DK144153B - MAGNETIC Bubble Domain Domain Apparatus - Google Patents

Description

(is) DENMARK (Φ t yp.a

^ f'2) PROPERTY WRITING (11) 1441 53 B

Dl THE RECTORATE OF THE PATENT AND TRADEMARK

(21) Application No. 4724/73 (51) lnt.Cl.3 H 01 F 10/10 (22) Submission day 28 Aug, 1973 Q Q 11/14 (24) Run day 28 Aug. 1973 (41) Aim. available 1 · mar. 1974 (44) Submitted 21. dec. 1981 (86) International application no.

(86) International filing date - (85) Continuation date (62) Master application no. -

(30) Priority 29 Aug. 1972, 284513, US

(71) Applicant INTERNATIONAL BUSINESS MACHINES CORPORATION, Armonk, US.

(72) Inventor Praveen _Chaudhari, US: Jerome John Cuomo, US: Ri = chard Joseph Gambino, US.

(74) Agent Engineer Budde, Schou & Co.

(54) Magnetic bubble domain device.

The invention relates to a magnetic bubble domain apparatus of the type specified in the preamble of claim 1.

Amorphous materials are known in the art, and these can generally be classified as being either metals or non-metals. The metals are described either by means of the Bernal model, where a dense random packing occurs, or by means of microcrystalline models. Amorphous metallic materials include Pd-Si and Mn-C alloys.

Non-metallic amorphous materials are generally covalently bonded, and the "ovonic" materials based on the Ovshinsky-j effect are an example of such materials. Non-metallic amorphous materials are, for example, SiO 2, Si, Ge and Ge-Te alloys.

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Non-metallic amorphous materials have been used in a variety of applications, including beam addressable information storage, as set forth in the specification of U.S. Patent No. 3,530,441. However, this prior art does not include the use of amorphous magnetic materials with uniaxial anisotropy in such applications as magneto-optical devices and bubble domain devices. Nor is the use of amorphous magnetic materials as permanent magnets known in the art. Such materials will be valuable in many applications in this field. For example, amorphous materials can be deposited on any type of substrate, and they do not have to correspond to the lattice in terms of lattice. Furthermore, internal substrate defects are not detrimental to the properties of the later deposited amorphous material.

Additional advantages of amorphous material include the fact that the composition can be adjusted in order to optimize the properties without the limitations due to the stoichiometry of the compound. This means that limitations due to the phase diagram of materials to be combined do not occur when making amorphous materials. Furthermore, amorphous materials can be produced at low temperatures and can be formed by a simple technique, such as evaporation, electrode sputtering, etc.

In the case of magnetic amorphous materials in particular, such structural defects do not occur in the amorphous materials which can damage the movement and nucleation of magnetic domains in the material. Furthermore, these materials have compositions that vary over large areas in order to improve the selected magnetic properties. The addition of impurities to the composition does not adversely affect the structural or magnetic properties of the layers and can be used to achieve greater flexibility in the design of the composition.

Amorphous films containing multicomponent cysts have been mentioned in the literature. For example, Sawatzky et al. in "Journal of Applied Physics", 42, January 1, 1971, on page 367 the type of film which is amorphous by electrode sputtering and then crystalline after a curing process. In another article in "Material Science Research", Vol. 4, 1969 describes E. Giess et al. page 493 gadolinium iron garnet film with crystal sizes between 30 and 50Å.

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A ferromagnetic, amorphous film consisting of an Fe-C-P alloy is described by Duwez et al. in "Journal of Applied Physics", 38, September 10, 1967, at page 4096. The amorphous films referred to in the above publications do not have uniaxial magnetic anisotropy.

Amorphous, magnetic films of Fe ^ Hd ^. is described by J.

Orehotsky in "Journal of Applied Physics", 43, May 5, 1972 on page 2413. In order to explain the non-saturation of these films, the authors suggest the presence of a right-angled anisotropy linked to an isotropic influence in the plane of the film.

In connection with the present invention, it has been found that uniaxial anisotropy can be induced in amorphous magnetic films and that the anisotropy can be provided independently of substrate constraints. This means that uniaxial anisotropy can be produced by pairing or by form-induced anisotropy. The present amorphous compounds may consist of a single element or of several elements. The use of these amorphous magnetic compounds in apparatus applications eliminates many of the disadvantages of the prior art where crystalline magnetic material must be used.

It is thus the object of the invention to provide a magnetic bubble domain apparatus of the kind set out in the preamble of claim 1, using amorphous magnetic materials to support the magnetic bubble domains, by which the domains can be easily propagated without regard to structural defects or contaminants in the material which carries the bubble domains, and this object is achieved by an apparatus which according to the invention is characterized by the criteria for the magnetic medium specified in the characterizing part of claim 1.

