DE2121596A1 - Hard-magnetic alloy - with high coercive force and magnetic energy and possessing one non-cubic crystalline structure - Google Patents

Abstract

Hard-magnetic alloy is opt. formula AxByCzD 1-x-y-z where A is an element from gp. 1 or 2, B is a rare earth metal, C is a transition element of gp. 4-8 or gp.lb (Cu, Ag, Au) and D is from gp 2b (Zn, Cd, Hs) or gp. 3-6, x is 0-0.8, y is 0-0.8 and z is 0-0.9 with the conditions that either x = 0.01-0.8 or the ratio z, (1-x-y-z) is 0.05-8.0 and equally (x+y) >=0.03. In either case one of the phases in the alloy has a non-cubic crystalline structure.

Description

HARD MAGNETIC ALLOY The invention relates to a hard magnetic alloy Alloy of the general composition AxByCzD1-x-y-z 'where A is the elements the 1st and 2nd main group of the periodic system, B the rare earth metals, C den Transition metals of the 4th to 8th subgroup and the 1st main group (Cu, Ag, Au) and D the metals of the 2nd

Subgroup (Zn, Cd, Hg) and the 3rd to 6th main group the invention relates to methods of making the alloy as well as to their use, especially in permanent magnets.

Hard magnetic materials are on the one hand by their presence of magnetic moments coupled with individual atoms that are below a are ordered at a certain temperature, so that a resulting total magnetization is observed and on the other hand by a finite coercive field strength of the order of magnitude 100 to 10,000 Oe. Hard magnetic alloys and compounds have been around for many Has been used for years and has recently been constantly finding new applications, such as

In permanent magnets used to convert mechanical to electrical Energy and vice versa are used in data processing systems in the form of magnetic Core memories or magneto-optical memories, etc. The main characteristics Hard magnetic materials are their saturation magnetization, measured in Gauss (C), as well as the so-called energy product (B. H) max 'measured in Gauss. Oersted (G. Oc.).

Permanent magnets should usually be at the respective operating temperature have an energy product as large as possible, while at Applications hard magnetic materials in data processing systems often have a certain ratio of energy product, toercial field strength and order temperature is necessary.

At present, permanent magnetic materials are becoming technical mainly Alnico magnets, ferrites, carbon steels and platinum-cobalt magnets are used.

The maximum possible energy product for Alnico magnets is 1.0. 107 G.Oe, for ferrites 3.7. 106 G. Oe, for carbon steels about 1.0. 106 G. Oe and 9.2 for platinum-cobalt magnets. 106 G. Oe.

(J. J. Becker, F. E. Luorsky, D. L. Martin, "Permanent magnet materials", IEEE Transactions on Magnetics MAG-4, 84-99 (1969)).

In recent times there is now a new class of permanent magnetic materials has been developed based on alloys of the rare earth metals (SE) with cobalt based on the approximate composition SECo5. (K. J. Strnat, "Alloys of Cobalt with rare earth metals, a new group of promising permanent magnet materials ", Kobalt, 1967, 119-128). The definition of the rare earth metals includes here the elements scandium (atomic number 21), yttrium (atomic number 39) and the lanthanoids (Lanthanum, atomic number 57, to lutetium, atomic number 71). Compounds of composition SECo5exist at least for SE ~, La, Ce. Pr. Nd9 Sm, Gd, Tb. Dy. Ho and He. These All connections have a dB hexagonal CaCu structure. The SECo5 connections this structure is almost always characterized by a high magnetic crystal anisotropy, so that the alloys in which SECo5 phases are present are permanently magnetic Possess properties. Hence the use of alloys of the approximate Composition SECo5 with U.S. Patent No. 3,424. 5/8 (K. J. Stuart, G. I. Hoffer, J. C. Olson, W. Ostertag).

