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US2994045A - Electrical transmission devices utilizing gyromagnetic ferrites - Google Patents

Electrical transmission devices utilizing gyromagnetic ferrites Download PDF

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US2994045A
US2994045A US500451A US50045155A US2994045A US 2994045 A US2994045 A US 2994045A US 500451 A US500451 A US 500451A US 50045155 A US50045155 A US 50045155A US 2994045 A US2994045 A US 2994045A
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ferrite
waveguide
ferrites
wave
manganese
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Le Grand G Van Uitert
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AT&T Corp
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Bell Telephone Laboratories Inc
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
    • C04B35/2608—Compositions containing one or more ferrites of the group comprising manganese, zinc, nickel, copper or cobalt and one or more ferrites of the group comprising rare earth metals, alkali metals, alkaline earth metals or lead
    • C04B35/2625—Compositions containing one or more ferrites of the group comprising manganese, zinc, nickel, copper or cobalt and one or more ferrites of the group comprising rare earth metals, alkali metals, alkaline earth metals or lead containing magnesium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/32—Non-reciprocal transmission devices

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  • This invention relates to ferrite materials, and to devices for the transmission of high frequency electrical signals, said devices being constructed in part of ferrite materials, and utilizing the gyromagnetic properties of said ferrite materials. Particularly, it relates to such devices for which said gyrom-agnetic ferrite materials are high-resistivity compositions deficient in iron and comprising small quantities of either manganese or cobalt, or both, and to said ferrite materials themselves.
  • FIG. 1 is a perspective view, partly in section, of a Faraday-rotation type of circulator mounted in a hollow metallic waveguide;
  • FIG. 2. is a perspective view, partly in section, of a round dielectric waveguide containing a ferrite loading for producing Faraday-rotation;
  • FIG. 3 is a perspective view, partly in section, of a directional coupling device utilizing non-reciprocal field displacement
  • FIG. 4 is a perspective view, partly in section, of a device having a ferrite-loaded resonance cavity
  • FIG. 5 is a perspective view, partly in section, of a ferrite-loaded non-reciprocal attenuating device employing a balanced wire line transmission system
  • FIG. 6 is a chart showing, for several firing temperatures, the dependence of the resistivity of some of the ferrite compositions herein disclosed on their manganese content.
  • rectangular waveguides 11 and 12 are tapered smoothly into a circular waveguide 13.
  • the rectangular ice waveguides 14 and 15 are joined to the circular waveguide 13 near a rectangular guide 11 at the left-hand end, and near a rectangular guide 12 at the right hand-end, respectively. If imaginary planes be passed through each of the four rectangular waveguides 11, 12, 14, and 15, parallel to the longest dimension of the rectangular section, the positioning of the guides 11 and 14 will be such that the planes mentioned above for this pair of guides will intersect perpendicularly.
  • the guides 12 and 15 are set at right angles to one another at the righthand end p of the drawing shown.
  • the planes passing through the guides 11 and 12 are, further, inclined to one another at an angle of 45 degrees, and the waveguides 14 and 15 are similarly relatively inclined at an angle of 45 degrees.
  • a pencil 16 of the ferrite materials considered later herein mounted in a non-magnetic dielectric material 17, such as, for example, polystyrene foam.
  • a magnetic source 18 such as an electromagnet or permanent magnet, capable of producing a longitudinal magnetic field.
  • a ferrite element In a magnetic field, a ferrite element has the property of rotating the plane of polarization of an incident plane polarized wave.
  • the rotation produced in the element 16 shown, for example, is determined by the nature of the ferrite used, by the dimensions of the ferrite element 16, and, in addition, by the strength of the magnetizing field from the field source 18, and by the specific geometry of the waveguide 13 and the mounting of the element 16 therein.
  • the sense of the Faradayu'otation is determined by the direction of the magnetizing field.
  • the length of the element 16 and the strength and direction of the magnetizing field from the source 18 may be chosen to give a 45-degree counterclockwise rotation viewed from n to p, in FIG. 1, for waves passing through the element 16 from n to p. In passing from p to n, waves are rotated in the same sense by the ferrite.
  • waves electrically polarized perpendicular to the longest dimension of the rectangular section of the waveguide 11 pass the guide 14 and penetrate the ferrite 16.
  • the waves entering 11 are unaffected by passing the guide 14.
  • the wave plane is oriented for transmission out through guide 12.
