US3100194A - Ferromagnetic material and method of making the same - Google Patents

Ferromagnetic material and method of making the same Download PDF

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US3100194A
US3100194A US783126A US78312658A US3100194A US 3100194 A US3100194 A US 3100194A US 783126 A US783126 A US 783126A US 78312658 A US78312658 A US 78312658A US 3100194 A US3100194 A US 3100194A
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mol percent
piezomagnetic
cuo
electromechanical coupling
nio
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Burgt Cornelis Martinus Va Der
Put Elias
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North American Philips Co 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

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  • Such vibrators are useful for converting electrical energy into mechanical energ for example, ultrasonic vibrations, and conversely (see for example Philips Technical Review, 18, 285-298, 1956/57).
  • the material have a maximum electromechanical coupling coefiicient and maximum mechanical tensile strength, while the magnetic and mechanical losses must be low and consequently the magnetic and mechanical quality factors must be high.
  • ferromagnetic materials e.g. nickelcopper ferrites and nickel-cobalt territes
  • their electromechanical coupling coefficients are low, viz. less than about 0.20.
  • a nicke-cobalt ferrite in which a portion of the iron has been replaced by chromium also known to exhibit piezomagnetic properties, has been found to be rather inefiicient, particularly when used in a piezomagnetic vibrator.
  • a still further object of our invention is to provide a new and novel piezomagnetic material which not only exhibits a larger electromechanical coupling coefiicient but which also has a maximum mechanical tensile strength.
  • Another object of our invention is to provide a new and novel material exhibiting not only a larger electromechanical coupling coefiicient and maximum mechanical tensile strength but also low magnetic and mechanical losses.
  • this new and novel ferromagnetic material which exhibits piezomagnetic properties with a large electromechanical coupling coeificient, w losses and high mechanical strength, consists of crystals having spinel structure having a composition corresponding to 29 to 47 mol percent NiO 3 to 20 mol percent CuO 0.5 to 2 mol percent 000 50 to 52 mol percent Fe O
  • compositions corresponding to 35 to 43 mol percent Nil) 6 to 14 mol percent CuO 0.8 to 1.4 mol percent C00 50 to 52 mol percent Fe O show the highest values of the electromechanical coupling coefiicient.
  • the nickel oxide and the copper oxide can be replaced in proportional amounts by at most 10 mol percent of ZnO.
  • Our invention also relates to bodies consisting of the said material and to piezomagnetic vibrators containing vibrator bodies which consist of the said material and must be made to vibrate by magnetic or acoustic alternating fields.
  • the materials in accordance with the invention have values of the electromechanical coupling coefficient substantially exceeding 0.20, the values or the mechanical quality factor exceeding 2000. Furthermore, the values of the magnetic losses and of the porosity are so low that the materials. can be used to advantage in piezomagnetic vibrators. As is known, a low value of the porosity is required for a high mechanical tensile strength and for a high erosion resistance. The term erosion as used herein is meant to be understood as the damage to the radiating surface of the vibrator owing to cavitation at high acoustic intensities. The absolute values of the iongitudinal saturation magnetostriction of the materials exceed 20 10- The materials in accordance with our invention are produced by sintering, at a temperature between 1000 C.
  • sintering is perifiormed at a temperature between 1200 C. and 1300 C.
  • the mixture is preferably heated in air or oxygen but other at mospheres such as nitrogen, car-hon dioxide, etc. may be employed. The latter temperatures are lower [than the temperatures at which in the known materials, optimum piezomagnetic properties are obtained.
  • the materials in accordance with our invention contain at least 50 mol percent of Fe O although larger amounts are permissible since materials which contain less than 50 mol percent of R 0 exhibit large mechanical and magnetic losses which would be a serious disadvantage to their application in piezornagnetic vibrators. Amounts. of Fe O in excess of 50 mol percent may result in a lowering of the resistivity of the material which is not detrimental to the desired piezomagnetic properties.
  • the reaction product was ground in a ball mill with water for 18 hours and afiter drying a small amount of an organic hinder, was added to the product which subsequently was pressed to form rings and rods which Were sintered in oxygen at the temperatures given in the following table for 2 hours.
  • the following table indicates the composition of the initial mixture, the sintering temperature and properties of the sintered rings.
