DE1558550B2 - PERMANENT MAGNET - Google Patents

Description

The invention relates to a permanent magnet based on M5R connections and to a Process for its manufacture.

From US-PS 28 13 789 a permanent magnet is known, which consists of up to 30% cobalt, 2.5 to 12% consists of at least one rare earth metal and the remainder iron. About the manufacturing method and the crystal structure of the permanent magnet is not specified.

The magnetic properties of many intermetallic compounds with the stoichiometric composition M5R have been measured. So are z. B. many compounds of the formula Co ₅ R have been investigated, in which R is a rare earth element, including Y is included. The magnetic moments and the temperature dependence of the saturation moments of these compounds have been measured. At the same time, the magnetic properties of the compounds Co ₄ CuTb, Co ₄ NiDy, GdYCo ₅ and CdNdCo _{5 were} determined. All of these compounds have a CaCus-type hexagonal structure.

With regard to the investigation on the compounds C05R, _{an exception had to be made for Co 5} La, as this substance, despite the fact that it was mentioned in "J. Phys. Chem. Solids ", 16 (1960) .. p. 123/130, could not be produced. The explanation given is that the ionic radius of La, if no special precautions are taken, would be too large to form the compound in question. From the investigations mentioned, it has been found that C05Y has a high uniaxial magnetic anisotropy and at the same time has a high saturation magnetization. In the finely divided state, Co ₅ Gd showed a high Ho, which also indicates a high uniaxial anisotropy. However, a high saturation magnetization was not found. For the other investigated compounds Co ₅ Z, measurements were only carried out with regard to the saturation magnetization, but not with regard to the magnetic anisotropy.
In »Paper No. 11.5 ", published in the" Abstracts of the Intermag Conference "1966, describes the magnetic properties of this compound Co ₅ Y. ^{A very high uniaxial anisotropy (5.7 · 10 7} erg / cm ³ ), a high moment of saturation, was found on Co ₅ Y single crystals, which have a hexagonal structure, at room temperature

= 114

erg

Oe

and a Curie temperature T ₀ of 630 ⁰ C was measured. This combination of properties suggests that Co ₅ Y would be a good material for making small particle magnets with a high energy product.

The invention is based on the object of creating _{permanent magnets from materials of the compounds Co 5 R.}

This object is achieved according to the invention in that the permanent magnet consists of a powder-metallurgically produced molded body of fine permanent magnetic particles with a hexagonal CaCu ₅ crystal structure of the composition Co ₅ R, Co being partially replaced by at least one of the elements Fe, Ni or Cu can and R = La or Th, where thorium can be partially replaced by at least one of the rare earth elements, or means a combination of at least three rare earth elements.

The invention is based on the knowledge that in compounds Co ₅ R with the same structure as Co ₅ Y, the aforementioned combination of magnetic properties, which makes the compound a good material for the production of permanent magnets (high uniaxial anisotropy, combined with a high saturation magnetization) can be obtained if two requirements are met with regard to the electronic structure of the compound in question:

First, the configuration of the electrons in the Co ions must not really be changed by R _{compared to that in the compound Co 5 Y;} that is, the occupation of the 3d shell in the Co-ion remains almost the same.

Second, the total magnetic moment of the connection, which consists of the amounts of both Co and R is not adversely affected by the contribution of R.

The first requirement is generally met by choosing those elements for R which can form compounds of the structure mentioned with cobalt and which in these compounds as trivalent ion are present. It turned out that Th, Ce and Yb, as well as certain combinations of elements meet this requirement.

The second requirement is fulfilled in that for R elements or combinations of elements are chosen whose total magnetic moments are directed parallel to those of the Co ions, or the do not contribute to the magnetic moment.

When both requirements are combined, it turns out that there is for R, besides those already known

Elements and combinations of elements, there are a large number of substitution options. Experiments have shown that from this large number of possible suitable substitutions for R, only the following elements and combinations of elements with Co can form a compound Co ₅ R, which can be used with good success (sufficiently large H _c and (BH) _max ) as a material for Manufacture of permanent magnets can be used: La, Th, or a combination of Th with one or more of the rare earth elements, or combinations of at least three rare earth elements.