  • the outgoing wave is unaffected by the guide 15 set at right angles to the plane of the polarized wave in guide 12. If a wave enters the guide 12, reversing the direction of transmission in the original illustration, it passes guide 15, is rotated by the ferrite in the same sense as before, and is thus, this time, oriented for transmission through the guide 14.
  • waves entering guide 14 are made:
  • FIG. 2 shows a Faraday-rotation device comprising a 3 ferrite loading 21 in a round dielectric waveguide 22.
  • the ferrite 21 comprises the materials considered later herein, and the waveguide 22 may consist of any dielectric material having a dielectric constant materially different from that of air, such as, specifically, polystyrene or polyethylene.
  • a linearly polarized wave for example, introduced at s into the waveguide 22 is propagated through the ferrite 21 and emerges at t with a rotation in the angle of polarization.
  • Means may be provided for utilizing the rotation observed in the construction of a circulator, as in FIG. 1, or the segment of the circuit shown in FIG. 2 may be adapted to other purposes.
  • FIG. 3 shows a multibranch network in which gyromagnetic materials are used to create field displacement effects. Shown are two rectangular metal waveguides 31 and 32.
  • the guide 31 is placed with one narrow wall contiguous to a wide wall of the guide 32, and is so located as to lie off the center line of said guide 32.
  • Apertures 33 extending through the contiguous walls of the guides 31 and 32, are used to couple the guides 31 and 32 electromagnetically. These apertures, lying on the center line of the narrow wall of the guide 31 are displaced, as is the guide 31 itself, from the center line of the guide 32.
  • means for producing a non-reciprocal displacement of the magnetic field pattern therein comprising, in this case, two slabs 34 of a ferrite material as later described herein.
  • Means, not shown, such as a solenoid or permanent magnet, are provided for creating a uniform magnetic field in each of the ferrite slabs 34, so that said slabs are magnetically polarized at right angles to the direction of propagation of wave energy in the waveguide 32. Both slabs 34 are polarized in the same direction.
  • the magnetic field of a dominant mode wave being propagated through the waveguide will be such that a clockwise-rotating and a counterclockwise-rotating component of the magnetic intensity will be found respectively at one or the other extremity of the longest rectangular dimension of the waveguide wall. That is, depending on the direction of wave propagation, the direction of the polarization at one of the waveguide walls will be clockwise or counterclockwise, with rotation in the opposite sense being found in the magnetic intensity at the other wall for a given direction of wave propagation. Upon reversing the direction of propagation, the sense of the polarization at each wall also reverses.
  • the electron spins and associated moments within the ferrite can be caused to precess about the line of the biasing magnetic field on the ferrite, producing a magnetic moment rotating in a plane normal to the biasing field, or, that is, in the plane of the magnetic component of the waves propagated along the waveguide 32.
  • the rotating moment produced by electron spin in the ferrite will correspond, on one side of the waveguide or the other, to the rotating component of the magnetic intensity of the wave, resulting in a permeability less than unity for one of the ferrite strips 34.
  • the biasing field produces precession with a moment in a sense opposite to the rotating component of the waves magnetic field, resulting in a per meability greater than unity for this second ferrite strip.
  • the discrepancy in permeability for the two strips 34 results in a displacement of the normal field pattern. Without the biasing magnetic field applied to the ferrite slabs 34, the magnetic field intensity of the propagated wave in the waveguide 32 is null along the center line of the waveguide, rising to a maximum at the sides of the guide. When a biasing field is applied to the ferrite, the
  • ' field pattern of the wave may be distorted to give a null value in the region immediately beneath the off-center coupling apertures 33. No coupling results in this case. Reversing the direction of wave propagation in the waveguide 32, without changing the direction of the bias on the ferrite elements 34, will result in a displacement of the null field area to a point on the other side of the center line of the waveguide 32, away from the coupling apertures 33. Coupling of the guides 31 and 32 will result for this direction of wave propagation.
  • FIG. 4 is a perspective view, partly in section, of waveguide structures coupled by a chamber containing a gyromagnetic ferrite element to produce a three-branch circulator.
  • a hollow rectangular waveguide 41 is abutted by a second waveguide 42 of a type capable of supporting circularly polarized waves.
  • the guide 42 is tapered smoothly into a rectangular waveguide 43 which will transmit linearly polarized waves only.
  • Means, such as positioned metal fins 73 and 74, are so disposed at the junction of waveguides 42 and 43 as to interconvert circularly polarized waves in guide 42 to and from linearly polarized waves in guide 43, by introducing a -degree phase shift in selected components of the impinging waves.
