US3480926A - Synthetic bulk element having thin-ferromagnetic-film switching characteristics - Google Patents

Synthetic bulk element having thin-ferromagnetic-film switching characteristics Download PDF

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US3480926A
US3480926A US646639A US3480926DA US3480926A US 3480926 A US3480926 A US 3480926A US 646639 A US646639 A US 646639A US 3480926D A US3480926D A US 3480926DA US 3480926 A US3480926 A US 3480926A
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layers
magnetizable
magnetization
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Paul E Oberg
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Unisys Corp
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Sperry Rand Corp
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    • 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

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  • the magnetizable layers possess the magnetic property of uniaxial anisotropy providing an easy axis thereby with adjacent magnetizable layers having their easy axes aligned along two respectively dverent axes forming a mean axis of magnetization M that is intermediate the two axes of the two sets, each set formed by the alternate magnetizable layers.
  • Operation as a transformer, or inductor, core is achieved by the application and detection of an AC field along a magnetic axis that is orthogonal to the mean axis M operation as a memory core is achieved by the application of drive fields and detection of switching fields along a magnetic axis that is parallel to the mean axis M BACKGROUND OF THE INVENTION
  • the invention herein described was made in the course of or under a contract or subcontract thereunder with the Department of the Navy.
  • the present invention relates to magnetizable elements comprising a plurality of stacked, magnetizable layers of thin-ferromagnetic-films, each layer possessing singledomain properties and the magnetic characteristic of uniaxial anisotropy providing an easy axis along which the remanent magnetization thereof lies in a first or a second and opposite direction.
  • the term single-domain property may be considered the magnetic characteristic of a threedimensional element of magnetizable material having a thin dimension that is substantially less than the width and length thereof wherein no magnetic domain walls can exist parallel to the large surfaces of the element.
  • magnetizable material shall designate a substance having a remanent magnetic flux density that is substantially high, i.e., approaches the flux-density at magnetic saturation.
  • each of the several thin-ferromagnetic-film layers that make up the magnetizable element possess such single-domain property whereby singledomain rotational switching of the magnetization M of such magnetizable element shall be achieved in a manner such as described in the S. M. Rubens et al. Patent No. 3,030,612.
  • Such magnetizable elements may be fabricated in a continuous vapor deposition process such as disclosed in the S. M. Rubens et a1.
  • such magnetizable elements may be formed by any one of the plurality of well-known methods of fabricating magnetizable memory elements within an evacuatable enclosure, e.g., cathodic sputtering.
  • a thin-ferromagnetic-film layer possessing singledomain properties is limited in its maximum thickness to the order of 10,000 angstroms A.) it is apparent that the net flux, which is a function of its cross-sectional area, is limited. Accordingly, it is desirable to have a magnetizable element that is capable of operating in a single-domain manner while providing substantially larger external magnetic fields that, upon the switching or rotation of the elements magnetization M, couple the lines associated therewith producing an output signal therein that is of a substantially larger magnitude than that achieved by a single thin-ferromagnetic-film layer.
  • the components of M that are perpendicular to the major surfaces of the layers are all in the same aligned direction through the thickness thereof tending to be continuous in the magnetizable and insulating layers.
  • internal pole pairs i.e., pole pairs on opposite surfaces of each insulating layer, tend to cancel out each other leaving only the poles on the top and bottom layers uncancelled.
  • This results in a small demagnetizing field i.e., the field applied to the magnetizable layer that tends to demagnetize the layers normal magnetization for the large thickness that is produced by the many magnetizable and insulating layers.
  • This small demagnetizing field approaches that of bulk magnetizable material of the same thickness causing the magnetizable layers to switch in a manner similar to bulk material switching.
