US3485759A - Hydrothermal growth of rare earth orthoferrites and materials so produced - Google Patents

Hydrothermal growth of rare earth orthoferrites and materials so produced Download PDF

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US3485759A
US3485759A US660643A US3485759DA US3485759A US 3485759 A US3485759 A US 3485759A US 660643 A US660643 A US 660643A US 3485759D A US3485759D A US 3485759DA US 3485759 A US3485759 A US 3485759A
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growth
rare earth
temperature
materials
nutrient
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Ernest D Kolb
Robert A Laudise
Edward G Spencer
Darwin L Wood
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AT&T Corp
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Bell Telephone Laboratories Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
    • H01F41/24—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates from liquids
    • H01F41/28—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates from liquids by liquid phase epitaxy
    • 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
    • C04B35/2675—Other ferrites containing rare earth metals, e.g. rare earth ferrite garnets
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C30B29/22—Complex oxides
    • C30B29/24—Complex oxides with formula AMeO3, wherein A is a rare earth metal and Me is Fe, Ga, Sc, Cr, Co or Al, e.g. ortho ferrites
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B7/00—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B7/00—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions
    • C30B7/005—Epitaxial layer growth

Definitions

  • the invention is concerned with the preparation of single crystals of rare earth orthoferrites. Such crystals are of interest in a large class of devices including those which depend for their operation on the nucleation and propagation of single wall magnetic domains of restricted cross-sectional area.
  • At least 80 atom percent of the R atoms should be selected from elements 39 and 62 through 70,
  • the rare earth orthoferrites are canted antiferromagnetic.
  • the magnetization and certain other magnetic properties depend on the canting angle and also on the degree to which the material is completely antiferromagnetic, that is, the extent to which the opposing moments are equal.
  • Partial substitutions for iron, for example, with gallium or aluminum may result in a variation of the saturation magnetization, or in alteration of other magnetic properties. Device significance may follow, for example, from the fact that increased magnetization results in a decrease in stable domain size.
  • Certain specific complete and partial substitutions have been outlined. Other variations, both in the rare earth and in the iron sites are feasible. Any such substitutions necessarily produce a concomitant change in magnetic properties. All substituted materials which retain the rare earth orthoferrite structure are desirably grown in accordance with the process of the invention and, in consequ nce, are considered within the inventive scope.
  • Crystals resulting from use of the inventive procedures are suitably incorporated in devices depending for their operation on the electrical, magnetic, or acoustic properties of these materials. Such crystals and devices form a part of the invention.
  • FIG. 1 is a perspective view, partly in cross-section, of apparatus suitable for practice of the inventive processes
  • FIG. 2 is a perspective view of an orthoferrite crystal grown in accordance with a process herein;
  • FIG. 3 is a schematic representation of a device depending for its operation upon the nucleation and propagation of single wall domains in a material of the invention.
  • the main body 10 contains a precious metal can 11, so defining a chamber 12.
  • a main nut 13 is threaded into the upper portion of the chamber.
  • a plunger 14' is fitted into thechamber 12 and is free to rise with increasing pressure in the chamber. As the plunger rises, it contacts a steel seal ring 15 and is finally stopped by bearing against the main nut 13 through the seal ring. This action provides an effective seal for the growth chamber.
  • the chamber is initially temporarily sealed by means of the set screws 16 which compress a resilient washer 19 against the shank of the plunger.
  • the space between the can 11 and the inner wall of body 10 is filled with water to a degree necessary to minimize pressure differential between the inside and outside of can 11.
  • the chamber 12 is charged with nutrient material.
  • the potassium hydroxide solution is added in the amount required to produce the requisite pressure at the desired operating temperature.
  • Seed crystals such as 17 are suspended as shown.
