JPH1197225A - Anisotropic sintered magnet, bonded magnet, and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Ba ferrite anisotropic sintered magnet, which is superior in temperature characteristic with coercive force HcJ, a bonded magnet, and a magnetic recording medium. SOLUTION: At least one kind of element selected from among rare-earth element (including Y) and Bi is set as R, while Co or Co and Zn is set as M, a hexagonal system magnet-plumbite type ferrite wherein, relating to a constituting ratio of a total of metal elements of Ba, R, Fe, and M, Ba is 1-13 atom %, R is 0.05-10 atom %, Fe is 80-95 atom %, and M is 2-6.5 atom % to total metal element amount is provided as a main phase, while a temperature change ΔHcJ/ΔT in coercive force at -50 to 50 deg.C is -5 to 50 e/ deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an anisotropic sintered magnet of hexagonal magnetoplumbite-type Ba ferrite, a bonded magnet, and a magnetic recording medium.

[0002]

2. Description of the Related Art Magnetoplumbite (M-type) hexagonal Sr ferrite or Ba ferrite is mainly used as an oxide permanent magnet material, and sintered magnets thereof are manufactured. Particularly important of these magnet properties are the residual magnetic flux density (Br) and the intrinsic coercive force (H
cJ).

The temperature dependency of HcJ of a conventional anisotropic M-type Ba 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. For this reason, HcJ is greatly reduced on the low temperature side and demagnetized. 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.

[0004] Ferrite magnets are often used in motors used in various parts of automobiles because of their excellent environmental resistance and low cost. Automobiles are sometimes used in cold or extremely hot environments, and motors are also required to operate stably in such harsh environments. But,
As described above, the conventional ferrite magnet has a problem in that the coercive force is significantly deteriorated in a low temperature environment.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a practically sufficient residual magnetic flux density and coercive force, and to have extremely excellent temperature characteristics of the coercive force. Anisotropic M-type Ba ferrite sintered magnet,
It is to provide a bonded magnet and a magnetic recording medium.

[0006]

This and other objects are achieved by any one of the following constitutions (1) to (9). (1) R is at least one element selected from rare earth elements (including Y) and Bi and is Co or Co
When Zn and M are M, the total composition ratio of each of the metal elements of Ba, R, Fe and M is such that Ba: 1 to 13 atomic% and R: 0.05 to 10 atomic% with respect to the total amount of the metal elements. , Fe: 80 to 95 atomic%, M: 2 to 6.5 atomic%, having a hexagonal magnetoplumbite-type ferrite as a main phase, and a temperature change of coercive force at −50 to 50 ° C.
An anisotropic sintered magnet having a HcJ / ΔT of -5 to 5 Oe / ° C. (2) the hexagonal magnetoplumbite ferrite, when expressed with the formula _{I Ba 1-x R x (} Fe 12-y M y) z O 19, 0.04 ≦ x ≦ 0.9, 0.3 <Y ≦ 0.8, 0.7 ≦ z ≦ 1.2, the anisotropic sintered magnet of the above (1). (3) The anisotropic sintered magnet according to (1) or (2), wherein R always contains La. (4) The anisotropic sintered magnet according to any one of the above (1) to (3), wherein the ratio of La in R is 40 atom% or more. (5) The anisotropic sintered magnet according to any one of the above (1) to (4), wherein the ratio of Co in M is 10 atomic% or more. (6) A motor having the anisotropic sintered magnet according to any one of (1) to (5). (7) R is at least one element selected from rare earth elements (including Y) and Bi, and is Co or Co
When Zn and M are M, the total composition ratio of each metal element of A, R, Fe and M is such that Ba: 1 to 13 atomic% and R: 0.05 to 10 atomic% with respect to the total amount of metal elements. , Fe: 80 to 95 atomic%, M: 2 to 6.5 atomic%, having a hexagonal magnetoplumbite type ferrite as a main phase, and a temperature change of coercive force at −50 to 50 ° C.
A bonded magnet containing a magnet powder having a HcJ / ΔT of -5 to 5 Oe / ° C. (8) A magnetic recording medium containing the magnet powder of (7). (9) When at least one element selected from rare earth elements (including Y) and Bi and always including La is R, and Co or Co and Zn are M, A, R, The composition ratio of the total of the metal elements of Fe and M is as follows: Ba: 1 to 13 atomic%, R: 0.05 to 10 atomic%, Fe: 80 to 95 atomic%, M: 2 A thin-film magnetic layer containing a main phase of hexagonal magnetoplumbite type ferrite of about 6.5 atomic% and having a temperature change of coercive force at −50 to 50 ° C. ΔHcJ / ΔT of −5 to 5 Oe / ° C. Magnetic recording medium.