This patent also mentions the addition of manganese and / or Elsen Protected to cobalt, but not explained in detail by any exemplary embodiment, etc. In U.S. Patent No. 3,421. 889 (W. Ostertag, K. J. Strnat) were also hard magnetic Materials of composition SE2Co17 protected. Already before that there were different magnetic alloys between rare earth metals and the 3d metals Manganese, iron, cobalt, and nickel in U.S. Patent No.

3,102,002 (W. E. Wallace et al.).

Nesbitt et al. (E.A. Nesbitt, G.Y. Chin, R.C. Sherwood and J.H. Wernick "Cast permanent magnets of the Co5RE type with a (B.H) max exceeding 12 million G.Oe ", Applied Physics Letters 16, 312-313 (1970)) reported permanent magnetic coatings consisting of rare earth metals, cobalt and copper, the sometimes also contained smaller amounts of iron. These alloys obviously exist from precipitations of SECo5-rich phases in a non- or soft magnetic Matrix. Carrier of the permanent magnetic properties of the alloys mentioned is therefore always a SECo5 phase, the unspecified proportions of Cu, Mn and May contain Fe built into the lattice. But it is important to note that no magnetic measurements on a clearly defined as pure SEFe5 phase or e.g. as an iron-rich RE (Fe, Co, Ni) 5 phase alloy, although on the existence of SEFe5 phases with the CaCu5 structure variously in literature is reported (see the compilation by H. R. Kirchmayr, "Kristallstruktur the compounds of rare earth metals with 3d metals ", magazine for metal science, 60, 778-784 (1969)).

Our own research shows that with the usual melting processes SEFe5 connections cannot be established in one phase, so that it can be assumed that the SEfe5 phases are not stable at room temperature and normal pressure.

Among the permanent magnetic materials based on SECo5 have So far, alloys with samarium in particular have gained technical importance. For sintered SmCo 5 permanent magnets have been reported to have an energy product of 2.0.107 G.Oe (D.K. The: "Twenty million energy product samarium-cobalt magnet", IEEE Trans. Magnetics MAG-5. 214-216 (1969)). With PrCo5 magnets, an energy product of 10 G.Oe achieved. (J.Tsui and K. Strnat: "Sintering of PrCo5-permanent magnets", Applied Physics Letters, 18, 107 (1971)). Attempts to use cerium ~ mischmetal, i. H. a cerium-rich one Milk of several rare earth metals instead of the pure rare ones Earth metals Samarium or praseodymium for the production of hard magnetic materials of the composition Using SECo5 with a high energy product has so far been technically unsuccessful.

(M. McCaig: "Investigations of RCo5 and similar permanent magnet alloys", IEEE Trans. Magnetics MAG-6, 198-201 (1970)).

Also those described in French Patent No. 1,529,048 (Philips) MCo5 alloys (M = Th, La; or La + Th or La + Th + alkaline earth metals) with partial Obviously, no replacement of cobalt by iron, copper or nickel has been achieved so far technical application found. The same goes for those in the Austrian Gadolinium and / or dysprosium alloys described in U.S. Patent No. 261,239 (IBM) with antimony and bismuth as well as for those in German patent no.

1,248,307 (IBM) described rare earth metal compounds of Formula A5M2, where A is a rare earth metal from the group Gd, Tb, Dy and Ho and M is a transition metal from the group consisting of Pd and Pt.

The current state of the art in the manufacture of hard magnetic Alloys and compounds of the highest energy product are therefore based on the compounds of the basic composition SECo5, whereby the rare earth metal is preferably samarium or praseodymium and the cobalt to a small extent by other 3d metals as well as can be replaced by copper. Such alloys are made up of several Reasons only suitable for individual special applications. Both samarium and Praseodymium metal is extremely expensive. Even if it were successful, cerium-mischmetal would be used instead the pure rare earth metals to hard magnetic alloys of the composition Processing SECo5 with an energy product of more than 10 'G.Oe would be the price of these alloys due to the relatively high price of cerium-mischmetal and cobalt too high for many conventional applications of hard magnetic materials. In addition comes that with SECo5 alloys e.g.

the Curie temperature, the saturation magnetization, the coercive field strength etc. hardly specifically aimed at the special requirements of hard magnetic materials in Magnetic core storage,, in magneto-optical storage or in other data carriers can be customized.