  • a baffle 18 may be interposed between the nutrient mass and the seed crystals so as to divide the chamber into two thermal zones. The baflie maintains a reliable temperature differential between the nutrient and the crystallization zone and expedites simultaneous growth of two or more seeds.
  • the fill is desirably from 70 percent to 95 percent by volume although these limits are not absolute.
  • the lower fill limit is based solely on growth rate, with rates dropping below a convenient level for lower fill.
  • Temperatures are interrelated with rates, so that temperatures above that indicated result in pressures which are unduly high for usual autoclave structures and with growth rate dropping unduly below the lower indicated temperature. While generally still higher temperatures are permitted for lower fills below the indicated minimum, there are some disadvantages in this procedure in that phases other than the orthoferrite tend to form. Still lower temperatures corresponding with still higher fill percentages do not generally result in acceptable growth rates. Pressures corresponding with these temperatures range from about 8,000 p.s.i. for 350 C. and 70 percent fill to about 35,000 p.s.i. for 425 C, and 95 percent fill.
  • a significant parameter is the temperature difierential between the seed and nutrient.
  • the use of smaller differentials reduces the growth rate, but, in common with the choice of other parameters which minimize the rate, results in greater perfection due to the fact that more time is permitted for rearrangement of atoms on the surface of the growing crystal.
  • a minimum gradient of about 5 C. is specified. This value arises from consideration of permissibly small growth rate and from the fact that temperature control of smaller gradients is generally diflicult with commercially available apparatus.
  • a preferred minimum of 10 C. is recommended.
  • the maximum tolerable gradient is considered to lie at about 50 C. since for significantly larger values spontaneous nucleation becomes a problem. A preferred maximum lies at about 30 C.
  • the crystal structure of the rare earth orthoferrites is orthorhombic.
  • Preferred seed plate orientation is [110] or [001].
  • growth-rate is most rapid on the former.
  • Use of an [001] seed is desirable for certain compositions and uses, since it results in an easy magnetization direction orthogonal to the crystal sheet.
  • Growth rates as high as 6 mils a day have been observed for a 20 mole KOH solution, percent fill, 375 C. crystallization temperature, and temperature differential of 30 C. (-8,000 p.s.i.).
  • the temperature gradient is largely controlled by a baffle such as baffle 18 in FIG. 1.
  • a convenient open area for the bafiie is about 5 percent. Much larger than 10 percent open tends to decrease the temperature gradient to values below that permitted in the usual apparatus.
  • EXAMPLE l Apparatus similar to that depicted in FIG. 1 of approximate inner dimensions 2% inch length by one inch diameter was utilized. 8 grams total of Fe O and Yb O in the mo-l ratio of 1:1 were placed in the bottom of the autoclave. The bafile, such as that shown as element 18. was then placed in position. seeds such as 17 were placed in the position shown. The autoclave was filled to 80 percent of its free volume, with 20 molal aqueous KOH. The autoclave was closed and was placed in a furnace where it was brought to a temperature of 375 C. at the seed position in a period of about five hours. The bottom of the inner vessel corresponding with the nutrient position was at this point at a temperature of about 405 C.
  • EXAMPLE 2 The preceding example was repeated as described, however, substituting presintered Fe O +Yb O for the starting materials indicated. The growth rate was substantially unchanged. The resulting crystal was about 1 cm. by 1 cm. by 210 mils and was sound and magnetically homogeneous.
  • Example 3 The procedure of Example 1 was repeated, however substituting a sintered mass of the composition Sm Er FeO for the nutrient therein indicated. The final crystal was of the same composition as that of the nutrient. Crystal size was of the order of 1 cm. by 1 cm. by 210 mils. Magnetic properties were of device caliber.
  • Example 4 The procedure of Example 1 was repeated, however substituting a sintered mass of the composition YFeO for the nutrient of that example.
  • Example 5 The procedure of Example 1 was repeated, however substituting a sintered mass of the composition HoFeO for the nutrient of that example.
  • Example 6 The procedure of Example 1 was repeated, however substituting a sintered mass of the composition TbFeO for the nutrient of that example.
  • Products of Examples 3 through 6 were of the same composition as the starting material and were sound and magnetically homogeneous.
