CA1050862A - Magnetic bubble devices and garnet films therefor - Google Patents
Magnetic bubble devices and garnet films thereforInfo
- Publication number
- CA1050862A CA1050862A CA210,109A CA210109A CA1050862A CA 1050862 A CA1050862 A CA 1050862A CA 210109 A CA210109 A CA 210109A CA 1050862 A CA1050862 A CA 1050862A
- Authority
- CA
- Canada
- Prior art keywords
- garnet
- film
- bubble
- gallium
- magnetic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/08—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers
- H01F10/10—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition
- H01F10/18—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition being compounds
- H01F10/20—Ferrites
- H01F10/24—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
- C30B19/00—Liquid-phase epitaxial-layer growth
- C30B19/02—Liquid-phase epitaxial-layer growth using molten solvents, e.g. flux
-
- 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
- C30B29/28—Complex oxides with formula A3Me5O12 wherein A is a rare earth metal and Me is Fe, Ga, Sc, Cr, Co or Al, e.g. garnets
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C19/00—Digital stores in which the information is moved stepwise, e.g. shift registers
- G11C19/02—Digital stores in which the information is moved stepwise, e.g. shift registers using magnetic elements
- G11C19/08—Digital stores in which the information is moved stepwise, e.g. shift registers using magnetic elements using thin films in plane structure
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C19/00—Digital stores in which the information is moved stepwise, e.g. shift registers
- G11C19/02—Digital stores in which the information is moved stepwise, e.g. shift registers using magnetic elements
- G11C19/08—Digital stores in which the information is moved stepwise, e.g. shift registers using magnetic elements using thin films in plane structure
- G11C19/0866—Detecting magnetic domains
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Power Engineering (AREA)
- Thin Magnetic Films (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
Abstract Garnet films suitable for bubble devices which are substituted with bismuth, aluminum or gallium and certain rare earth ions have improved magneto optic properties and can be formed at low temperatures on gadolinium gallium garnet substrates.
Description
6 7, 3 8 4 ~L~508~;Z
l~!PI~OVEl) I~ ;NI I`l( l~lJ13L3LI. I)L.V~ NL) - (IA RN ~ I S r I I ~ R~ ~ o R
l This in~ention relates to novel magnetic garnet films and devices incorporating them. ~lore particularLy, .:, .
this invention relates ~o novel magnetic garnet films, a process for making them and bubble domain devices incorpora ting them which display improved magneto-optic capabilities.
;:
Magnetic devices, commonly referred to as bubble domain devlces, depend on the use of materials which can ;~
maintain and propagate small cylindrical domains or huhbles ;~
of reversed magnetization in appropriate magnetic fields.
~.
These materials are generally in the form of thin single ~.
crystals supported on a non-magnetic, compatible substrate having a matching lattice constant. The~devices comprise a fllm of magnetic bubble material, means~for generating ~-, 15 localized reversed domalns, means for propagating the domains :i along a predetermined path, such~as a conductor circuit, to , .
another portion of the film and means for detecting the presence of the bubbles. The latter is generally accom~
plished by magneto-resistive techniques which detects the presence of a bubble as an information ~it. A high bit density, or small bubble size, for a given film is generally desirable within the limits of conventional photolithographic i~ ;
:~
fabrication techniques used to make the propagation circuits.
Materials research to~ date has resulted in garnet materials ;~
l 25 which can form bubbles less than l mil in dlameter, preferab~
.1 about 1/4 - 1/3 mil ln diameter, so as to obtain a bit density of 105 to 106 bits/square lnch of film. However, the bubbles must be greatly expanded, e.g., about 100-300 times, in order to detect them by magneto-resistive techniques and this results in a large decrease in the useful area of a
l~!PI~OVEl) I~ ;NI I`l( l~lJ13L3LI. I)L.V~ NL) - (IA RN ~ I S r I I ~ R~ ~ o R
l This in~ention relates to novel magnetic garnet films and devices incorporating them. ~lore particularLy, .:, .
this invention relates ~o novel magnetic garnet films, a process for making them and bubble domain devices incorpora ting them which display improved magneto-optic capabilities.
;:
Magnetic devices, commonly referred to as bubble domain devlces, depend on the use of materials which can ;~
maintain and propagate small cylindrical domains or huhbles ;~
of reversed magnetization in appropriate magnetic fields.