  • p is the porosity which is equal to where d is the X-ray density and d the density,
  • p is the resistivity in ohms om.
  • n is the initial permeability at 30 kc./s.
  • tan 6 is the associated loss factor which is equal to is equal to 1
  • I (as) is the imaginary part of E is the modulus of elasticity at constant magnetic field strength.
  • Q (ring) all e se quantities are material quantities: in ⁇ the values given for Q (ring) the bearing losses of the ring are allowed for. Since the value of Q measured on a rod substantial-1y is a material quantity, the value of Q (m1) is given also. Since magnetic vibrators can be used in baths having temperatures materially exceeding room temperature, or some preparations the values of k and of Q (mg) at 50 C. are given.
  • the longitudinal saturation magnetostriction at room temperature of all these preparations lies between 25 X10 and 30 10 where is the real part and properties and consisting essentially of crystals having a spinel structure and a composition corresponding to about 35 to 43 mol percent of NiO, about 6 to 14 mol percent CuO, about 0.8 to 1.4 mol percent of C00, and at least 50 to about 52 mol percent of Fe o said material having an electromechanical coupling coeflicient substantially exceeding 0.20.
  • a ferromagnetic material having piezcmagnetic properties and consisting essentially of crystals having a spinel structure and a composition corresponding to about 35 to 43 mol percent NiO, about 6 to 14 mol percent CuO, up to about 10 mol percent ZnO, about 0.8 to 1.4 mol percent C00, and at least 50 to about 52 mol percent Fe O said material having an electromechanical coupling coefiicient substantially exceeding 0.20.
  • a method of making a ferromagnetic material having piezomagnetic properties comprising the steps, forming a finely-divided mixture of about 29 to 47 mol percent of NiO, about 2 to 20 mol percent of CuO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of Fe O and heating said mixture in a non- -reducing atmosphere at a temperature of about 1000 to 1400 C.
  • a method of making a ferromagnetic material having piezomagnetic propertie comprising the steps, formlog a finely-divided mixture of about 29 to 47 mol per- Compcsition, mol percent Siinlter- Room temp. C.
  • a ferromagnetic material having piezomagnetic properties and consisting essentially of crystals having a spinel structure and a composition corresponding to about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, about 0.5 to 2 mol percent C00, and at least 50 to about 52 mol percent of Fe Og, said material having an electromechanical coupling coeificient substantially exceeding 0.20.
  • a method of making a ferromagnetic material having piezomagnetic properties comprising the steps, torming a mixture of about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, up to about 10 mol percent of ZnO, about 0.5 to 2 mol percent (300, and at least 50 mol percent to about 52 mol percent -Fe O and heating said mixture in a non-reducing atmosphere to a temperature of about 1200 to 1300" C.
  • a ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical c0upling .coefiicient substantially exceeding 0.20, said body consisting essentiflly of a sintered coherent body composed of crystals having a spinel structure and a composition corresponding to: about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of Fe O 10.
  • a ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coefiicient substantially exceeding 0.20, said body consisting essentially of a sintered coherent body composed of crystals having a spinel structure and a com position corresponding to about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, up to about mol percent of ZnO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of F6203.
  • a ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coefficient substantiafly exceeding 0.20, said body consisting essentially of a sintered coherent body composed of crystals having a spinel structure and a composition corresponding to about 35 to 43 mol percent of NiO, about 6 to 14 mol percent CuO, about 0.8 to 1.4 mol percent C00, and at least 50 to about 52 mol percent Fe O 12.
  • a ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coeflicient substantially exceeding 0.20, said body consisting essentially of a sintered coherent body composed of crystals having a spinel structure and a composition corresponding to about 35 to 43 mol percent of NiO, about 6 to 14 mol percent of CuO, up to about 10 mol percent of ZnO, about 0.8 to 1.4 mol percent of C00, and at least 50 to about 52 mol percent Fe O 13.
  • a method of making a fenromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coefiicient substantially exceedjng 0.20 comprising the steps, forming a finely-divided mixture of about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of Fe O compacting said mixture into a coherent body, and heating said body in a non-reducing atmosphere to a temperature of about 1000 to 1400 C.