[0007]

According to the present invention, in the M-type Ba ferrite, an optimum amount of R and M is contained so that a high H content is obtained.
The temperature dependence of cJ can be significantly reduced.

[0008] The anisotropic sintered magnet, bonded magnet and magnetic recording medium of the present invention have extremely low temperature dependence of HcJ. Specifically, -50 to
The temperature change of HcJ at 50 ° C. ΔHcJ / ΔT is −5 to
5 Oe / ° C, -3 to 3 Oe / ° C, particularly -2.5 to 2.
It is 5 Oe / ° C, and more preferably −2 to 2 Oe / ° C, and can easily be set to 0 Oe / ° C. Further, the anisotropic sintered magnet, the bonded magnet and the magnetic recording medium of the present invention may have a size of -50 to -5.
The temperature coefficient (absolute value) of HcJ at 0 ° C. is 0.2% / ° C.
Hereinafter, it is particularly 0.1% / ° C. or less, and the temperature coefficient can be set to zero. Such characteristics in a low-temperature environment cannot be achieved with a conventional Ba ferrite anisotropic sintered magnet. For this reason, it is possible to improve the reliability of a product used even in a low-temperature environment where there is a risk of low-temperature demagnetization (permanent demagnetization) of a Ba ferrite magnet.

By the way, Bull.Acad.Sci.USSR, phys.Ser.
(English Transl.) Vol.25, (1961) pp1405-1408 (hereinafter,
Literature 1) describes a Ba ferrite represented by Ba _1-x M ³⁺ _x Fe _12-x M ²⁺ _x O ₁₉ . This Ba
In ferrite, M ³⁺ is La ³⁺ , Pr ³⁺ or Bi
³⁺ , and M ²⁺ is Co ²⁺ or Ni ²⁺ . It is unclear whether the Ba ferrite of Document 1 is a powder or a sintered body, but even if it is a sintered body, it is considered to be an isotropic magnet without suggesting that it is an anisotropic magnet. . However, it is the same as the Ba ferrite of the present invention in containing La and Co. In Fig. 1 of Reference 1, the change in saturation magnetization of Ba ferrite containing La and Co with the change of x is described. In Fig. 1, the saturation magnetization decreases as x increases. ing. Further, although there is a description in Document 1 that the coercive force has increased several times, no specific numerical value is described. No mention is made of the temperature dependence of the coercive force of anisotropic magnets, bonded magnets, or magnetic recording media.

On the other hand, in the present invention, the temperature dependency of HcJ is remarkably improved by using a composition containing the optimum amounts of La and Co in the Ba ferrite anisotropic sintered magnet. . The fact that such an effect is obtained when the composite addition of La and Co is applied to a Ba ferrite anisotropic sintered magnet is not even shown in Document 1, but was first discovered in the present invention. It is.

[0011] Japanese Patent Application Laid-Open No. 62-100147 (hereinafter, referred to as
The literature 2), 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 sintered magnet 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 the temperature dependence of the coercive force is significantly 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. Sho 62-119760 (hereinafter referred to as "
Reference 3) describes a magneto-optical recording material characterized in that part of Ba of magnetoplumbite-type barium ferrite is replaced with La and part of Fe is replaced with Co. In this Ba ferrite, La
It is the same as the Ba ferrite of the present invention in containing Co and Co. However, the ferrite of Document 3 records information by writing magnetic domains in a magnetic thin film using the thermal effect of light,
This is a material for "magneto-optical recording" in which information is read out by using the magneto-optical effect. The technical field is different from the anisotropic magnet, the bonded magnet, and the magnetic recording medium of the present invention. That is, as described above, the Ba ferrite of the present invention can significantly improve the temperature dependency of HcJ by using a composition in which La and Co are respectively added in optimal amounts to the Ba ferrite anisotropic sintered magnet. It is what it was.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The anisotropic sintered magnet of the present invention, the magnet powder of a bonded magnet or a magnetic recording medium, and the thin film of a magnetic recording medium are at least selected from rare earth elements (including Y) and Bi. When one type of element is R and Co or Co and Zn is M, the total composition ratio of each of Ba, R, Fe and M metal elements is such that Ba: 1 to Ba with respect to the total amount of metal elements. 13 atomic%, R: 0.05-10
It has a hexagonal magnetoplumbite-type (M-type) ferrite having an atomic%, Fe: 80 to 95 atomic%, and M: 2 to 6.5 atomic% as a main phase.