In these possible compounds, Co can be a combination of Co with one or more of the Elements Fe, Ni, Cu can be selected. Such connections are mostly less sensitive to deformation the coercive force and the saturation magnetization.

The extent to which Co, while maintaining favorable magnetic properties by Fe, Ni, Cu, or a Combination of these can be replaced, depends on R and the selected substituents. It was found, for example, that when R = La, a maximum of 5 atomic percent in a combination of Co and Fe Fe may be present, while if R = Th, this content can be a maximum of 60 atpm percent. if the Fe content exceeds the percentages mentioned, the examples mentioned no longer have the required hexagonal structure, whereby the magnetic properties suddenly deteriorate. In however, other examples may decrease in some atomic percentage of the substituent on the the magnetic properties, for example, have a gradual course.

The invention also relates to a method for manufacturing a permanent magnet as described above. This process, in which a casting is first produced by melting the components and then cooled, is characterized in that the casting is homogenized by annealing in an atmosphere protected against oxidizing influences, the temperature ¹ 'being as close as possible to the melting point, and that then "is cooled to room temperature, whereupon the casting is pulverized and the powder is optionally annealed and finally shaped into a magnetic body by pressing together, if necessary in a magnetic field.

The compounds of the formula M5R generally have an incongruent melting point. This means that in addition to M5R, other compounds of R and M are also formed when solidifying. When the casting is annealed at a temperature which is just below the melting temperature, all compounds formed during solidification are converted into the compound M5R, ie they are homogenized. For this, the highest possible temperature is chosen, among other things to give the particles the greatest possible mobility, which promotes _{an effective conversion into M 5 R.}

After homogenization, the mixture is cooled to room temperature. This cooling down can take place slowly go if no undesirable phases arise during the cooling. However, should this be the Be the case, then the casting is after a further execution of the method according to the invention the homogenizer was quenched to room temperature. Quenching offers the other The advantage that the casting becomes more brittle as a result, which is advantageous with regard to the subsequent pulverization.

The invention will now be based on the magnetic properties associated with the following Embodiments of permanent magnets were measured according to the invention, explained in more detail.

Γ., - κ, ^σ '(τ ° ^ε ) / H _c (Oe) Co ₅ La 850 90 3600 Co ₅ Th 635 51 2000 Co ₄ CuLa 690 60 3000 Co ₃ Fe ₂ Th 690 70 1900 Co ₅ Th ₀₁₂ Y ₀₈ 810 77 2200 Co ₅ La ₀ 33Sm ₀ 33Th ₀ 34 825 80 6100 Co ₅ La ₀₅ Ce ₀₂₅ Sm ₀₁₂₅ 835 89 6550 Co ₄ Ni ₀ 5 Cu ₀₅ La 690 63 3300 Co ₃ Fe ₁₁₅ Cu ₀₁₅ Th 640 62 2050 Co ₃ FeCu ₀₁₅ Ni ₀₁₅ La 680 60 1900 Co ₅ La ₀₂₅ Sm ₀ ^ Nd ₀₁₂₅ Th ₀₂₅ 760 82 5500

The maximum energy product (BH) _{max was also} measured on Co ₅ La ₀₅ Ce ₀₂₅ Sm _025. This amounts to • 1 η ⁶ η. no

5-10 ⁶ G Oe.

Claims (3)

Patent claims: 1. Permanent magnet, characterized in that it consists of a molded body produced by powder metallurgy of fine permanent magnetic particles with a hexagonal CaCus crystal structure of the composition Co ₅ R, where Co can be partially replaced by at least one of the elements Fe, Ni or Cu and R = La or Th, where thorium can be partially replaced by at least one of the rare earth elements, or means a combination of at least three rare earth elements. 2. A method for producing a permanent magnet according to claim 1, wherein by melting the Components a casting is made and then cooled, characterized in that the Casting homogenized by annealing in an atmosphere protected against oxidizing influences is, the temperature is as close as possible to the melting point, and that then to room temperature is cooled, whereupon the casting is pulverized and the powder is optionally annealed and finally by pressing them together, optionally in a magnetic field, to form a magnetic body is shaped. 3. The method according to claim 2, characterized in that the casting after homogenization is quenched to room temperature.