JPH0122205B2 - - Google Patents
Info
- Publication number
- JPH0122205B2 JPH0122205B2 JP13212680A JP13212680A JPH0122205B2 JP H0122205 B2 JPH0122205 B2 JP H0122205B2 JP 13212680 A JP13212680 A JP 13212680A JP 13212680 A JP13212680 A JP 13212680A JP H0122205 B2 JPH0122205 B2 JP H0122205B2
- Authority
- JP
- Japan
- Prior art keywords
- fine particles
- hexagonal ferrite
- magnetic
- ferrite
- sio
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229910000859 α-Fe Inorganic materials 0.000 claims description 31
- 239000010419 fine particle Substances 0.000 claims description 28
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 239000000126 substance Substances 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 6
- 239000006247 magnetic powder Substances 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
- 238000007496 glass forming Methods 0.000 claims description 3
- 238000002844 melting Methods 0.000 claims description 3
- 230000008018 melting Effects 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 2
- 238000010306 acid treatment Methods 0.000 claims 1
- 238000001035 drying Methods 0.000 claims 1
- 230000005415 magnetization Effects 0.000 description 11
- 239000002245 particle Substances 0.000 description 9
- 239000011230 binding agent Substances 0.000 description 7
- 239000011521 glass Substances 0.000 description 7
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 6
- 238000002425 crystallisation Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000002253 acid Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 239000003973 paint Substances 0.000 description 3
- 230000003746 surface roughness Effects 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 229910010413 TiO 2 Inorganic materials 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 230000005381 magnetic domain Effects 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Description
【発明の詳細な説明】
本発明は、磁気記録媒体用磁性粉の製造方法に
関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing magnetic powder for magnetic recording media.
磁気記録は、一般に記録媒体の面内長手方向の
磁化を用いる方式によつている。しかし、この面
内長手方向の磁化を用いる記録方式にあつては、
記録の高密度化を図ろうとすると、記録媒体内の
減磁界が増加するため、記録密度をそれ程向上さ
せることはできない。 Magnetic recording generally relies on a method that uses magnetization in the in-plane longitudinal direction of a recording medium. However, in a recording method that uses magnetization in the in-plane longitudinal direction,
If an attempt is made to increase the recording density, the demagnetizing field within the recording medium will increase, so the recording density cannot be improved that much.
そこで、このような不具合を解消するために、
近年、記録媒体の表面と垂直な方向の磁化を用い
る垂直磁気記録方式が提案されている。この垂直
磁気記録方式では、記録密度が高まる程、記録媒
体中の減磁界が減少するので、本質的に高密度記
録に適した記録方式と云える。 Therefore, in order to eliminate such problems,
In recent years, perpendicular magnetic recording methods have been proposed that use magnetization in a direction perpendicular to the surface of a recording medium. In this perpendicular magnetic recording method, as the recording density increases, the demagnetizing field in the recording medium decreases, so it can be said to be a recording method essentially suitable for high-density recording.
しかして、このような垂直磁気記録方式を採用
するには、表面とは垂直な方向に磁化容易軸を有
する磁気記録媒体を必要とする。このような要望
を満す記録媒体として、従来、記録膜をCo−Cr
スパツタ膜で形成するものや記録膜を磁性微粒子
の塗布層で形成するものが提案されている。 However, in order to employ such a perpendicular magnetic recording method, a magnetic recording medium having an axis of easy magnetization in a direction perpendicular to the surface is required. Conventionally, as a recording medium that satisfies these demands, the recording film was made of Co-Cr.
There have been proposed methods in which the recording film is formed from a sputtered film and a recording film formed from a coated layer of magnetic fine particles.
