US3636531A - Domain propagation arrangement - Google Patents

Domain propagation arrangement Download PDF

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Publication number
US3636531A
US3636531A US49273A US3636531DA US3636531A US 3636531 A US3636531 A US 3636531A US 49273 A US49273 A US 49273A US 3636531D A US3636531D A US 3636531DA US 3636531 A US3636531 A US 3636531A
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Prior art keywords
domain
strip
domains
width
input
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Expired - Lifetime
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US49273A
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English (en)
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John Alexander Copeland
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AT&T Corp
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Bell Telephone Laboratories Inc
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    • 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
    • G11C19/0841—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 electric current

Definitions

  • ABSTRACT A magnetically soft overlay strip defines a multiposition shift register path in a slice of material in which single-wall domains can be moved.
  • the strip also defines a stable location for a single-wall domain to either side thereof for each position in the register. Domains are moved along the path by consecutively offset fields operative simultaneously to both sides of the strip,
  • a single-wall domain is a magnetic domain encompassed, in the plane of a material in which it can be moved, by a domain wall which closes on itself to form a stable entity free to move in the plane.
  • a typical material for such an arrangement is a rare earth orthoferrite or a garnet crystal having a preferred direction of magnetization along an axis out of the plane of movement, nominally normal to the plane.
  • Single-wall domains in a sheet of material are constrained to a given diameter typically by a bias field of a polarity to constrict domainsa negative polarity according to the assumed convention. Domains are moved in the sheet by a field (viz, a field gradient) which is provided in positions consecutively offset from the position occupied by a domain.
  • Field gradients for moving domains are provided generally by pulses applied to an array of conductor loops adjacent the surface of the material in which the domains are moved. By pulsing a succession of conductors consecutively offset from the position occupied by a domain, consecutively offset gradients are established for causing domain displacement.
  • the conductors are interconnected serially in three sets to provide a familiar three-phase shift register operation for domain patterns. A propagation arrangement of this type is disclosed in U.S. Pat. No. 3,460,116, supra.
  • information is represented in a domain propagation path in binary form by having the presence of a domain at a particular position represent a one and the absence of a domain represent a zero.
  • a domain it is possible for a domain to shift from one position into an adjacent empty position during propagation thus causing a double error in the stored information.
  • These operations require additional circuit elements and, in addition, input currents much larger than those needed for domain propagation.
  • the minimum spacing between domains is on the order of four domain diameters in material with low coercive force.
  • An object of this invention is to provide a domain propagation arrangement which permits a reduction in the minimum spacing between consecutive positions and obviates circuitry for domain creation and annihilation.
  • a propagation channel for single-wall domains in accordance with this invention is defined in a sheet of material, in which such domains can be moved, by a strip of magnetically soft material adjacent the surface of the sheet and extending from an input to an output position.
  • the strip has a thickness-to-width ratio which defines a stable location for a domain to either side of it.
  • a pair of interleaved conductors crisscrosses the strip to define a sequence of positions each including a pair of such locations. When the conductors are pulsed in the alternative, domains move to like locations of consecutive location pairs.
  • a single conductor is employed for moving domains. Permalloy dots or recesses are utilized to offset domains moved by that conductor thus functioning as would a second conductor.
  • FIG. 1 is a schematic illustration of a domain propagation arrangement in accordance with the invention
  • FIGS. 2 and 3 are schematic illustrations of a portion of the arrangement of FIG. 1 showing the magnetic condition thereof during operation;
  • FIG. 4 is a cross-sectional view of the portion of the arrangement shown in FIG. 3.
  • FIG. 1 shows a domain propagation arrangement including a slice or sheet 11 in which a representative channel for domain movement is defined.
  • the channel comprises a magnetically soft strip 12 of, for example, low coercive force permalloy aligned with the axis of the channel represented by broken line 13 in FIG. 1 and shown as a closed loop, for the recirculation of information.
  • Strip 12 is crisscrossed by electrical conductors l4 and 15 offset with respect to one another and having, illustratively, a serpentine geometry.
  • the conductors are conveniently deposited on opposite sides of a plastic substrate and juxtaposed with sheet 11.
  • the repeat patterns of the conductors define consecutive positions along the channel for single-wall domains as indicated by the domains D in FIG. 1.
  • Permalloy strip 12 defines a stable location for a domain to either side thereof for each position defined by the conductors. Thus locations below strip 12 as viewed in FIG. 1 may be taken to represent binary zero locations, whereas locations above the strip may be taken as representing binary one locations. In operation, all the binary zero locations are occupied normally by domains for recirculation about closed loop 13 as conductors 14 and 15 are pulsed in the alternative, first with positive and then negative pulses. If a binary one is required in a particular position, the domain occupying the zero location in that position is moved to the corresponding one location as shown for domain D in FIG. 2.
  • Movement of a domain from a zero to a one location is accomplished by an input conductor 20.
  • Conductor 20 is connected between an input pulse source 21 of FIG. 1 and ground.
  • source 21 When a pulse of a polarity to constrict domains is applied to conductor 20 by source 21, domain D of FIG. 2 is repelled to a one location.
  • domain D When a pulse of a polarity to attract domains is applied, domain D moves to the zero location, as shown in FIG. 3.
  • Selective activation of conductor 20 introduces a pattern of domains in first and second locations for movement, by consecutively offset fields, as conductors l4 and 15 are pulsed, thus representing binary information in channel 13.
  • Information so formed and moved in the channel is detected at an output position indicated by an encircled X in FIG. 1.
  • a familiar electrical probe is placed to indicate the passage of a domain in a one location at the output position.
  • the probe may be a simple conductor loop or a Hall probe, or detection may be accomplished by optical means such as via the Faraday or Kerr effect. Such alternatives are familiar in the art and are not discussed in detail here. Any signal so generated is applied to a utilization circuit 24 of FIG. 1.
  • the diameter of a domain in the arrangement of FIG. 1 is maintained at a nominal value by a bias field of a polarity to constrict domains.
  • a source of such a field is represented by block 25 in FIG. 1.
  • Sources 21 and 25 and circuit 24 are connected to a control circuit 26 for synchronization and control.
  • the various sources and circuits may be any such elements capable of operating in accordance with this invention.
  • a propagation channel in accordance with this invention includes a plurality of consecutive positions for domains, each of which comprises first and second stable locations laterally displaced with respect to one another thus forming a location pair for each position.
  • first and second location sets in a single propagation channel define associated binary one and binary zero channels respectively.
  • the realization of two stable locations at each bit position depends on the thickness-to-width ratio of the permalloy strip and the ratio of width of the permalloy strip to the diameter of the domain being moved. Unless the thickness-to-width ratio is less than the ratio of the domain magnetization to the permalloy magnetization, domains occupy positions directly below the permalloy strip rather than in first or second stable positions.
  • the internal demagnetizing fields in the permalloy strip which are proportional to the product of permalloy magnetization and thickness of the strip divided by the width of the strip, must be smaller than the external demagnetizing field of the domain over most of the volume of the strip in order to avoid an energy minimum when a domain occupies a position directly under the strip.
  • FIG. 4 shows a cross section through sheet 11 and conductors l4 and 15 of FIG. 1 taken along line 44 as shown in FIG. 3.
  • the two stable positions are indicated as the 1" and the sides.
  • the domain is shown on the 0" side with its wall under strip 12.
  • the lateral location of the domain is stable when the length of domain wall beneath the permalloy pattern is at a local maximum. For a single permalloy strip, there are two stable lateral positions only when the width of the strip is less than the domain diameter. The amount of force required to move a domain from zero to one" position is greatest when the strip width is about one-half the domain diameter so this width is optimum for regions of the path where only propagation takes place.
  • a reduction in width of the strip to about 0.2 domain diameters is advantageous at output positions to increase the lateral separation between the zero and one" position.
  • An increase to about 0.7 domain diameters in the width of the strip is advantageous at input positions to reduce the current needed to shift the lateral position of the domain.
  • sheet 11 can be notched (notch 30-FIG. 4) as a substitute for strip 12.
  • domains having diameters of 100 micrometers are moved in a slice of thulium orthoferrite 50 micrometers thick, each domain having a magnetization of 0.0l weber per meter square.
  • the propagation channel is defined by a permalloy strip having a (magnetization of 0.8 weber per meter square and a) coercive force of 300 amperes per meter (less than 4 oersteds) and a width and thickness of 50 micrometers and 50 nanometers, respectively.
  • a bias field of 2,000 amperes per meter maintains the domain diameter and currents of about 50 milliamperes cause domain movement. Domains are spaced about 200 micrometers apart during operation. Write currents of about 40 milliamperes are employed.
  • a domain propagation arrangement comprising a material in which single-wall domains can be moved, and propagation means for moving a domain from an input to an output position in said materiaLsaid propagation means comprising means for providing in a sequence of positions between said input and output positions patterns of magnetic fields for moving domains from position to position in a channel therebetween, and means for defining in each of said positions first and second stable locations for a domain, said last-mentioned means being of a geometry to require movement of domains to like locations of consecutive positions of said channel in response to said magnetic fields.
  • a domain propagation arrangement in accordance with claim 1 wherein said means for defining comprises a permalloy strip extending between said input and output positions having a thickness and width to define said first and second 10- cations to either side thereof.
  • each of said domains has a first magnetization and said strip has a second magnetization where the ratio of the thickness of said strip to the width thereof is less than the ratio of said first to said second magnetization.
  • a domain propagation arrangement in accordance with claim 7 including means for selectively moving domains between first and second stable locations at said input position, and means for selectively detecting domains at said output position.
  • a domain propagation arrangement in accordance with claim 1 wherein said means for defining comprises a groove in said material extending between said input and output positions.
  • a domain propagation arrangement comprising a material in which single-wall domains can be moved, and means for moving a domain from an input to an output position in said material, said means comprising a strip of magnetically soft material overlying said material and extending between said input and output positions, said strip having a thickness-to-width ratio for defining first and second stable locations to first and second sides thereof, and means for provid ing like magnetic fields in a sequence of positions along said strip for simultaneously moving domains in said first or second stable locations of said positions to like locations of consecutive positions.

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  • Thin Magnetic Films (AREA)
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  • Mram Or Spin Memory Techniques (AREA)
US49273A 1970-06-24 1970-06-24 Domain propagation arrangement Expired - Lifetime US3636531A (en)

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US4927370A 1970-06-24 1970-06-24

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US (1) US3636531A (de)
BE (1) BE768895A (de)
CH (1) CH544374A (de)
DE (1) DE2130442A1 (de)
ES (1) ES393083A1 (de)
FR (1) FR2099838A5 (de)
GB (1) GB1354770A (de)
IE (1) IE36253B1 (de)
NL (1) NL7108429A (de)

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3711840A (en) * 1971-12-13 1973-01-16 Bell Telephone Labor Inc Write circuit using enhanced propagation pulses for lateral displacement coding of patterns of single-wall magnetic domains
US3711842A (en) * 1971-12-30 1973-01-16 Bell Telephone Labor Inc Single wall magnetic domain logic arrangement
US3735145A (en) * 1970-10-16 1973-05-22 North American Rockwell Magnetic bubble domain system
US3774182A (en) * 1972-08-15 1973-11-20 Bell Telephone Labor Inc Conductor-pattern apparatus for controllably inverting the sequence of a serial pattern of single-wall magnetic domains
US3790935A (en) * 1971-03-26 1974-02-05 Bell Canada Northern Electric Bubble in low coercivity channel
US3806899A (en) * 1972-04-10 1974-04-23 Hughes Aircraft Co Magnetoresistive readout for domain addressing interrogator
US3811120A (en) * 1973-04-05 1974-05-14 Bell Telephone Labor Inc Magnetic domain propagation arrangement having channels defined by straight line boundaries
JPS4952542A (de) * 1972-06-22 1974-05-22
US3827036A (en) * 1971-03-12 1974-07-30 Rockwell International Corp Magnetic bubble domain system
US3831156A (en) * 1971-12-06 1974-08-20 Hughes Aircraft Co Biasing apparatus for magnetic domain stores
US3893089A (en) * 1971-04-12 1975-07-01 Ibm Two-phase propagation of cylindrical magnetic domains
US3927398A (en) * 1974-10-21 1975-12-16 Canadian Patents Dev Magnetic bubble propagation circuit
FR2401488A1 (fr) * 1977-08-24 1979-03-23 Philips Nv Dispositif a domaines magnetiques a bulles
US4207614A (en) * 1972-09-02 1980-06-10 U.S. Philips Corporation Magnetic bubble shift register store
US7724558B1 (en) * 1999-03-19 2010-05-25 Nec Corporation Magnetic signal transmission line

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT947683B (it) * 1971-04-12 1973-05-30 Ibm Sistema di propagazione mediante conduttori di domini magnetici cilindrici

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3735145A (en) * 1970-10-16 1973-05-22 North American Rockwell Magnetic bubble domain system
US3827036A (en) * 1971-03-12 1974-07-30 Rockwell International Corp Magnetic bubble domain system
US3790935A (en) * 1971-03-26 1974-02-05 Bell Canada Northern Electric Bubble in low coercivity channel
US3893089A (en) * 1971-04-12 1975-07-01 Ibm Two-phase propagation of cylindrical magnetic domains
US3831156A (en) * 1971-12-06 1974-08-20 Hughes Aircraft Co Biasing apparatus for magnetic domain stores
US3711840A (en) * 1971-12-13 1973-01-16 Bell Telephone Labor Inc Write circuit using enhanced propagation pulses for lateral displacement coding of patterns of single-wall magnetic domains
US3711842A (en) * 1971-12-30 1973-01-16 Bell Telephone Labor Inc Single wall magnetic domain logic arrangement
US3806899A (en) * 1972-04-10 1974-04-23 Hughes Aircraft Co Magnetoresistive readout for domain addressing interrogator
JPS4952542A (de) * 1972-06-22 1974-05-22
JPS5644509B2 (de) * 1972-06-22 1981-10-20
US3774182A (en) * 1972-08-15 1973-11-20 Bell Telephone Labor Inc Conductor-pattern apparatus for controllably inverting the sequence of a serial pattern of single-wall magnetic domains
US4207614A (en) * 1972-09-02 1980-06-10 U.S. Philips Corporation Magnetic bubble shift register store
US3811120A (en) * 1973-04-05 1974-05-14 Bell Telephone Labor Inc Magnetic domain propagation arrangement having channels defined by straight line boundaries
US3927398A (en) * 1974-10-21 1975-12-16 Canadian Patents Dev Magnetic bubble propagation circuit
FR2401488A1 (fr) * 1977-08-24 1979-03-23 Philips Nv Dispositif a domaines magnetiques a bulles
US7724558B1 (en) * 1999-03-19 2010-05-25 Nec Corporation Magnetic signal transmission line

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Publication number Publication date
ES393083A1 (es) 1974-07-01
IE36253B1 (en) 1976-09-29
IE36253L (en) 1971-12-24
DE2130442A1 (de) 1971-12-30
BE768895A (fr) 1971-11-03
CH544374A (de) 1973-11-15
NL7108429A (de) 1971-12-28
GB1354770A (en) 1974-06-05
FR2099838A5 (de) 1972-03-17

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