  • compositions including single or mixed cations of elements 39 and 62 through 70, as well as compositions containing up to atom percent of the other elements lanthanum and Nos. 58 through 60, as well as compositions containing other substituents permitted in the orthoferrite phase, are expediently grown without altering the outlined growth conditions.
  • the rare earth orthoferrites are desirably utilized in a class of devices which include a sheet or layer of a single crystalline material which is magnetically isotropic in the plane of the sheet and which has an easy direction out of the plane of the sheet.
  • An exemplary use is in a shift register. The device of FIG. 3 is described in such terms.
  • a register 20 comprises a sheet 21 of a rare earth orthoferrite in accordance with the invention.
  • the sheet is so oriented that at the operating temperature the preferred magnetization direction (easy direction) is normal to the plane of the sheet. Flux direction out of the paper as viewed is represented by a plus sign. Flux directed into the paper is represented by a minus sign.
  • Conductors 22, 23, and 24, which may be deposited on the surface of sheet 21, form triplets of loops 22a, 23a, 24a; 22b, 23b, 24!), et seq. Loop size is somewhat smaller than the size of a corresponding stable single wall domain so that in operation any magnetized domain is partly within an adjoining loop.
  • Such domains once nucleated, for example, by means of a domain nucleating source 25 and loop 26, are stepped from loop position 22a to 23a to 24a to 22b and so forth by successive energization of conductors 22, 23, and 24 in that order by means not shown. Readout is accomplished by means of loop 27 and sensing means 28.
  • Switches other types of memory elements, logic elements, etc. Some such devices may operate at constant temperature at or near the spin flop temperature. Others may depend on a temperature variation sometimes local to flip the magnetization and so provide a means for easily nucleating a domain.
  • Sheet material has been prepared by growth of a limited thickness on a seed as indicated in the examples. Subsequent treatment may include slicing and, finally, back sputtering to remove damaged portions. Crystals have also been grown epitaxially. Single crystal growth, of course, requires a substrate material having lattice' dimensions closely approximating those of the orthoferrite to be grown. For device purposes, it is generally desired that the substrate be essentially nonmagnetic.
  • the paramagnetic material terbium aluminate (TbAlO has been found an appropriate substrate for the epitaxial growth of YbFeO
  • the invention has been described in terms of a limited number of embodiments.
  • Method for growing crystalline material which comprises disposing a crystal and a mass of nutrient capable of yielding the said material in an alkaline solution within a closed vessel, heating said solution to a temperature of at least 300 C. while under a pressure exceeding its critical pressure and maintaining a temperature difference between said seed and said mass of nutrient of at least 5 C.
  • the said solution consists essentially of a 10 to 25 molal aqueous solution of potassium hydroxide and in that the said crystalline material consists essentially of the composition RFeO where R is at least one element selected from the group consisting of yttrium Samarium, europiurn, gadolinium, terbium, dysprosium, holmium, erbium, thulium and ytterbium, additionally containing from O to 20 atom percent of at least one element of the group consisting of lanthanum, cerium, praseodymium and neodymium.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Metallurgy (AREA)
  • Manufacturing & Machinery (AREA)
  • Power Engineering (AREA)
  • Ceramic Engineering (AREA)
  • Structural Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
US660643A 1967-08-15 1967-08-15 Hydrothermal growth of rare earth orthoferrites and materials so produced Expired - Lifetime US3485759A (en)

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BE (1) BE719455A (de)
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FR (1) FR1603057A (de)
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3648260A (en) * 1969-11-17 1972-03-07 Bell Telephone Labor Inc Magnetic devices
US6767498B1 (en) 1998-10-06 2004-07-27 Hills, Inc. Process of making microfilaments

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CN114890784A (zh) * 2022-04-29 2022-08-12 广东金绿能科技有限公司 一种陶瓷基复合材料及其制备方法

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3648260A (en) * 1969-11-17 1972-03-07 Bell Telephone Labor Inc Magnetic devices
US6767498B1 (en) 1998-10-06 2004-07-27 Hills, Inc. Process of making microfilaments

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DE1769969A1 (de) 1971-11-04
GB1243021A (en) 1971-08-18
FR1603057A (de) 1971-03-15
NL6811543A (de) 1969-02-18
BE719455A (de) 1969-01-16

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