  • the magnetization M in adjacent magnetizable layers rotate in opposite directions whereby the components of M that are perpendicular to the major surfaces of the layers are in opposite, but aligned, directions perpendicular to the thickness of the element.
  • the internal pole pairs do not tend to cancel out each other.
  • This large demagnetizing field forces the magnetization M of the individual magnetizable layers to switch in a single-domain manner similar to that achieved by magnetizable elements of a single thin-ferromagneticfilm layer.
  • this large demagnetizing field is present the magnetization M vector remains essentially in the plane of the magnetizable layer during its rotation; this is a requirement and the reason for the high speed change in magnetization provided by single-domain films.
  • the present invention is an improvement of such above discussed prior art arrangements of magnetizable elements comprising a plurality of stacked, similar magnetizable layers of thin-ferromagnetic-films that are separated by interstitial layers of insulating material. All of the magnetizable layers are of substantially the same material and thickness and possess the magnetic characteristics of single-domain property and uniaxial anisotropy for providing an easy axis along which the remanent magnetization thereof shall lie in a first or a second and opposite direction.
  • Alternate magnetizable layers forming a first set of layers are formed with their easy axes aligned along a first axis with the interstitial magnetizable layers forming a second set of layers with their easy axes aligned along a second axis that is different from the first axis.
  • first and second sets each of a plurality of magnetizable layers, with their easy axes at an angle forming a mean magnetization axis M that substantially bisects the acute angle formed by the easy axes of the two sets.
  • the magnetizable elements of the present invention have the ability to be operated as a transformer, or inductor, core or as a bistable memory core. Operation as an inductor core is achieved by the application and detection of an AC field along a magnetic axis that is orthogonal to the mean magnetization axis M Operation as a bistable memory core is achieved by the application of a drive field and the detection of a switching field along a magnetic axis that is parallel to the mean magnetization axis M Drive and sense lines, or windings, that are magnetically, or conductively, coupled to the magnetizable elements of the present invention may be of the Well known printed circuit type as particularly adapted in bistable memory core operation or more conventional transformer winding techniques when operated as an inductor core.
  • readout may be by any of the well known methods, such as magnetoresistive or magnetooptic. Accordingly, it is a primary object of the present invention to provide a magnetizable element that may be utilized as an inductor core or as a bistable memory core that is comprised of a plurality of stacked, magnetizable layers of thin-ferromagnetic-filrns separated by interstitial layers of insulating material forming an element of substantial thickness while yet permitting the individual, and collective magnetizable layers to rotate, or switch, in a single-domain manner.
  • FIG. 1 is a side view of a magnetizable element of a plurality of magnetizable layers separated by interstitial layers of insulating material as proposed by the present invention.
  • FIG. 2 is a plan view of the magnetizable element of FIG. 1 illustrating the orientation of the two easy axes of the respectively associated sets of magnetizable layers of the magnetizable element of FIG. 1.
  • FIG. 3 is a schematic illustration of the related vectors involved with the switching mechanism of adjacent magnetizable layers as proposed by the present invention.
  • FIG. 4- is a plan view of a magnetizable element of the present invention illustrating the orientation of the easy axes M and M of the respectively associated two sets of magnetizable layers of FIG. 1 when utilized as a transformer element.
  • FIG. 5 is a plan view of a magnetizable element i1- lustrating the orientation of the two easy axes M and M of the respectively associated two sets of magnetizable layers of FIG. 1 when utilized as a memory element.
  • FIG. 6 is a composite illustration of the hysteresis loop characteristics of the magnetizable elements of FIG. 4 and FIG. 5.
  • FIG. 7 is an illustration of another embodiment of the present invention in which the magnetizable element is comprised a plurality of stacked, magnetizable layers having a washer-like configuration.