~.
These materials are generally in the form of thin single ~.
crystals supported on a non-magnetic, compatible substrate having a matching lattice constant. The~devices comprise a fllm of magnetic bubble material, means~for generating ~-, 15 localized reversed domalns, means for propagating the domains :i along a predetermined path, such~as a conductor circuit, to , .
another portion of the film and means for detecting the presence of the bubbles. The latter is generally accom~
plished by magneto-resistive techniques which detects the presence of a bubble as an information ~it. A high bit density, or small bubble size, for a given film is generally desirable within the limits of conventional photolithographic i~ ;
:~
fabrication techniques used to make the propagation circuits.
Materials research to~ date has resulted in garnet materials ;~
l 25 which can form bubbles less than l mil in dlameter, preferab~
.1 about 1/4 - 1/3 mil ln diameter, so as to obtain a bit density of 105 to 106 bits/square lnch of film. However, the bubbles must be greatly expanded, e.g., about 100-300 times, in order to detect them by magneto-resistive techniques and this results in a large decrease in the useful area of a
-2-,, .
~CA 67,38~
~5~8G;~
1 particular fi1m on which informa-tion can be stored.
Magneto optic techniques have also been tried for detecting bubbles, but in magnetic bubble materials available heretofore, the optical properties, particularly Farad~y rotation, are low and high powered lasers or very sensitive light detectors are required to detect the presence or ~
absence of bubbles optically. ~-Magnetic materials, to be suitable as bubble materials, must satisfy the following general requirements:
I0 they must have a uniaxial magnetic anisotropy (K~) with the easy axis of magnetization perpendicular to the film surface;
; and they mus-t have a saturation magnetization (~s) such that 2 K~ > 2~Ms , Owing to their cubic magnetic anisotropy, simp1e garnets such as YIG (yttrium-iron garnet) are unsuitable for bubble device applications. Liquid phase epitaxial films of doped garnets can acquire uniaxial anisotropy as a result of ionic segregation that occurs during growth. To satisfy the -requirements given above, the saturation magnetizatlon of doped garnets is reduced by substituting gallium or aluminum for some of the tetrahedral iron ions. Known garnets are temperature sensitive, such that close control of temperature during operation of devices incorporating them is required.
In addition to the magnetic and optical properties required or desirable for good bubble materials employed in `
conjunction with magneto-optic bubble detection, the film should also be able to be grown as thin, defect free, single : crystal films onto a supporting compatible substrate. Pre-ferably, single crystal films are grown by liquid phase !~' .: ' ' ' R(..~ 67, 3R~
, ,' ~.
~ 6~508~Z ~ ~
l epitaxial techniclues from a suitable flux. A lattice constant match within about 0.002 Angstroms is required bet~een the film and that o commercially available sub-strates, such as gadolinium gallium garnet.
We have discovered certain bismuth doped magnetic garnet compositions which have a high Faraday rotation in the visible and infrared wavelength range and in addition -have magnetic properties required for bubble materials, e.g.S
growth induced uniaxial anisotropy. Such materials can be incorporated into bubble devices wherein the bubbles can be detected optically. These compositions can be grown from a suitable flux by conventional epitaxial techniques at low temperatures in the form of single crystal, strain--free 15 films directly on~o a nonmagnetic garnet substrate. ;
' '.
FIG. 1 shows a single crystal garnet film on a substrate suitable for use in a bubble device.
FIG. 2 is a schematic representation o-E a magnetic bubble device utilizing a single crystal garnet fil~ of the invention and magneto-optic detection. ~`
~ FIG. 3 is an exploded view of the magneto-optic ; detection system.
~ ' 25The new-bismuth doped magnetic garnet compositions have the formula {BiXA3 x} [Fe2] ~Fe3 yMy)~l2 w gallium or aluminum or both, y can range from about 0.6 up to about 1.2, x(3-y) is equal to or more than 1.2 and A
is Y3 and/or one or more trivalent rare earth ions. The rare earth metals include the elements having atomic numbers ., RCA 67,384 ~0~8~6Z ,, 1 o~ 57 to 72. Suitable rare earth ions for use in garnet films are well kno~n. The desired magnetic moment of 30 ;~
to 500 Gauss is obtained by proper choice oE y, as is known.