  • a resonant cavity 48 is formed in the lower portion of the waveguide 42, said cavity being bounded at the top by a perforated reactive diaphragm 47 and at the bottom by the waveguide 41.
  • the diaphragm 47 is so positioned as to render the length of the cavity 48 a multiple of one-half of the guide wavelength of the waves to be transmitted therethrough.
  • Apertures 45 and 46 couple wave energy to and from guides 41 and 42 and guides 42 and 43, respectively.
  • the aperture 45 is of such geometry and is so positioned, by techniques known to those skilled in the art, relative to the waveguides 42 and 41, that for waves transmitted through Waveguide 41 from u to w in the diagram, a circularly polarized wave will be introduced into the cavity 48, while for those waves transmitted through the guide 41 from w to u, a wave circularly polzrsized in the opposite sense will be found in the cav- W
  • the ferrite 49 is mounted in a material 71 of low dielectric constant, such as polyfoam.
  • means 72 Surrounding the cavity 48 in which the ferrite 49 is located are means 72, such as a solenoidal Winding, for producing a steady polarizing magnetic field parallel to the direction of wave propagation in the waveguide 42.
  • the circulator shown in FIG. 4 employs this gyromagnetic property of the ferrite element 49 in its operation.
  • the position of the aperture 45 be such as to produce a counterclockwise polarized wave in waveguide 42 when a Wave is transmitted along guide 41 from u to w.
  • the biasing field from the source 72 be in a direction as to permit transmission of such a polarized wave through the ferrite element 49 in the cavity 48.
  • the cavity 48 is made of a length which is a multiple of the half wavelength of the transmitted Wave, by positioning of the diaphragm 47, the cavity 48 is resonant for the wave, and the wave, after conversion by the fins 73 and 74 appears as a linearly polarized wave at v.
  • a wave transmitted in waveguide 41 from w to u will be clockwise polarized in waveguide 42, in this example.
  • the biasing field on the ferrite 49 produces a low permeability for such a wave, and no resonance or transmission to terminal v ensues. Waves introduced at w, thus, emanate only at u.
  • the impedances of the terminals u, v, and w, which terminals are coupled by the apertures through the cavity 48 can be matched as to give tranmission without reflection along the paths u to v, v to w, and w to u, so that the element pictured is a non-reciprocal circulator.
  • the ferrite elements previously shown have been incorporated in devices particularly useful in the microwave region, they may be also used in the construction of devices to be used in the ultrahigh-frequency and very-high-frequency range, below a few thousand megacyc es.
  • FIG. 5 is shown one such circuit element, which may be used as an isolator, suitable for connection directly into a two-wire balanced line transmission system.
  • the embodiment pictured comprises two pairs of parallel conductors 51, 52, 53 and 54, equally spaced and symmetrically aligned relative to each other.
  • the conductors are bridged in pairs by connecting elements 55, 56, 57 and 58.
  • Thin discoid dielectric spacers 81 through 84 are longitudinally placed along the line to support the conductors in their above-described relationship.
  • Spacers 82 and 83 may serve to support a gyromagnetic ferrite body 59 comprising materials of the type herein later described.
  • a shield 86 serves tosupport the structure and protects the conductors 51 through 54 from external mechanical and electrical influences.
  • a longitudinal magnetic field is supplied by a winding to polarize the ferrite 59. Control of the energizing field is provided so that strengths sufficient to produce a ferromagnetic resonance condition in the ferrite 59 may be produced if desired.
  • Loading vanes 88 and 89 are disposed, respectively, between the Wire pairs 51 and 53 at the right-hand end of the circuit element shown, and between the pairs 52 and 54 at the left-hand end.
  • the vanes of a material having a high dielectric constant, extend longitudinally between the wire pairs mentioned for a length sufficient to introduce a 90-degrce delay in a voltage between the conductors comprising a pair.
  • the rotation produced in the polarized wave in the region of the ferrite 59 is similar in sense to the precession of electron spins and the moment associated therewith in the ferrite, the wave is transmitted almost unaffected by the conductors 51 through 54 from the source to the circuit load. If the polarized wave rotates in a sense opposite to the rotating magnetic component generated in the ferrite 59, however, almost no transmission past the ferrite is observed when the ferrite is excited to its resonant frequency by the magnetic source 85. Since attempted transmission in opposite directions through a circuit element such as that shown in FIG.