  • a method of making a ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coefiicient substantially exceeding 0.20 comprising the steps, forming a finely-divided mix ture of about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, about 0.5 to 2 mol percent of C00,
  • a method of making a ferromagnetic body adapted for use in a piezornagnetic vibrator and having an electromechanical coupling coeflicient substantially exceeding 020 comprising the steps, forming a finely-divided mixture of about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, up to about 10 mol percent of ZnO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of Fe O compacting said mixture into a coherent body, and heating said body in a nonreducing atmosphere to a temperature of about 1000 to 1400 C.
  • a method of making a ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coeflicient substantially exceeding 0.20 comprising the steps, forming a finely-divided mixture of about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, up to 10 mol percent of ZnO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of Fe O compacting said mixture into a coherent body, and heating said body in a non-reducing atmosphere to a temperature of about 1200 to 1300 C.

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  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
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  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Magnetic Ceramics (AREA)
  • Soft Magnetic Materials (AREA)
  • Compositions Of Oxide Ceramics (AREA)

Description

United States Patent Ofiice 3,l00,l04 Patented Aug. 6, 1963 3,100,194 FERRQMAGNETHC MATEREAL AND METHGD F MAKlNG THE SAME Cornelis Martinus van der Burgt and Elias Put, Eludhoven, Netherlands, assignors to North American Philips Company, Inc, New York, N.Y., a corporation of Delaware N0 Drawing. Filed Dec. 29, 1958, Ser. No. 783,126 Claims priority, application Netherlands Jan. 15, 1953 16 Claims. (Cl. 252-625) This invention relates to ferromagnetic materials more particularly for piezornagnetic vibrators and to methods or making the same.
Such vibrators are useful for converting electrical energy into mechanical energ for example, ultrasonic vibrations, and conversely (see for example Philips Technical Review, 18, 285-298, 1956/57). For this use it is desirable that the material have a maximum electromechanical coupling coefiicient and maximum mechanical tensile strength, while the magnetic and mechanical losses must be low and consequently the magnetic and mechanical quality factors must be high.
While certain ferromagnetic materials, e.g. nickelcopper ferrites and nickel-cobalt territes, exhibit piezomagnetic properties, their electromechanical coupling coefficients are low, viz. less than about 0.20. Similarly, a nicke-cobalt ferrite in which a portion of the iron has been replaced by chromium, also known to exhibit piezomagnetic properties, has been found to be rather inefiicient, particularly when used in a piezomagnetic vibrator.
It is a principal object of our invention to provide a new and novel material having piezomagnetic properties which has a larger electromechanical coupling coeificient and is more efficient in converting mechanical to electrical energy and vice versa.
It is another object of our invention to provide a method of making a piezomagnetic material having a larger electromechanical coupling coefiicient.
A still further object of our invention is to provide a new and novel piezomagnetic material which not only exhibits a larger electromechanical coupling coefiicient but which also has a maximum mechanical tensile strength.
Another object of our invention is to provide a new and novel material exhibiting not only a larger electromechanical coupling coefiicient and maximum mechanical tensile strength but also low magnetic and mechanical losses.
These and rurther objects of our invention will appear as the specification progresses.
In accordance with our invention, this new and novel ferromagnetic material which exhibits piezomagnetic properties with a large electromechanical coupling coeificient, w losses and high mechanical strength, consists of crystals having spinel structure having a composition corresponding to 29 to 47 mol percent NiO 3 to 20 mol percent CuO 0.5 to 2 mol percent 000 50 to 52 mol percent Fe O In a preferred embodiment of our invention we have found that compositions corresponding to 35 to 43 mol percent Nil) 6 to 14 mol percent CuO 0.8 to 1.4 mol percent C00 50 to 52 mol percent Fe O show the highest values of the electromechanical coupling coefiicient. Moreover, the nickel oxide and the copper oxide can be replaced in proportional amounts by at most 10 mol percent of ZnO.
Our invention also relates to bodies consisting of the said material and to piezomagnetic vibrators containing vibrator bodies which consist of the said material and must be made to vibrate by magnetic or acoustic alternating fields.