ところで、記録膜を磁性微粒子の塗布層で形成
するものにあつては、次のような製造方法が考え
られる。すなわち、磁性微粒子として、たとえば
BaFe12O19等の六方晶系フエライトを用いる（た
とえば特開昭55−86103号公報参照）。六方晶系フ
エライトを用いる理由は、このフエライトは平板
状をなしており、しかも磁化容易軸が板面に垂直
であるため、磁場配向処理もしくは機械的配向処
理によつて容易に垂直配向を行ない得るからであ
る。このような六方晶系フエライトの磁性微粒子
と有機バインダとを混合し、これをたとえば非磁
性テープの表面に塗布した後、この塗布層を磁場
中にその表面が磁界の方向と直交するように配置
することによつて各磁性微粉子粉の磁化容易軸を
磁界の方向に一致させて配列させた後、塗料を乾
燥させれば、垂直磁気記録に適した記録媒体を得
ることができる。 By the way, in the case where the recording film is formed by a coating layer of magnetic fine particles, the following manufacturing method can be considered. That is, as magnetic fine particles, for example
A hexagonal ferrite such as BaFe 12 O 19 is used (see, for example, Japanese Patent Application Laid-open No. 86103/1983). The reason for using hexagonal ferrite is that this ferrite has a flat plate shape and the axis of easy magnetization is perpendicular to the plate surface, so it can be easily vertically aligned by magnetic field alignment treatment or mechanical alignment treatment. It is from. After mixing such magnetic fine particles of hexagonal ferrite and an organic binder and applying this to the surface of a non-magnetic tape, for example, this coated layer is placed in a magnetic field so that the surface is perpendicular to the direction of the magnetic field. By doing this, the axes of easy magnetization of each magnetic fine powder are aligned in the direction of the magnetic field, and then the paint is dried to obtain a recording medium suitable for perpendicular magnetic recording.
しかして、上述した六方晶系フエライトの微粒
子を使い、いわゆる塗布法によつて垂直磁気記録
媒体を製造する場合には、次のような点を考慮す
る必要がある。 However, when manufacturing a perpendicular magnetic recording medium using the above-mentioned hexagonal ferrite fine particles by a so-called coating method, the following points need to be taken into consideration.
すなわち、上記六方晶系フエライトは、保磁力
iHcが高く、記録時にヘツドが飽和するため、構
成原子の一部を特定の他の原子で置換することに
よつて、その保磁力を垂直磁気記録に適した値ま
で低減化させることが必要である。また、上記六
方晶系フエライトの結晶粒径を0.01〜0.3μｍの範
囲に選択する必要がある。その理由は、0.01μｍ
未満では磁気記録に要する強い磁性を呈しない
し、また0.3μｍを超えると、高密度記録としての
垂直磁気記録を有利に行ない難いからである。 In other words, the above-mentioned hexagonal ferrite has a coercive force
Since the iHc is high and the head is saturated during recording, it is necessary to reduce the coercive force to a value suitable for perpendicular magnetic recording by replacing some of the constituent atoms with specific other atoms. be. Further, it is necessary to select the crystal grain size of the hexagonal ferrite in the range of 0.01 to 0.3 μm. The reason is 0.01μm
If it is less than 0.3 μm, it will not exhibit the strong magnetism required for magnetic recording, and if it exceeds 0.3 μm, it will be difficult to advantageously perform perpendicular magnetic recording as high-density recording.
さらに、上記の如く、保磁力及び粒径ともに、
制御された磁性粉であつても、塗料中に、均一に
分散する性状を有していないと、良好な記録媒体
が得られないため、少なくとも磁性粉作製時にお
いて、個々の粒子が焼結凝集しないことも、必要
である。 Furthermore, as mentioned above, both coercive force and particle size,
Even if the magnetic powder is controlled, if it does not have the property of being uniformly dispersed in the paint, a good recording medium will not be obtained. It is also necessary not to do so.
本発明者らは、種々の実験研究を行なつた結
果、ガラス形成物質に、上記フエライトの基本成
分及び置換成分を含む原料をある比率で混合し、
溶解させた後、その溶解物を急速冷却することに
よつて得られる非晶質体に、熱処理を施すことに
よつて、その中に目的にかなつたフエライト微粒
子が析出することを見出した（特願昭54−143859
号＝特開昭56−67904号公報）。そして、この目的
にかなつたフエライト微粒子を分離抽出するに
は、リン酸、酢酸などろ希酸によりガラス形成物
質を洗浄し、水洗して除去すればよいことを見出
した。 As a result of various experimental studies, the present inventors have found that a glass-forming substance is mixed with raw materials containing the basic components and substituted components of the ferrite in a certain ratio,
After melting, we found that by heat-treating the amorphous material obtained by rapidly cooling the melt, fine ferrite particles suitable for the purpose could be precipitated (particularly Gansho 54-143859
No. = Japanese Patent Application Publication No. 56-67904). They have also discovered that in order to separate and extract fine ferrite particles suitable for this purpose, the glass-forming substance can be removed by washing with dilute acids such as phosphoric acid and acetic acid, and then washing with water.