Preferably, Ba: 2 to 11 at%, R: 0.2 to 6 at%, Fe: 80 to 95 at%,
M: 3 to 5 atomic%, more preferably B
a: 3 to 9 atomic%, R: 0.5 to 4 atomic%, Fe: 83
９４94 at%, M: 3.3-4.7 at%.

If the content of Ba is too small, M-type ferrite will not be formed, or a non-magnetic phase such as αFe ₂ O ₃ will increase. On the other hand, if the content of Ba is too large, M-type ferrite will not be generated, or the amount of nonmagnetic phase such as BaO.Fe ₂ O ₃ will increase. If the amount of R is too small, the amount of solid solution of M decreases, and Br and HcJ decrease. If there is too much R,
Non-magnetic hetero phase such as orthoferrite increases. If M is too small or M is too large, the temperature characteristics of HcJ deteriorate.

In each of the above constituent elements, a part of Ba is
It may be substituted with at least one of Sr, Ca and Pb. These substitution amounts with respect to Ba are preferably 49 atomic% or less, more preferably 30 atomic% or less.

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 is always contained. If the amount of R is too small, the amount of solid solution of M decreases, and the effect of the present invention cannot be obtained. If R is too large, non-magnetic hetero phase such as orthoferrite increases. 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 ratio of La in R is too low, the amount of solid solution of R cannot be increased, and as a result, the amount of solid solution of element M cannot be increased. Is getting smaller. 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. The ratio of Co in M is preferably at least 10 atomic%, more preferably at least 20 atomic%. If the ratio of Co is too low, the improvement of the coercive force becomes insufficient.

Further, the main phase hexagonal magnetoplumbite-type of the present invention (M-type) ferrite, when expressed with the formula _{I Ba 1-x R x (} Fe 12-y M y) z O 19, 0 0.04 ≦ x ≦ 0.9, 0.3 <y ≦ 0.8, and 0.7 ≦ z ≦ 1.2.

More preferably, 0.1 ≦ x ≦ 0.4, 0.3 ≦ y ≦ 0.7, particularly 0.4 ≦ y ≦ 0.6, 0.8 ≦ x / y ≦ 5, 0 0.8 ≦ z ≦ 1.1, and particularly preferably 0.9 ≦ z ≦ 1.05.

In the above formula I, if x is too small, that is, if the amount of the element R is too small, the solid solution amount of the element M in the hexagonal ferrite cannot be increased, and the saturation magnetization and the anisotropic magnetic field decrease. Will come. If x is too large, the element R cannot be substituted and solid-solved in the hexagonal ferrite, and for example, orthoferrite containing the element R is generated, and the saturation magnetization decreases. If y is too small, the saturation magnetization and the anisotropic magnetic field decrease. If y is too large, the element M cannot be substituted and solid-solved in the hexagonal ferrite. Further, even in a range where the element M can be substituted for a solid solution, the anisotropy constant (K ₁ ) and the anisotropic magnetic field (H _A ) greatly deteriorate. If z is too small or z is too large, the temperature characteristics of the coercive force deteriorate. Particularly, the deterioration of the temperature characteristic of the coercive force occurs critically when the amount of M is less than 3 atomic% and exceeds 5 atomic%.

In the above formula I, if x / y is too small or too large, it becomes difficult to balance the valence of the element R and the element M, and a heterogeneous phase such as W-type ferrite is easily formed. come. Since the element M is divalent, x / y = 1 is ideal when the element R is a trivalent ion. In addition,
The reason why the allowable range is large in the region where x / y exceeds 1 is that even when y is small, the valence can be balanced by the reduction of Fe ³⁺ → Fe ²⁺ .

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
May also change to divalent, 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 the ferrite can be measured by a fluorescent X-ray quantitative analysis or the like. The presence of the main phase is confirmed by X-ray diffraction.

The magnet 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. The content of B ₂ O ₃ is preferably 0.5% by weight or less of the whole magnet. If the B ₂ O ₃ content is too large, the saturation magnetization will be low.