The materials in accordance with the invention have values of the electromechanical coupling coefficient substantially exceeding 0.20, the values or the mechanical quality factor exceeding 2000. Furthermore, the values of the magnetic losses and of the porosity are so low that the materials. can be used to advantage in piezomagnetic vibrators. As is known, a low value of the porosity is required for a high mechanical tensile strength and for a high erosion resistance. The term erosion as used herein is meant to be understood as the damage to the radiating surface of the vibrator owing to cavitation at high acoustic intensities. The absolute values of the iongitudinal saturation magnetostriction of the materials exceed 20 10- The materials in accordance with our invention are produced by sintering, at a temperature between 1000 C. and 1400 C., a finely powdered mixture of nickel oxide, copper oxide, cobalt oxide, iron oxide and the required zinc oxide, which oxides can entirely or partly be replaced by compounds which On heating are converted into these oxides. Preferably sintering is perifiormed at a temperature between 1200 C. and 1300 C. The mixture is preferably heated in air or oxygen but other at mospheres such as nitrogen, car-hon dioxide, etc. may be employed. The latter temperatures are lower [than the temperatures at which in the known materials, optimum piezomagnetic properties are obtained.
It is essential that the materials in accordance with our invention contain at least 50 mol percent of Fe O although larger amounts are permissible since materials which contain less than 50 mol percent of R 0 exhibit large mechanical and magnetic losses which would be a serious disadvantage to their application in piezornagnetic vibrators. Amounts. of Fe O in excess of 50 mol percent may result in a lowering of the resistivity of the material which is not detrimental to the desired piezomagnetic properties.
The following example is illustrative of the method employed in preparing the compositions specified in the table in which lists. the properties of a number of examples of material according to our invention.
Example A mixture of nickel oxide, copper carbonate, cobalt ball mill for 18 hours and subsequently prefired at 950 C. in air for 4 hours. The reaction product was ground in a ball mill with water for 18 hours and afiter drying a small amount of an organic hinder, was added to the product which subsequently was pressed to form rings and rods which Were sintered in oxygen at the temperatures given in the following table for 2 hours.
The following table indicates the composition of the initial mixture, the sintering temperature and properties of the sintered rings. In the heading of the table p is the porosity which is equal to where d is the X-ray density and d the density,
p is the resistivity in ohms om.,
3 n is the initial permeability at 30 kc./s., tan 6 is the associated loss factor which is equal to is equal to 1 I (as) is the imaginary part of E is the modulus of elasticity at constant magnetic field strength. With the exception of Q (ring) all e se quantities are material quantities: in \the values given for Q (ring) the bearing losses of the ring are allowed for. Since the value of Q measured on a rod substantial-1y is a material quantity, the value of Q (m1) is given also. Since magnetic vibrators can be used in baths having temperatures materially exceeding room temperature, or some preparations the values of k and of Q (mg) at 50 C. are given. The longitudinal saturation magnetostriction at room temperature of all these preparations lies between 25 X10 and 30 10 where is the real part and properties and consisting essentially of crystals having a spinel structure and a composition corresponding to about 35 to 43 mol percent of NiO, about 6 to 14 mol percent CuO, about 0.8 to 1.4 mol percent of C00, and at least 50 to about 52 mol percent of Fe o said material having an electromechanical coupling coeflicient substantially exceeding 0.20.
' 3. A ferromagnetic material having piezomagnetic properties and consisting essentially of crystals having a spinel structure and a composition corresponding to about 29 to 47 mol percent of NiO, about 3 to 20 mol percent CuO, up to about 10 mol percent Z-nO, about 0.5 to 2 mol percent (300, and at least 50 to about 52 mol percent Fe O said material having an electromechanical coupling coefficient substantially exceeding 0.20.
4. A ferromagnetic material having piezcmagnetic properties and consisting essentially of crystals having a spinel structure and a composition corresponding to about 35 to 43 mol percent NiO, about 6 to 14 mol percent CuO, up to about 10 mol percent ZnO, about 0.8 to 1.4 mol percent C00, and at least 50 to about 52 mol percent Fe O said material having an electromechanical coupling coefiicient substantially exceeding 0.20.
5. A method of making a ferromagnetic material having piezomagnetic properties comprising the steps, forming a finely-divided mixture of about 29 to 47 mol percent of NiO, about 2 to 20 mol percent of CuO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of Fe O and heating said mixture in a non- -reducing atmosphere at a temperature of about 1000 to 1400 C.