  • the element shown may be used as an isolator, permitting transmission in one direction only, when the ferrite biasing field is maintained in a constant direction and at a strength producing a ferromagnetic resonance condition in the ferrite material 59.
  • FIG. 6 depicts graphically one aspect of the resistivity behavior of a ferrite typical of those described herein.
  • the ordinate measures the logarithm of the resistivity of several nickel ferrite compositions containing added manganese, with the abscissa indicating the manganese content of these compositions.
  • curves 61, 62, 63 and 64 respectively depict the dependence of resistivity on manganese content for ferrite compositions fired at l200 C., 1250 C., 1300 C. and 1350 C.
  • Conduction in ferrite materials is generally considered dependent upon the presence of metal ions in more than a single valence state within the ferrite.
  • conduction in a nickel ferrite is probably elfectuated by electron transfer between ions of divalent and trivalent nickel, and also between divalent and trivalent iron.
  • the ferrite may be compounded with divalent nickel salts or oxides and with ferric salts or oxides, considerable quantities of oxygen may be absorbed by the ferrite upon cooling after firing, presumably as some of the nickelous material is converted to nickelic compounds.
  • some reduction of ferric iron to a divalent state may occur, and if cooling is rapid, reconversion of the ferrous iron to the trivalent state may not be completely accomplished.
  • Cobalt and manganese are themselves contaminants for ferrites. If they were to be added in excessive amounts, such addition might result in lowering the resistivity of the ferrites to values lower than those normally observed when the ferrites are contaminated only by trace quantities of ferrous iron. Consequently, the amount of the added elements is kept small.
  • ferrites are obtained when the atom percent of these added metals is kept between the values 0.167 and 2.67, calculated on the basis of the total number of metal atoms present in the composition.
  • the better ferrites preferably contain no more than 2.00 atom percent of added cobalt, manganese, or their mixture, and, more preferably, contain less than 1.67 atom percent of these ingredients.
  • the best materials are found to contain less than 1.32 atom percent of the added elements.
  • the ferrites are compounded to give an iron-deficient material.
  • Such an iron deficiency greatly reduces the tendency to formation of Fe O in solid solution with the ferrite.
  • By inhibiting the formation of such a solid solution of magnetite with the ferrite the presence of ferrous iron in more than trace amounts is avoided. Such trace amounts can then be eliminated by manganese or cobalt additions.
  • iron deficiency will sigs nify a departure from the stoichiometry represented by the generalized ferrite formula for which, it is seen, two iron atoms are present for each divalent metal atom A.
  • the ratio of the number of atoms of iron or of iron and added aluminum, if any, to the total number of divalent atoms of other metals present will fall beneath the value 2.0.
  • the ratio mentioned above preferably will take values intermediate to an upper limit of 1.99 and a lower limit of 1.6, though more deficient compositions are possible if replacement of iron with other trivalent atoms, such as aluminum, is accomplished. in some cases, when aluminum is present, the ratio mentioned may reach a value of 1.5 in the compounding of desirable materials.
  • the first such ferrite system to be used for illustration comprises the nickel-zinc ferrites.
  • the compositions contemplated in the present case may be described by reference to the metallic constituents present in the composition only, the non-metallic element required for a charge balance being understood to be oxygen.
  • the component metals are present in the following proportions:
  • M may be manganese or cobalt or mixtures thereof.
  • the subscripts signify the relative number of gram atoms of the element indicated which are present, and thus are also proportional to the relative numbers of atoms of each metal present in the ferrite composition.
  • the value of :t may lie between 0 and 0.45, and is also usually limited, for the better compositions, to a figure between 0 and 0.40. It can be seen that when x has a null value the ferrites correspond to nickel ferrite with added cobalt or manganese.
  • the content of these latter two materials more preferably may have a value lying between 0.01 and 0.06 in the formula given above, and the most useful compositions are obtained when said content is held between 0.01 and 0.04.
  • the second ferrite system to be used for illustration may be described as that comprising the nickel-zinccopper ferrites, with metal contents, as before, indicated by the proportions:
  • M represents cobalt, manganese, or mixtures of these elements.
  • Preferred limits on the content of such additions may be set, as stated, at 0.0] and 0.06, or, more preferably, at 0.01 and 0.04.
  • b may vary between 0 and 0.45, and a between 0 and 0.40. It can be seen that if a is given a null value, the category includes the nickel-zinc ferrites of the earlier discussion, and if b is also kept at Zero, a nickel ferrite is obtained.
