CA1071328A - Device operating on the displacement of magnetic domain walls - Google Patents
Device operating on the displacement of magnetic domain wallsInfo
- Publication number
- CA1071328A CA1071328A CA241,275A CA241275A CA1071328A CA 1071328 A CA1071328 A CA 1071328A CA 241275 A CA241275 A CA 241275A CA 1071328 A CA1071328 A CA 1071328A
- Authority
- CA
- Canada
- Prior art keywords
- layer
- domain walls
- plane
- magnetisation
- 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
-
- 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
- G11C19/0808—Digital stores in which the information is moved stepwise, e.g. shift registers using magnetic elements using thin films in plane structure using magnetic domain propagation
- G11C19/0816—Digital stores in which the information is moved stepwise, e.g. shift registers using magnetic elements using thin films in plane structure using magnetic domain propagation using a rotating or alternating coplanar magnetic field
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Power Engineering (AREA)
- Thin Magnetic Films (AREA)
Abstract
PHN. 7851 ABSTRACT
In a magnetic domain wall propagation device comprising a layer of magnetisable material having an easy axis of magnetisation normal to the plane of the layer, in which layer magnetic domain walls exist, the presence in the walls of a magnetic field component parallel to the plane of the layer ensures that the walls can be displaced with enhanced velocity. Said magnetic field component is effectuated by providing on the first layer a second layer of magnetisable material having an easy axis of magnetisation normal to the plane of the layer, the saturation magnetisation of the second layer being higher than that of the first layer.
In a magnetic domain wall propagation device comprising a layer of magnetisable material having an easy axis of magnetisation normal to the plane of the layer, in which layer magnetic domain walls exist, the presence in the walls of a magnetic field component parallel to the plane of the layer ensures that the walls can be displaced with enhanced velocity. Said magnetic field component is effectuated by providing on the first layer a second layer of magnetisable material having an easy axis of magnetisation normal to the plane of the layer, the saturation magnetisation of the second layer being higher than that of the first layer.
Description
~LC37~L32~ PHN. 7851 "Magnetic domain wall propagation device"
The invention relates to a magnetic domain wall propagation deY;ce comprising a layer of magnetisable mater;al having an easy axis of magnetisation normal to the plane of the layer, in which layer magnetic domain walls exist, the layer S having a plurality of fixed positions for the domain walls, biassing means being provided for ~ransversely magnetizing the layer as well as displacement means for moving magnetic domain walls between previously determined positions.
A field of application for devices of this kind are, for example, da~a handling systems, notably de-; vices in which magnetisable media through which magnetic domain walls can be moved are used for the performance of logic, display and memory functions. In this connection it is to be noted that both straight domain walls and, for example, domain wal~s which are closed in themselves and whîch form the boundary of so-called magnetic "bubbles" are to be included.
`- From the publication "Magnetic bubbles a Technology in the making", Electronics, September, 1969~ ;
pp. 83-89, for example, devices are known in which thin .
; films of magnetisable material are used having an easy axis of magnetisation normal to the plane of the film, in which films~ magnetic~"bubble" domains, i.e. magnetic domains which~are bounded by a wall closed in itself and can assume the shape of a cylinder are created. A bias :.:
' ~ - 2 -1~713Z8 PHN. 7851.
magnetisation field is generated having such a strength and polarity that the mdividual doma ms can be maintained and be moved as stable units.
The displacement of both straight domain walls and of domain walls closed in themselves fron one position to the other can be carried out by means of localized mag-netic fields.
A controlled m~vement of domain walls is possible by means of a pattern of elec~ric oonductors to which cur~
rents a~e applied in such manner that the wall is m~ved along a previously detenmined track successively from one point to the other. ~ ' Another possibility for a controlled m~vement of domain walls consists of the'use of a patt~rn of nickel-iron elements which have such a shape that, together with a r~ta-ting magnetic field which can be generated by means of electric windings arranged'around the above-mentioned'device, they force the domains to displace in a given'direction. ~
~; It is a requLrement in particular ~or use in data - ~;
handling systems that the displacement velocity of the magne-; tic domain walls be'so high that the same bit rates can be realized as are achieved'with other'data handling systems.
In this connection it .LS known from the publication "Influence of an In-Plane ~agnetic Field on ~he Domain Wall Velocity in Ga:YIG Films" in ~ Transactions on M~gnetics, Vol.-Mag.-9, No. 4, December, .
;
, .. . .
.