~hen the garnet film is to be grown onto a gadolinium gallium S garnet substrate, and when M is gallium, A is preferahly one or more ions selected from the group consisting of thulium, ytterbium, yttrium and lutecium; when M is aluminum, A is preferably one or more ions selected from the group consisting of thulium, ytterbium, yttrium, lutecium, erbium and europium. The choice among these ions will be determined by the size of the bubble domain des1red, the speed o-f propagation or mobility of the bubbles desired and the maximum temperature sensitivity which can be tolerated. -For example, very small bubbles with high mobility will be 15 obtained when A is lutecium and M is gallium. Relatively ~ ;
temperature stable compositions g1ving bubbles about 6 microns in diameter contain bismuth, thulium and gallium. The addi- -tion of small amounts of vanadium, silicon or calcium may improve the stoichiometry and reduce the optical absorption of the garnet films described above~
The magnet1c garnet compositions described above `~ -~
can be grown onto a suitable substrate support by conventional ;
liquid phase epitaxial techniques u.sing an appropriate flux composition. A flux composition may be chosen from the lead oxide-bismuth oxide-iron oxide ternary phase diagram and ~ used to dissolve the remaining garnet constituents. It is `~ to be noted that the presence of boron trioxide, generally added to lead oxide fluxes, is not desirable since boron trioxide increases the viscosity and increases the temperature required for growth of the crystal. The increased viscosity RCA G7,~84 :~5~86Z :;
would preclude the growtll Or high quality films at the Iower temperatures~ and the increased temperature required would clecrease the amount of bismuth able to be added to the garnet composition. Flux compositions having a low melting point S range contain abou~ 75 mol percent of lead oxide~ abo~t 15 mol percent of bismuth oxide and about 10 mol percent of iron oxide. Using such a flux, and including additional - desired garnet constituents as their oxides, growth can ~ -~
proceed at temperatures of 740 to 780C. under isothermal conditions. The low temperature increases the amount of bismuth which can be incorporated into the growing magnetic garnet film, thereby increasing its Faraday rotation.
The crystals are grown by melting the fiux and garnet components and bringing the melt to ~he desired temperature. The substrate is then lowered into the molten -solution and the desired garnet composition grows onto the substrate. Growth of the single crystal -film is continued ~ until the desired thickness is obtained, generally about 3-20 microns, depending on the size of the bubbles desired. For .. ..
; 20 example, when 1/4 mil diameter bubbles are desired, the films can be from about 3-12 microns thick.
.
The magnetic garnet compositions as described hereinabove are excellent media for bubble propagation.
~he bubbles can be detected optically? thus increasing the -film space available for information storage. The single crystal garnet films described above can also be employed i~ page composers and other information processing devices.
The garnet films can be employed in a bubble device with a shift register with magneto-optic readout using a low power laser or solid state light emitting diode as the light RC..~ 67 ,.78 4 ~5C~8~2 1 source and a conventiona:l si.licon photo cletector.
Referring now to the drawings, Er(,. :1 shows a single crystal garnet :film 10 as descrlbed above epitaxially grown onto a gadolinium gallium garnet sul)strate wafer i2.
FIG. 2 is a schematic view of a bubble device including the single crystal garnet film 10 as shown in - FIG. 1 upon which is overlaid a Y-bar nickel-iron storage register 14 whereby bubbles can be propagated from one section of the film to another. The bar widths and spacings are chosen so that they are appropriate for the size o:E the bubbles being propagated. The devi.ce also includes a nickel- .
iron bubble generator 16 with a gold cutter loop 18, a bubble steerer loop 20, a by-pass line 22 for recirculation : .
of the bubbles, a bubble annihalator 24 and an optical 15 detector 26. .
,~ ;
FIG. 3 is a schematic exploded view of the optical ~ ~
;,, ;: bubble detector 26. The detector 2~ comprises an edge~
emitting light-emitting diode 28, a polarizer 30, the single crystal film 10 on the substrate wafer 12, an analyzer 32 and :` 20 a silicon PIN photodiode 34. An aperture 36 is optionally provided between the edge-emitting light-emitting diode 28 and the polarizer 30 to en~ance detection of the bubbles. ~ ::
The invention will be further illustrated by the following example but it is to be understood that the in-vention is not meant to be limited to the details describedtherein.