  • FIG. 8 is an illustration of another embodiment of the present invention in which the magnetizable element is comprised of a plurality of concentric, different-diameter toroidal-shaped magnetizable layers.
  • Magnetizable element 10 is comprised of a substrate 12 and a plurality of magnetizable layers 14, 16 insulatively separated by a plurality of insulating layers 18. Magnetizable element 10 is particularly adaptable to be fabricated in successive deposition steps of alternate layers of magnetizable material and insulating material in an evacuatable enclosure.
  • Magnetizable layers 14, 16 are thin-ferromagnetic-film layers that possess the magnetic characteristics of single-domain properties and uniaxial anisotropy for providing an easy axis along which the remanent magnetization thereof shall lie in a first or a second and opposite direction.
  • magnetizable element 10 is preferably fabricated in a continuous vapor deposition process such as disclosed in the S. M. Rubens et a1.
  • Patent No. 2,900,282 and 3,155,561 or the A. V. Pohm Patent No. 3,065,105 The multi-layer element 10 may be deposited upon a substrate 12 of many well known materials such as glass or metal.
  • FIG. 2 there is illustrated a plan view of the magnetizable element 10 of FIG. 1 for purposes of illustrating the orientation of the easy axes M and M each respectively associated with the two associated sets of layers; one set formed by the alternate layers 14a, 14b, 14c, and 14d, and the other set formed by the alternate layers 16a, 16b, 16c, and 16d as illustrated in FIG. 1.
  • the two sets of different alternate magnetizable layers 14, 16 have the respectively associated easy axes M M separated by an acute angle oz.
  • magnetizable element 10 is basically comprised of two sets of stacked, superposed, magnetizable layers (14, 16 in which adjacent magnetizable layers are separated by an insulating layer (18).
  • All layers of each set have their easy axes (easy axes M of the first set of magnetizable layers 14, and easy axis M of the second set of magnetizable layers 16) aligned with the two respective easy axes of the two sets (easy axes M and M of sets one and two, respectively) oriented at an acute angle (a) forming an effective or mean easy axis (M that bisects the so-formed acute angle.
  • the vector magnetization M either aligned along, or rotated out of alignment with, the associated easy axis, and the associated easy axis M shall be identified by similar terms; i.e., magnetization M, of layer 14 having an easy axis M
  • the present invention relates to a magnetizable element that comprises a plurality of stacked, superposed, magnetizable layers of thin-ferromagnetic-films separated by interstitial layers of insulating material.
  • the magnetizable layers possess the magnetic property of uniaxial anisotropy providing an easy axis thereby with alternate magnetizable layers having their easy axes aligned along two respectively different axes M and M forming a mean axis of magnetization M,
  • Each of the layers of magnetizable material such as adjacent layers 14, 16, possess single-domain properties that are capable of having their magnetization switched, or rotated, in a single-domain manner such as disclosed in the above referenced S. M. Rubens et al. Patent No. 3 ,030,612.
  • the magnetization M as in magnetizable layer 16 is effected by an applied drive field H along the mean axis M the magnetization M is induced to rotate in the direction away from the applied drive field H toward a position M through an angle
  • the demagnetizing field of the magnetizable layer 16 limits this normal component to extremely small values causing the magnetization M to rotate through path 30 which path is substantially in the plane of layer 16. This mechanism is more fully discussed in the text Amplifier And Memory Devices: With Films and Diodes McGraw-Hill Book Company, 1965, Chapter 13.
  • an applied drive field H would cause the magnetization M of all such layers 16 to rotate in the same direction.
  • the components M that are perpendicular to the major surfaces of layer 16 are all in the same aligned direction through the plurality of layers tending to be continuous therethrough.
  • these adjacent layers 16 would form internal pole pairs with respect to adjacent layers 16, such as components M that tend to cancel each other leaving only the poles on the top and bottom layers 16 uncancelled.
  • the magnetization in the adjacent magnetizable layers 14 and 16 rotate in opposite directions whereby the components of M that are perpendicular to the major surfaces of the layers are in opposite, but aligned, directions through the thickness of the magnetizable element provided by the plurality of pairs of layers 14, 16 and the associated insulating layers 18see FIG. 1.