PHN. 7851 3~3 1973 to cause an external magnetic field to act upon a layer of magnetisable material in which a stra;ght domain wall exists, said field having a field direction which lies in the plane of the layer. It has been found that by applying such a field a considerably higher velocity of the domain wall is possible than when said field is not present. This phenomenon also occurs in walls which are closed in themse1ves and which form the boundary o~
"bubble" domains.
However, a drawback of the use of said external magnetic field ;s that in displacement devices in which patterns of soft magnetic material (for example, nickle-iron alloys) are used for controlling the domain walls, the soft magnetic material may beco~e saturated so that said devices no longer operate as they should do.
In addition, external means which render the device complicated are necessary for generating the external magnetic field.
It is an object of the present invention to increase the velocity wîth which domain walls can be displaced in a device of the kind mentioned in the preamble without the application of an external magnetic field being a priori necessary for that purpose.
Therefore, the device according to the invention is characterized in that in absence of external magnetic ~ields parallel to the plane of the layer averaged throughout the height of the domain walls a magnetic field component parallel to hhe plane of the layer is present in the domain walls.
The strength of the said field component ~in _ ,d, _ ~ ' PHN. 7851 L3:~
Oersteds) throughout the height of the layer is pre-ferably at least equal to eight times the prevailing magnetisation of the layer outside the wall (in Gauss).
It has been found that suchan "internal"
field component has the same effect as the above-ment;oned external field parallel to the plane of the layer. It can be generated in various manners w;thout therefore requiring external means whioh might disturb the operat;on of the soft magnetic patterns.
An internal field in a domain wall may be the result of a non-homogeneous distribution of the magnetisation in the wall in the direction of height of the magnetisable layer.
, :
PHN. 7851 3L~7 ~L3~
In the framework of the present ;nvent;on, a practical embodiment of the above-mentioned construction is characterized in that the layer is grown by liquid phase epitaxy on a substrate of non-magnetisable ~aterial, the magnetisation of the first grown portion of the layer being higher than that of the rest of the layer.
The measures according to the invention are of particular importance when the domain walls exist in layers having an iron garnet composition. In the already mentioned article in IEEE Transactions on Magnetics it is described that garnet materials are afflected with the property that there is a small range of values of the driving field (the so-called operating regi~n) for which the velocity of the wall is proportionally to the applied driving field. Above a certain value of the driving field the wall velocity decreases and assumes a substantially constant value which is independent of a further increase of the driving field. This phenomenon restricts the maximally achievable velocity in garnet materials. The increase ot` the wall velocity which ~s necessary just in these materials can be realized in a simple manner with the device according to the invention.
The magnetisation of iron garnet material ' ~' .
~1~3 7~l3~ PHN. 7851 depends on the gallium content. The higher the ~allium con-tent, the lower is the magnetisation. A further embodiment of the device according to the inven~ion is characterized ;n that the layer consists of gallium-substituted yttrium-iron garnet, the ~irst grown portion of the layer consisting of gallium-substituted yttrium-iron garnet having a higher gallium content than the rest of the layerO
The invention will be described in greater detail, by way of example, w;th reference to the drawing, in which Fig. 1 shows diagrammatically a device for displacing domain walls, Fig. 2 is a sectional view of a part of the device shown in Fig. 1.
In the Figures corresponding components are referred to by the same reference numerals.
Reference numeral 1 in Fig. 1 denotes a -non-magnetisable (111) substrate crystal of the composition (Gd3Ga5012). On said crystal is grown by means of liquid phase epitaxy a layer 2 of magnetisable material of the Posi~ion Y2.9Lao.lFe3.8Gal.2ol2 On the starting layer
The invention relates to a magnetic domain wall propagation deY;ce comprising a layer of magnetisable mater;al having an easy axis of magnetisation normal to the plane of the layer, in which layer magnetic domain walls exist, the layer S having a plurality of fixed positions for the domain walls, biassing means being provided for ~ransversely magnetizing the layer as well as displacement means for moving magnetic domain walls between previously determined positions.
A field of application for devices of this kind are, for example, da~a handling systems, notably de-; vices in which magnetisable media through which magnetic domain walls can be moved are used for the performance of logic, display and memory functions. In this connection it is to be noted that both straight domain walls and, for example, domain wal~s which are closed in themselves and whîch form the boundary of so-called magnetic "bubbles" are to be included.
`- From the publication "Magnetic bubbles a Technology in the making", Electronics, September, 1969~ ;
pp. 83-89, for example, devices are known in which thin .