The magnet may contain at least one of Na, K and Rb. These are respectively Na
When converted to ₂ O, K ₂ O and Rb ₂ O, the total of these contents is preferably 3 wt% or less of the whole magnet. If these contents are too large, the saturation magnetization will be low. When these elements expressed in M ^I, the M ^I in a ferrite for example ^{_{Ba 1.3-2a R a M I a-}} 0.3 F
e It is contained in the form of _11.7 M _0.3 O ₁₉ . In this case,
It is preferable that 0.3 <a ≦ 0.5. 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 for manufacturing an anisotropic sintered magnet, a bonded magnet and a magnetic recording medium will be described. First,
Magnet powder is produced by calcination. The calcined magnet powder has the above composition. And, even if the average particle diameter exceeds 1 μm, a higher coercive force can be obtained as compared with the related art. The average particle size is preferably 2 μm or less, more preferably 1 μm or less, and still more preferably 0.1 to 1 μm. If the average particle size is too large, the ratio of multi-domain particles in the magnet powder will increase and the HcJ will decrease. If the average particle size is too small, the magnetism will decrease due to thermal disturbance or the orientation during molding in a magnetic field will be reduced. And the moldability deteriorates. The Curie temperature of the magnet powder having the above composition is usually 415 to 460 ° C.

The magnet powder is usually used for a bonded magnet in which the powder is bonded with a binder. The binder is usually NBR rubber, chlorinated polyethylene, nylon 1
2 (polyamide resin), nylon 6 (polyamide resin)
Are used. Further, a magnetic recording medium may be used.

The ferrite-containing magnet powder is usually made of iron oxide powder, Ba-containing powder,
It is produced by using a powder containing the element R and a powder containing the element M and calcining a mixture of these powders. Ba
The powder containing the element, the powder containing the element R, and the powder containing the element M may be any of an oxide or a compound that becomes an oxide by firing, such as a carbonate, a hydroxide, or a nitrate. 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. Ba is preferably a carbonate or a hydroxide from the viewpoint of stability at the time of stocking.

In addition to the above-mentioned raw material powder, if necessary, B ₂ O ₃ and the like and other compounds such as Si, Al, Ga, I
n, Li, Mg, Mn, Ni, Cr, Cu, Ti, Z
r, Ge, Sn, V, Nb, Ta, Sb, As, W, M
A compound containing o or the like may be contained as an additive or an impurity such as an unavoidable component.

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 its 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, the calcined body is usually pulverized or pulverized to obtain a magnet powder. Then, this magnet powder is kneaded with various binders such as resin, metal, rubber and the like, and molded in a magnetic field or in a non-magnetic field. Thereafter, curing is performed as necessary to obtain a bonded magnet, preferably an anisotropic bonded magnet.

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 sintered magnet is manufactured by pulverizing the calcined body, if necessary, molding and sintering. Specifically, it is preferable to manufacture according to the following procedures.

Since the calcined particles are generally in the form of granules, in order to pulverize or disintegrate them, it is preferable to first carry out dry coarse pulverization. Dry coarse pulverization also has the effect of introducing crystal strain into the calcined particles to reduce the coercive force HcB. Due to the decrease in coercive force, aggregation of particles is suppressed, and dispersibility is improved.
Further, by suppressing the aggregation of the particles, the degree of orientation is improved. The crystal strain introduced into the particles is released in a later sintering step, and the coercive force is restored, so that the particles can be made permanent magnets. In the case of dry coarse pulverization, usually,
SiO ₂ and CaCO ₃ which becomes CaO upon firing are added. SiO ₂ and CaCO ₃ may be partially added before calcining. Impurities and added Si and Ca
Is segregated mostly at grain boundaries and triple junctions, but a part is also taken into the ferrite part (main phase) in the grains. Especially Ca
Is likely to be on the Sr site.

After the dry rough pulverization, it is preferable to prepare a pulverization slurry containing the calcined particles and water, and to perform wet pulverization using the slurry.

After the wet pulverization, the pulverizing slurry is concentrated to prepare a molding slurry. Concentration may be performed by centrifugation, a filter press, or the like.

The molding may be performed by a dry method or a wet method, but it is preferable to perform a wet method in order to increase the degree of orientation. 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.

In wet molding, a non-aqueous dispersion medium or an aqueous dispersion medium may be used. When a non-aqueous dispersion medium is used, for example, as described in JP-A-6-53064, a surfactant such as oleic acid is added to an organic solvent such as toluene or xylene. And a dispersion medium. By using such a dispersion medium, it is possible to obtain a high degree of magnetic orientation of about 98% at the maximum even when ferrite particles having a submicron size that are difficult to disperse are used. On the other hand, as the aqueous dispersion medium, one obtained by adding various surfactants to water may be used.