  • the internal pole pairs i.e., the M components M and M that are perpendicular to the major surfaces of the layers 14 and 16, do not tend to cancel out each other. This results in a very large demagnetizing field for the large thickness produced by the many magnetizable layers 14, 16 and insulating: layers 18.
  • This large demagnetizing field forces the magnetization M of the individual magnetizable layers 14, 16 to switch in a single-domain manner similar to that achieved by magnetizable elements of a single thin-ferromagnetic-film layer.
  • this large demagnetizing field is present the magnetization M vector of each layer 14, 16 remains essentially in the plane of the associated magnetizable layer 14, 16; this is a requirement and the reason for high speed rotational change in magnetization.
  • FIG. 4 there is illustrated a plan view of a magnetizable element 10a illustrating the orientation of the easy axes M M formed by the two sets of magnetizable layers 14, 16 respectively, when magnetizable element 10 is to be utilized as a transformer core.
  • magnetizable element 10a illustrating the orientation of the easy axes M M formed by the two sets of magnetizable layers 14, 16 respectively, when magnetizable element 10 is to be utilized as a transformer core.
  • a permeable layer having a permeability greater than that of air and with substantially no remanent magnetization could function as a transformer, or inductor, core.
  • magnetizable element 10a as a transformer, or inductor
  • the easy axes of the two sets of magnetizable layers 14, 16 are established along the respective easy axes M M generating a mean easy axis M that bisects the acute angle therebetween.
  • Operation of magnetizable elements 10a as a transformer, or inductor, core is achieved by the application and detection of an AC field along a magnetic axis that is orthogonal to the mean axis M
  • the AC magnetizing field :H applied along axis 40 by winding 42 causes the magnetization associated with axes M M to oscillate about the mean axis M through the respective angles e5 Q.
  • winding 44 The flux variations of magnetizable element 10 due to the oscillation of the magnetization thereof about its mean axis M is detected by winding 44; as an inductor core only one winding 42 is required.
  • windings 42 and 44 function as the primary and secondary windings, respectively, that are inductively coupled to the magnetizable element 10a.
  • winding 42 coupling a magnetizing force i-H of an intensity (H H just sufiicient to cause the magnetizations M M to oscillate :45 about the mean axis M i.e., equal to the total flux change in magnetizable element 10a is equal to approximately 0.7 of the total switchable flux therein.
  • loop 60 that is an approximate representation of the magnetic flux path traversed by the magnetic flux of magnetizable element 10a when operated in the transformer mode as described with particular reference to FIG. 4.
  • Loop 60 represents the substantially lossless operation of magnetizable element 10a such as is usually associated with the operation of thin-ferromagnetic-film layers when driven in the hard direction.
  • loop 62 represents the approximate path traversed by the magnetic flux of element 1012 when operated as a memory element in accordance with the embodiment of FIG. 5.
  • Loops 60 and 62 of FIG. 6 are typical BH loops of thinferromagnetic-film elements having uniaxial anisotropy and being driven in the hard and easy directions, respectively.
  • FIG. 5 there is illustrated a plan view of a magnetizable element 10b when utilized as a memory element. Operation as a memory element, or bistable core, is achieved by the application of a drive field :H, where +H may be representative of the storing of a 1 and H may be representative of the storing of a O in memory element 101).
  • This drive field H is coupled to memory element b 'by means of coil 52 providing a drive field that is oriented parallel to the mean axis M,,.
  • the applied drive field H is of an intensity in the area of magnetizable element 101), approximating H causing the magnetizations M and M to completely switch, i.e., be rotated a full 180 to assume a magnetization polarization along their respective easy axes M and M that is opposite to that of their original polarizations.
  • the magnetic flux change in magnetizable element 1% due to the switching, or not switching of the magnetization M M is detected by the output, or sense, coil 54 whose magnetic axis is oriented parallel to the mean axis M of magnetizable element 1% inducing a signal therein that is representative of the informational state of magnetizable element 1012 when operated as a memory core.