; films of magnetisable material are used having an easy axis of magnetisation normal to the plane of the film, in which films~ magnetic~"bubble" domains, i.e. magnetic domains which~are bounded by a wall closed in itself and can assume the shape of a cylinder are created. A bias :.:
' ~ - 2 -1~713Z8 PHN. 7851.
magnetisation field is generated having such a strength and polarity that the mdividual doma ms can be maintained and be moved as stable units.
The displacement of both straight domain walls and of domain walls closed in themselves fron one position to the other can be carried out by means of localized mag-netic fields.
A controlled m~vement of domain walls is possible by means of a pattern of elec~ric oonductors to which cur~
rents a~e applied in such manner that the wall is m~ved along a previously detenmined track successively from one point to the other. ~ ' Another possibility for a controlled m~vement of domain walls consists of the'use of a patt~rn of nickel-iron elements which have such a shape that, together with a r~ta-ting magnetic field which can be generated by means of electric windings arranged'around the above-mentioned'device, they force the domains to displace in a given'direction. ~
~; It is a requLrement in particular ~or use in data - ~;
handling systems that the displacement velocity of the magne-; tic domain walls be'so high that the same bit rates can be realized as are achieved'with other'data handling systems.
In this connection it .LS known from the publication "Influence of an In-Plane ~agnetic Field on ~he Domain Wall Velocity in Ga:YIG Films" in ~ Transactions on M~gnetics, Vol.-Mag.-9, No. 4, December, .
;
, .. . .
.
PHN. 7851 3~3 1973 to cause an external magnetic field to act upon a layer of magnetisable material in which a stra;ght domain wall exists, said field having a field direction which lies in the plane of the layer. It has been found that by applying such a field a considerably higher velocity of the domain wall is possible than when said field is not present. This phenomenon also occurs in walls which are closed in themse1ves and which form the boundary o~
"bubble" domains.
However, a drawback of the use of said external magnetic field ;s that in displacement devices in which patterns of soft magnetic material (for example, nickle-iron alloys) are used for controlling the domain walls, the soft magnetic material may beco~e saturated so that said devices no longer operate as they should do.
In addition, external means which render the device complicated are necessary for generating the external magnetic field.
It is an object of the present invention to increase the velocity wîth which domain walls can be displaced in a device of the kind mentioned in the preamble without the application of an external magnetic field being a priori necessary for that purpose.
Therefore, the device according to the invention is characterized in that in absence of external magnetic ~ields parallel to the plane of the layer averaged throughout the height of the domain walls a magnetic field component parallel to hhe plane of the layer is present in the domain walls.
The strength of the said field component ~in _ ,d, _ ~ ' PHN. 7851 L3:~
Oersteds) throughout the height of the layer is pre-ferably at least equal to eight times the prevailing magnetisation of the layer outside the wall (in Gauss).
It has been found that suchan "internal"
field component has the same effect as the above-ment;oned external field parallel to the plane of the layer. It can be generated in various manners w;thout therefore requiring external means whioh might disturb the operat;on of the soft magnetic patterns.
An internal field in a domain wall may be the result of a non-homogeneous distribution of the magnetisation in the wall in the direction of height of the magnetisable layer.
, :
PHN. 7851 3L~7 ~L3~
In the framework of the present ;nvent;on, a practical embodiment of the above-mentioned construction is characterized in that the layer is grown by liquid phase epitaxy on a substrate of non-magnetisable ~aterial, the magnetisation of the first grown portion of the layer being higher than that of the rest of the layer.
The measures according to the invention are of particular importance when the domain walls exist in layers having an iron garnet composition. In the already mentioned article in IEEE Transactions on Magnetics it is described that garnet materials are afflected with the property that there is a small range of values of the driving field (the so-called operating regi~n) for which the velocity of the wall is proportionally to the applied driving field. Above a certain value of the driving field the wall velocity decreases and assumes a substantially constant value which is independent of a further increase of the driving field. This phenomenon restricts the maximally achievable velocity in garnet materials. The increase ot` the wall velocity which ~s necessary just in these materials can be realized in a simple manner with the device according to the invention.
The magnetisation of iron garnet material ' ~' .
~1~3 7~l3~ PHN. 7851 depends on the gallium content. The higher the ~allium con-tent, the lower is the magnetisation. A further embodiment of the device according to the inven~ion is characterized ;n that the layer consists of gallium-substituted yttrium-iron garnet, the ~irst grown portion of the layer consisting of gallium-substituted yttrium-iron garnet having a higher gallium content than the rest of the layerO
The invention will be described in greater detail, by way of example, w;th reference to the drawing, in which Fig. 1 shows diagrammatically a device for displacing domain walls, Fig. 2 is a sectional view of a part of the device shown in Fig. 1.