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 a sintered anisotropic ferrite magnet.

The average crystal grain size of the sintered 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. , A sufficiently high coercive force can be obtained. The crystal grain size can be measured by a scanning electron microscope. The specific resistivity is 10 ⁰ [Omega] m or more.

The compact is crushed with a crusher or the like, and the average particle size is 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. Further, a magnetic recording medium may be obtained from the pulverized 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 represented by the above formula I, similarly to the above-described magnet powder of the present invention. Further, the content of impurities and the like is equivalent to that of the powder magnet.

For the formation of the thin film magnetic layer, it is usually preferable to use a sputtering method. When using the sputtering method,
The sintered magnet may be used as a target, or a multi-source sputtering method using at least two types of oxide targets may be used. After forming the sputtered film, heat treatment is usually performed to form a hexagonal magnetoplumbite structure.

By using the ferrite magnet of the present invention, the following effects can be generally obtained, and excellent application products 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. Further, if the same function as in the related art is sufficient, the size (thickness) of the magnet can be reduced (thinned), which contributes 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. In addition, 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 bonded magnet and sintered magnet using the magnetic powder of the present invention are processed into a predetermined shape and used for a wide range of applications 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 axis, indirect 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.

[0050]

【Example】

Example 1 Ba _1-x La _x Fe _12-y Co _y O ₁₉ where x = y = 0, 0.1, 0.2, 0.3, 0.4, 0.
The raw materials were weighed and mixed so that the ratio of 6, 0.8, 1.0 Ba: La: Co: Fe was in the above formula. The raw materials used are α-Fe ₂ O ₃ (for industrial use), La ₂ O ₃ (99.9%), BaCO ₃ , and cobalt oxide (reagent, Co content 71 wt%). At this time, S
iO ₂ (0.4 wt%) and CaCO ₃ (1.25 wt%) were simultaneously added. The weighed raw materials were mixed with a wet attritor and then dried. The obtained mixed powder is placed in a batch furnace.
Calcination was performed in the air at 1200 ° C. for 3 hours.

Thereafter, SiO ₂ (0.4 wt.
%), 1 ml of CaCO ₃ (1.25 wt%) and ethanol were added, and pulverized by a dry vibration type rod mill for 20 minutes. 1.3 wt% of oleic acid was added to the pulverized powder, and ball mill pulverization was performed in xylene for 40 hours. The obtained slurry was adjusted by a centrifugal separator so that the slurry concentration became about 85%. Next, a wet press (press pressure 0.4 ton / cm ² ) is performed in a magnetic field of about 10 kOe,
A cylindrical sample of 30φ × 15 mm was prepared. The obtained molded body was heated at 200 ° C. and 1240 ° C. in the air, respectively.
The firing was performed for a time.

After firing, the sample was polished, and the magnetic properties were evaluated using a BH tracer. In addition, 5mmφ
× 6.5 column (height direction is c-axis direction)
Using SM, in the temperature range of -195 ° C to + 150 ° C, c
An axial magnetization curve was measured.

<Results> The element ratio of each calcined sample was as shown in Table 1.

[0054]

[Table 1]

FIG. 1 shows Br and HcJ of the sintered body. x
At> 0.8, Br and Hcj dropped sharply. FIG. 2 shows the saturation magnetization (σs) per weight of the sintered body. At the same time, it shows σs of the calcined powder. In the case of the calcined powder, σs monotonously decreased with an increase in x, but s of the sintered body was 0 ≦ x
At ≦ 0.8, no significant change was observed. FIG. 3 shows the squareness (Hk / Hcj) of the sintered body at this time.

FIG. 4 shows the temperature dependence of Hcj of the sintered body at 1180 ° C. From this data, Hcj in the range of ± 50 ° C.
FIG. 5 shows the result of calculating the temperature change rate (Oe / ° C.) of the sample. FIG. 6 shows the result of calculating the temperature coefficient (% / ° C.) from the same data. It can be seen that the sign of the temperature coefficient of Hcj changes from plus to minus as x increases, and the temperature change of Hcj becomes almost zero near x = 0.5.
At this time, the composition was Ba = La = Co = 3.9 at%, Fe =
86.8 at%, Si = 0.6 at%, and Ca = 1.1 at%.

Example 2 When a part of La was replaced with Bi in the Ba ferrite prepared in Example 1, it was found that the calcination temperature could be lowered by adding Bi. That is, the calcination temperature at which the best characteristics were obtained was shifted to the lower temperature side, and the temperature characteristics of the coercive force were hardly deteriorated. Further, when a calcined body and a sintered body were produced with a composition in which La was partially replaced by another rare earth element, improvement in the temperature characteristics of HcJ was recognized as in Example 1 above.