The object of the invention is therefore to produce hard magnetic alloys with sufficiently large saturation magnetization, coercive field strength and energy product to develop in which the pure rare earth metals as well as the cobalt partially or have been completely replaced by other elements.

This object was achieved according to the invention on the basis of the consideration that the high magnetic crystal anisotropy of the SECo5 alloys largely from the non-cubic crystal structure is determined that the magnetic moment of the Rare earth metal is not of critical importance, since YCo5, in that yttrium has no moment, is hard magnetic, and that finally iron has a higher moment compared to cobalt, so that if it succeeds, iron to be built into the hard magnetic phases, under otherwise identical conditions one higher saturation magnetization is to be expected. Therefore, for the time being, such -alloys were made manufactured and studied in which the rare earth metals partly or wholly by elements or mixtures of elements with a comparable htomradius or below approximate retention of the valence electron concentration were replaced. Furthermore Alloys were made in which cobalt is preferentially replaced by some others 3d metals, most of all iron, has been partially or wholly replaced, with the stabilization non-cubic crystalline structures, if necessary through the addition of non-transition metals, has been thoroughly investigated.

These series of tests surprisingly showed that numerous alloys Have hard magnetic properties if on the one hand partial or total Replacement of rare earth metals alkali and / or alkaline earth metals and on the other hand in addition to or instead of cobalt, other 3d metals, such as Zr, Mn, Fe, Ni, if appropriate be alloyed with admixture of e.g. Zn, Al, As, Si, Sn, if at least one of the corresponding phases has a non-cubic crystal structure. Quite In general, these hard magnetic alloys have a negative impact due to their composition AxByCzD1-x-y-z denote, where A is the elements of the 1st and 2nd main group of the Periodic table, B the rare earth metals, C the transition metals the 4th to 8th subgroup and the 1st subgroup (Cu, Ag, Au) and D the metals the 2nd group (Zn, Cd, Hg) and the 3rd to 6th main group.

It has been shown that for x the value range 0.0 to 0.8, for y the value range 0.0 to 0.80 and for z the value range 0.0 to 0.90 comes, provided the following conditions are also met: Either the Value range from x to 0.01 to 0.80, i.e. alkali and / or alkaline earth metals are present in the alloy or the ratio z: (1-x-y-z) must be 0.05 to 8.0 and at the same time the sum (x + y) must be at least 0.03. on Due to these restrictions, it is ensured that if rare earth metals and / or alkali and alkaline earth metals are present, including 3d metals together with Non-transition metal components of the alloy must represent that are non-cubic Contains phases and thus has hard magnetic properties.

The advantages of the alloys according to the invention, the xLn individual Examples are explained below, consist mainly in the following possibilities, namely a) also iron, which has a very high magnetic moment, into a non-cubic, to incorporate hard magnetic alloy; b) alloys with variable, the respective Use of adjusted Curie temperature and coercive force to produce; c) Desires to obtain high energy product and d) Metals with low Price (iron, alkaline earth metals, etc.) for hard magnetic materials of high quality to process and so new numerous areas of application for hard magnetic materials to tap into.

As from the claims and the examples given below shows, alloys with high maximum energy product and high saturation magnetization can be used which contain no or only a small proportion of rare earth metals contain or instead of cobalt iron as a carrier of the magnetic moment have, if certain conditions with regard to the htoaradien, the number of valence electrons and electronegativity are met. These alloys consistently show im essentially has a non-cubic crystal structure. The stability these alloys and the crystal structure is given by the fact that alkali and / or Alkaline earth metals and / or elements of the 2nd subgroup and the 3rd to 6th main group of the periodic table in addition to transition metals, especially 3d metals.

