DE1095900B - Mixed crystal for ferromagnetic non-reciprocal elements in microwave systems - Google Patents

Description

Mixed crystal for ferromagnetic non-reciprocal elements in microwave systems The invention relates to the use of bodies which consist of mixed crystals, for ferromagnetic non-reciprocal elements in microwave systems, in particular in microwave transmission systems.

It is known that the compound BaFe "01s permanent magnetic properties owns. The crystal structure of this compound is the same as that of the mineral magnetoplumbite, this is the hexagonal structure with a c-axis of about 23.3 Å and an a-axis of about 5.9 Ä. These crystals have anisotropic magnetic properties. Because of the large magnetic crystal anisotropy in the direction of the hexagonal axis of the Crystals made up of such compounds can be used for various bodies, among other things Microwave applications can be used, e.g. B. in those cases where the Faraday rotation or magnetic resonance is used. The magnetic Anisotropy can be described by an effective anisotropy field, which in this case is about 17,000 Örsted. As a result, Faraday rotation is possible at 1 to cm wavelength (15000 to 30000 MHz), while resonance applications at about 6 mm wavelength (50,000 MHz) are possible. If there is also an external magnetic field is applied, is an extension of the area of application to even smaller wavelengths possible. In this case, however, there is no expansion to longer wavelengths possible. Other ferromagnetic oxide materials are known which are used in microwave apparatus Can be used at larger wavelengths, namely ferrites with a spinel structure. The swept wavelength range is then through with respect to the upper limit the minimum magnetic field required for the saturation of these soft magnetic materials and with regard to the lower limit by that in practice in a waveguide maximum magnetic field to be realized is conditional. This is how magnetic resonance applications are possible in a range from 3 to 15 cm (2000 to 10000 MHz). So it remains Another wavelength range in which the known ferromagnetic oxide materials not, or possibly only with strong magnetic fields and therefore large magnets, are usable. The invention is based on materials that because of their magnetic Anisotropy, especially for applications in this wavelength range in question come without the need for large external magnetic fields.

The invention relates to the use of bodies made of mixed crystals of compounds having a hexagonal crystal structure equal to that of the compound BaFe "0" exist, the mixed crystals having a composition corresponding to Formula Ba (l. A_b_,) Sra Pbb Ca, D "Me (d_e) Coe Fe (12_Zd_f) Mnfuz 0l a have, in the D at least one of the tetravalent metals Ti, Ge, Zr, Hf and Sn and Me at least is one of the divalent metals Mn, Ni, Zn, Mg and Cu, and where O <_ a <_ 1 O <_ b _ <1 O _ <c <0.4 O <d <_ 2.5 O <e <1 O < f <3, as a ferromagnetic non-reciprocal element in microwave systems, especially microwave transmission systems.

The magnetic anisotropy of these crystals can be effective by Anisotropic fields from 16000 Örsted to low values in the direction of the hexagonal Axis. Since the materials are oxidic, theirs is more specific Relatively high resistance. Especially with the materials where Me represents at least Cu, and in those in which trivalent manganese is present is (f, n # _ O), high values of the specific resistance can occur.

In the applications of the materials described above, naturally made use of molded articles made of these materials. As it is in conscience In some cases it is desired that the bodies are magnetically anisotropic then especially those bodies are used that have a certain texture, d. H. Bodies in which the particles in more or less large measure in each other oriented state are present.

From the ferromagnetic non-reciprocal element according to the invention existing bodies and especially those in which to some extent some texture present could be particularly beneficial in microwave transmission systems be used. Due to the anisotropy field these materials are magnetic Resonance applications in the range from 6 to 30 mm wavelength (10,000 to 50,000 MHz) possible. This area is determined not only by the anisotropy, but also by due to the demagnetization. As with the application described above of ferrites with a spinel structure, when using the body according to the invention the lower limit of the wavelength is still due to the application of an external magnetic field be reduced. The wavelength is then determined by the anisotropy field, the demagnetization and the external magnetic field conditional.

The materials according to the invention are preferably produced by heating (sintering) a finely divided one selected in roughly the correct ratio Mixture of the constituent metal oxides of the new compounds. Here can one or more of the composing metal oxides naturally or completely partially replace with compounds that convert to metal oxides when heated can e.g. B. carbonates, oxalates and acetates. You can also use the composing Metal oxides in whole or in part by one or more reaction products of replace two or more of the constituent metal oxides, e.g. B. BaFe1201s.

The "correct ratio" here becomes a ratio of the amounts of metal understood in the starting mixture to be the same as in the materials to be produced. Possibly you can first pre-sinter the finely divided starting mixture, the reaction product grind again and sinter the powder obtained in this way. This series of edits can be repeated once or several times if necessary.

The temperature of the sintering or the final sintering is between approx 1000 and about 1450 ° C, e.g. B. between 1200 and 1350 ° C selected. To make things easier Sintering agents such as silicates and fluorides can be added to the sintering process.

Moldings consisting of the ferromagnetic materials described here can be prepared in that the starting mixture of metal oxides or the like. is already sintered immediately in the desired shape, or by the fact that the Mill the reaction product of the presintering and, if necessary, after the addition a binder, brought into the desired shape and re-sintered.

Moldings consisting of the ferromagnetic materials described, in which a certain texture is present can be produced by that the particles of ferromagnetic material are mutually exclusive are freely movable, directed in a magnetic field and become a coherent Structures are fixed. It is still possible to form a contiguous Forms of fixed particles to be sintered into a compact body. The powder persists preferably from single crystal particles if possible.

It is also possible to use the ferromagnetic materials described to produce existing moldings with a certain texture that the particles a finely divided starting mixture selected in the correct ratio, which from metal oxides and / or compounds that convert into these metal oxides when heated, and / or compounds of two or more of the constituent metal oxides and which contains at least one ferromagnetic compound consisting of magnetic orientable particles are made to be aligned in a magnetic field as long as the particles are still to a certain extent freely movable with respect to one another, and then the whole is sintered into a compact body. In this case, too, the powder exists as far as possible with regard to the aforementioned orientable ferromagnetic connection from single crystal particles. This method has the advantage that the texture is preserved is determined by the orientation of particles present in the starting mixture, which have a larger Have anisotropy and are therefore easier to orientate than the particles of the above-mentioned compositions of which the body is made after final sintering.

Since it is beneficial for certain uses, body with a To use a relatively high density, this must be taken into account during manufacture will. This can be done in that the starting mixture and optionally the Product of pre-sintering ground extremely finely and the body at a higher Temperature is sintered. The latter can have the disadvantage that a small Part of the iron goes into the bivalent state, so that the specific resistance of the body is given a low, possibly even undesirably low value. Example A mixture of Ba Fe1201s, Ba C02, Ti 02 and Co C03 in a mutual Ratio of 0.9 mole BaFel201 "0.1 mole BaC03, 0.6 mole Ti02 and 0.6 mole CoC03, what corresponds to the desired connection BaTi "sCog, gFelg, g019, was 8 hours long ground with alcohol in a shaker mill. The mill product was in acetone slurried, and a part was under a pressure of almost 1 t, [cm2 in one DC magnetic field with a field strength of 8000 Örsted parallel to the direction of pressing compressed into a tablet. It is possible to carry out a straightening process with this mixture to be used because the ferromagnetic connection BaFel201e made of magnetically orientable Particle consists. The tablet was up to in 16 hours from room temperature 500 ° C and heated from 500 to 1210 ° C in 5 hours and 2 hours. long at 1210 ° C sintered in oxygen. The reaction can be expressed by equation 9 BaFe "0" + BaC03 -I- 6 Ti02 -f- 6 CoC03 10 BaTio, gCoo, gFelo, 3019 + 7 C02.

The density of this tablet was 3.9 g / cm3 and the specific resistance 2 - 101 ohm-cm. With the help of a torsion process, as it is, for. B. in. Physica, 8, pp. 562 to 565, 1941, the magnetic anisotropy of this tablet was determined in the direction of the magnetic field during pressing; its value, expressed in an effective field HA , was 9800 Örsted. With the aid of an X-ray diffractometer, as in the following examples, it was found that the tablet was made up of particles with a crystal structure similar to that of the compound BaFel20 "and that the particles were present in the body in a mutually almost completely oriented state.

A 10-3 # 0.15 mm plate was cut from the tablet, with the side of 3 mm parallel to the direction of the magnetic field when pressing the Tablet was. The plate was on a trapezoidal quartz plate with a Thickness of 0.7 mm glued. The whole thing was in a rectangular Waveguides with dimensions from 7.1 to 3.55 mm arranged parallel to the short side wall.

In the direction perpendicular to the ferromagnetic plate, a Magnetic field Hp applied, aimed at maximum energy absorption in the reverse direction was set at a frequency of 35000 MHz. Then the distance between the plate and the short side wall with the field Hp applied until the Transmission loss was minimal, which was the case at a distance of about 0.6 mm. The transmission attenuation is the attenuation of the microwaves in the direction of propagation. The damping ratio d 1 was determined here; that is the relationship between the attenuation of the microwaves in the opposite direction to the direction of propagation Direction and attenuation of the microwaves in the direction of propagation. dp, scam 12.0, and Hp was 700 Örsted.

In a similar manner, tablets, which were sintered at the temperature shown in the table, were prepared according to the reaction equations below. The density, the specific resistance and the effective anisotropy field HA were determined from these tablets. From some tablets, plaques were cut in the manner indicated, and these were tested in the manner described above. The values of the damping ratio dv and the applied magnetic field Hp are also shown in the table. 2. 0.8233 BaFe "0" -I- 0.1767 BaC03 + 0.8 TiO2 + 0.8 Zn0 + 0.52 MnO, BaTio, BZno, BFee "8Mn" 5.019 - + - 0.1767 C02 - + - 0.13 02 3. 14 BaFe1201s + BaC03 -E- 6 TiO2 + 6 CoC03 - - . 15 BaTio, 4Coo, 4Fell, 201a + 7 C02 4. 0.9167 BaFel201o + 0.0833 BaC03 -f- 0.15 CuC03 .-! - 0.35 CoC03 + 0.5 TiO2 --a BaTio, bCoo, 35Cuo, 1sFellO "-I- 05833 C02 5. 8 BaFel2019 + 2 BaC03 + 12 TiO2 + 12 NiC03 --- 3. 10 BaTi1,2Nil "Fe9,8019 -E- 14 C0.>' 6. 8 BaFe12019 -I- 2 BaC03 - + - 12 TiO2 + 12 Cu0 - @. 10 BaTil, 2Cu1, zFe9, s01s -f- 2 C02 7. 8 BaFel20 "-f- 2 BaC03 -f- 12 Ge02 + 12 CoC03 --- @ 10 BaGe1,2Co1" Fe9, o019 + 14 C02 B. 8 BaFel2019 + 2 BaC03 + 12 Ge02 + 12 Zn0 - @ 10 BaGel, 2Znl, 2Fe "g0" + 2 C02 9. 9 BaFel201s + BaC03 -E- 6 Sn02 -E- 6 CoC03 10 BaSno, gCoo, sFelo, 8019 -E- 7 C02 10.9 BaFel201s - + - BaC03 -f- 6 Sn02 + 6 Zn0 - @ 10 BaSno, sZno, gFelo, 8019 -I- C02 11.9 BaFe1201s -f- BaC03 + 6 ZrO2 + 6 CoC03 - @ 10 BaZro, BCoo, sFelo, 80 "-1- 7 C02 12.9 BaFel201s -f- BaC03 + 6 Zr02 -j- 6U0 - @ 10 BaZro "Zno, sFelo, 8010 - + - C02 Sinter density Specific No. Composition temperature Resistance HA Hp ° c g (cm $ 0 # cm örsted örsted 1 BaTio, eCoo, eFelo, 8019.............. 1210 3.9 2.106 9800 12, 0 700 2 BaTio, BZno, BFeo "8Mno," 019.......... 1330 5.0 5 - 107 9200 15.0 1760 3 BaTio, 4Coo, 4Fel1> 2019.......... ......... 1240 4.1 3-106 8200 18.5 0 4 BaTio, SCoo, 35Cuo, 15Fel1019.......... 1260 4.3 8,106 8000 16.8 0 5 BaT11,2N1l, 2Fe9,8019................ 1275 4.2 3-104 5000 6 BaTi1,2Cu1,2Fe9 "019........... ...... 1275 4.6 2,104 7600 7 BaGel, 2Co1,2Fes, s019. .... .... .... ... 1275 5.1 7-103 7400 8 BaGe1,2Zn1,2Fe "8019 .................. 1275 5.1 3-102 10000 9 BaSno, 6Coo, eFelo, 8019............... 1275 4.3 5 - 104 6780 10 BaSno, eZno, eFelo, 8019 ..... ... .... ... 1275 4.3 3-104 5330 11 BaZro, eCoo, sFelo, 8019..... ..........: 1275 4.2 5.105 6900 12 Ba7, ro, oZno, eFelo, 801s .... .... .... .. 1275 4.1 3. 105 4500

Claims (1)

PATENT CLAIM: Use of bodies made from mixed crystals of Compounds with a hexagonal crystal structure equal to that of the compound BaFe12019 exist, the mixed crystals having a composition according to the formula Ba (1_a_b-1) SraPbb CacDdMe (d_e) CoeFe (12-2d_,) MnfjjiOla have, in the D at least one of the tetravalent metals Ti, Ge, Zr, Hf and Sn and Me at least one of divalent metals Mn, Ni, Zn, Mg and Cu, and where 0 <a <1 0 < b <1 0 <_ c <_ 0.4 0 <d <_ 2.5 0 <e <_ 1 0 <f <3 is, as a ferromagnetic non-reciprocal element in microwave systems, in particular Microwave transmission systems.