  • loop 62 that describes the magnetic flux path traversed by the magnetic flux of magnetizable element 10b when operated as a memory core in accordance with the embodiment of FIG. 5. It can be seen that loop 62 has a substantially rectangular form that approaches the ideal characteristic for a magnetizable memory element.
  • Magnetizable element 70 is comprised of a plurality of stacked, superposed thin-ferromagnetic-film layers 74a, 76a, 74b, 76b similar to the layers 14, 16 of FIG. 1. Adjacent magnetizable layers are separated by suitable insulating layers as in FIG. 1, but are not illustrated for purposes of clarity. However, in this embodiment each of the magnetizable layers is in the form of a washer providing a closed flux path around the central aperture for the magnetizing field :H that is applied to magnetizable element 70 by input winding 72.
  • Layers 74, 76 are fabricated so as to have radial easy axes that are orthogonal to the :H closed flux path. Adjacent cores, such as cores 74a and 76a provide substantially closed flux paths in a radial direction therebetween whereby there are provided two substantially orthogonally closed flux paths by each of two adjacent cores.
  • Application of the AC drive field by means of winding 72 forces the magnetization M M of layers 74, 76, respectively, to oscillate about their radially aligned easy axes in the nature as discussed with respect to FIG. 4 whereby there is produced by layers 74, 76 a magnetic flux change which is in turn coupled to output winding 78.
  • FIG. 1 As with respect to the embodiment discussed with respect to FIG.
  • windings 72 and 78 function as the primary and secondary windings, respectively, of transformer core 70; as an inductor core only winding 72 is required.
  • the magnetic flux change in core 70 traverses a BH loop similar to that of loop 60 as discussed with particular reference to FIG. 6.
  • Magnetizable element is comprised of a plurality of concentric rings of thin-ferromagnetic-films with adjacent layers separated by suitable insulating layers as in FIG. 1, but not illustrated herein for purposes of clarity.
  • the magnetization of rings 84, 86 are aligned in opposite directions that are substantially parallel to the major axis 81.
  • the concentric rings 84, 86 provide closed flux paths for the iH drive field coupled thereto by input winding 82.
  • the magnetization M M of adjacent layers 84, 86 are provided substantially closed flux paths through such adjacent rings.
  • application of the :H drive field to magnetizable element 80 by input winding 82 causes the magnetization M M of layers 84, 86, respectively, to rotate out of alignment with their easy axes and to become aligned in a first or second and opposite direction along a line substantially parallel to the major axes 81.
  • a synthetic bulk element operated in a domain rotational mode comprising:
  • each of said layers possessing the magnetic characteristic of single-domain property and having a preferred axis of magnetization along which the magnetization thereof may lie;
  • said first set formed by alternate ones of said layers having their preferred axes aligned along a first axis M said second set formed by alternate ones of said layers,
  • input means inductively coupling a drive field to said layers along said axis M said drive field causing the magnetization of said first and second sets to rotate in a domain rotational manner in opposite rotational directions;
  • a bistable memory operable in a domain rotational mode comprising:
  • each of said magnetizable layers possessing the magnetic characteristics of single-domain property and of uniaxial anisotropy providing an easy axis along which the remanent magnetization thereof may lie in a first or a second and opposite direction;
  • said first set formed by alternate ones of said magnetizable layers having their easy axes aligned along a first axis M
  • said second set formed by alternate ones of said magnetizable layers, other than those of said first set, having their easy axes aligned along a second axis 2;
  • said first and second axes M and M forming an angle a therebetween for providing a mean axis M input and output means inductively coupled to said magnetizable layers having a magnetic axis that is parallel to said means axis M said input means coupling a drive field H to said layers for causing the magnetization of said first and second sets to rotate in opposite directions about the mean axis M for providing a signal to said output means, and for establishing the magnetization of said first and second sets in a first or a second and opposite direction along their respective first and second axes M and M equal but opposite polarity field components M and M normal to the planes of adjacent layers of said first and second sets formed by said rotating magnetization;

