US3647574A - Method of reducing the coercive force of permanent-magnetisable material - Google Patents

Method of reducing the coercive force of permanent-magnetisable material Download PDF

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Publication number
US3647574A
US3647574A US853964A US3647574DA US3647574A US 3647574 A US3647574 A US 3647574A US 853964 A US853964 A US 853964A US 3647574D A US3647574D A US 3647574DA US 3647574 A US3647574 A US 3647574A
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United States
Prior art keywords
coercive force
permanent
reducing
compound
hydrogen gas
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Expired - Lifetime
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US853964A
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English (en)
Inventor
Frans Frederik Westendorp
Hinne Zijlstra
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US Philips Corp
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US Philips Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/023—Hydrogen absorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/14—Treatment of metallic powder
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/07—Alloys based on nickel or cobalt based on cobalt
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/06—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder

Definitions

  • the invention relates to a method of reducing the coercive force of permanent-magnetisable material consisting of the hexagonal compound M R, wherein M is Co or a combination of Co with one or more of the elements Fe, Ni and Cu and R is one or more of the elements of the rare earth metals and/ or Th.
  • the rare earth metals are understood to include herein also the element yttrium.
  • the intermetallic compounds M R belong to a group of magnetisable materials of hexagonal crystals structure and a high single-axis crystal anisotropy. It is noted, that by M R also are meant the hexagonal compounds M R the existence region of which is integral with the existence region of the compound M R. 'In general they have a high coercive force (H and are suitable as a raw material for permanent magnets, having a high energy product. This is for instance known from Journal of Applied Physics 38, 1001 (1967), in which it is particularly described how such compounds may serve as raw material for fine-particle magnets. In Applied Physics Letters 12, 361 (1968) it is described how these compounds may also be used as raw material for cast magnets.
  • Magnetisation and demagnetisation of fine particles as well as larger bodies of the above-mentioned compounds involve the problem of requiring in general strong magnetic fields. These fields have to be of such a strength that the coercive force can be overcome, which usually means that they have to be considerably stronger than the coercive force. Particularly in mass production this gives rise to difficulties.
  • the invention is based on the discovery that measures have to be taken so that during the (de)magnetizing process the coercive force resisting the (de)magnetisation is low, whereas after the (de)magnetisation it regains the desired higher value.
  • the method of reducing the coercive force of said M R compounds in accordance with the invention is characterized in that the material is exposed to hydrogen gas at a given pressure.
  • the curve 1 of the graph shows the H as a function of the hydrogen concentration measured on the compound SmCo DESCRIPTION OF THE EXPERIMENT By melting Co and Sm in a protective atmosphere, SmCo was obtained. This compound was then pulverized. The powder was orientated in a magnetic field and then compressed hydrostatically without a binder to form a block. This block was enclosed in a stainless steel tube in which a hydrogen gas pressure up to 30 atmospheres can be maintained. Prior to each measurement the block was magnetized in a pulsatory field of a strength of 10K oersted; magnetic fields up to 17,000 oersted were used for measuring. Apart from the coercive force the hydrogen pressure P was measured as a function of the hydrogen content in the material (see curve 2 of the graph). The measurements were carried out at room temperature.
  • MM Ce-n'ch Mischemetal (mixed metal) having the composition: 60% Ce; 10% La; 10% mixture of other rare earth metals).
  • the method according to the invention can be employed for the said M R compounds both in the form of a powder and of larger bodies. Since for many uses powder-metallurgical techniques are employed, a preferred form of the method according to the invention is characterized in that prior to the exposure to pressurized hydrogen gas, the material is pulverized.
  • the mehod of reducing the coercive force is particularly important for magnetizing and demagnetizing the material concerned.
  • a method of magnetizing or demagnetizing of these materials is characterized in that during or immediately after the reduction of the coercive force by means of hydrogen pressure the material is introduced into a magnetizing or demagnetizing field of such a strength that the coercive force of the material is overcome.
  • magnetisation or demagnetisation may also be performed immediately after elimination of the hydrogen gas pressure when it is considered that H resumes its initial value only after about one hour.
  • the restoration of the initial value may, if desired, be further delayed by cooling.
  • a permanent magnet can be manufactured of the fine particles of the M R compounds magnetized by the aforesaid method by eliminating the hydrogen pressure after magnetisation of the particles and by uniting the particles in a magnetic field to form a magnet body. Owing to the presence of the magnetic field the particles are orientated in parallel with their magnetic preferred axes so that an optimum anisotropic permanent magnet is obtained.v
  • the method of reducing the coercive force in accordance with the invention is also employed in recording or erasing magnetic records on a magnetisable layer containing the M R compound as the constituent which is essential for recording.
  • a written medium has to be resistant to stronger demagnetizing fields, it is advantageous to record and to erase with the aid of the method in accordance with the invention, that is to say, to have these processes performed on a recording layer having temporarily a reduced coercive force.
  • the invention furthermore relates to permanent magnetisable material consisting of the compound M R, whose corecive force is reduced and which may subsequently be magnetized or demagnetized with the aid of one of the methods in accordance with the invention.
  • the invention also relates to permanent magnets whose essential part for the magnetic properties is formed by small particles of the M R compound manufactured by the method in accordance with the invention.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Hard Magnetic Materials (AREA)
US853964A 1969-03-14 1969-08-28 Method of reducing the coercive force of permanent-magnetisable material Expired - Lifetime US3647574A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6903931A NL6903931A (fr) 1969-03-14 1969-03-14

Publications (1)

Publication Number Publication Date
US3647574A true US3647574A (en) 1972-03-07

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Family Applications (1)

Application Number Title Priority Date Filing Date
US853964A Expired - Lifetime US3647574A (en) 1969-03-14 1969-08-28 Method of reducing the coercive force of permanent-magnetisable material

Country Status (11)

Country Link
US (1) US3647574A (fr)
AT (1) AT302501B (fr)
AU (1) AU1251670A (fr)
BE (1) BE747286A (fr)
BR (1) BR7017383D0 (fr)
CA (1) CA918044A (fr)
CH (1) CH524876A (fr)
ES (1) ES377414A1 (fr)
FR (1) FR2038898A5 (fr)
GB (1) GB1262594A (fr)
NL (1) NL6903931A (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1554384A (en) * 1977-04-15 1979-10-17 Magnetic Polymers Ltd Rare earth metal alloy magnets

Also Published As

Publication number Publication date
BE747286A (fr) 1970-09-14
CH524876A (de) 1972-06-30
ES377414A1 (es) 1972-07-01
CA918044A (en) 1973-01-02
AT302501B (de) 1972-10-25
NL6903931A (fr) 1970-09-16
DE2008191B2 (de) 1977-06-30
DE2008191A1 (de) 1970-10-01
AU1251670A (en) 1971-09-16
FR2038898A5 (fr) 1971-01-08
BR7017383D0 (pt) 1973-01-16
GB1262594A (en) 1972-02-02

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