The production of these alloys can be done with conventional melting and Sintering process take place. As a starting material for the manufacture of the alloys technically pure metals are normally used. The rare earth metals technical grade usually contain other rare earth metals as well as non-metals such as hydrogen, oxygen, nitrogen, carbon, etc. as impurities. Instead of rare earth metals, mixtures are often used for economic reasons of rare earth metals, such as "Didym" or Cermischmetall used with advantage.

It is expedient to start from master alloys. The listed Alloys were either in a high frequency furnace in ceramic crucibles or in an electric arc furnace or produced in an electron beam melting furnace. Melting is large-scale To be preferred in ceramic or metal crucibles under a salt cover. These procedures are well known from reactive metals technology. The starting materials or Master alloys can also be used if there are major differences in terms of the melting point or the boiling point, advantageously by sintering to the finished alloy get connected. The alloy already present is also advantageous after a corresponding Comminution by sintering further processed into the finished product, if either one certain sample shape is sought or if by the sintering process in one Magnetic field at the same time a magnetic alignment is to be achieved.

The listed magnetic parameters were taken from pressings of the Remanence and the coercive field strength determined on small test magnets. These test magnets were made by pressing the appropriate alloy powder with organic binders manufactured. Usually the pressing took place in a magnetic field of about 10 kOe. The alloy powders were made by grinding the molten alloys in one Vibrating ball mill obtained. All the technology of manufacture the permanent magnets made from the alloys according to the invention are closely connected the well-known technology of ferrites. The permanent magnetic Alloys e.g. finely ground, pressed with or without a magnetic field and using suitable Means, such as bound to solid bodies by sintering or binding agents. These are brought into suitable shapes or reworked and magnetized transferred to the permanent magnetic state. The magnetic properties the alloys can also be changed by a heat treatment of the molten alloys, for example, below the Curie temperature with or is carried out without the presence of a magnetic field.

On the basis of the alloys according to the invention, permanent magnetic Materials or permanent magnets also by pressing, hot pressing, extrusion or made by sintering. These procedures often promote in well-known Expand the formation of directional single-domain particles, resulting in improved permanent magnetic Properties leads.

Melting the alloys under increased pressure can therefore be advantageous to prevent evaporation of the alloy partners or because higher pressures can lead to the formation of crystalline structures, especially high magnetic crystal anisotropy and therefore particularly high magnetic energy products exhibit.

If the starting materials or master alloys are evaporated in a vacuum, the alloys according to the invention can thus be produced in a thin layer. Such hard magnetic coating layers, possibly with a e.g. heat treatment or texture obtained by the presence of a magnetic field, are suitable e.g. for magneto-optical storage purposes, for magnetic data storage (e.g. 3.

The various technical uses of hard magnetic Alloys in the form of permanent magnets, e.g. B. as cast or sintered or made of fine Particle built matter; in the form of magnetic storage elements e.g. B. as magnetic core memory or magneto-optical memory; in the form of thin layers and in finely divided form are essentially known.

The alloys of the present invention are for these uses particularly suitable because due to a suitable composition (niche ratio between transition metals and non-transition metals or between rare earth metals and alkaline earth and alkali metals) the specifications of the alloys to each technical requirements can be adapted.

The following examples illustrate the invention without restricting it.

Example 1 Approx. 100 g of an alloy with the composition Ca0.033Ce0.133Fe0.834 is made using a calcium-cerium master alloy melted in a high-frequency furnace Melted in an electric arc furnace with a water-cooled copper mold. This desire has a hexagonal crystal structure and d shows as saturation magnetization 12,000 G, and the energy product 3.6,107 G.Oe. If cerium is replaced by cerium mixed metal, so the energy product is reduced to 2.1,107 G.Oe.

Example 2 Approx. 25 gr of an alloy with the composition Ca0, 10Fe0, 70Co0, 10Zn0, 10 is made by mixing in a ball mill under an argon protective gas atmosphere manufactured metal powder of technical purity (grain size 20 - 40 µm) in the appropriate Quantity ratio, then pressing into tablets of about 25 gr and sintering produced in a stream of hydrogen at 9500 C.