"1 , .
Example A bismuth doped magnetic garnet film on a gadolinium ~ gallium garnet substrate was grown as follows: a platinum ;: 30 crucible 1 3/4 inches in diameter and 2 inches high containing , .
~ A ()7,~
I l5 mol percent of bismuth oxide, 0.48 mol percent of thulium oxide, 8.40 mol percent of iron oxide, 1.12 mol percent of gallium oxlde alld 75.0 mol percent of lead oxide was charged to a two zone resistance heated furnace having a 6 centimeter .`~
5 isothermal growth zone. The crucible was heated at 1080C. ;
to dissolve the components and then held at 780C.+ 1/2C.
An epitaxially polished ~111) gadolinium gallium garnet wafer suspended by a platinum fixture attached to an alumina rod and rotated by a variable speed motor was immersed into the crucible. The rod was rotated at 100 revolutions per minute and growth rates of 1-1.5 microns/minute were observed. At the end of growth, the excess flux was spun off at 500 revolu-tions per minute.
The resultant transparent light brown garnet film had the compositiOn Blo 5g4Tm2.33gFe4.02GaO.980l2 and a unlform thickness o-f 6.8 + 0.12 microns. A small amount of ~;
lead, . 3 3 mol percent, was present as an impurity.
The lattice constant, as measured by x-ray diffra-tion (using molybdenum radiation~ was 12.381 + 0.004 ;~
Angstroms. This matched the gadolinium gallium garnet sub-.
strate employed.
; The magnetic film had the following room tempera-ture magnetic properties: wall energy, 0.22 erg/cm2; ~;
~; saturation magnetization, 250 Gauss; translational wall ; 25 coercivity) 0.2 Oersteds; and high field wall mobility, ~ 370 cm/second Oersted. The wall energy ohtained implies . .
~ that films having a saturation magnetization of 150 Gauss . ., will produce bubbles up to about 6 microns in diameter.
Operating bubble diameter is relatively stable at tempera-tures within the range of about O-lnOC.
, .:, - 8-"
: ` .
. . . . ..
~ A f, 7, 3~,4 ~L~50~36Z
Ihe Faraday ro~at ion at 632~ ngstrom I~I~S O . fi7/,u (as compared to ().058/u for a convent;onal (Yl.il)3(FeGa)5012 garnet~.
;
`
'.'$, '''' ~ ''" "~
`.~
! :
:' . ' ': . ' ,.. ~ :
,': . ,;
. ' ' .,~ , , , ;~ :' ~' :
' .'~
; 25 :
:'' : , .'`~ , ~ 30 ~:
, .~' : ::,, .
." , ~.
.. ,. . ~ . : -,,
~CA 67,38~
~5~8G;~
1 particular fi1m on which informa-tion can be stored.
Magneto optic techniques have also been tried for detecting bubbles, but in magnetic bubble materials available heretofore, the optical properties, particularly Farad~y rotation, are low and high powered lasers or very sensitive light detectors are required to detect the presence or ~
absence of bubbles optically. ~-Magnetic materials, to be suitable as bubble materials, must satisfy the following general requirements:
I0 they must have a uniaxial magnetic anisotropy (K~) with the easy axis of magnetization perpendicular to the film surface;
; and they mus-t have a saturation magnetization (~s) such that 2 K~ > 2~Ms , Owing to their cubic magnetic anisotropy, simp1e garnets such as YIG (yttrium-iron garnet) are unsuitable for bubble device applications. Liquid phase epitaxial films of doped garnets can acquire uniaxial anisotropy as a result of ionic segregation that occurs during growth. To satisfy the -requirements given above, the saturation magnetizatlon of doped garnets is reduced by substituting gallium or aluminum for some of the tetrahedral iron ions. Known garnets are temperature sensitive, such that close control of temperature during operation of devices incorporating them is required.
In addition to the magnetic and optical properties required or desirable for good bubble materials employed in `
conjunction with magneto-optic bubble detection, the film should also be able to be grown as thin, defect free, single : crystal films onto a supporting compatible substrate. Pre-ferably, single crystal films are grown by liquid phase !~' .: ' ' ' R(..~ 67, 3R~
, ,' ~.