  • the zinc content for this second system, b may also vary between 0 and 0.40 to yield the more useful ferrites in this class, while the copper content, as determined by a, is preferably limited to values between 0.05 and 0.25.
  • M is again cobalt, manganese, or other mixture.
  • the subscripts of M are preferably varied to give compositions in which the content of cobalt or maganese lies between 0.01 and 0.06, with the most useful compositions being found when M lies in the range between 0.01 and 0.05.
  • the aluminum content, 1' on which is dependent the iron deficiency for this class of materials, may range between and 1.0 in value, though preferred compositions are obtained when the aluminum is kept between the values 0.1 and 0.6.
  • the copper content, k may lie between 0 and 0.40, though preferred compositions are obtained when the copper content is limited to the range from 0.05 to 0.25.
  • a fourth ferrite system, the magnesium-copper-aluminum ferrites, contains manganese, cobalt, or mixtures of the two, according to the scheme:
  • M once more symbolizes the added cobalt, manganese, or cobalt-manganese mixture.
  • the more useful compositions in this system are obtained when the subscripts on M are limited to values between 0.01 and 0.06, or, more preferably, between 0.01 and 0.05.
  • the value of 1, which is determinative of both the magnesium and the copper content most generally takes values between 0 and 0.40, though the better ferrites are found when f varies between 0.05 and 0.25.
  • the aluminum content, g which also in part fixes the iron deficiency, is best kept within the overall range 0 to 0.75, though the more useful compositions are obtained when g lies between the values 0.05 and 0.7. Particularly good materials result when g lies between the values 0.05 and 0.25.
  • the parameter q merely descriptive of the iron deficiencies in these ferrites, may be given a value between 0 and 0.50, or more preferably, between 0.10 and 0.25.
  • the metallic constituents may be introduced into the preparation as oxides, or as compounds which when fired will yield the oxides, Such other compounds, for example, may be the hydroxides, the oxalates, or carbonates.
  • Particular advantage in the preparation of ferrites containing aluminum is obtained when aluminum hydroxide is the compound from which the ferrite is synthesized. Such advantage stems in part from the greater ease with which aluminum hydroxide is dispersed throughout the ceramic mixture.
  • Manganese and cobalt are preferably added as the carbonates, though other compounds may, as mentioned, be used.
  • the ingredients are first mixed, with or without a preliminary dry mix, in a paste mixer as a slurry.
  • a paste mixer as a slurry.
  • the water solubility of some of the component compounds used may dictate the preferential use of a non-aqueous liquid, as, for example, acetone, carbon tetrachloride, or ethanol.
  • the paste or slurry is usually dried by removal of the supernatant liquid by filtration, or, if a volatile liquid has been used, by evaporation.
  • the dried material may then be calcined in air, oxygen, or other oxidizing medium at a temperature preferably between 800 C. and 1100 C. for from 5 hours to 15 hours. After the calcining, the mixture is broken into particles, for example by ball-milling for a period of 5 hours to 15 hours.
  • a liquid such as water, ethanol, carbon tetrachloride, or acetone, is preferably used in the ball-mill, as in the paste mixer.
  • the solid may again be dried by evaporation or filtration, and recalcined according to the calcining procedure set out just above.
  • a second ball-milling, similar to the first is usually next used again to break up the solid.
  • a binder and lubricant may be incorporated into the ceramic materiali during this ball-milling step.
  • Polyvinyl alcohol or Op-al- Wax hydrohalogenated castor oil
  • parafiin or Halowax chlorinated naphthalene
  • the binder may be added either as a solid, in which case it is dissolved by the fluid used in the milling, or already in solution in a solvent.
  • Halowax which is most commonly used, an amount of wax equal in weight to 10 percent of the weight of the ceramic solids has beenfound to give best results.
  • the solvent may be removed by filtration or by evaporation while the ceramic material and the binder residue are stirred to assure uniform dispersion of the binder throughout the inorganic mixture.
  • the resultant dried powder, in which the binder is to: act as a lubricant during subsequent shaping steps, is: preferably then granulated to size. This may be accomplished by forcing the mixture through a sieve, for example, and a No. 20 Standard sieve, with a mesh opening of 0.84 millimeter, has been used for this purpose: with success.
  • a vacuum drying of the granulated particles at a. temperature between 40 C. and 50 C. may be optional-- 1y introduced at this point if further removal of any possibly remaining solvent is desired.
  • the pressed articles are preferably dewaxed by heating in air.