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US646639A 1967-06-16 1967-06-16 Synthetic bulk element having thin-ferromagnetic-film switching characteristics Expired - Lifetime US3480926A (en)

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Cited By (7)

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Publication number Priority date Publication date Assignee Title
US3673581A (en) * 1970-02-27 1972-06-27 Hitachi Ltd Plated magnetic wire
US3848217A (en) * 1971-12-22 1974-11-12 Co Int Pour L Inf Magnetoresistive devices and transducers
US3913080A (en) * 1973-04-16 1975-10-14 Electronic Memories & Magnetic Multi-bit core storage
US4845454A (en) * 1986-07-29 1989-07-04 Toko, Inc. Inductance element with core of magnetic thin films
US20070056159A1 (en) * 2002-09-16 2007-03-15 Harding Philip A Electronic transformer/inductor devices and methods for making same
US20100011568A1 (en) * 2000-05-19 2010-01-21 Multi-Fineline Electronix, Inc. Method of making slotted core inductors and transformers
US7690110B2 (en) 2004-12-07 2010-04-06 Multi-Fineline Electronix, Inc. Methods for manufacturing miniature circuitry and inductive components

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Publication number Priority date Publication date Assignee Title
CA1109916A (en) 1977-09-21 1981-09-29 Yoshio Kishi Stator yoke for electrical apparatus
US20040017721A1 (en) 1998-10-30 2004-01-29 Schwabe Nikolai Franz Gregoe Magnetic storage device
GB2343308B (en) * 1998-10-30 2000-10-11 Nikolai Franz Gregor Schwabe Magnetic storage device
DE10163507A1 (de) * 2001-12-21 2003-07-10 Infineon Technologies Ag Schichtfolge für ein magnetisches Bauelement und Verfahren zur Herstellung der Schichtfolge

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US3080549A (en) * 1957-03-25 1963-03-05 Sperry Rand Corp Magnetic cores
US3375091A (en) * 1964-03-17 1968-03-26 Siemens Ag Storer with memory elements built up of thin magnetic layers

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US2900282A (en) * 1956-07-20 1959-08-18 Sperry Rand Corp Method of treating magnetic material and resulting articles
US3030612A (en) * 1956-12-07 1962-04-17 Sperry Rand Corp Magnetic apparatus and methods
US3065105A (en) * 1958-06-12 1962-11-20 Sperry Rand Corp Process and apparatus for producing magnetic material and resulting article
US3155561A (en) * 1960-03-07 1964-11-03 Sperry Rand Corp Methods for making laminated structures
US3224074A (en) * 1960-06-24 1965-12-21 Sylvania Electric Prod Method of making a magnetic recording head structure
DE1299034B (de) * 1961-07-20 1969-07-10 Sperry Rand Corp Parametron
DE1265314B (de) * 1961-08-22 1968-04-04 Siemens Ag Duenne ferromagnetische Schicht mit uniaxialer Anisotropie
DE1190523B (de) * 1962-11-02 1965-04-08 Siemens Ag Reaktanzverstaerker mit einer nichtlinearen Induktivitaet
GB1054751A (enrdf_load_stackoverflow) * 1963-03-29
CH416745A (de) * 1963-11-27 1966-07-15 Ibm Dünnschichtzelle mit anisotropen magnetischen Eigenschaften und Verfahren zu ihrer Herstellung und zu ihrem Betrieb

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US3375091A (en) * 1964-03-17 1968-03-26 Siemens Ag Storer with memory elements built up of thin magnetic layers

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3673581A (en) * 1970-02-27 1972-06-27 Hitachi Ltd Plated magnetic wire
US3848217A (en) * 1971-12-22 1974-11-12 Co Int Pour L Inf Magnetoresistive devices and transducers
US3913080A (en) * 1973-04-16 1975-10-14 Electronic Memories & Magnetic Multi-bit core storage
US4845454A (en) * 1986-07-29 1989-07-04 Toko, Inc. Inductance element with core of magnetic thin films
US20100011568A1 (en) * 2000-05-19 2010-01-21 Multi-Fineline Electronix, Inc. Method of making slotted core inductors and transformers
US20070056159A1 (en) * 2002-09-16 2007-03-15 Harding Philip A Electronic transformer/inductor devices and methods for making same
US7696852B1 (en) 2002-09-16 2010-04-13 Multi-Fineline Electronix, Inc. Electronic transformer/inductor devices and methods for making same
US7690110B2 (en) 2004-12-07 2010-04-06 Multi-Fineline Electronix, Inc. Methods for manufacturing miniature circuitry and inductive components

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GB1237904A (enrdf_load_stackoverflow) 1971-07-07
DE1764483C2 (enrdf_load_stackoverflow) 1975-02-06
FR1570297A (enrdf_load_stackoverflow) 1969-06-06

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