In the Figures corresponding components are referred to by the same reference numerals.
Reference numeral 1 in Fig. 1 denotes a -non-magnetisable (111) substrate crystal of the composition (Gd3Ga5012). On said crystal is grown by means of liquid phase epitaxy a layer 2 of magnetisable material of the Posi~ion Y2.9Lao.lFe3.8Gal.2ol2 On the starting layer
2 a layer 3 is grown of the composition (Y2 gLa0 1Fe4 0Gal 012) is grown on the layer 2. The thickness oF layer 2 is 1.5~ m, that of layer 3 l.l~m.
Under the influence oF the transverse bias field Hb (which is generated by means not shown~ a single-wall mag-netic domain 4 exists in the layer 2 and continues in the layer 3. The magnetisation of the layer 2 is denoted by the arrow Ml, the magnet;sation of layer 3 wh;ch is .. . , ,, :
PHN. 7851 ~L~ L 3~
larger than that of the layer 2 ;s denoted by the arrow M2, and the magnetisation within the single-walled domain 4 the direction of which is opposite to that of the transverse bias field Hb is denoted by the arrow M.
The domain 4 is bounded by the domain wall 7. The assembly can be displaced by means of a rotating magnetic field Hrot which is generated by means of windings ~not shown) arranged around the structure of layers and which induces poles in the T and I-shaped structures 6, 61 and 61~ of nickel-iron which are provided on the separating layer 5.
A secti~onal view of a part of the structure of layers of Fig. 1 is shown in Fig. 2. This sectional view has been taken on the line II-II. An internal field component Hj is present in the wall 7 of the domain 4.
Internal field components Hj having a strength of a few tens of Oersteds have been effectuated in this man-~ ner~ which resulted in an increase of the domain wall velocity - at a given strength of the propagation field by a factor two.
Alternatively this effect may be utilized to lower the strength of the in-plane field, which is normally usecl to enhance the domain wall velocity, by a factor two (e.g. from 100 q~sted to SO Oersted) ',. :
.-: '' : :. .
- .~
- ~
: . .
Under the influence oF the transverse bias field Hb (which is generated by means not shown~ a single-wall mag-netic domain 4 exists in the layer 2 and continues in the layer 3. The magnetisation of the layer 2 is denoted by the arrow Ml, the magnet;sation of layer 3 wh;ch is .. . , ,, :
PHN. 7851 ~L~ L 3~
larger than that of the layer 2 ;s denoted by the arrow M2, and the magnetisation within the single-walled domain 4 the direction of which is opposite to that of the transverse bias field Hb is denoted by the arrow M.
The domain 4 is bounded by the domain wall 7. The assembly can be displaced by means of a rotating magnetic field Hrot which is generated by means of windings ~not shown) arranged around the structure of layers and which induces poles in the T and I-shaped structures 6, 61 and 61~ of nickel-iron which are provided on the separating layer 5.
A secti~onal view of a part of the structure of layers of Fig. 1 is shown in Fig. 2. This sectional view has been taken on the line II-II. An internal field component Hj is present in the wall 7 of the domain 4.
Internal field components Hj having a strength of a few tens of Oersteds have been effectuated in this man-~ ner~ which resulted in an increase of the domain wall velocity - at a given strength of the propagation field by a factor two.
Alternatively this effect may be utilized to lower the strength of the in-plane field, which is normally usecl to enhance the domain wall velocity, by a factor two (e.g. from 100 q~sted to SO Oersted) ',. :
.-: '' : :. .
- .~
- ~
: . .
Claims (4)
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A magnetic domain wall propagation device comprising a layer of magnetisable material having an easy axis of magneti-sation normal to the plane of the layer, in which layer magnetic domain walls exist, the layer having a plurality of fixed posi-tions for the domain walls, biassing means being provided for transversely magnetizing the layer as well as displacement means for moving magnetic domain walls between previously determined positions, characterized in that the layer is grown by liquid phase epitaxy on a substrate of non-magnetisable material, the magnetisation of the first grown portion of the layer being lower than that of the rest of the layer whereby in absence of external magnetic fields parallel to the plane of the layer averaged throughout the height of the domain walls a magnetic field component parallel to the plane of the layer is produced in the domain walls.