  • a convenient dewaxing schedule comprises bringing the pressed parts to a temperature of 400 C. over a period of 6 hours and then maintaining a 400 C. temperature for an additional 6 hours.
  • This dewaxing step, designed for articles of intermediate size, may be modified by lengthening or shortening the heating period for larger or smaller bodies.
  • Final firing is generally carried out at temperatures between 1050 C. and 1350" C., depending to some extent on the material fired, and is done in an oxygen-containing atmosphere.
  • firing at temperatures between 1200" C. and 1300 C. in oxygen has been found best, with optimum results being obtained when the material is fired at 1250 C.
  • the firing temperature may be conveniently reduced to as low as 1050 C., an upper limit still being found at 1300 C.
  • Nickel ferrite containing between 0.05 and 0.25 atom percent of copper, calculated on the basis of the total metal atoms present, may be fired in air in the neighborhood of 1150 C. with excellent high values of density and resistivity in the resultant materials.
  • magnesium-copper-aluminum ferrites For the magnesium-copper-aluminum ferrites, a firing range between 1100 C. and 1350 C. has been found to give good results, with an optimum in the properties of the fired bodies being found at 1250 C. These bodies may be fired in either air or atmospheres containing a greater proportion of oxygen than does air.
  • the firing time may be kept conveniently at about hours, or, if concentrations of copper near the upper limits given on the concentration values are present, may even be minimized to 3 hours or 4 hours.
  • firing is preferably carried out for intervals between 10 hours and 20 hours in length.
  • the atmosphere during firing should be, as mentioned, oxygen-containing, and may be of pure oxygen, or air, or a mixture of oxygen with an inert gas such as nitrogen, helium, or argon.
  • the oxygen content is preferably kept at a level equal to, or greater than, that found in air, however. It is desired that the iron content of the ferrites be kept in a fully oxidized condition during firing, and as the dissociation pressure of oxygen over the ferrite materials tends to increase with increasing temperature, pure oxygen or oxygen-rich atmospheres are preferably supplied to the ferrites when firing temperatures near the upper temperature limits previously set are used. When firing nearer the lower-temperature end of the permissible temperature range, the dissociation pressure of oxygen over the ferrites is smaller, and the partial pressure of oxygen in air is sufficiently high to inhibit the reduction of the ferrite compositions by oxygen loss therefrom.
  • Example 1 119 grams of nickel carbonate, 152 grams of ferric oxide, and 2.30 grams of manganese carbonate were mixed in an Eppenbach mixer with sutficient distilled water to form a thin slurry. The resultant suspension was dried by filtering and calcined for hours in air at a temperature of 900 C. The calcined solids were then ball-milled for 15 hours in Water, filtered dry, and recalcined for a second 15 hour period in air, this time at a temperature of 1000 C. The product of the calcination was again ball-milled in water for 15 hours, filtered, and then dried more thoroughly by heating for several hours in an oven at 110 C.
  • the product was given a final ball-milling for 3 hours in carbon tetrachloride, during which period sufficient Halowax was added to the slurry to reach 10 percent by weight of the original dry ingredients.
  • the organic solvent was then removed by evaporation while the inorganic component and the wax residue were stirred to promote a homogeneous composition.
  • the mass from which the solvent had been evaporated was granulated by forcing it through a mesh screen, the openings of which are specified by the United States Standard Sieve Scale to be 0.84 millimeter in size. Parts were pressed from the granulated material and dewaxed by heating for 6 hours at 400 C. in air after having been brought to temperature over a six hour period. The pieces were then fired at 1250 C. for 20 hours in pure oxygen.
  • the resultant material showed a resistivity of 1x10 ohm-centimeters, and had an approximate density of 4.9 grams per cubic centimeter.
  • Measurements were made on a tapered rod of the material 2.5 inches in length and 0.160 inch in diameter.
  • the rod was mounted in polyfoam in a inch diameter round waveguide section and tested at a frequency of 11.2 kilomegacycles at a magnetic field intensity of 300 oersteds.
  • An insertion loss of 0.04 decibel and a Faraday rotation of 40.5 degrees were observed, giving a figure of merit, obtained as the quotient of the observed rotation and the insertion loss, of 1000 degrees per decibel for the rod in question.
  • the intensity of magnetization (411M) for the material at saturation was 2960 gausses.
  • Example 2 A tapered ferrite rod 2.5 inches in length and 0.160 inch in diameter was machined from a material prepared by the method described in Example 1, except that the second calcination there described was accomplished at 900 C. for the material herein, rather than at 1000 C. as in Example 1.