しかし、このようにして得たフエライト微粒子
はその結晶粒径が0.01μｍ〜0.3μｍの範囲は単磁
区構造であり、磁場を作用させることなく微粒子
同志が磁気的に凝集しやすい。さらに、この微粒
子は平板状であり、板に平行に積み重さなつて凝
集体を形成する。かかる微粒子を使つて磁気記録
媒体を作成するために有機バインダー等と混合
し、ベースフイルム上に塗布し、磁界ないしは機
械的にかかる微粒子の結晶軸を一定方向に配向さ
せた場合、有機バインダ中に上記微粒子が十分に
分散されていないと、十分な配向が得られないた
め、得られた磁気記録媒体の再生出力を決める磁
化曲線の角形比が小さく、かつ媒体ノズルが多く
なり、満足すべきものが得られない。 However, the ferrite fine particles obtained in this manner have a single magnetic domain structure when the crystal grain size is in the range of 0.01 .mu.m to 0.3 .mu.m, and the fine particles tend to aggregate magnetically without applying a magnetic field. Further, the fine particles are plate-shaped and stacked parallel to the plate to form aggregates. In order to create a magnetic recording medium using such fine particles, when they are mixed with an organic binder, etc., coated on a base film, and the crystal axes of the fine particles are oriented in a certain direction using a magnetic field or mechanically, the particles are mixed with an organic binder. If the fine particles are not sufficiently dispersed, sufficient orientation will not be obtained, and the squareness ratio of the magnetization curve that determines the reproduction output of the obtained magnetic recording medium will be small, and the number of medium nozzles will be large, resulting in unsatisfactory results. I can't get it.
本発明はこのような事情に鑑みてなされたもの
で、上述のようなガラス結晶化法で形成された六
方晶系フエライト粒子の分離性およびバインダ中
での分散性を良好ならしめることができる磁気記
録媒体用磁性粉の製造方法を提供することを目的
としている。 The present invention has been made in view of the above circumstances, and is a magnetic material that can improve the separability and dispersibility in a binder of hexagonal ferrite particles formed by the above-mentioned glass crystallization method. The purpose of the present invention is to provide a method for producing magnetic powder for recording media.
本発明等は、このような目的を達成するために
種々実験した結果、次のような結論を得た。 In order to achieve the above object, the present invention and others have conducted various experiments and have reached the following conclusion.
すなわち、ガラス結晶化法においては、ガラス
組成物とフエライト組成物とを含んだ溶融物を急
速冷却して得た非晶質体に熱処理を施してフエラ
イト成分を微粒子状にガラス質中に析出させた
後、弱酸によりこのガラス質の洗浄を行い、六方
晶フエライト微粒子の集合体を１個１個にほぐし
て六方晶フエライト微粒子を得ているが、上記の
六方晶系フエライトの作製方法において、フエラ
イト微粒子を１個１個にほぐすと同時にその表面
にSiO2を主成分とする微粒子を付着させれば凝
集を防止でき、しかもバインダ中での分散性を大
幅に向上させることができることを見出した。 That is, in the glass crystallization method, an amorphous body obtained by rapidly cooling a melt containing a glass composition and a ferrite composition is heat-treated to precipitate the ferrite component in the form of fine particles in the glass. After that, the glassy substance is washed with a weak acid and the aggregate of hexagonal ferrite fine particles is loosened one by one to obtain hexagonal ferrite fine particles. We have discovered that by loosening fine particles one by one and simultaneously attaching fine particles containing SiO 2 as a main component to their surfaces, agglomeration can be prevented and dispersibility in the binder can be greatly improved.
以下、本発明の詳細を実施例によつて説明す
る。 Hereinafter, the details of the present invention will be explained with reference to Examples.
B2O317.4wt％、BaO48.2wt％、Fe2O330.5wt
％、TiO22.0wt％、CoO1.9wt％の組成物となる
ように、BaCO3、H3BO4、Fe2O3、TiO2、
CoCO3を秤量し、混合機にて十分混合した後、
この混合物を白金製ルツボに仕込み、高周波溶解
炉にて溶解させた。次に上記溶解物を双ロールに
注いで急速冷却して非晶質体を形成した。このよ
うにして得た非晶質体を電気炉中にて800℃で４
時間加熱し、フエライト粒子を析出させた後、20
％酢酸溶液でガラス質をとかし、水にて洗浄をく
りかえし、フエライト微粒子を得た。このフエラ
イトを含んだ溶液にフエライトに対して0.5wt％
のSiO2微粒子（粒径130Å）を加え、超音波洗浄
器中に５時間放置した後、乾燥させてSiO2の付
着した六方晶系フエライト微粒子を得た。このよ
うにして得た微粒子粉の磁気特性は飽和磁化Ms
＝58.7emu／ｇ、保磁力Hc＝750（Oe）であり、
化学分析の結果SiO2が0.48wt％付着しているこ
とが確認された。このようにSiO2の付着した微
粒子を有機バインダー等と混合し、分散して塗料
を得た後、ベースフイルム上に塗布し磁場3000
（Oe）にてフエライト微粒子を配向させて、磁気
記録媒体を作成した。この磁気記録媒体の再生出
力の大きさに関与する磁化曲線の角形比を測定し
たところ0.92であり、また、目視観察により塗り
むらはなかつた。さらに表面アラサは0.1μｍ以下
であり、入射角60゜で測定した光の反射による光
沢度は42％であつた。 B2O3 17.4wt %, BaO48.2wt%, Fe2O3 30.5wt
%, TiO 2 2.0wt%, CoO 1.9wt%, BaCO 3 , H 3 BO 4 , Fe 2 O 3 , TiO 2 ,
After weighing CoCO 3 and thoroughly mixing it with a mixer,
This mixture was placed in a platinum crucible and melted in a high frequency melting furnace. The melt was then poured into twin rolls and rapidly cooled to form an amorphous body. The amorphous material obtained in this way was heated to 800℃ in an electric furnace for 4 hours.
After heating for 20 hours to precipitate ferrite particles,
% acetic acid solution and repeated washing with water to obtain ferrite fine particles. This ferrite-containing solution contains 0.5wt% of ferrite.
SiO 2 fine particles (particle size: 130 Å) were added thereto, left in an ultrasonic cleaner for 5 hours, and then dried to obtain hexagonal ferrite fine particles to which SiO 2 was attached. The magnetic properties of the fine particles obtained in this way are the saturation magnetization Ms
= 58.7emu/g, coercive force Hc = 750 (Oe),
As a result of chemical analysis, it was confirmed that 0.48wt% of SiO 2 was attached. The fine particles with SiO 2 adhered to them are mixed with an organic binder, etc., and dispersed to obtain a paint, which is then applied onto a base film and exposed to a magnetic field of 3,000 yen.
A magnetic recording medium was prepared by orienting ferrite fine particles at (Oe). The squareness ratio of the magnetization curve, which is related to the magnitude of the reproduction output of this magnetic recording medium, was measured and found to be 0.92, and visual observation showed that there was no uneven coating. Furthermore, the surface roughness was 0.1 μm or less, and the gloss level by light reflection measured at an incident angle of 60° was 42%.
比較のため、同じガラス結晶化法により作製し
た六方晶系フエライト微粒子を乾燥させた後、水
に懸濁してSiO2を付着させ、このSiO2の付着し
た六方晶系フエライト粉末を同じ方法により有機
バインダー等と混合、分散して、フイルム上に塗
布し、配向させて磁気記録媒体を作成した。この
磁気記録媒体の磁化曲線の角形比は0.86であり、
かつ同じ方法で測定した光沢度は30％であつた。
また表面粗さは0.2μｍ以上であつた。 For comparison, hexagonal ferrite fine particles produced by the same glass crystallization method were dried and suspended in water to attach SiO 2 , and the hexagonal ferrite powder with SiO 2 attached was then synthesized using the same method. A magnetic recording medium was prepared by mixing and dispersing the mixture with a binder and the like, coating it on a film, and orienting it. The squareness ratio of the magnetization curve of this magnetic recording medium is 0.86,
Moreover, the gloss level measured by the same method was 30%.
Moreover, the surface roughness was 0.2 μm or more.
このことから判るように、ガラス結晶化法を採
用し、かつガラス成分を除去後、フエライト粒子
を１個１個にほぐす時SiO2を共存させてフエラ
イト粒子にSiO2を付着させるようにした本発明
製造方法で得られた磁性粉の方が磁化曲線の角形
比の向上化、光沢度の向上化および表面粗さの減
少化に寄与できすぐれた磁気記録媒体製造に寄与
できる。 As can be seen from this, this book adopts the glass crystallization method, and after removing the glass component, when the ferrite particles are loosened one by one, SiO 2 coexists and SiO 2 is attached to the ferrite particles. The magnetic powder obtained by the production method of the invention contributes to an improvement in the squareness ratio of the magnetization curve, an improvement in glossiness, and a reduction in surface roughness, thereby contributing to the production of an excellent magnetic recording medium.