2. A device as claimed in Claim 1, characterized in that the strength of the said field component (expressed in Oersteds) throughout the height of the layer is at least equal to eight times the prevailing magnetisation of the layer outside the wall (expressed in Gauss).
3. A device as claimed in Claim 1, characterized in that the layer consists of a magnetisable material having a iron-garnet composition.
4. A device as claimed in Claim 3, characterized in that the layer consists of gallium-substituted yttrium-iron garnet, the first grown portion of the layer consisting of gallium-substituted yttrium-iron garnet having a higher gallium content than the rest of the layer.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7415967A NL7415967A (en) | 1974-12-09 | 1974-12-09 | DEVICE WORKING WITH THE RELOCATION OF MAGNETIC DOMAIN WALLS. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1071328A true CA1071328A (en) | 1980-02-05 |
Family
ID=19822608
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA241,275A Expired CA1071328A (en) | 1974-12-09 | 1975-12-04 | Device operating on the displacement of magnetic domain walls |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5183432A (en) |
| CA (1) | CA1071328A (en) |
| DE (1) | DE2554307A1 (en) |
| FR (1) | FR2294511A1 (en) |
| GB (1) | GB1526767A (en) |
| IT (1) | IT1050006B (en) |
| NL (1) | NL7415967A (en) |
| SE (1) | SE405424B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01286193A (en) * | 1988-05-12 | 1989-11-17 | Canon Inc | Magnetic bubble recording element, magnetic bubble transfer method, magnetic bubble recording and reproducing device, magnetic bubble recording method, magnetic bubble erasing and reproducing method |
-
1974
- 1974-12-09 NL NL7415967A patent/NL7415967A/en not_active Application Discontinuation
-
1975
- 1975-12-03 DE DE19752554307 patent/DE2554307A1/en not_active Withdrawn
- 1975-12-04 CA CA241,275A patent/CA1071328A/en not_active Expired
- 1975-12-05 IT IT30072/75A patent/IT1050006B/en active
- 1975-12-05 GB GB49997/75A patent/GB1526767A/en not_active Expired
- 1975-12-05 SE SE7513733A patent/SE405424B/en unknown
- 1975-12-06 JP JP50145874A patent/JPS5183432A/ja active Pending
- 1975-12-09 FR FR7537661A patent/FR2294511A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE2554307A1 (en) | 1976-06-10 |
| SE7513733L (en) | 1976-06-10 |
| SE405424B (en) | 1978-12-04 |
| FR2294511A1 (en) | 1976-07-09 |
| NL7415967A (en) | 1976-06-11 |
| JPS5183432A (en) | 1976-07-22 |
| IT1050006B (en) | 1981-03-10 |
| GB1526767A (en) | 1978-09-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Perneski | Propagation of cylindrical magnetic domains in orthoferrites | |
| US3711841A (en) | Single wall domain arrangement | |
| Spain | Controlled domain tip propagation. Part I | |
| CA1071328A (en) | Device operating on the displacement of magnetic domain walls | |
| US3982234A (en) | Hard-magnetic film overlay apparatus and method for magnetic mobile domain control | |
| US4171408A (en) | Device operating on the displacement of magnetic domain walls | |
| US4012724A (en) | Method of improving the operation of a single wall domain memory system | |
| US4059828A (en) | Bubble lattice file structure | |
| US3736579A (en) | Circular magnetic domain devices | |
| US3942165A (en) | Device operating with the displacement of magnetic domain wall | |
| US3714640A (en) | Single wall domain propagation arrangement | |
| US3938111A (en) | Magnetic device for producing domains | |
| US3470550A (en) | Synthetic bulk element having thin ferromagnetic film switching characteristics | |
| US4058801A (en) | Field access method for bubble memories | |
| Kempter | Cylindrical-domain propagation by Permalloy bar stray fields | |
| Bourne et al. | A transient solution for domain wall motion | |
| Bartran et al. | Wall contraction in Bloch wall films | |
| US4027297A (en) | Gapless magnetic bubble propagation path structure | |
| JPS6211302A (en) | Yig thin film microwave device | |
| JPH039079B2 (en) | ||
| US3461442A (en) | Magnetic logic systems comprising stacked layers of magnetic films which contain low coercive force channels | |
| US3140457A (en) | Gradiated magnetic flux path produced by plurality of transverse ducts | |
| JPH039080B2 (en) | ||
| Kump | Demagnetization of flat uniaxial thin films under hard direction drive | |
| GB1564137A (en) | Digital magnetic memory systems |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |