production process.

Another object is to provide a motor and a magnetic recording medium having good characteristics.

[0019]

This and other objects are achieved by any one of the following constitutions (1) to (20). (1) Main phase of hexagonal ferrite containing A (A is Sr, Ba or Ca), Co and R (R represents at least one element selected from rare earth elements (including Y) and Bi) A magnet powder having at least two different Curie temperatures, wherein the two different Curie temperatures are in the range of 400 ° C. to 480 ° C. and the absolute value of these differences is greater than or equal to 5 ° C. Powder. (2) The magnet powder according to the above (1), wherein the R contains at least La. (3) The magnet powder according to (1) or (2), wherein the hexagonal ferrite is a magnetoplumbite ferrite. (4) The hexagonal ferrite is at least one element selected from Sr, Ba, Ca, and Pb, and always includes Sr or Ba as A ', rare earth elements (including Y) and Bi. At least one element selected from the group consisting of R and Co or Co and Zn
Where A ′: R, Fe and M, and the total composition ratio of each metal element is A ′: 1 to 13 atomic%, R: 0.05 to 10 with respect to the total metal element amount. Atomic%, Fe: 80 to 95 atomic%, M: 0.1 to 5 atomic%. (5) The magnet powder according to any one of (1) to (4), wherein the ratio of Co in M is 10 atomic% or more. (6) The magnetic powder according to any one of (1) to (5), wherein the temperature coefficient (absolute value) of the coercive force at −50 to 50 ° C. is 0.1% / ° C. or less. (7) A bonded magnet including the magnet powder according to any one of (1) to (6). (8) A motor having the bond magnet of (7). (9) A magnetic recording medium comprising the magnet powder according to any one of (1) to (6).

(10) A (A is Sr, Ba or C
a) a sintered magnet having a main phase of hexagonal ferrite containing Co and R (R represents at least one element selected from rare earth elements (including Y) and Bi), wherein at least 2 A sintered magnet having two different Curie temperatures, wherein the two different Curie temperatures are in the range of 400 ° C. to 480 ° C. and the absolute value of these differences is greater than or equal to 5 ° C. (11) The sintered magnet according to the above (10), wherein the R contains at least La. (12) The sintered magnet according to the above (10) or (11), wherein the hexagonal ferrite is a magnetoplumbite ferrite. (13) The hexagonal ferrite is composed of Sr, Ba, Ca
At least one element selected from Pb and Pb, which necessarily contains Sr or Ba, A '; at least one element selected from a rare earth element (including Y) and Bi; R; Or Co and Zn by M
Where A ′: 1 to 13 atomic% and R: 0.05 to 10 are composed of A ′, R, Fe, and M with respect to the total amount of metal elements. The sintered magnet according to any one of the above (10) to (12), wherein the atomic%, Fe: 80 to 95 atomic%, and M: 0.1 to 5 atomic%. (14) The sintered magnet according to any one of the above (10) to (13), wherein the ratio of Co in M is 10 atomic% or more. (15) The sintered magnet according to any one of the above (10) to (14), wherein the squareness Hk / HcJ is 90% or more. (16) The sintered magnet according to any one of the above (10) to (15), wherein the degree of orientation Ir / Is is 96% or more. (17) The sum of the X-ray diffraction intensities from the c-plane (ΣI (00
L)) and the sum of X-ray diffraction intensities from all surfaces (ΔI (h
kL)) is 0.85 or more.
The sintered magnet according to any one of (15). (18) The temperature coefficient (absolute value) of the coercive force at −50 to 50 ° C. is 0.25% / ° C. or less.
The sintered magnet according to any one of (17). (19) A motor having the sintered magnet according to any one of (10) to (18).

(20) A (A is Sr, Ba or C
a), Co, R [R is a rare earth element (including Y) and B
i) and a main phase of hexagonal ferrite containing Fe and having at least two different Curie temperatures, wherein the two different Curie temperatures are from 400C to 480C. Exists in the range of
A magnetic recording medium having a thin-film magnetic layer in which the absolute value of the difference is 5 ° C. or more.

[0022]

The present inventors have studied the improvement of the above magnetic characteristics in Japanese Patent Application No. 9-56856. As a result, for example, in a magnetoplumbite-type Sr ferrite containing La or Co, high magnetic characteristics and excellent HcJ It was found that the temperature characteristic of was obtained. However, when a ferrite sintered magnet having this composition is manufactured by a conventional manufacturing method, that is, a method of calcining, pulverizing, molding, and firing after mixing all the raw materials having the basic composition, a square shape of 80 to 90% is obtained. Only (Hk / HcJ). here,
The “production method by addition at the time of mixing the raw materials” as described above is a method of adding the main composition components such as Sr, Fe and La or Co at the raw material mixing stage before calcining, and the uniformity of the components is improved. Conventionally, it was considered to be an excellent manufacturing method because it is easy.

For example, Japanese Patent Application Laid-Open No. 10-149910, page 3, column 4, lines 11 to 17 states, "The above basic composition is obtained in the calcination stage of the standard ferrite magnet production process shown below. It is desirable to mix, calcine, pulverize, mold, and sinter to substantially form the material and then subject it to pulverization as raw material powder. After two high-temperature steps, solid diffusion proceeds and a more uniform composition is obtained. " In the examples described in Japanese Patent Application No. 9-56856, sintered magnets are all manufactured by this manufacturing method. On the other hand, the present inventors have disclosed in International Publication WO98 / 2.
In Japanese Patent Application No. 5278 (Japanese Patent Application No. 8-337445), a production method capable of obtaining a high degree of orientation even in an aqueous process has been proposed. However, even if this manufacturing method is used, for example, the degree of orientation I obtained by a process using an organic solvent system as proposed in Japanese Patent Application Laid-Open No. 6-53064 is proposed.
Compared with r / Is = 97-98%, it was not sufficient.

Therefore, the present inventors consider these points,
As a result of intensive studies, magnets having high squareness can be manufactured by using a structure having two different Curie temperatures in magnetoplumbite type ferrite as disclosed in Japanese Patent Application No. 9-56856. I found something. Further, by adopting this structure, the Co content can be reduced.

The present inventors have also realized 1 that realizes this structure.
A (A is Sr, Ba, or Ca)
R [R represents at least one element selected from rare earth elements (including Y) and Bi], Co, and at least part or all of at least one element among Co and Fe It was found that a method of adding to or excluding all of the ferrite, followed by molding and firing was suitable. In the case of this production method, for example, when an aqueous dispersant such as calcium gluconate described in International Publication WO98 / 25278 (Japanese Patent Application No. 8-337445) is further added, it is comparable to an organic solvent system. It has been found that such a degree of orientation can be obtained.

Here, this manufacturing method will be described more specifically. For example, Sr: La: Fe: Co = 0.8:
In the case of producing a sintered magnet having a composition of 0.2: 11.8: 0.2, conventionally, all elements except additives as sintering aids such as SiO ₂ and CaCO ₃ are prepared before calcination. And then calcined at the stage of mixing the raw materials, followed by adding SiO ₂ , CaCO _3, etc., followed by pulverization, molding and firing.

On the other hand, for example, when mixing the raw materials, S
r: Fe = 0.8: 9.6 (= 1: 12) is mixed and calcined (at this time, the calcined powder becomes M-type Sr ferrite), and then La, Fe, Co For each 0.2:
By adding at a ratio of 2.2: 0.2, Sr: L
The final composition can be a: Fe: Co = 0.8: 0.2: 11.8: 0.2. In this case, La, Fe,
Co may be added to the Sr ferrite powder produced by, for example, a coprecipitation method, a flux method, or the like.

At the time of compounding, Sr: Fe = 0.8: 1
1.8 (= 1: 14.75) and calcined.
(At this time, the calcined powder is composed of M-type Sr ferrite and α-Fe
_TwoO_Three ), And then La and Co are each brought to 0.
By adding at a ratio of 2: 0.2, Sr: La:
Fe: Co = 0.8: 0.2: 11.8: 0.2 final
It can also be a composition.

As in the above example, A (A is Sr, Ba or Ca), Co, R (R represents at least one element selected from rare earth elements (including Y) and Bi), and In a method for producing a sintered magnet having a main phase of a hexagonal magnetoplumbite-type ferrite containing Fe, the constituent elements, at least a part of R and Co,
Alternatively, a structure having two different Curie temperatures (Tc) can be realized in the case of a method of manufacturing a sintered magnet in which all of them are added after calcination, molded, and main-baked, and the excellent characteristics as described above are obtained. Can be realized. In addition, A (A is Sr, Ba or Ca), Co, R (R represents at least one element selected from rare earth elements (including Y) and Bi), and Fe object,
Alternatively, it may be added as a compound that becomes an oxide by firing carbonate, hydroxide, or the like.

The above is a method for producing a sintered magnet having two Curie points Tc, but it can be applied to a method for producing ferrite particles. That is, ferrite particles having at least two Tc can be obtained by performing granulation instead of molding in the above-described sintered magnet production process, and then performing pulverization again as necessary after firing. Also, Sr,
Even in the method of adding the main composition components such as Fe and La and Co at the raw material mixing stage before the calcination, the diffusion process of La and Co is controlled by controlling the temperature, time, atmosphere and the like during the calcination. Thus, ferrite particles having at least two Tc can be obtained.

The reason why a structure having two different Curie temperatures can be obtained by the above-described manufacturing method is unknown, but is considered as follows. That is, in the case of the above example, the reaction between the Sr (or Ba, or Ca) ferrite and the additive (La, Co, Fe) added later occurs during the main firing, and the concentration of La and Co in the process. It is considered that an M-type ferrite portion having a high density and an M-type ferrite portion having a low concentration are formed. If La and Co diffuse into the M-type ferrite particles, it is considered that the concentration of La and Co is higher in the surface layer than in the center of the particles (sintered grains). Since the Curie temperature depends on the amount of La or Co substitution, particularly the amount of La substitution, the phenomenon in which at least two Curie temperatures appear reflects such a structure in which the composition is non-uniform. It is thought that it is.

The M-type ferrite having a preferred composition according to the present invention contains at least La and C
The composition is such that both o are contained in optimal amounts. As a result, Is does not decrease, but rather increases Is and simultaneously
_HA could be increased by increasing ₁ , thereby achieving high Br and high HcJ. Specifically, in the sintered magnet of the present invention, the coercive force HcJ (unit: kOe) and the residual magnetic flux density Br (unit: kG) at room temperature of about 25 ° C.
When HcJ ≧ 4, characteristics satisfying the formula IBr + ／ HcJ ≧ 5.75, and when HcJ <4, characteristics satisfying the formula IIBr + 1 / 10HcJ ≧ 4.82 can be easily obtained. It has been reported that 4.4 kG of Br and 4.0 kOe of HcJ were obtained with the conventional sintered Sr ferrite magnet, but HcJ of 4 kOe or more and having characteristics satisfying the above formula I were obtained. Things have not been obtained. That is, when HcJ is increased, Br is decreased. In the sintered magnet of the present invention, Co and Z
When n is added in combination, the coercive force is lower than that of Co alone and may be less than 4 kOe, but the residual magnetic flux density is significantly improved. At this time, magnetic properties satisfying the above-described formula II are obtained. Heretofore, no Sr ferrite sintered magnet having an HcJ of less than 4 kOe satisfying the above formula II has been obtained.

The ferrite according to the present invention has a larger anisotropy constant (K ₁ ) or anisotropic magnetic field (H _A ) than the conventional ferrite, so that a larger HcJ can be obtained with the same particle size, and If the same HcJ is obtained, the particle size can be increased. For example, if the average particle size of the sintered body is 0.3 to 1 μm, HcJ of 4.5 kOe or more can be obtained, and even if it is 1 to 2 μm, HcJ of 3.5 kOe or more can be obtained. When the particle size is increased, the pulverization time and the molding time can be shortened, and the product yield can be improved.

Although the present invention has a great effect of improving HcJ especially when applied to a sintered magnet, a bonded magnet in which ferrite powder produced according to the present invention is mixed with a binder such as plastic or rubber may be used.

Further, if the magnetic powder is kneaded with a binder to form a paint, and this is applied to a substrate made of a resin or the like, and cured if necessary to form a magnetic layer, a coating type magnetic recording medium is obtained. be able to.

The temperature dependence of HcJ is small in the magnet material of the present invention, and the temperature dependence of HcJ is particularly small in the magnet powder of the present invention. Specifically, the sintered magnet of the present invention has a -50 to
The temperature coefficient (absolute value) of HcJ at 50 ° C. is 0.25%
/ ° C or lower, and can be easily reduced to 0.20% / ° C or lower. Further, the temperature coefficient (absolute value) of HcJ at −50 to 50 ° C. of the magnetic powder of the present invention is 0.1% / ° C. or less, and can be easily reduced to 0.05% / ° C. or less. Can be set to zero. Since the temperature characteristics of HcJ are good, good magnetic characteristics satisfying the following formula III can be obtained at −25 ° C. Such high magnetic properties in a low-temperature environment cannot be achieved with a conventional Sr ferrite magnet. Formula III Br + ／ HcJ ≧ 5.95

By the way, Bull. Acad. Sci. USSR, phys.
(English Transl.) Vol.25, (1961) pp1405-1408 (hereinafter,
Reference 1) contains Ba_1-xM³⁺ _xFe_12-xM²⁺ _xO₁₉ Is described. This Ba
In ferrite, M ³⁺Is La³⁺, Pr³⁺Or Bi
³⁺And M²⁺Is Co²⁺Or Ni²⁺It is. Document 1
For Ba ferrite, the production method is unclear, and
It is not clear whether it is a body or a sintered body, but contains La and Co
In terms of composition, it is similar to the ferrite of the present invention.
You. Fig. 1 of Reference 1 shows that B containing La and Co
For a ferrite, the change in saturation magnetization with change in x
Although it is described, in this Fig. 1, as x increases,
And the saturation magnetization decreases. Reference 1 shows that the coercive force
Although there is a statement that the number has increased several times,
No. Also, there is no description about Curie temperature Tc.
Absent.

On the other hand, according to the present invention, the hexagonal ferrite sintered magnet has a composition in which La and Co are respectively contained in the optimum amounts, and has a structure having at least two Tc, so that HcJ can be remarkably improved. , Br, and a remarkable improvement in the temperature dependency of HcJ. The present invention also provides a hexagonal ferrite magnet powder having a composition containing La and Co in optimal amounts and having two Tc, thereby increasing HcJ and remarkably reducing its temperature dependence. It has been reduced. It has been found for the first time in the present invention that such an effect can be obtained when a structure containing La and Co and having at least two Tc is obtained.

[0039] Indian Journal of Pure & Applied Physi
cs Vol. 8, July 1970, pp. 412-415 (hereinafter referred to as Reference 2) includes the formula La ³⁺ Me ²⁺ Fe ³⁺ ₁₁ O ₁₉ (Me ²⁺ = Cu ²⁺ , Cd ²⁺ , Zn ^{2 +} , Ni ²⁺ , Co ²⁺ or Mg ²⁺ ). This ferrite differs from the magnet material of the present invention in that it does not contain Sr or Ba or Ca. Further, in Reference 2, the saturation magnetization σ in the case of Me ²⁺ = Co ²⁺
s is a low value of 42 cgs unit at room temperature and 50 cgs unit at 0K. Also, although no specific values are shown,
Document 2 states that the coercive force is low and does not become a magnet material. This is considered to be because the composition of ferrite described in Document 2 is different from the range of the present invention. Furthermore, Me
^Although there is a description that the Tc of 2 ⁺ = Co ²⁺ is 800 ° K (= 527 ° C.), Tc greatly deviates from the temperature range of the present invention, and there is no description that Tc has two steps. Absent.

Japanese Patent Application Laid-Open No. Sho 62-100417 (hereinafter referred to as “
The literature 3), equiaxed hexaferrite pigments of the composition represented by the formula _{M x (I) M y (} II) M z (III) Fe 12- (y + z) O 19 is described. In the above formula, M (I) is Sr, Ba,
It is a combination of a rare earth metal or the like and a monovalent cation, wherein M (II) is Fe (II), Mn, Co, Ni, C
u, Zn, Cd or Mg, and M (III) is Ti or the like. The hexaferrite pigments described in Document 3 are the same as the magnet material of the present invention in that they can simultaneously contain a rare earth metal and Co. However, Reference 3 does not disclose an example in which La and Co are simultaneously added, and does not disclose that both the saturation magnetization and the coercive force are improved by the simultaneous addition of La and Co. Moreover, among the examples of Reference 3, C
In the case where o is added, at the same time, T
i is added. Since the element M (III), particularly Ti, is an element that lowers both the saturation magnetization and the coercive force, it is obvious that Document 3 does not suggest the configuration and effect of the present invention.

Japanese Patent Application Laid-Open No. 62-119760 (hereinafter, referred to as
Reference 4) describes a magneto-optical recording material characterized in that a part of Ba of magnetoplumbite-type barium ferrite is replaced with La and a part of Fe is replaced with Co. In this Ba ferrite, La
It also looks similar to the Sr ferrite of the present invention in that it contains Co and Co. However, the ferrite of Document 4 is a material for “magneto-optical recording” in which magnetic domains are written in a magnetic thin film using the thermal effect of light to record information, and information is read out using the magneto-optical effect. The technical field is different from the magnet material of the present invention. Reference 4 describes (I)
Ba, La, and Co are essential in the composition formula, and formulas (II) and (III) show a case where a trivalent or tetravalent or more metal ion (not specified) is added thereto. There is only. In the formula (III), Ga, A
There is a description that Tc decreases when a trivalent ion such as l, In or the like is added, but there is no description at all that Tc becomes two steps.

Japanese Patent Application Laid-Open No. 10-149910 (hereinafter referred to as Reference 5) discloses “(Sr ₁ -xR _x ) On · ((Fe _{1 -y My} )
₂ O ₃ ] (where R is at least one of La, Nd, and Pr, and M is at least one of Mn, Co, Ni, and Zn). 0.05 ≦ x ≦ 0.5 [x / (2.2n)] ≦ y ≦ [x · (1.8n)] 5.70 ≦ n <6.00 (Note that this document 5 is a prior application and falls under the provisions of Article 29-2 of the Patent Act). The ferrite particles partially have the same composition as the present invention in that they simultaneously contain La and Co. However, in Reference 5, there is no description about the Curie temperature, and the characteristics of the examples are also Br = 4.3 kG, HcJ = 3.5 kOe.
It is of low degree. Further, on page 3, column 4, lines 11 to 17, "The above basic composition is mixed, calcined, pulverized, molded, and calcined in the calcining stage of the standard ferrite magnet production process described below. It is desirable that the R and M elements are substantially formed and then subjected to pulverization as raw material powders, that is, when the R and M elements are added in the mixing stage of the above process, they undergo two high-temperature steps of calcination and sintering, and Diffusion proceeds to obtain a more uniform composition. "Is clearly different from the production method of the present invention, and it is considered that the structure of the obtained sintered body is also different.

It has been known that a hexagonal ferrite different from the composition of the present invention may have two stages at a Curie temperature of 400 to 480 ° C. For example,
FIG. 2 of JP-A-9-115715 discloses La and Zn.
Is shown in the case where Sr ferrite containing two Tc has two Tc.

However, at this time, the magnetic characteristics and the like are not improved, and it can be seen from Example 7 that it is preferable to increase the Curie temperature by adding B ₂ O ₃ or the like. Rather, the uniformity of the composition components is improved to improve the magnetic properties and the like.

On the other hand, in the case of hexagonal ferrite having a composition containing A, Co and R, a certain non-uniform structure having a Curie temperature of at least two steps provides excellent magnetic properties. That is what the present inventors have found for the first time.

[0046]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic material of the present invention is Sr, Ba
Or Ca, Co, R [R represents at least one element selected from rare earth elements (including Y) and Bi]
And containing at least two different Curie temperatures Tc1,
Tc2, the two different Curie temperatures Tc1,
Tc2 is 400 to 480 ° C.
The absolute value of the difference of Tc2 is 5 ° C. or more. With such a structure having two different Curie temperatures, the squareness Hk / HcJ is remarkably improved, and the contents of expensive Co and R can be reduced.

The Curie temperature (Tc) is the temperature at which the magnetic material changes from ferromagnetic to paramagnetic. There are several methods for measuring Tc. Particularly, in the case of a magnetic material having a plurality of Tc, a magnetization-temperature curve (σ-T curve) is drawn while changing the temperature of the measurement sample with a heater or the like. Tc is obtained by this. Here, to measure the magnetization,
A vibrating magnetometer (VSM) is often used. This is because it is easy to secure a space for installing a heater and the like around the sample.

The sample may be a powder or a sintered body. In the case of a powder, it is necessary to fix the sample with a heat-resistant adhesive. Further, in order to improve the temperature uniformity and the followability, it is preferable to make the sample as small as possible as long as the measurement accuracy of the magnetization can be ensured (in the embodiment of the present invention, the diameter:
5mm, height: about 6.5mm). Further, in order to make the temperature of the sample equal to the ambient temperature, it is preferable to reduce the changing speed of the ambient temperature.

The sample may be anisotropic or isotropic, but in the case of an anisotropic sample, it is preferable to measure in the c-axis direction after magnetization in the c-axis direction, which is the direction of easy magnetization. In the case of an isotropic sample, the magnetization in the same direction as the magnetization direction is measured. The magnetization of the sample is performed by applying a sufficiently large magnetic field of 10 kOe or more. Usually, after magnetization at room temperature, the magnetization of the sample is measured while increasing the temperature. At this time, it is preferable to measure the sample under a weak magnetic field of 1 kOe or less, even if no magnetic field is applied. This is because, when measurement is performed while applying a large magnetic field, a paramagnetic component having a Curie temperature or higher is also detected, and Tc tends to be unclear.

FIG. 22 shows an example in which two Curie temperatures appear. As shown in the figure, the σ-T curve at a temperature higher than Tc1 is convex upward. In this case, the first-stage Curie temperature (Tc1) can be obtained from the intersection of the tangents. The Curie temperature (Tc2) of the second stage is obtained from the intersection of the tangent and the axis at σ = 0.

Two different Curie points Tc1, Tc2
Has an absolute value of the difference of 5 ° C. or more, preferably 10 ° C. or more. These Curie temperatures are 400 to 480 ° C, preferably 400 to 470 ° C, and more preferably 430 to 460 ° C.
Range. The Tc of pure M-type Sr ferrite
Is about 465 ° C.

Here, the magnetization (σ1) at the temperature Tc1
Is preferably 0.5% to 30%, more preferably 1% to 20%, even more preferably 2% to 10% with respect to the magnetization (σRT) at room temperature of 25 ° C.
%. When σ1 / σRT is less than 0.5%, it becomes difficult to substantially detect Tc2 in the second stage. Also, σ
If 1 / σRT is out of this range, it is difficult to obtain the effects of the present invention.

It is considered that these two Curie temperatures appear because the structure of the ferrite crystal of the present invention becomes a two-phase structure of M-type ferrite which is magnetically different due to a manufacturing method described later. However, in the ordinary X-ray diffraction method, an M-phase single phase is detected.

The squareness Hk / HcJ of the sintered magnet of the present invention is
Preferably 90% or more, especially 92% or more is obtained. The maximum is 95%. Further, the orientation degree Ir / Is of the sintered magnet of the present invention is preferably 96.5% or more, and more preferably 97% or more. The maximum is 98
%. High Br can be obtained by improving the degree of orientation. In the case of a molded article, the degree of magnetic orientation is affected by the density of the molded article, so that accurate evaluation may not be possible.
Therefore, X-ray diffraction measurement is performed on the surface of the molded body, and the degree of crystallographic orientation (X-ray orientation degree) of the molded body is determined from the plane index and the intensity of the diffraction peak. That is, ΣI (00L) / ΣI (hkL) is used as the X-ray orientation degree. here,
(00L) is a general term for c-planes such as (004) and (006), and ΔI (00L) is the sum of all peak intensities of the (00L) plane. (HkL) represents all detected peaks, and ΔI (hkL) is the sum of their intensities. Actually, CuKα is applied to the characteristic X-ray.
When a line is used, for example, measurement is performed in a range of 2θ of 10 ° to 80 °, and the peak intensity in this range is used for calculation. The degree of X-ray orientation of this compact governs the degree of orientation of the sintered body to a considerable extent. {I (00L) /} of c-plane of sintered body
I (hkL) is preferably 0.85 or more, more preferably 0.9 or more, and its upper limit is 1.0.
In each of the following examples, the degree of orientation in the figures was ΔI (0
0l) / ΣI (hkl) in some cases.

The magnet of the present invention comprises Sr, Ba or Ca,
A hexagonal magnetoplumbite ferrite containing Co, R (R represents at least one element selected from rare earth elements (including Y) and Bi) as a main phase;
This main phase is preferably at least one element selected from Sr, Ba, Ca, and Pb, and the element which always contains Sr or Ba is A ′, and is selected from rare earth elements (including Y) and Bi. When at least one element is R and is Co or Co and Zn are M,
A ′: 1 to 13 atomic%, R: 0.05 to 10 atomic%, and Fe: 80 to 95 with respect to the total amount of metal elements. Atomic%, M: 0.1 to 5 atomic%.

More preferably, A 'is 3 to 11 atomic%, R is 0.2 to 6 atomic%, Fe is 83 to 94 atomic%, and M is 0.3 to 4 atomic%, and further preferably. Is
A ': 3 to 9 atomic%, R: 0.5 to 4 atomic%, Fe: 8
6 to 93 atomic%, M: 0.5 to 3 atomic%.

In each of the above constituent elements, A ′ is Sr,
At least one element selected from Ba, Ca and Pb, which always contains Sr or Ba. If A ′ is too small, no M-type ferrite is formed or α-Fe ₂
Non-magnetic phases such as O ₃ increase. A 'preferably contains Sr. If A' is too large, M-type ferrite will not be formed or a non-magnetic phase such as SrFeO _3-x will increase. The ratio of Sr in A ′ is preferably at least 51 atomic%, more preferably at least 70 atomic%, and further preferably 100 atomic%. If the ratio of Sr in A ′ is too low, it will not be possible to obtain both the enhancement of the saturation magnetization and the remarkable improvement of the coercive force.

R is a rare earth element (including Y) and Bi
At least one element selected from the group consisting of: In R,
It is preferable that La, Nd, and Pr, particularly La are always contained. If R is too small, the solid solution amount of M will be small, and it will be difficult to obtain the effects of the present invention. If R is too large, non-magnetic hetero phases such as orthoferrite increase. The proportion of La in R is preferably at least 40 at%, more preferably at least 70 at%, and it is most preferable to use only La as R in order to improve the saturation magnetization. This is because, when comparing the solid solution limit amount to hexagonal M-type ferrite, La is the largest. Therefore, if the proportion of La in R is too low, the solid solution amount of R cannot be increased, and as a result, the solid solution amount of element M cannot be increased, and the effect of the present invention is reduced. I will. Further, if Bi is used in combination, the calcining temperature and the sintering temperature can be lowered, which is advantageous in production.

The element M is Co or Co and Zn. If M is too small, the effect of the present invention is difficult to obtain, and M
Is too large, Br and HcJ decrease conversely, making it difficult to obtain the effects of the present invention. The ratio of Co in M is preferably at least 10 atomic%, more preferably at least 20 atomic%. Co
Is too low, the improvement in coercive force becomes insufficient.

Preferably, the hexagonal magnetoplumbite-type ferrite is represented by A ′ _1−x R _x (Fe _12−y M _y ) _z O ₁₉ , where 0.04 ≦ x ≦ 0.9. In particular, 0.04 ≦ x ≦ 0.6, 0.04 ≦ y ≦ 0.5, 0.8 ≦ x / y ≦ 5, and 0.7 ≦ z ≦ 1.2.

More preferably, 0.04 ≦ x ≦ 0.5, 0.04 ≦ y ≦ 0.5, 0.8 ≦ x / y ≦ 5, 0.7 ≦ z ≦ 1.2, More preferably, 0.1 ≦ x ≦ 0.4, 0.1 ≦ y ≦ 0.4, 0.8 ≦ z ≦ 1.1, and particularly preferably 0.9 ≦ z ≦ 1.05.

In the above formula, when x is too small, that is, when the amount of the element R is too small, the amount of the element M dissolved in the hexagonal ferrite cannot be increased, and the effect of improving the saturation magnetization and / or improving the anisotropic magnetic field can be obtained. The effect becomes insufficient. If x is too large, the element R in hexagonal ferrite
Cannot be substituted and form a solid solution, for example, orthoferrite containing the element R is generated, and the saturation magnetization decreases. If y is too small, the effect of improving the saturation magnetization and / or the effect of improving the anisotropic magnetic field become insufficient. If y is too large, substitutional solid solution of element M in hexagonal ferrite cannot be achieved. Further, even in a range where the element M can be substituted for solid solution, the anisotropy constant (K ₁ ) and the anisotropic magnetic field (H _A ) greatly deteriorate. If z is too small, the non-magnetic phase containing Sr and the element R increases, so that the saturation magnetization decreases. If z is too large, the α-Fe ₂ O ₃ phase or the nonmagnetic spinel ferrite phase containing the element M increases, and the saturation magnetization decreases. Note that the above formula is defined as including no impurities.

In the above formula I, even if x / y is too small,
Even if it is too large, the valence of element R and element M cannot be balanced.
As a result, a different phase such as W-type ferrite is easily generated. Former
Since element M is divalent, the element R is a trivalent ion.
In this case, ideally, x / y = 1. Note that x / y exceeds 1
The reason that the allowable range is large in the region is that even if y is small,
³⁺→ Fe²⁺Valence can be balanced by the reduction of
You.

In the above formula I representing the composition, the number of atoms of oxygen (O) is 19, which means that when R is all trivalent and x = y, z = 1, It shows a stoichiometric composition ratio. The number of oxygen atoms varies depending on the type of R and the values of x, y, and z. Further, for example, when the firing atmosphere is a reducing atmosphere, oxygen deficiency (vacancy) may occur. Further, Fe is M
Usually, trivalent is present in the type ferrite, but this may change to divalent or the like. Also, M such as Co
The valence of the element represented by may also change, and these change the ratio of oxygen to the metal element. In this specification, the number of oxygen atoms is indicated as 19 regardless of the type of R and the values of x, y, and z, but the actual number of oxygen atoms slightly deviates from the stoichiometric composition ratio. Is also good.

The composition of ferrite can be measured by, for example, quantitative X-ray fluorescence analysis. The presence of the main phase is confirmed by X-ray diffraction, electron diffraction and the like.

The magnet powder may contain B ₂ O ₃ . By including B ₂ O ₃ , the calcining temperature and the sintering temperature can be lowered, which is advantageous in production. B ₂ O ₃
Is preferably 0.5% by weight or less of the whole magnet powder. If the B ₂ O ₃ content is too large, the saturation magnetization will be low.

The magnet powder may contain at least one of Na, K and Rb. These when converted into Na ₂ O, K ₂ O and Rb ₂ O, respectively, the total content thereof is preferably not more than 3 wt% of the total magnetic powder. If these contents are too large, the saturation magnetization will be low. When these elements expressed in M ^I, M ^I in ferrite is contained, for example, in the form of ^{_{Sr 1.3-2a R a M I a-}} 0.3 Fe 11.7 M 0.3 O 19. In this case, 0.3 <a ≦ 0.
It is preferably 5. When a is too large, in addition to the saturation magnetization becomes low, a problem that the element M ^I is thus a large amount of evaporation occurs during firing.

In addition to these impurities, for example, Si,
Al, Ga, In, Li, Mg, Mn, Ni, Cr, C
u, Ti, Zr, Ge, Sn, V, Nb, Ta, Sb,
As, W, Mo, etc. in the form of oxides, each containing 1% by weight or less of silicon oxide, 5% by weight or less of aluminum oxide, 5% by weight or less of gallium oxide, 3% by weight or less of indium oxide,
1% by weight or less of lithium oxide, 3% by weight of magnesium oxide
Below, manganese oxide 3% by weight, nickel oxide 3% by weight, chromium oxide 5% by weight, copper oxide 3% by weight, titanium oxide 3% by weight, zirconium oxide 3% by weight, germanium oxide 3% by weight , Tin oxide 3% by weight or less, vanadium oxide 3% by weight or less, niobium oxide 3
% By weight, 3% by weight or less of tantalum oxide, 3% by weight or less of antimony oxide, 3% by weight or less of arsenic oxide, 3% by weight or less of tungsten oxide, and 3% by weight or less of molybdenum oxide.

Next, a method of manufacturing a sintered magnet will be described.

The sintered magnet having the above ferrite is usually made of Fe, A (A is Sr, Ba or C
a, and if necessary, Pb), Co, R [R
Is a powder of a compound containing a rare earth element (including Y) and at least one element selected from Bi), and a mixture of two or more of these raw material powders (F
e and A). And after calcination,
Further, Fe, A (A is Sr, Ba or Ca, and has Pb if necessary), Co, R (R is at least one element selected from rare earth elements (including Y) and Bi) It is manufactured by adding and mixing at least one kind or two or more kinds of powders of the compound to be contained, pulverizing, molding and firing. Fe, A (A is Sr, Ba or Ca, and optionally has Pb), Co, R
Examples of the compound powder containing [R is at least one element selected from rare earth elements (including Y) and Bi] include oxides or compounds that become oxides by firing, such as carbonates and hydroxides. , Nitrate or the like. The average particle size of the raw material powder is not particularly limited,
Particularly, iron oxide is preferably a fine powder, and the average particle size of the primary particles is preferably 1 μm or less, particularly preferably 0.5 μm or less. In addition to the above raw material powder, if necessary, B ₂ O ₃ and the like, and other compounds such as Si, Al, Ga, In, L
i, Mg, Mn, Ni, Cr, Cu, Ti, Zr, G
Compounds containing e, Sn, V, Nb, Ta, Sb, As, W, Mo, etc. may be contained as additives or impurities such as unavoidable components.

The calcination is performed, for example, in the
The heat treatment may be performed at 1350 ° C. for 1 second to 10 hours, particularly about 1 second to 3 hours.

The calcined body thus obtained has a substantially magnetoplumbite-type ferrite structure, and the primary particles have an average particle size of preferably 2 μm or less, more preferably 1 μm or less, and still more preferably. Is 0.1-1μ
m, most preferably 0.1-0.5 μm. The average particle size may be measured with a scanning electron microscope.

Next, after or at the time of pulverizing the calcined body, the Fe, A (A is Sr, Ba or Ca, and if necessary, Pb), Co, R [R is a rare earth element (Y is At least one element selected from Bi) and Bi).
It is manufactured by mixing seeds or two or more kinds, molding and sintering. Specifically, it is preferable to manufacture according to the following procedures. The addition amount of the compound powder is 1 to 10 of the calcined body.
0% by volume, more preferably 5 to 70% by volume, especially 10 to 10% by volume
50% by volume is preferred.

The R oxide of the above compounds has a relatively high solubility in water and has a problem that it flows out during wet molding. In addition, since it has hygroscopicity, it tends to cause a weighing error. Therefore, as the R compound,
Carbonates or hydroxides are preferred.

The timing of addition of the compound is not particularly limited as long as it is after calcination and before calcination, but it is preferable to add the compound during pulverization described below. The type and amount of the raw material powder to be added are arbitrary, and the same raw material may be added separately before and after calcination. However, it is preferable that 30% or more, particularly 50% or more of the total amount of Co or R is added in a post-process performed after calcination. The average particle size of the compound to be added is usually about 0.1 to 2 μm.

In the present invention, it is preferable to carry out wet molding using a molding slurry containing magnetic oxide particles, water as a dispersion medium, a dispersant and additives. In order to increase the height, it is preferable to provide a wet pulverization step before the wet molding step. Further, when calcined particles are used as the oxide magnetic particles, the calcined particles are generally in a granular form. It is preferable to provide a pulverizing step. In addition, when the oxide magnetic particles are manufactured by a coprecipitation method or a hydrothermal synthesis method, the dry coarse pulverizing step is not usually provided, and the wet pulverizing step is not essential. Is preferably provided with a wet grinding step. Hereinafter, a case where the calcined particles are used as the oxide magnetic particles and a dry coarse pulverization step and a wet pulverization step are provided will be described.

In the dry coarse pulverization step, pulverization is usually performed until the BET specific surface area becomes about 2 to 10 times. The average particle size after pulverization is about 0.1-1 μm, and the BET specific surface area is 4-1
It is preferably about 0 m ² / g, and the CV of the particle size is 80%.
Hereinafter, it is particularly preferable to maintain the content at 10 to 70%. The pulverizing means is not particularly limited. For example, a dry vibrating mill, a dry attritor (medium stirring type mill), a dry ball mill and the like can be used, and it is particularly preferable to use a dry vibrating mill. The pulverization time may be appropriately determined according to the pulverization means. In addition, it is preferable to add a part of the raw material powder during the dry grinding step.

The dry coarse pulverization also has an effect of reducing the coercive force HcB by introducing crystal strain into the calcined particles. Due to the decrease in coercive force, magnetic aggregation of particles is suppressed, and dispersibility is improved. This improves the degree of orientation. The crystal strain introduced into the particles is released in a subsequent sintering step, and after sintering, a permanent magnet having a high coercive force can be obtained.

In the case of dry coarse pulverization, SiO
₂ and CaCO ₃ which becomes CaO upon firing are added. SiO ₂ and CaCO ₃ may be partially added before calcination, in which case the improvement in properties is observed. Further, SiO ₂ and CaCO ₃ may be added at the time of later wet pulverization.

After the dry coarse pulverization, a pulverization slurry containing the pulverized particles and water is prepared, and wet pulverization is performed using the slurry. The content of the calcined particles in the slurry for pulverization is 10
It is preferably about 70% by weight. The pulverizing means used for the wet pulverization is not particularly limited, but usually a ball mill, an attritor, a vibration mill, or the like is preferably used. The pulverization time may be appropriately determined according to the pulverization means.

After the wet pulverization, the pulverizing slurry is concentrated to prepare a molding slurry. Concentration may be performed by centrifugation or the like. The content of the calcined particles in the molding slurry is preferably about 60 to 90% by weight.

In the wet molding step, molding in a magnetic field is performed using a molding slurry. Molding pressure is 0.1-0.5ton / cm
^The applied magnetic field may be about ² to 15 kOe.

It is preferable to use a non-aqueous dispersion medium for the molding slurry because a high degree of orientation can be obtained, but in the present invention, a molding slurry in which a dispersant is added to an aqueous dispersion medium is preferably used. The dispersant preferably used in the present invention is an organic compound having a hydroxyl group and a carboxyl group, a neutralized salt thereof, a lactone thereof, an organic compound having a hydroxymethylcarbonyl group, or an acid compound. It is preferable that the compound is an organic compound having an enol-type hydroxyl group which can be dissociated, or a neutralized salt thereof.

When a non-aqueous dispersion medium is used,
For example, as described in JP-A-6-53064, a surfactant such as oleic acid, stearic acid, and a metal salt thereof is added to an organic solvent such as toluene and xylene. And a dispersion medium. By using such a dispersion medium, even when submicron-size ferrite particles that are difficult to disperse are used, the maximum is 98%.
% Of magnetic orientation can be obtained.

When the above aqueous dispersion medium is used, the organic compound as a dispersant has a carbon number of 3 to 20, preferably 4 to 20.
12, and a hydroxyl group is bonded to 50% or more of carbon atoms other than the carbon atom double-bonded to the oxygen atom. If the number of carbon atoms is 2 or less, the effects of the present invention cannot be realized. Further, even when the number of carbon atoms is 3 or more, the effect of the present invention cannot be realized if the bonding ratio of the hydroxyl group to carbon atoms other than the carbon atom double-bonded to the oxygen atom is less than 50%. The bonding ratio of the hydroxyl group is limited for the above-mentioned organic compound, and is not limited for the dispersant itself. For example, when a lactone of an organic compound (hydroxycarboxylic acid) having a hydroxyl group and a carboxyl group is used as the dispersant, the limitation of the bonding ratio of the hydroxyl group is applied to the hydroxycarboxylic acid itself, not to the lactone.

The basic skeleton of the organic compound may be linear or cyclic, and may be saturated or contain an unsaturated bond.

As the dispersant, specifically, a hydroxycarboxylic acid or a neutralized salt thereof or a lactone thereof is preferable. Particularly, gluconic acid (C = 6; OH = 5; COOH
= 1) or a neutralized salt thereof or a lactone thereof, lactobionic acid (C = 12; OH = 8; COOH = 1), tartaric acid (C = 4; OH = 2; COOH = 2) or a neutralized salt thereof, glucoheptone Acid γ-lactone (C = 7; OH
= 5) is preferred. Among these, gluconic acid or its neutralized salt or its lactone is preferable because it has a high effect of improving the degree of orientation and is inexpensive.

As the organic compound having a hydroxymethylcarbonyl group, sorbose is preferred.

Ascorbic acid is preferred as the organic compound having an enol-type hydroxyl group which can be dissociated as an acid.

In the present invention, citric acid or a neutralized salt thereof can also be used as a dispersant. Citric acid has a hydroxyl group and a carboxyl group, but does not satisfy the condition that a hydroxyl group is bonded to 50% or more of carbon atoms other than a carbon atom double-bonded to an oxygen atom. However, the effect of improving the degree of orientation is recognized.

For some of the preferred dispersants described above,
The structure is shown below.

[0092]

Embedded image

The degree of orientation by the magnetic field orientation is affected by the pH of the supernatant of the slurry. Specifically, if the pH is too low, the degree of orientation decreases, which affects the residual magnetic flux density after sintering. When a compound exhibiting an acid property in an aqueous solution, such as hydroxycarboxylic acid, is used as the dispersant, the pH of the supernatant of the slurry becomes low. Therefore, it is preferable to adjust the pH of the slurry supernatant, for example, by adding a basic compound together with the dispersant. As the basic compound, ammonia and sodium hydroxide are preferable. Ammonia may be added as aqueous ammonia. In addition, by using the sodium salt of hydroxycarboxylic acid, the pH can be prevented from lowering.

As a subcomponent, such as a ferrite magnet,
In the case of adding O ₂ and CaCO ₃ , when hydroxycarboxylic acid or its lactone is used as a dispersant, S
iO ₂ and CaCO ₃ flow out, and desired performance cannot be obtained such as a decrease in HcJ. When the pH is increased by adding the above basic compound,
The outflow of SiO ₂ and CaCO ₃ is greater. On the other hand, when the calcium salt of hydroxycarboxylic acid is used as the dispersant, the outflow of SiO ₂ and CaCO ₃ can be suppressed. However, adding the above basic compound,
Even when a sodium salt is used as a dispersant,
If iO ₂ and CaCO ₃ are excessively added to the target composition, shortages of SiO ₂ and CaO in the magnet can be prevented. When ascorbic acid is used, almost no outflow of SiO ₂ and CaCO ₃ is observed.

For the above reasons, the pH of the slurry supernatant is
It is preferably 7 or more, more preferably 8 to 11.

The type of the neutralizing salt used as the dispersing agent is not particularly limited, and may be any of a calcium salt and a sodium salt. For the above-mentioned reason, the calcium salt is preferably used. When a sodium salt is used as the dispersant or when ammonia water is added, there is a problem that, in addition to the outflow of subcomponents, cracks are easily generated in the formed body and the sintered body.

The dispersants may be used in combination of two or more.

The amount of the dispersant added is preferably 0.05 to 3.0% by weight, more preferably 0.10 to 2.0% by weight, based on the calcined particles which are the oxide magnetic particles. . If the amount of the dispersant is too small, the degree of orientation will not be sufficiently improved. On the other hand, if the amount of the dispersing agent is too large, cracks are likely to occur in the molded body and the sintered body.

When the dispersant is ionizable in an aqueous solution, for example, an acid or a metal salt, the amount of the dispersant added is an ion equivalent. That is, the amount of addition is determined in terms of organic components excluding hydrogen ions and metal ions.
When the dispersant is a hydrate, the amount of addition is determined excluding water of crystallization. For example, when the dispersant is calcium gluconate monohydrate, the amount to be added is calculated in terms of gluconate ions.

When the dispersant is made of lactone or contains lactone, the amount of addition is calculated in terms of hydroxycarboxylic acid ions, assuming that all of the lactone is opened to form hydroxycarboxylic acid.

The timing of adding the dispersant is not particularly limited, and may be added during dry coarse pulverization, may be added during the preparation of a slurry for wet pulverization, or may be partially added during dry coarse pulverization. And the remainder may be added during wet grinding. Alternatively, it may be added by stirring after wet pulverization. In any case, the effect of the present invention is realized because the dispersant is present in the molding slurry. However, the effect of improving the degree of orientation is higher at the time of pulverization, particularly at the time of dry coarse pulverization. In a vibration mill or the like used for dry coarse pulverization, larger energy is given to the particles than in a ball mill or the like used for wet pulverization, and the temperature of the particles increases, so that the chemical reaction is likely to proceed. Therefore, if a dispersant is added during dry coarse grinding,
It is considered that the amount of the dispersant adsorbed on the particle surface is increased, and as a result, a higher degree of orientation is obtained. Actually, when the residual amount of the dispersing agent in the molding slurry (which is considered to be almost equal to the adsorption amount) is measured, the amount of the dispersing agent added during the dry coarse grinding is larger than that when the dispersing agent is added during the wet grinding. The ratio of the residual amount to is increased. In addition, when the dispersant is added in a plurality of times,
What is necessary is just to set the addition amount of each time so that the total addition amount may be in the preferable range described above.

After the forming step, the formed body is subjected to a heat treatment at a temperature of 100 to 500 ° C. in the air or in nitrogen to sufficiently decompose and remove the added dispersant. Next, in the sintering step, the molded body is preferably for example 1150-12 in air.
Sintering is performed at a temperature of 50 ° C., more preferably 1160 to 1220 ° C. for about 0.5 to 3 hours to obtain an anisotropic ferrite magnet.

The average crystal grain size of the magnet of the present invention is preferably 2 μm or less, more preferably 1 μm or less, and still more preferably 0.5 to 1.0 μm. In the present invention, the average crystal grain size exceeds 1 μm. However, a sufficiently high coercive force can be obtained. The crystal grain size can be measured by a scanning electron microscope. Incidentally, the resistivity is at least about 10 ⁰ [Omega] m.

The above compact was crushed using a crusher or the like, and the average particle size was reduced to 100 to 700 μm by sieving or the like.
m to obtain a magnetic field-oriented granule, which is subjected to dry magnetic field molding, and then sintered to obtain a sintered magnet.

After the calcination using the calcined body slurry, the powder may be dried and then fired to obtain magnet powder.

The present invention also includes a magnetic recording medium having a thin-film magnetic layer. This thin-film magnetic layer has a hexagonal magnetoplumbite-type ferrite phase similarly to the above-described magnet powder of the present invention. The contents of impurities and the like are the same as above.

By using the magnet of the present invention, the following effects can be generally obtained, and an excellent applied product can be obtained. In other words, if the shape is the same as that of a conventional ferrite product, the magnetic flux density generated from the magnet can be increased, so that a motor can achieve higher torque, etc., and if it is a speaker or headphone, the magnetic circuit can be strengthened. It can contribute to high performance of applied products, such as obtaining good sound quality with linearity. Also, if the same function as in the past is sufficient, the size (thickness) of the magnet is reduced (thin).
It can contribute to downsizing and weight reduction (thinning). Further, even in a motor in which a field magnet is conventionally a winding type electromagnet, this can be replaced with a ferrite magnet, which contributes to weight reduction, shortening of a production process, and cost reduction. Furthermore, because of its excellent coercive force (HcJ) temperature characteristics, it can be used even in low-temperature environments where there was a risk of low-temperature demagnetization (permanent demagnetization) of ferrite magnets, especially in cold regions and in the sky. The reliability of the manufactured product can be significantly increased.

The magnet material of the present invention is processed into a predetermined shape and is used for a wide range of uses as described below.

For example, for fuel pump, power window, ABS, fan, wiper, power steering, active suspension, starter,
Automotive motors for door locks, electric mirrors, etc .; FD
For D spindle, VTR capstan, VTR rotary head, VTR reel, VTR loading, VT
For R camera capstan, VTR camera rotating head,
Motors for OA and AV equipment such as VTR camera zoom, VTR camera focus, boombox capstan, CD, LD, MD spindle, CD, LD, MD loading, CD, LD optical pickup, etc .; Motors for home appliances such as for refrigerator compressor, electric tool drive, electric fan, microwave oven fan, microwave plate rotation, mixer drive, dryer fan drive, shaver drive, electric toothbrush, etc .;
Motors for FA equipment such as robot axes, joint drive, robot main drive, machine tool table drive, machine tool belt drive, etc .; motor generators, magnets for speakers and headphones, magnetron tubes, magnetic field generation for MRI It is suitably used for devices, clampers for CD-ROMs, sensors for distributors, sensors for ABS, fuel / oil level sensors, magnet latches, and the like.

[0110]

Example 1 Example 1 [Sintered magnet: Samples 1 and 2 (aqueous
The following materials were used as raw materials. Fe ₂ O ₃ powder (primary particle diameter 0.3 μm), 1000.0 g (including Mn, Cr, Si, Cl as impurities) SrCO ₃ powder (primary particle diameter 2 μm), 161.2 g (Ba and Ca as impurities Including)

As an additive, 2.30 g of SiO ₂ powder (primary particle diameter: 0.01 μm) and 1.72 g of CaCO ₃ powder (primary particle diameter: 1 μm) were used.

The above starting materials and additives were pulverized with a wet attritor, dried and sized, and dried in air.
It was calcined at 250 ° C. for 3 hours to obtain a granular calcined body.

The calcined body obtained was treated with SiO 2_Two, CaC
O_Three, Lanthanum carbonate [La_Two(CO_Three) _Three・ 8H_TwoO], acid
Cobalt oxide (CoO) in the amounts shown in Table 1
Then, calcium gluconate was added in the amount shown in Table 1.
Dry coarse powder for 20 minutes by vibrating rod mill of batch
Crushed. At this time, distortion due to grinding is introduced, and the calcined body
The HcJ of the particles had dropped to 1.7 kOe.

Next, the coarsely pulverized material 17 obtained in the same manner
7 g was collected, 37.25 g of the same iron oxide (α-Fe ₂ O ₃ ) as used as a raw material was added, and 400 cc of water was added as a dispersion medium and mixed to prepare a slurry for grinding.

Using this slurry for wet grinding, wet grinding was performed in a ball mill for 40 hours. The specific surface area after the wet pulverization was 8.5 m ² / g (average particle size: 0.5 μm). The pH of the supernatant of the slurry after the wet milling was 9.5.

After the wet pulverization, the pulverization slurry was centrifuged to adjust the concentration of the calcined particles in the slurry to 78%, thereby obtaining a molding slurry. Compression molding was performed while removing water from the molding slurry. This molding is
This was performed while applying a magnetic field of about 13 kOe in the compression direction. The obtained molded body was a cylindrical shape having a diameter of 30 mm and a height of 18 mm. The molding pressure was 0.4 ton / cm ² . A part of the slurry was dried and calcined at 1000 ° C. to be processed into an oxide, and then the amount of each component was analyzed by a fluorescent X-ray quantitative analysis method. The results are shown in Tables 2 and 3.

Next, the molded body is heat-treated at 100 to 300 ° C. to sufficiently remove gluconic acid.
The temperature was raised at a rate of 5 ° C./min, and firing was performed by maintaining the temperature at 1220 ° C. for 1 hour to obtain a sintered body. After processing the upper and lower surfaces of the obtained sintered body, residual magnetic flux density (Br), coercive force (HcJ and Hcb), and maximum energy product [(BH) ma
x], saturation magnetization (4πIs), degree of magnetic orientation (Ir / I
s) and squareness (Hk / HcJ) were measured. Next, the sample was processed into a cylinder having a diameter of 5 mm and a height of 6.5 mm (the height direction was the c-axis direction). After magnetizing the sample with a sample vibration magnetometer (VSM), the Curie temperature Tc was determined by measuring the temperature dependence of the residual magnetization in the c-axis direction without applying a magnetic field.

This measuring method will be described in more detail. First, the room temperature (2) is set in the height direction (c-axis direction) of the cylindrical sample.
(5 ° C.) and a magnetic field of about 20 kOe was applied for magnetization. Next, the magnetic field current is set to zero (however, a magnetic field of about 50 (Oe) is generated due to the residual magnetization of the magnetic pole), and the heater arranged around the sample is heated to about 10 (Oe).
The temperature was increased at a rate of ° C./min, and the temperature and magnetization of the sample were measured simultaneously, thereby drawing a σ-T curve. The results are shown in FIGS. In addition, a-axis direction of sample No. 1 and c
SEM photographs of the structure in the axial direction are shown in FIGS.

As is clear from FIGS. 5 and 6, the Curie temperatures Tc of Sample Nos. 1 and 2 of the present invention were 440 ° C. and 45 ° C.
It can be seen that there are two stages of 6 ° C. and 434 ° C. and 454 ° C. respectively. The ratio of σ at the point of Tc (Tc1) in the first stage to σ at 25 ° C. was 5.5% and 6.0%, respectively. Note that the σ-T curve becomes an upwardly convex curve at a temperature equal to or higher than Tc1, and Tc1 and Tc2 can be clearly determined. From this, it is considered that the sintered body of the sample of the present invention has a two-phase structure having different magnetic properties. When each sample was analyzed by X-ray diffraction, it was found that each sample was a single phase of M-type ferrite. No significant difference was found in the lattice constant.

Comparative Example 1 [Sintered magnet: Sample 3 (before aqueous system)
Addition)] The following materials were used. Fe ₂ O ₃ powder (primary particle diameter 0.3 μm), 1000.0 g (including Mn, Cr, Si, Cl as impurities) SrCO ₃ powder (primary particle diameter 2 μm), 130.3 g (Ba, Ca as impurities (Including) Cobalt oxide 17.56 g La ₂ O ₃ 35.67 g

As an additive, 2.30 g of SiO ₂ powder (primary particle diameter: 0.01 μm) and 1.72 g of CaCO ₃ powder (primary particle diameter: 1 μm) were used.

The starting materials and additives were pulverized with a wet attritor, dried and sized, and then dried in air.
It was calcined at 250 ° C. for 3 hours to obtain a granular calcined body. As a result of measuring the magnetic properties of the obtained calcined body with a sample vibration magnetometer (VSM), the saturation magnetization σs was 68 emu / g, and the coercive force H was
cJ was 4.6 kOe.

The calcined body obtained was treated with SiO ₂ , CaC
O ₃ was mixed in the amounts shown in Table 1 and calcium gluconate was further added in the amounts shown in Table 1, followed by dry coarse pulverization for 20 minutes by a batch vibrating rod mill. At this time, distortion due to pulverization is introduced, and HcJ of the calcined body particles is
It had dropped to 1.7 kOe.

Next, 210 g of the thus-obtained coarsely pulverized material was sampled, and 400 cc of water was added as a dispersion medium and mixed to prepare a slurry for pulverization.

Using the slurry for wet grinding, wet grinding was performed in a ball mill for 40 hours. The specific surface area after the wet pulverization was 8.5 m ² / g (average particle size: 0.5 μm). The pH of the supernatant liquid of the slurry after the wet pulverization is 9 to 10
Met.

After the wet pulverization, the pulverization slurry was centrifuged to adjust the concentration of the calcined particles in the slurry to about 78%, thereby obtaining a molding slurry. Compression molding was performed while removing water from the molding slurry. This molding was performed while applying a magnetic field of about 13 kOe in the compression direction. The obtained molded body was a cylindrical shape having a diameter of 30 mm and a height of 18 mm. The molding pressure was 0.4 ton / cm ² . Also,
After a part of the slurry was dried and calcined at 1000 ° C. to be processed into an oxide, the amount of each component was analyzed by a fluorescent X-ray quantitative analysis method. Table 2 and Table 3
Shown in

Next, after heat-treating the molded body at 100 to 360 ° C. to sufficiently remove gluconic acid,
The temperature was raised at a rate of 5 ° C./min, and firing was performed by maintaining the temperature at 1220 ° C. for 1 hour to obtain a sintered body. After processing the upper and lower surfaces of the obtained sintered body, the residual magnetic flux density (Br), coercive force (HcJ and HcB), and maximum energy product [(BH) ma
x], saturation magnetization (4πIs), degree of magnetic orientation (Ir / I
s), squareness (Hk / HcJ) and sintered density were measured. Table 4 shows the results. The sample was then processed to a diameter of 5 mm and a height of 6.5 mm. In the same manner as in Embodiment 1, the VSM
The Curie temperature Tc was determined by measuring the temperature dependence of the magnetization in the c-axis direction. FIG. 7 shows the results. As is clear from the figure, Tc was one stage at 444 ° C.

Next, the specific resistance of each of the sintered sample Nos. 1 to 3 in the a-axis direction and the c-axis direction was measured. Table 5 shows the results. FIGS. 3 and 4 show SEM photographs of a structure obtained by observing the obtained sample No. 3 from the a-axis direction and the c-axis direction. As is clear from FIGS. 1, 2 and FIGS. 3 and 4, the ferrite of the present invention has a slightly larger grain size than the conventional product shown in FIGS.

[0129]

[Table 1]

[0130]

[Table 2]

[0131]

[Table 3]

[0132]

[Table 4]

[0133]

[Table 5]

As is clear from Table 4, the sintered body cores according to the present invention show extremely excellent properties.

As is clear from Table 5, Samples 1 and 2 of the present invention obtained by the post-addition step have smaller specific resistance values of 1/10 to 1/100 as compared with the samples obtained by the pre-addition step of the comparative example. showed that. From this, it is considered that the microstructure of the sintered body is different between the sample obtained in the pre-addition step and the sample obtained in the post-step. Further, also in the sample of the present invention, the sample having the La-rich composition of No. 2 had a specific resistance smaller by ４ to 方. In all samples, the value in the a-axis direction was smaller than the specific resistance in the c-axis direction.

[0136]Example 2 (after adding Fe, La, Co)
Comparison) The composition of Example 1 [SrFe₁₂O₁₉+ SiO_Two: 0.2
% By weight + CaCO_Three: 0.15% by weight] as in Example 1.
Calcination was performed in the same manner to obtain a calcined body. Granulated calcination obtained
The composition after addition to the body is Sr_1-xLa_xFe_12-xCo_xO₁₉ , X = y = 0, 0.1, 0.2, 0.3
Like, La_Two(CO_Three) _Three・ 8H_TwoO, CoO_x(CoO
+ Co_ThreeO_Four), The same iron oxide (α
-Fe_TwoO_Three) And SiO_Two(0.4% by weight), CaC
O_Three(1.25% by weight), calcium gluconate (0.
6% by weight) and coarsely pulverized by a small vibration mill.
Then, water pulverization was performed for 40 hours in the same manner as in Example 1.
I fired. Also, do not add calcium gluconate.
Using only water, xylene as solvent as dispersion medium
Using oleic acid as a dispersant
I thought.

FIG. 8 shows the degree of orientation of the compact according to the amounts of La and Co added to each of the obtained sintered compact samples, and FIG. 9 shows the HcJ-Br characteristics.
Shown in Here, Fe, La, amount after Co indicates the composition after the addition by the value of x in the case of the _{Sr 1-x La x Fe 12} -x Co x O 19. When calcium gluconate was used as the aqueous dispersant, the degree of orientation was clearly improved as the added amount after calcining (post-added amount) was increased.
In the 4-substitution, the value is close to the case where xylene is used as the non-aqueous solvent and oleic acid is used as the surfactant. On the other hand, when gluconic acid is not added to water, the degree of orientation is not improved. In many cases, the characteristics of the sintered body were Hk / HcJ> 90%, and those having x = 0.2 were the highest. On the other hand, when the addition amount increases (x>
0.3) Moldability deteriorated.

FIG. 10 shows the dependence of Tc on x at this time in comparison with the sintered body produced by the pre-addition of the organic solvent system (the method of Example 5). Of the two Curie temperatures, the lower Tc (Tc1) decreased with increasing x, but the higher Tc (Tc2) did not show much change. From this, Tc1 is La and Co
Sr with a large amount of substitution (at least a large amount of substitution with La)
It is expected to be Tc of the ferrite portion.

FIG. 11 shows the dependence of HcJ on x of the sintered body, which was obtained by adding the organic solvent before (the method of Example 5) and the aqueous body (by the method of Comparative Example 1). It is a figure shown in comparison with. Thereby, in the case of the pre-addition, the maximum value of HcJ is obtained when x = 0.3,
In the case of post-addition, it can be seen that the maximum value is obtained at x = 0.2. This indicates that high magnetic properties can be obtained in the case of post-addition even if the amount of expensive Co or the like added is reduced to about の of that in the case of pre-addition.

FIG. 12 shows the squareness (Hk) of the sintered body.
/ HcJ) with respect to x was determined by using an organic solvent-based pre-addition method (method of Example 5) and an aqueous pre-addition method (method of Comparative Example 1).
The results are shown in comparison with the sintered body manufactured by the above method. This allows
In the case of post-addition, it can be seen that high squareness (Hk / HcJ) can be obtained even in a composition having a large substitution amount x. Further, FIG. 13 shows the anisotropic magnetic field ( _HA ) calculated using the anisotropy constant (K1) measured by a torque meter, in comparison with the case of pre-addition of the organic solvent system. As is clear from the figure, _HA was almost the same value as in the case of the organic solvent-based pre-addition.

[0141]Example 3 (Pre-addition of Fe only, La and Co
Post-addition: comparison by calcination temperature) Sr: Fe = 0.8: 11.8 = 1: 14.75
The raw materials are weighed as described above and
Example except for calcining at 00 ° C, 1250 ° C, and 1300 ° C
In the same manner as in Example 1, a calcined body was obtained. Obtained calcined body sample
Was analyzed by X-ray diffraction to find that the M phase and the hematite phase (α
-Fe_TwoO_Three) Was confirmed. Where stoichiometry
Fe in excess of the composition (Sr: Fe = 1: 12)
α-Fe _TwoO_ThreePhase and the rest is SrM phase
Σs of the SrM phase in the calcined powder
It is almost equal to σs of SrM calcined material at the same calcining temperature.
Was.

The resulting calcined granular material was subjected to La ₂ (C ₂ ) in Sr _{1 -x} La _x Fe _{12 -y} Co _y O ₁₉ such that x = y = 0.2.
_{O 3) 3 · 8H 2 O} , CoO x (CoO + Co 3 O 4) + Si
O ₂ (0.4% by weight), CaCO ₃ (1.25% by weight), and calcium gluconate (0.6% by weight) were added and coarse grinding was performed with a small vibration mill. Coarse crushed material 2 obtained
To 10 g, 400 cc of water was added, and wet pulverization was carried out for 40 hours in the same manner as in Example 1 (but no Fe ₂ O ₃ was added), followed by sintering after wet magnetic field molding.

The degree of orientation of the obtained molded body was examined by X-ray diffraction, and the result is shown in FIG. As is clear from FIG. 14, the sample using the calcined body at 1250 ° C. has a high degree of orientation of the formed body, which is equivalent to that of the sample to which all of the calcined body is added later. FIG. 15 shows the relationship between the sintering density and the degree of magnetic orientation (Ir / Is) when the calcination temperature is 1250 ° C. In spite of the same degree of orientation of the formed body, the sample added after La and Co only has a higher density and orientation degree after firing. FIG. 16 shows the case where the calcination temperature was 1250 ° C.
cJ-Br and Hk / HcJ are shown. In the sample added after only La and Co, HcJ was low, but Br was high because of high density and high degree of orientation, and the characteristic level was almost the same as the sample of Example 2.

According to this production method, fine Fe ₂
Excellent magnetic properties can be obtained without adding a large amount of O ₃ . Further, since the moldability is relatively good, there is an advantage that the production is easy. When the Curie temperature of each of these samples was measured, it was confirmed that the samples had two or more different Curie temperatures.

Example 4 (before addition of Fe and La, after only Co)
The raw materials were weighed so that Sr: La: Fe = 0.8: 0.2: 11.8, and this was weighed at 1200 ° C. and 125 ° C., respectively.
A calcined body was obtained in the same manner as in Example 1 except for calcining at 0 ° C. When the obtained calcined body sample was analyzed by X-ray diffraction, the presence of the M phase and the hematite phase (α-Fe ₂ O ₃ phase) was confirmed, but orthoferrite (FeLaO ₃ ) was not confirmed.

The obtained granulated calcined product was subjected to CoO _x (C O _x (C O _x (C _x O _x C 2)) so that x = y = 0.2 in Sr _1-x La _x Fe _12-y Co _y O ₁₉ .
oO + Co ₃ O ₄ ) + SiO ₂ (0.4% by weight), CaC
O ₃ (1.25% by weight), calcium gluconate (0.
6% by weight) and coarsely pulverized by a small vibration mill.
Thereafter, water fine pulverization was performed for 40 hours, and after forming, firing was performed in the same manner as in Example 1.

Table 6 shows HcJ-Br and Hk / HcJ.

[0148]

[Table 6]

The characteristics were almost the same as in Examples 2 and 3.

Example 5 (In a post-addition step using a solvent-based dispersion medium)
Comparative Example ) Composition of Example 1 [SrFe ₁₂ O ₁₉ + SiO ₂ : 0.2
% + CaCO ₃ : 0.15% by weight], and the composition after addition is Sr _1-x La _x Fe _12-y Co _y O ₁₉ , where x = y = 0.1, 0.2, 0 A sintered body was prepared in the same manner as in Example 1 except that the dispersant was changed to calcium gluconate and oleic acid, and the dispersion medium was changed to xylene instead of water. .

On the other hand, the composition was adjusted such that x = y = 0.1, 0.2, 0.3, 0.4 in Sr _1-x La _x Fe _12-y Co _y O ₁₉ , A sintered body was prepared in the same manner as in Comparative Example 1, except that oleic acid was used instead of calcium gluconate and xylene was used instead of water as the dispersion medium.

FIG. 17 shows the squareness ratio Hk / HcJ of the obtained sintered body sample at 1220 ° C., and FIG. 18 shows the magnetic orientation degree (Ir / Is) characteristics depending on the amount of addition. Although the degree of orientation was almost at the same level, Hk / HcJ was improved by post-addition.

Example 6 (Study on Split Addition of La and Co) The following materials were used. Fe ₂ O ₃ powder (primary particle diameter 0.3 μm), 1000.0 g SrCO ₃ powder (primary particle diameter 2 μm), 161.2 g

The starting material was pulverized with a wet attritor, dried and sized, and calcined in air at 1250 ° C. for 3 hours to obtain a granular calcined body.

With respect to the obtained calcined body, SiO ₂ = 0.6% by weight and CaCO ₃ = 1.4% by weight at the time of dry vibration mill pulverization.
Together with lanthanum carbonate [La ₂ (CO ₃ ) ₃ .8H ₂ O],
Cobalt oxide (CoO), calcium gluconate (0.
9% by weight). At that time, the La / Co ratio was changed by changing the amount of La added. In addition, iron oxide (Fe ₂ O ₃ ) was added at the time of ball milling. The calcined body (referred to as a base material in the table) is made of lanthanum carbonate [La ₂ (C
O _{3) 3} · 8H ₂ O], it was prepared which was added quantity x = 0 and 0.1 prior to cobalt oxide (CoO). Table 7 shows the composition ratio of each sample and the analysis value of the finely pulverized material.

[0156]

[Table 7]

Each of the obtained samples was heated at 1200 ° C. and 122 ° C.
Baking was performed at 0 ° C. and 1240 ° C., respectively, and the magnetic properties were measured. FIG. 19 shows the results. In each sample,
Relatively high HcJ and Hk were obtained with the La-rich composition (La / Co = 1.14 to 1.23). La / C
Comparing at the optimal point of o, for the base material of x = 0.1, x
= 0.1 after addition, Hk tends to deteriorate, and x =
In the case of adding x = 0.2 after the base material of 0, high sintered magnetic properties were obtained. Addition of La and Co during pulverization (post addition)
Shows that Hk higher than that at the time of compounding (pre-addition) can be obtained, but in this example, an intermediate behavior between the two was obtained, and no characteristic result was obtained.

In the above examples, ferrites containing Sr were described, but it was confirmed that equivalent results were obtained with ferrites containing Ca or Ba.

Further, in each of the above embodiments, a C-shaped sintered magnet for a motor was obtained in the same manner except that the sample of the present invention was changed from a cylindrical shape for measurement to a field magnet for a C-type motor. Was. The obtained core material was incorporated into a motor in place of a conventional sintered magnet, and when operated under rated conditions, good characteristics were exhibited. When the torque was measured, it was higher than that of the motor using the conventional core material.
Similar results were obtained with bonded magnets.

Example 7 (HcJ Temperature Characteristics Added Later) The coercive force (HcJ) temperature characteristics of the sintered body samples produced in Example 1 and Comparative Example 1 were measured. -100 ° C to +1
The measured value of HcJ at 00 ° C. was a correlation coefficient of 99.9% or more, and the least square method linear approximation was performed. When the temperature characteristics of HcJ were calculated based on this, the results shown in Table 8 below were obtained. This shows that the LaCo-containing ferrite having two Tc's produced by the post-addition manufacturing method also has excellent HcJ temperature characteristics equal to or better than those of the pre-addition.

[0161]

[Table 8]

Example 8 (Post-Pr addition) Pr ₂ (CO ₃ ) was used instead of La ₂ (CO ₃ ) ₃ 8H ₂ O.
_A sintered magnet was prepared in the same manner as in Example 2 except that 30.5 H ₂ O was used, and the magnetic properties and the like were evaluated. FIG. 20 shows the dependence of the Curie point Tc on the substitution amount x in comparison with a sintered body produced by pre-addition of an organic solvent system (the method of Example 5). The lower Tc (Tc1) of the two Curie temperatures Tc decreased with an increase in the substitution amount x,
The higher Tc (Tc2) did not show much change. From this, it is expected that Tc1 is the Tc of the Sr ferrite portion having a large substitution amount of Pr and Co (at least having a large Pr substitution amount).

FIG. 21 shows the dependence of HcJ on x of the sintered body in comparison with the sintered body produced by the addition of the organic solvent system (the method of Example 5). Thus, in the case of the post-addition, the maximum value was obtained at x = 0.1, and a higher HcJ was obtained than in the case of the pre-addition of the organic solvent system.

[0164]

As described above, according to the present invention, by increasing the saturation magnetization and magnetic anisotropy of the M-type ferrite simultaneously, a high residual magnetic flux density which cannot be achieved with the conventional M-type ferrite magnet is obtained. Ferrite magnet with excellent coercive force and temperature characteristics of coercive force, especially excellent magnetic characteristics with little decrease in coercive force even at low temperatures, and excellent squareness of demagnetization curve And a method for manufacturing the same.

Further, it is possible to provide a ferrite magnet capable of obtaining high characteristics even if the content of expensive Co is reduced, and a method of manufacturing the same.

In addition, it is possible to provide a ferrite magnet having a degree of orientation comparable to that of a solvent-based ferrite magnet even in a water-based manufacturing process, and a method for manufacturing the same.

Furthermore, a motor and a magnetic recording medium having good characteristics can be provided.

[Brief description of the drawings]

FIG. 1 shows the structure of the a-plane of the sintered magnet sample 1 of the present invention as S
It is a drawing substitute photograph taken by EM.

FIG. 2 shows the structure of the c-plane of the sintered magnet sample 1 of the present invention as S
It is a drawing substitute photograph taken by EM.

FIG. 3 is a drawing substitute photograph taken by SEM of a structure of an a-plane of Comparative Sample 3.

FIG. 4 is a drawing substitute photograph of the c-plane structure of Comparative Sample 3 taken by SEM.

FIG. 5 is a graph showing a σ-T curve of Sample 1 of the present invention.

FIG. 6 is a graph showing a σ-T curve of Sample 2 of the present invention.

FIG. 7 is a graph showing a σ-T curve of Comparative Sample 1.

FIG. 8 is a graph showing the degree of orientation according to the amount of LaCo substitution in the sample of the present invention.

FIG. 9 is a graph showing HcJ-Br characteristics of the sample of the present invention.

FIG. 10 is a graph showing the dependence of the Curie point Tc on x of a sample of the present invention added after an aqueous system and a comparative sample added before an organic solvent.

FIG. 11 is a graph showing the dependence of HcJ on x for a sample of the present invention added after an aqueous system and a comparative sample added before an organic solvent.

FIG. 12 shows the squareness (Hk / HcJ) x of the sample of the present invention added after the aqueous system and the comparative sample added before the organic solvent.
6 is a graph showing the dependency on.

FIG. 13 is a graph showing the anisotropic magnetic field (H _A ) of a sample of the present invention added after an aqueous system and a comparative sample added before an organic solvent.

FIG. 14 is a graph showing the degree of orientation of the sample of the present invention.

FIG. 15 is a graph showing the degree of magnetic orientation according to density of the sample of the present invention at a calcining temperature of 1250 ° C.

FIG. 16 shows H at a calcining temperature of 1250 ° C. of the sample of the present invention.
It is a graph which showed cJ-Br and Hk / HcJ.

FIG. 17 is a graph showing the squareness Hk / HcJ of the sample of the present invention at 1220 ° C.

FIG. 18 shows the degree of magnetic orientation (I
(r / Is). is there.

FIG. 19 is a graph showing magnetic properties of samples fired at 1200 ° C., 1220 ° C., and 1240 ° C., respectively.

FIG. 20 is a graph showing the dependence of the Curie point Tc on x of a sample of the present invention before addition of an organic solvent and a comparative sample after addition of an aqueous solvent.

FIG. 21 is a graph showing the dependence of HcJ on x of a sample of the present invention before addition of an organic solvent and a comparative sample after addition of an aqueous solvent.

FIG. 22 is a reference graph for explaining how to determine two Curie temperatures.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI // H02K 15/03 H02K 15/03 A (72) Inventor Kazumasa Iida 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside (72) Inventor Mitsuaki Sasaki 1-1-13 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Fumihiko Hirata 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation ( 58) Field surveyed (Int.Cl. ⁷ , DB name) H01F 1/09-1/117 G11B 5/706 C04B 35/26-35/40

Claims (20)

(57) [Claims] 1. A (A is Sr, Ba or Ca), Co
And R [R represents at least one element selected from the group consisting of rare earth elements (including Y) and Bi], and has a main phase of hexagonal ferrite, and has at least two different Curie temperatures. A magnetic powder wherein the two different Curie temperatures are in the range of 400 ° C. to 480 ° C. and the absolute value of the difference is greater than or equal to 5 ° C. 2. The magnetic powder according to claim 1, wherein said R contains at least La. 3. The magnetic powder according to claim 1, wherein the hexagonal ferrite is a magnetoplumbite ferrite. 4. The hexagonal ferrite is at least one element selected from the group consisting of Sr, Ba, Ca and Pb, and always contains Sr or Ba as A ′, and rare earth elements (including Y). When at least one element selected from R and Bi is R, and Co or Co and Zn is M, it is composed of A ′, R, Fe and M, and the total composition ratio of each metal element is A ′: 1 to 13 atomic%, R: 0.05 to 10 atomic%, Fe: 80 to 95 atomic%, M: 0.1 to 5 atomic%, based on the total metal element amount. 3. The magnet powder of any one of (3). 5. The magnetic powder according to claim 1, wherein the ratio of Co in M is 10 atomic% or more. 6. The magnetic powder according to claim 1, wherein the temperature coefficient (absolute value) of the coercive force at −50 to 50 ° C. is 0.1% / ° C. or less. 7. A bonded magnet comprising the magnet powder according to claim 1. 8. A motor having the bonded magnet according to claim 7. 9. A magnetic recording medium comprising the magnet powder according to claim 1. 10. A (A is Sr, Ba or Ca), C
A sintered magnet having a main phase of hexagonal ferrite containing o and R (R represents at least one element selected from rare earth elements (including Y) and Bi), wherein at least two different Curie A sintered magnet having a temperature, wherein the two different Curie temperatures are in the range of 400 ° C. to 480 ° C. and the absolute value of these differences is greater than or equal to 5 ° C. 11. The sintered magnet according to claim 10, wherein said R includes at least La. 12. The sintered magnet according to claim 10, wherein the hexagonal ferrite is a magnetoplumbite ferrite. 13. The hexagonal ferrite is at least one element selected from the group consisting of Sr, Ba, Ca and Pb, and always contains Sr or Ba as A ′ and a rare earth element (including Y). When at least one element selected from R and Bi is R, and Co or Co and Zn is M, it is composed of A ′, R, Fe and M, and the total composition ratio of each metal element is A ′: 1 to 13 atomic%, R: 0.05 to 10 atomic%, Fe: 80 to 95 atomic%, and M: 0.1 to 5 atomic%, based on the total amount of metal elements. 12. The sintered magnet according to any one of 12 above. 14. The sintered magnet according to claim 10, wherein a ratio of Co in M is 10 atomic% or more. 15. The sintered magnet according to claim 10, wherein the squareness Hk / HcJ is 90% or more. 16. The sintered magnet according to claim 10, wherein the degree of orientation Ir / Is is 96% or more. 17. The sum of the X-ray diffraction intensities from the c-plane (ΔI
(00L)) and the sum of X-ray diffraction intensities from all surfaces (Σ
I (hkL)) is at least 0.85.
The sintered magnet according to any one of to 15, wherein 18. The temperature coefficient (absolute value) of the coercive force at −50 to 50 ° C. is 0.25% / ° C. or less.
The sintered magnet according to any one of Items 1 to 17, 19. A motor having the sintered magnet according to claim 10. 20. A (A is Sr, Ba or Ca), C
o, R (R represents at least one element selected from rare earth elements (including Y) and Bi) and a hexagonal ferrite main phase containing Fe, and has at least two different Curie temperatures. A magnetic recording medium having a thin-film magnetic layer in which the two different Curie temperatures are in the range of 400 ° C. to 480 ° C., and the absolute value of the difference is 5 ° C. or more.