  • the ferrite prepared from 107 grams of nickel carbonate, 12.4 grams of copper carbonate, 152 grams of ferric oxide and 2.30 grams of manganese carbonate has a metal content which may be specified as:
  • the resistivity of the material was 2 (10 ohmcentimeters, and the intensity of magnetization (411M) at saturation was 2960 gausses.
  • Example 3 A material whose metallic constituents, in terms of gram atoms, were present in the proportions o.s 0.i as i.a troz was prepared from 59.3 grams of nickel carbonate, 12.4 grams of copper carbonate, 32.5 grams of zinc oxide, 152 grams of ferric oxide and 2.30 grams of manganese carbonate.
  • a tapered rod 3.4 inches long and 0.140 inch in diameter was machined from the material, prepared by the method described in Example 2 above.
  • the rod with a density of 5.3 grams per cubic centimeter and a resistivity of 2x10 ohm-centimeters, was mounted in polyfoam in a hollow waveguide with an inside diameter of 'M; inch.
  • the ferrite showed a Faraday-rotation of 47 degrees and an insertion loss of 0.09 decibel giving a figure of merit of 520 degrees per decibel.
  • the intensity of magnetization (411M) at saturation was 4800 gausses for this sample.
  • Example 4 Starting with 107 grams of nickel carbonate, 12.4 grams of copper carbonate, 15.6 grams of aluminum hydroxide, 136 grams of ferric oxide, and 4.60 grams of manganese carbonate, a ferrite containing metals in the following proportions, in terms of gram atoms of the constituents, was prepared:
  • Example 2 The preparative method followed the details of Example 2.
  • the resultant ferrite had a resistivity of 2X10 ohmcentimeters, an intensity of magnetization (4IIM) at saturation of 1900 gausses, and a density of 5.15 grams per cubic centimeter.
  • IIM intensity of magnetization
  • Example 5 A ferrite composition
  • Example 2 was prepared according to the detailed procedure of Example 2 from the following starting materials: magnesium carbonate, 75.8 grams; copper carbonate, 12.4 grams; aluminum hydroxide, 11.7 grams; ferric oxide, 128 grams; and manganese carbonate, 4.60 grams.
  • the resultant material showed a resistivity of 2x10 ohm-centimeters and had a density of 4.4 grams per cubic centimeter.
  • the intensity of magnetization (411M) of the material at saturation was 1700 gausses.
  • a high resistivity ferrite material having a resistance of at least 2 10 ohm centimeters selected from the group consisting of ferrite materials having the following compositions:
  • x is bounded between 0 and 0.45
  • f is 0.05
  • g is bounded between 0.05 and 0.7
  • q is bounded between 0.1 and 0.25
  • M is at least one element selected from the group consisting of cobalt and manganese, said ferrite materials being the reaction product formed by shaping an oxide mixture of initial ingredients under pressure and firing said shaped mixture in an oxidizing atmosphere at a temperature of 1050 C. to 1350 C.
  • the high resistivity ferrite material of claim 1 having the following composition:
  • M is at least one element selected from the group consisting of cobalt and manganese.
  • the high resistivity ferrite material of claim 1 having the following composition:
  • M is at least one element selected from the group consisting of cobalt and manganese.
  • a device comprising at least one waveguide and a gyromagnetic ferrite body subjecting waves in the 300 megacycle per second to 50,000 megacycle per second frequency range transmitted therethrough to a Faraday rotation, said ferrite body having the composition of claim 1.
  • a device comprising at least one waveguide and a gyromagnetic ferrite material subjecting waves in the 300* megacycle per second to 50,000 megacycle per second frequency range transmitted therethrough to a Faraday rotation, said ferrite material being selected from the group consisting of ferrite materials having the following compositions:
  • x is bounded between 0 and 0.45
  • f is bounded between 0.05 and 0.25
  • g is bounded between 0.05 and 0.7
  • q is bounded between 0.1 and 0.25
  • M is at least one element selected from the group consisting of cobalt and manganese, said ferrite materials being the reaction product formed by shaping an oxide mixture of initial ingredients under pressure and firing said shaped mixture in an oxidizing atmosphere at a temperature of 1050 C. to 1350 C.

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FR1148111D FR1148111A (fr) 1955-04-11 1956-03-22 Dispositifs électriques de transmission utilisant des ferrites gyromagnétiques
GB10898/56A GB797566A (en) 1955-04-11 1956-04-10 Improvements in or relating to electrical devices incorporating elements of ferromagnetic ceramic materials

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US3234494A (en) * 1961-07-28 1966-02-08 Bell Telephone Labor Inc Ferromagnetic compound and devices including elements thereof
US3403357A (en) * 1966-04-14 1968-09-24 Hughes Aircraft Co Switching apparatus for selectively coupling a predetermined number of microwave devices between an input and an output port

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US3059194A (en) * 1958-12-29 1962-10-16 Bell Telephone Labor Inc Microwave ferrite devices
DE1696446B1 (de) * 1964-01-20 1969-10-23 Siemens Ag Ferromagnetischer Ferritkoerper mit einem bei hoher Erregung negativen Temperaturkoeffizienten der Wechselfeldverluste

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US1976230A (en) * 1930-12-25 1934-10-09 Mitsubishi Electric Corp Permanent magnet and method of manufacturing same
US2576456A (en) * 1946-12-31 1951-11-27 Rca Corp Materials of high magnetic permeability
FR1031530A (fr) * 1950-05-27 1953-06-24 Steatite Res Corp Masse céramique ferromagnétique de forte perméabilité maximum et son procédé de préparation
US2644930A (en) * 1949-03-24 1953-07-07 Gen Precision Lab Inc Microwave polarization rotating device and coupling network
US2685568A (en) * 1950-05-10 1954-08-03 Gen Electric Soft ferromagnetic mixed ferrite material
GB717269A (en) * 1951-04-09 1954-10-27 Azfa Ag Fuer Photofabrikation Magnetizable metal oxides
FR1080515A (fr) * 1951-12-22 1954-12-09 Philips Nv Aimant permanent anisotrope
GB721630A (en) * 1951-08-29 1955-01-12 Anorgana Gmbh Method for the production of ª†-fe o of improved magnetic properties
FR1086346A (fr) * 1953-07-09 1955-02-11 Perfectionnements aux aimants permanents
US2719274A (en) * 1951-07-09 1955-09-27 Gen Precision Lab Inc Microwave switches
US2723239A (en) * 1952-09-29 1955-11-08 Rca Corp Ferrospinel compositions
US2736708A (en) * 1951-06-08 1956-02-28 Henry L Crowley & Company Inc Magnetic compositions
US2860105A (en) * 1953-12-21 1958-11-11 Philips Corp Method of manufacturing ferromagnetic cores

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US1976230A (en) * 1930-12-25 1934-10-09 Mitsubishi Electric Corp Permanent magnet and method of manufacturing same
US2576456A (en) * 1946-12-31 1951-11-27 Rca Corp Materials of high magnetic permeability
US2644930A (en) * 1949-03-24 1953-07-07 Gen Precision Lab Inc Microwave polarization rotating device and coupling network
US2685568A (en) * 1950-05-10 1954-08-03 Gen Electric Soft ferromagnetic mixed ferrite material
FR1031530A (fr) * 1950-05-27 1953-06-24 Steatite Res Corp Masse céramique ferromagnétique de forte perméabilité maximum et son procédé de préparation
GB717269A (en) * 1951-04-09 1954-10-27 Azfa Ag Fuer Photofabrikation Magnetizable metal oxides
US2736708A (en) * 1951-06-08 1956-02-28 Henry L Crowley & Company Inc Magnetic compositions
US2719274A (en) * 1951-07-09 1955-09-27 Gen Precision Lab Inc Microwave switches
GB721630A (en) * 1951-08-29 1955-01-12 Anorgana Gmbh Method for the production of ª†-fe o of improved magnetic properties
FR1080515A (fr) * 1951-12-22 1954-12-09 Philips Nv Aimant permanent anisotrope
US2723239A (en) * 1952-09-29 1955-11-08 Rca Corp Ferrospinel compositions
FR1086346A (fr) * 1953-07-09 1955-02-11 Perfectionnements aux aimants permanents
US2860105A (en) * 1953-12-21 1958-11-11 Philips Corp Method of manufacturing ferromagnetic cores

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3234494A (en) * 1961-07-28 1966-02-08 Bell Telephone Labor Inc Ferromagnetic compound and devices including elements thereof
US3403357A (en) * 1966-04-14 1968-09-24 Hughes Aircraft Co Switching apparatus for selectively coupling a predetermined number of microwave devices between an input and an output port

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BE546412A (fr)
GB797566A (en) 1958-07-02

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