6. A method of making a ferromagnetic material having piezomagnetic properties comprising the steps, forming a finely-divided mixture of about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, up to about 10 m=ol percent of ZnO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of Fe O and heating said mixture in a non-reducing atmosphere to a temperature of about 1000 to 1400 C.
7. A method of making a ferromagnetic material having piezomagnetic propertie comprising the steps, formlog a finely-divided mixture of about 29 to 47 mol per- Compcsition, mol percent Siinlter- Room temp. C.
1; P temo, N10 0110 000 F3203 C. S2 cm p Tan 5 k Qn (ring) Qstma L Qn (ring) While we have thus described our invention in connection with specific embodiments and specific applica tions thereof, we do not Wish to be limited thereto since other modifications and applications thereof will be readily apparent to those skilled in the art.
What we claim is:
1. A ferromagnetic material having piezomagnetic properties and consisting essentially of crystals having a spinel structure and a composition corresponding to about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, about 0.5 to 2 mol percent C00, and at least 50 to about 52 mol percent of Fe Og, said material having an electromechanical coupling coeificient substantially exceeding 0.20.
2. A ferromagnetic material having piezomagnetic cent of NiO, about 3 to 20 mol percent of CuO, about 0.5 to 2 mol percent 000, and at least 50 to about 52 mol percent Fe O and heating said mixture in a non reducing atmosphere to a temperature of about 1200 to 1300 C.
8. A method of making a ferromagnetic material having piezomagnetic properties comprising the steps, torming a mixture of about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, up to about 10 mol percent of ZnO, about 0.5 to 2 mol percent (300, and at least 50 mol percent to about 52 mol percent -Fe O and heating said mixture in a non-reducing atmosphere to a temperature of about 1200 to 1300" C.
9. A ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical c0upling .coefiicient substantially exceeding 0.20, said body consisting essentiflly of a sintered coherent body composed of crystals having a spinel structure and a composition corresponding to: about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of Fe O 10. A ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coefiicient substantially exceeding 0.20, said body consisting essentially of a sintered coherent body composed of crystals having a spinel structure and a com position corresponding to about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, up to about mol percent of ZnO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of F6203.
11. A ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coefficient substantiafly exceeding 0.20, said body consisting essentially of a sintered coherent body composed of crystals having a spinel structure and a composition corresponding to about 35 to 43 mol percent of NiO, about 6 to 14 mol percent CuO, about 0.8 to 1.4 mol percent C00, and at least 50 to about 52 mol percent Fe O 12. A ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coeflicient substantially exceeding 0.20, said body consisting essentially of a sintered coherent body composed of crystals having a spinel structure and a composition corresponding to about 35 to 43 mol percent of NiO, about 6 to 14 mol percent of CuO, up to about 10 mol percent of ZnO, about 0.8 to 1.4 mol percent of C00, and at least 50 to about 52 mol percent Fe O 13. A method of making a fenromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coefiicient substantially exceedjng 0.20, comprising the steps, forming a finely-divided mixture of about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of Fe O compacting said mixture into a coherent body, and heating said body in a non-reducing atmosphere to a temperature of about 1000 to 1400 C.
14. A method of making a ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coefiicient substantially exceeding 0.20 comprising the steps, forming a finely-divided mix ture of about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, about 0.5 to 2 mol percent of C00,
and at least to about 52 mol percent of 1e 0,, compacting said mixture into a coherent body, and heating said body in a non-reducing atmosphere to a temperature of about 1200 to 1300 C.
1-5. A method of making a ferromagnetic body adapted for use in a piezornagnetic vibrator and having an electromechanical coupling coeflicient substantially exceeding 020 comprising the steps, forming a finely-divided mixture of about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, up to about 10 mol percent of ZnO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of Fe O compacting said mixture into a coherent body, and heating said body in a nonreducing atmosphere to a temperature of about 1000 to 1400 C.