The same alloy can also be based on 2 master alloys with of the composition Ca0.5Zn0.5 and Fe0.875Co0.125, obtained by melting in a high-frequency furnace be obtained, mixing the master alloys according to the previous oil granulation and melting at 1,300 ° C in a high-frequency furnace. the predominant crystal structure is rhomic. It becomes a saturation magnetization 70n 11,300 G and an energy product of 3.1. 107 G. Oe observed.

Example 3 100 g of an alloy of the composition Fe0.55Co0.10Mg0.08Sm0.07 Al0.07Zn0.06 Zr0.05Sr0.02 is prepared according to the procedure given in Example 2. Owns this desire a saturation magnetizer: mg of 7,100 G, and an energy product of 1,3,107 G.Oe.

Example 4 An alloy of the composition Ca0.15 Co0.30 Ni0.55 is made by vaporizing calcium metal and a cobalt-nickel master alloy in the High vacuum (1Q 6 Torr) using 2 independently controllable electron beam evaporators made in a thin layer on quartz load carriers. The alloy has a coercive field strength of 500 Ge and a Curie temperature of 1400 C.

It is therefore suitable for thermal Curie point writing, i.e. use as a magnetic data carrier.

Claims (16)

P a t e n t a n s p r ü c h e 1) Hard magnetic alloy with the general composition AxByCzD1-x-y-z ' characterized in that A corresponds to the elements of the 1st and 2nd main group of the periodic table, B the rare earth metals, C the transition metals of the 4th to 8th subgroups and the 1st subgroup (Cu, Ag, Au) and D the metals of the 2nd subgroup (Zn, Cd, Hg) and the 3rd to 6th Main group corresponds to, where x 0.0 to 0.80, y 0.0 to 0.83 and z is 0.0 to 0.9, with the proviso that either x = 0.01 to 0.80 or the ratio z: (I-x-y-z) 0.05 to 8.0 and at the same time the sum (x + y) at least 0.03 and always at least one of the phases contained in the alloy is a possesses a non-cubic crystal structure. 2) Alloy according to claim 1), characterized in that A is magnesium and calcium, C chromium, iron and cobalt and D aluminum, silicon, zinc and tin mean. 3) alloy according to claim 1), characterized in that x is the same 0.05 to 0.20, y is 0.0 to 0.25, and z is 0.40 to 0.85. 4) Alloy according to claim, characterized in that the sum (x + y) is 0.14 to 0.-. 5) Process for producing the alloy according to claims 1) to 4), characterized in that the starting materials or master alloys by Sintered to be connected. 6) Process for producing the alloy according to claims) to 4), characterized by the fact that the starting materials are produced in an electric arc or by means of high frequency be melted together. 7) Method according to claim 6), characterized in that the melted Alloy is crushed and re-bonded by sintering. 83 The method according to claims 6) and 7), characterized in that that a melting or sintering process under an external pressure of more than 3 atm is made. 9). Method according to claims 5) to 8), characterized in that that a melting or sintering process in a magnetic field, preferably from 1000 to 4000 Gauss is made. 10) Process for producing the alloy according to claims 1) to 4), characterized in that the starting materials or master alloys under Pressurized, hot-pressed or extruded. 11) Process for producing the alloy according to claims 1) to 4) - in a thin layer, characterized in that the starting materials or master alloys evaporated in vacuo and deposited on a carrier material. 12) Method according to claims 5) to II), characterized in that that a heat treatment is carried out below the Curie temperature of the alloy will. 13) Method according to claim 12), characterized. that the heat treatment is carried out in an external magnetic field, preferably from 1000 to 4000 Gauss. 14) Use of the alloy according to claims 1) to 4) in permanent magnets, which are made up of fine lilies. 15) Use of the alloy according to claims .1) to 4) in magnetic Storage elements, preferably magnetic core memories and magneto-optical memories. 16) Use of the alloy according to claims 1) to 4) in finely divided Form or as a thin layer in magnetic data carriers.