なお、酸洗浄後、六方晶フエライトを１個１個
ほぐす時、超音波洗浄器を用いたが、ボールミ
ル、グラインドミル、ビスコミルなどの粉砕、混
合機を用いて分散洗浄させても同じ結果を得た。 Although an ultrasonic cleaner was used to loosen the hexagonal ferrite one by one after acid washing, the same results could be obtained by grinding with a ball mill, grind mill, visco mill, etc., or dispersing and washing with a mixer. Ta.
Claims (1)
低減のための置換成分とガラス形成物質とを混合
し溶解させた後、急速冷却を施して非晶質体を作
成する工程と、上記非晶質体に熱処理を施してガ
ラス質中に微粒子状の六方晶系フエライトを析出
させる工程と、この工程を経たものにガラス質を
溶かすための酸処理を施し、水洗した後、そのま
ま水の存在下のもとでSiO2を主成分とする微粒
子を加えて残存している六方晶系フエライト微粒
子を分散させる工程と、しかる後に乾燥させて前
記SiO2を主成分とする微粒子を六方晶系フエラ
イト微粒子に付着させる工程とを具備してなるこ
とを特徴とする磁気記録媒体用磁性粉の製造方
法。1. A step of mixing and melting the basic components of hexagonal ferrite, a substituted component for reducing coercive force, and a glass-forming substance, followed by rapid cooling to create an amorphous body; The process involves applying heat treatment to precipitate hexagonal ferrite in the form of fine particles in the glassy substance, and applying acid treatment to dissolve the glassy substance after this process, washing with water, and then leaving it in the presence of water. A step of adding fine particles mainly composed of SiO 2 to disperse the remaining hexagonal ferrite fine particles, and then drying to attach the fine particles mainly composed of SiO 2 to the hexagonal ferrite fine particles. 1. A method for producing magnetic powder for magnetic recording media, comprising the steps of:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13212680A JPS5756327A (en) | 1980-09-22 | 1980-09-22 | Manufacture of magnetic powder for magnetic recording medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13212680A JPS5756327A (en) | 1980-09-22 | 1980-09-22 | Manufacture of magnetic powder for magnetic recording medium |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5756327A JPS5756327A (en) | 1982-04-03 |
| JPH0122205B2 true JPH0122205B2 (en) | 1989-04-25 |
Family
ID=15074005
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13212680A Granted JPS5756327A (en) | 1980-09-22 | 1980-09-22 | Manufacture of magnetic powder for magnetic recording medium |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5756327A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6081804A (en) * | 1983-10-12 | 1985-05-09 | Toda Kogyo Corp | Hexagonal plate type ba ferrite fine-grained powder for magnetic recording and manufacture thereof |
| JPS60262403A (en) * | 1984-06-08 | 1985-12-25 | Toshiba Glass Co Ltd | Manufacture of magnetic powder |
-
1980
- 1980-09-22 JP JP13212680A patent/JPS5756327A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5756327A (en) | 1982-04-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JPS6136685B2 (en) | ||
| US4690768A (en) | Process for the preparation of ferrite magnetic particulate for magnetic recording | |
| JPS6323134B2 (en) | ||
| JP5420959B2 (en) | Hexagonal ferrite powder, magnetic recording medium using the same, and method for producing the same | |
| JPH0122205B2 (en) | ||
| JPS6324935B2 (en) | ||
| JPS6250890B2 (en) | ||
| JPS6353134B2 (en) | ||
| JPS6323133B2 (en) | ||
| JPH0312442B2 (en) | ||
| JPS6199306A (en) | Oxide magnetic material and manufacture thereof | |
| JPS6324934B2 (en) | ||
| JPS6181608A (en) | Preparation of powder of hexagonal ferrite particle | |
| JPS60161341A (en) | Preparation of hexagonal ferrite | |
| JP2802653B2 (en) | Magnetic powder for high-density magnetic recording and method for producing the same | |
| JP2717720B2 (en) | Method for producing magnetic powder for magnetic recording medium | |
| JPS6340302A (en) | Magnetic powder for high-density magnetic recording | |
| KR960000501B1 (en) | Method of preparing high density magnetic hexagonal ferrite powder | |
| JPH0341964B2 (en) | ||
| JPH0581970B2 (en) | ||
| KR960000502B1 (en) | Method of preparing magnetic hexagonal ferrite powder | |
| JPH0685370B2 (en) | Method for producing hexagonal ferrite powder | |
| KR0139130B1 (en) | Method of preparing cubic ferrite powder for magnetic tape | |
| JPS6127329B2 (en) | ||
| JPH0472601A (en) | Manufacture of magnetic powder for magnetic recording medium |