16. A method of making a ferromagnetic body adapted for use in a piezomagnetic vibrator and having an electromechanical coupling coeflicient substantially exceeding 0.20 comprising the steps, forming a finely-divided mixture of about 29 to 47 mol percent of NiO, about 3 to 20 mol percent of CuO, up to 10 mol percent of ZnO, about 0.5 to 2 mol percent of C00, and at least 50 to about 52 mol percent of Fe O compacting said mixture into a coherent body, and heating said body in a non-reducing atmosphere to a temperature of about 1200 to 1300 C.
References Cited in the file of this patent UNITED STATES PATENTS 2,565,861 Leverenz et a1. Aug. 28, 1951 2,640,813 Berge June 2, 1953 2,656,319 Berge Oct. 20, 1953 2,685,568 Wilson Aug. 3, 1954 2,723,239 Harvey Nov. 8, 1955 2,736,708 Crowley et a1. Feb. 28, 1956 2,925,388 Harvey Feb. 16, 1960 2,951,810 Kikuchi Sept. 6, 1960 2,989,476 Eckert June 20, 1961 3,039,966 Brockman et a1. June 19, 1962 FOREIGN PATENTS 161,403 Australia Feb. 23, 1955 1,100,865 France Apr. 13, 1955 1,148,861 France July 1, 1957 302,709 Switzerland Jan. 3, 1955 OTHER REFERENCES Albers-Schoenberg: Ceramic Age, May 1952, pp. 30 and 32-35, J. Institute of Electrical Eng, Japan, November 1937, pp. 5, 7.

Claims (1)

1. A FERROMAGNETIC MATERIAL HAVING PIEZOMAGNETIC PROPERTIES AND CONSISTING ESSENTIALLY OF CRYSTALS HAVING A SPINEL STRUCTURE AND A COMPOSITION CORRESPONDING TO ABOUT 29 TO 47 MOL PERCENT OF NIO, ABOUT 3 TO 20 MOL PERCENT OF CUO, ABOUT 0.5 TO 2 MOL PERCENT COO, AND AT LEAST 50 TO ABOUT 52 MOL PERCENT OF FE2O3, SAID MATERIAL HAVING AN ELECTROMECHANICAL COUPLING COEFFICIENT SUBSTANTIALLY EXCEEDING 0.20.
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US3160576A (en) * 1959-11-16 1964-12-08 Steatit Magnesia Ag Method of producing thin ferromagnetic layers of uniaxial anisotropy
US3274110A (en) * 1962-12-21 1966-09-20 Ibm Ferrite process
US3425666A (en) * 1963-02-21 1969-02-04 Chevron Res Process for producing ferrimagnetic materials
US5456734A (en) * 1993-05-07 1995-10-10 Fuji Photo Film Co., Ltd. Abrasive member
EP0694913A1 (en) 1991-08-23 1996-01-31 Fuji Photo Film Co., Ltd. Magnetic recording medium manufacturing method
EP0710951A1 (en) 1994-10-14 1996-05-08 Fuji Photo Film Co., Ltd. Magnetic recording medium
EP0717396A1 (en) 1994-12-16 1996-06-19 Fuji Photo Film Co., Ltd. Magnetic recording medium
EP0797190A1 (en) 1992-01-08 1997-09-24 Fuji Photo Film Co., Ltd. Magnetic recording medium
US5876833A (en) * 1995-05-10 1999-03-02 Fuji Photo Film Co., Ltd. Magnetic recording medium containing magnetic powder and a polyurethane binder having a specified radius of gyration
US6261647B1 (en) 1995-01-02 2001-07-17 Fuji Photo Film Co., Ltd. Method and apparatus for manufacturing magnetic recording medium
US6548160B2 (en) 1999-12-01 2003-04-15 Fuji Photo Film Co., Ltd. Magnetic recording media
EP1640974A2 (en) 2004-09-28 2006-03-29 Fuji Photo Film Co., Ltd. Cleaning medium
EP2001014A2 (en) 2007-05-31 2008-12-10 FUJIFILM Corporation Magnetic signal reproduction system and magnetic signal reproduction method
EP2234106A1 (en) 2009-03-27 2010-09-29 Fujifilm Corporation Magnetic recording medium, magnetic signal reproduction system and magnetic signal reproduction method
EP2237273A1 (en) 2009-03-31 2010-10-06 FUJIFILM Corporation Magnetic tape cartridge

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