Further, when an anisotropic bonded magnet was produced using the calcined Sr ferrite produced in each of the above Examples, good HcJ temperature characteristics were obtained.

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 column 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.

Further, when the coating type magnetic layer containing the calcined Sr ferrite body prepared in each of the above embodiments was formed on a substrate to produce a magnetic card, good HcJ temperature characteristics were obtained.

Further, a thin film is formed on a substrate by a sputtering method, and the thin film is heat-treated to form a hexagonal magnetoplumbite-type ferrite phase similar to that of the above embodiment to form a thin film magnetic layer. As a result, good temperature characteristics of HcJ were obtained.

[Brief description of the drawings]

FIG. 1. La and Co for Ba ferrite sintered body
3 is a graph showing the relationship between the substitution rate (x) and the coercive force and residual magnetic flux density.

FIG. 2 shows La and Co for a Ba ferrite sintered body.
5 is a graph showing the relationship between the substitution rate (x) and saturation magnetization.

FIG. 3 shows La and Co for Ba ferrite sintered body.
3 is a graph showing the relationship between the substitution rate (x) and squareness.

FIG. 4 shows that La and Co are used for Ba ferrite sintered body.
3 is a graph showing the relationship between the substitution rate (x) and the temperature dependence of the coercive force.

FIG. 5 shows La and Co for a Ba ferrite sintered body.
Is a graph showing the relationship between the substitution rate (x) and the rate of temperature change of the coercive force.

FIG. 6 shows La and Co for Ba ferrite sintered body.
3 is a graph showing the relationship between the substitution rate (x) and the temperature dependence of the coercive force.

Continued on the front page (72) Inventor Kazumasa Iida 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation

Claims (9)

[Claims] 1. When at least one element selected from a rare earth element (including Y) and Bi is R, and Co or Co and Zn are M, each metal of Ba, R, Fe and M The total composition ratio of the elements is as follows: Ba: 1 to 13 at%, R: 0.05 to 10 at%, Fe: 80 to 95 at%, M: 2 to 6.5 at% with respect to the total metal element amount. Having a hexagonal magnetoplumbite ferrite as a main phase, and a temperature change of coercive force at −50 to 50 ° C. ΔHcJ / ΔT
Is -5 to 5 Oe / ° C. 2. The hexagonal magnetoplumbite ferrite represented by the formula IBa _1-x R _x (Fe _12-y M _y ) _z O ₁₉ , wherein 0.04 ≦ x ≦ 0.9, 0 3. The anisotropic sintered magnet according to claim 1, wherein 0.3 <y ≦ 0.8 and 0.7 ≦ z ≦ 1.2. 3. The anisotropic sintered magnet according to claim 1, wherein R always contains La. 4. The anisotropic sintered magnet according to claim 1, wherein a ratio of La in R is 40 atomic% or more. 5. The anisotropic sintered magnet according to claim 1, wherein a ratio of Co in M is 10 atomic% or more. 6. A motor having the anisotropic sintered magnet according to claim 1. 7. When at least one element selected from a rare earth element (including Y) and Bi is R, and Co is Co or Zn is M, each metal of A, R, Fe and M The total composition ratio of the elements is as follows: Ba: 1 to 13 at%, R: 0.05 to 10 at%, Fe: 80 to 95 at%, M: 2 to 6.5 at% with respect to the total metal element amount. Having a hexagonal magnetoplumbite ferrite as a main phase, and a temperature change of coercive force at −50 to 50 ° C. ΔHcJ / ΔT
A magnet powder containing -5 to 5 Oe / ° C. 8. A magnetic recording medium comprising the magnet powder according to claim 7. 9. When at least one element selected from the group consisting of rare earth elements (including Y) and Bi and always containing La is represented by R, and Co or Co and Zn is represented by M, The total composition ratio of each of the metal elements of R, Fe and M is as follows: Ba: 1 to 13 atom%, R: 0.05 to 10 atom%, Fe: 80 to 95 atom%, M: : Containing a main phase of hexagonal magnetoplumbite ferrite of 2 to 6.5 atomic%, and temperature change of coercive force at −50 to 50 ° C. ΔHcJ / ΔT
A magnetic recording medium having a thin-film magnetic layer having a temperature of −5 to 5 Oe / ° C.