~ 6~508~Z ~ ~
l epitaxial techniclues from a suitable flux. A lattice constant match within about 0.002 Angstroms is required bet~een the film and that o commercially available sub-strates, such as gadolinium gallium garnet.
We have discovered certain bismuth doped magnetic garnet compositions which have a high Faraday rotation in the visible and infrared wavelength range and in addition -have magnetic properties required for bubble materials, e.g.S
growth induced uniaxial anisotropy. Such materials can be incorporated into bubble devices wherein the bubbles can be detected optically. These compositions can be grown from a suitable flux by conventional epitaxial techniques at low temperatures in the form of single crystal, strain--free 15 films directly on~o a nonmagnetic garnet substrate. ;
' '.
FIG. 1 shows a single crystal garnet film on a substrate suitable for use in a bubble device.
FIG. 2 is a schematic representation o-E a magnetic bubble device utilizing a single crystal garnet fil~ of the invention and magneto-optic detection. ~`
~ FIG. 3 is an exploded view of the magneto-optic ; detection system.
~ ' 25The new-bismuth doped magnetic garnet compositions have the formula {BiXA3 x} [Fe2] ~Fe3 yMy)~l2 w gallium or aluminum or both, y can range from about 0.6 up to about 1.2, x(3-y) is equal to or more than 1.2 and A
is Y3 and/or one or more trivalent rare earth ions. The rare earth metals include the elements having atomic numbers ., RCA 67,384 ~0~8~6Z ,, 1 o~ 57 to 72. Suitable rare earth ions for use in garnet films are well kno~n. The desired magnetic moment of 30 ;~
to 500 Gauss is obtained by proper choice oE y, as is known.
~hen the garnet film is to be grown onto a gadolinium gallium S garnet substrate, and when M is gallium, A is preferahly one or more ions selected from the group consisting of thulium, ytterbium, yttrium and lutecium; when M is aluminum, A is preferably one or more ions selected from the group consisting of thulium, ytterbium, yttrium, lutecium, erbium and europium. The choice among these ions will be determined by the size of the bubble domain des1red, the speed o-f propagation or mobility of the bubbles desired and the maximum temperature sensitivity which can be tolerated. -For example, very small bubbles with high mobility will be 15 obtained when A is lutecium and M is gallium. Relatively ~ ;
temperature stable compositions g1ving bubbles about 6 microns in diameter contain bismuth, thulium and gallium. The addi- -tion of small amounts of vanadium, silicon or calcium may improve the stoichiometry and reduce the optical absorption of the garnet films described above~
The magnet1c garnet compositions described above `~ -~
can be grown onto a suitable substrate support by conventional ;
liquid phase epitaxial techniques u.sing an appropriate flux composition. A flux composition may be chosen from the lead oxide-bismuth oxide-iron oxide ternary phase diagram and ~ used to dissolve the remaining garnet constituents. It is `~ to be noted that the presence of boron trioxide, generally added to lead oxide fluxes, is not desirable since boron trioxide increases the viscosity and increases the temperature required for growth of the crystal. The increased viscosity RCA G7,~84 :~5~86Z :;
would preclude the growtll Or high quality films at the Iower temperatures~ and the increased temperature required would clecrease the amount of bismuth able to be added to the garnet composition. Flux compositions having a low melting point S range contain abou~ 75 mol percent of lead oxide~ abo~t 15 mol percent of bismuth oxide and about 10 mol percent of iron oxide. Using such a flux, and including additional - desired garnet constituents as their oxides, growth can ~ -~
proceed at temperatures of 740 to 780C. under isothermal conditions. The low temperature increases the amount of bismuth which can be incorporated into the growing magnetic garnet film, thereby increasing its Faraday rotation.
The crystals are grown by melting the fiux and garnet components and bringing the melt to ~he desired temperature. The substrate is then lowered into the molten -solution and the desired garnet composition grows onto the substrate. Growth of the single crystal -film is continued ~ until the desired thickness is obtained, generally about 3-20 microns, depending on the size of the bubbles desired. For .. ..
; 20 example, when 1/4 mil diameter bubbles are desired, the films can be from about 3-12 microns thick.
.
The magnetic garnet compositions as described hereinabove are excellent media for bubble propagation.
~he bubbles can be detected optically? thus increasing the -film space available for information storage. The single crystal garnet films described above can also be employed i~ page composers and other information processing devices.
The garnet films can be employed in a bubble device with a shift register with magneto-optic readout using a low power laser or solid state light emitting diode as the light RC..~ 67 ,.78 4 ~5C~8~2 1 source and a conventiona:l si.licon photo cletector.
Referring now to the drawings, Er(,. :1 shows a single crystal garnet :film 10 as descrlbed above epitaxially grown onto a gadolinium gallium garnet sul)strate wafer i2.
FIG. 2 is a schematic view of a bubble device including the single crystal garnet film 10 as shown in - FIG. 1 upon which is overlaid a Y-bar nickel-iron storage register 14 whereby bubbles can be propagated from one section of the film to another. The bar widths and spacings are chosen so that they are appropriate for the size o:E the bubbles being propagated. The devi.ce also includes a nickel- .
iron bubble generator 16 with a gold cutter loop 18, a bubble steerer loop 20, a by-pass line 22 for recirculation : .
of the bubbles, a bubble annihalator 24 and an optical 15 detector 26. .
,~ ;
FIG. 3 is a schematic exploded view of the optical ~ ~
;,, ;: bubble detector 26. The detector 2~ comprises an edge~
emitting light-emitting diode 28, a polarizer 30, the single crystal film 10 on the substrate wafer 12, an analyzer 32 and :` 20 a silicon PIN photodiode 34. An aperture 36 is optionally provided between the edge-emitting light-emitting diode 28 and the polarizer 30 to en~ance detection of the bubbles. ~ ::
The invention will be further illustrated by the following example but it is to be understood that the in-vention is not meant to be limited to the details describedtherein.
"1 , .
Example A bismuth doped magnetic garnet film on a gadolinium ~ gallium garnet substrate was grown as follows: a platinum ;: 30 crucible 1 3/4 inches in diameter and 2 inches high containing , .
~ A ()7,~
I l5 mol percent of bismuth oxide, 0.48 mol percent of thulium oxide, 8.40 mol percent of iron oxide, 1.12 mol percent of gallium oxlde alld 75.0 mol percent of lead oxide was charged to a two zone resistance heated furnace having a 6 centimeter .`~
5 isothermal growth zone. The crucible was heated at 1080C. ;
to dissolve the components and then held at 780C.+ 1/2C.
An epitaxially polished ~111) gadolinium gallium garnet wafer suspended by a platinum fixture attached to an alumina rod and rotated by a variable speed motor was immersed into the crucible. The rod was rotated at 100 revolutions per minute and growth rates of 1-1.5 microns/minute were observed. At the end of growth, the excess flux was spun off at 500 revolu-tions per minute.
The resultant transparent light brown garnet film had the compositiOn Blo 5g4Tm2.33gFe4.02GaO.980l2 and a unlform thickness o-f 6.8 + 0.12 microns. A small amount of ~;
lead, . 3 3 mol percent, was present as an impurity.
The lattice constant, as measured by x-ray diffra-tion (using molybdenum radiation~ was 12.381 + 0.004 ;~
Angstroms. This matched the gadolinium gallium garnet sub-.
strate employed.
; The magnetic film had the following room tempera-ture magnetic properties: wall energy, 0.22 erg/cm2; ~;
~; saturation magnetization, 250 Gauss; translational wall ; 25 coercivity) 0.2 Oersteds; and high field wall mobility, ~ 370 cm/second Oersted. The wall energy ohtained implies . .
~ that films having a saturation magnetization of 150 Gauss . ., will produce bubbles up to about 6 microns in diameter.
Operating bubble diameter is relatively stable at tempera-tures within the range of about O-lnOC.
, .:, - 8-"
: ` .
. . . . ..
~ A f, 7, 3~,4 ~L~50~36Z
Ihe Faraday ro~at ion at 632~ ngstrom I~I~S O . fi7/,u (as compared to ().058/u for a convent;onal (Yl.il)3(FeGa)5012 garnet~.
;
`
'.'$, '''' ~ ''" "~
`.~
! :
:' . ' ': . ' ,.. ~ :
,': . ,;
. ' ' .,~ , , , ;~ :' ~' :
' .'~
; 25 :
:'' : , .'`~ , ~ 30 ~:
, .~' : ::,, .
." , ~.
.. ,. . ~ . : -,,
Claims (5)
1. In a magnetic bubble device comprising a film of magnetic material having growth-induced uniaxial anisotropy, means for generating bubble domains of reversed magnetic polarization in the film, means for propagating the bubble domains along a predetermined path to another portion of the film and means for detecting the presence of a bubble domain, the improvement which comprises employing as the film a single crystal of a garnet of the formula (BixA3-x) (Fe2) (Fe3-yMy)O12 wherein M is selected from the group consisting of gallium and aluminum or both, A is selected from one or more of the group consisting of yttrium and trivalent rare earth ions, y ranges from about 0.6 to about 1.2 and x(3-y) is at least 1.2.
2. A device according to claim 1 wherein M is gallium and A is one or more ions selected from the group consisting of thulium, ytterbium, yttrium and lutecium.
3. A device according to claim 1 wherein M is aluminum and A is one or more ions selected from the group consisting of thulium, ytterbium, yttrium, lutecium, erbium and europium.
4. A device according to claim 1 wherein M is gallium and A is thulium.
5. A device according to claim 4 wherein y is about 1.0 and x is about 0.6.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US40339373A | 1973-10-04 | 1973-10-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1050862A true CA1050862A (en) | 1979-03-20 |
Family
ID=23595605
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA210,109A Expired CA1050862A (en) | 1973-10-04 | 1974-09-26 | Magnetic bubble devices and garnet films therefor |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5427958B2 (en) |
| CA (1) | CA1050862A (en) |
| DE (1) | DE2447509A1 (en) |
| FR (1) | FR2246937A1 (en) |
| GB (1) | GB1441353A (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2600959C2 (en) * | 1976-01-13 | 1984-06-28 | Philips Patentverwaltung Gmbh, 2000 Hamburg | Ferrimagnetic garnet layer for magneto-optical memories and their manufacture |
| JPS5459915A (en) * | 1977-10-20 | 1979-05-15 | Sony Corp | Method and apparatus for reading of magnetic recording signal |
| JPS56155515A (en) * | 1980-05-01 | 1981-12-01 | Olympus Optical Co Ltd | Magnetic garnet film and manufacture |
| EP0044109B1 (en) * | 1980-07-11 | 1986-05-28 | Koninklijke Philips Electronics N.V. | Device for propagating magnetic domains |
| US4433034A (en) * | 1982-04-12 | 1984-02-21 | Allied Corporation | Magnetic bubble layer of thulium-containing garnet |
| JPS5981570A (en) * | 1982-11-01 | 1984-05-11 | Hitachi Ltd | Optical magnetic field measuring device |
| US4520460A (en) * | 1983-08-15 | 1985-05-28 | Allied Corporation | Temperature stable magnetic bubble compositions |
| FR2572844B1 (en) * | 1984-11-02 | 1986-12-26 | Commissariat Energie Atomique | MAGNETIC MATERIAL OF THE GRENATE TYPE, MAGNETIC FILM WITH HIGH ROTATION FARADAY COMPRISING SUCH A MATERIAL AND METHOD FOR MANUFACTURING THE SAME |
| JP2001348297A (en) | 2000-06-06 | 2001-12-18 | Tokin Corp | Bismuth substituted-type garnet thick film material and method of producing the same |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5020300A (en) * | 1973-06-27 | 1975-03-04 |
-
1974
- 1974-09-26 CA CA210,109A patent/CA1050862A/en not_active Expired
- 1974-09-26 GB GB4190574A patent/GB1441353A/en not_active Expired
- 1974-10-02 FR FR7433179A patent/FR2246937A1/fr not_active Withdrawn
- 1974-10-02 JP JP11425974A patent/JPS5427958B2/ja not_active Expired
- 1974-10-04 DE DE19742447509 patent/DE2447509A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5064797A (en) | 1975-06-02 |
| FR2246937A1 (en) | 1975-05-02 |
| DE2447509A1 (en) | 1975-04-17 |
| GB1441353A (en) | 1976-06-30 |
| JPS5427958B2 (en) | 1979-09-13 |
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