Amorphous magnetic compounds are produced either in bulk or in thin film form. Furthermore, amorphous magnetic particles can be prepared in a binder for use on either tapes or disks. These compositions consist of a single element or a multi-component system, where at least one of the components has an "unpaired spin". The compositions thus have a magnetic moment and constitute magnetically ordered materials.

These amorphous materials have a non-magnetic, crystalline, uniaxial magnetic anisotropy that can be parallel to or perpendicular to the plane of film made from these compounds. The anisotropy appears in one of the following ways or by combination thereof: pair arrangement, formanisotropy or influence-induced anisotropy.

These amorphous compositions occur in a microcrystalline region, where the atomic arrangement, if any, exists over regions of the order of 25-100 Å. In addition, amorphous materials exist in accordance with the present invention, which materials have a structure which, independently of the present atomic arrangement, exists over stretches of less than 25 Å.

Binary and ternary compositions are particularly suitable for practicing the invention. This includes both compounds and alloys, and a suitable example is state transitions in compositions of rare earths and metals, e.g. Gd-Co alloys or Gd-Fe alloys are particularly useful.

The magnetic properties of these substantially amorphous compositions can be altered during manufacture by altering the manufacturing process or the interrelationship of the components of the composition. Furthermore, the magnetic properties of the compositions can be changed after manufacture, and the films can be easily doped without adversely affecting the magnetic properties. For example, the amorphous compositions of a rare earth and cobalt as well as of a rare earth and iron can be easily doped with oxygen, nitrogen, carbon, etc. in order to influence the magnetic properties.

These magnetic compositions can be used in many embodiments. For example, if the anisotropy forms a right angle with the plane of the layer, the films can be used in magneto-optical devices and in magnetic-bubble domain devices. It is understood that the present, generally amorphous magnetic films provide space for magnetic domains therein, and in particular for magnetic bubble domains.

Furthermore, these magnetic bubble domains can be propagated in the magnetic film in ways identical to those well known in the art of moving domains. Due to the fact that amorphous films do not have to be produced on exactly lattice-adapted surfaces, and due to the fact that defects and contaminants in the film do not damage the domain propagation, great advantages can be obtained from mainly amorphous bubble domain materials. Furthermore, since the magnetic properties of these amorphous films can be altered, they can be utilized as permanent magnetic bias layers in connection with magnetic bubble domain material of prior art and with the amorphous bubble domain materials of the present invention.

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Since the present amorphous materials can be prepared as magnetic particles in a suitable binder, a use in strip and disc design can also be immediately envisaged. Furthermore, the amorphous films can be deposited on metallic or non-metallic substrates, including flexible substrates. They can therefore be used as storage media in information processing facilities of any type.

The amorphous materials of the invention can be used as light modulators in which the intensity of light passing through the amorphous film is affected by the presence and absence of a domain at the site where the light spot hits. Polarized, incident light has its polarization rotated according to the state of the amorphous material where the light beam strikes. An analyzer is used to detect whether or not a magnetic domain is present at the light spot in the amorphous film. By selectively generating a magnetic domain in the amorphous film within the range of incidence of a polarized input light beam, the intensity of the beam received by a detector after passage through the amorphous film can be caused to vary, thereby providing a light modulator.

In general, the intensity of light passing through the amorphous film is affected by the fraction of the film area covered by domains magnetized in the direction of light propagation. This fraction is easily controlled by means of an externally applied magnetic field, which is used to place the domain magnetization in a preferred direction.

By changing the properties of the amorphous material in question, permanent magnetic structures can be provided. These can be used as bias layers in magnetic bubble devices and in other areas where permanent magnetic material is required.

It has further been found that the amorphous materials of the invention can be used in beam addressable archive applications if the magnetic properties of the amorphous compositions are impaired.

The invention will be explained in more detail below with reference to the drawing, in which fig. 1A shows an electron beam photomicrograph of the diffraction pattern of an amorphous magnetic material according to the invention, FIG. 1B shows an electron beam microphotograph! of the diffraction g U4153 pattern for the same material after it has hardened in order to impart a crystalline structure to the material.

FIG. 2A and 2B are photographs of magnetic edge domains in the amorphous material of FIG. 1A, which photographs illustrate the motion of the magnetic domains when the amorphous material is applied to a magnetic field, FIG. 3A a curve for the magnetization 4. jMs as a function of the cobalt concentration in an amorphous Gd-Co alloy, '«ν' fig. Fig. 3B is a second graph of magnetization 4JJMg as a function of the composition of an amorphous Gd-Co alloy used to indicate the change in magnetization that occurs when dopants are added to the amorphous material; Fig. 4A is a graph of the inverse characteristic length Ku / 41l (1 / L) as a function of the cobalt concentration in an amorphous Gd-Co alloy; Fig. 4B shows a curve for the length L as a function of the thickness of an amorphous magnetic film according to the invention; Fig. 5 is a domain boundary energy curve (4)) (w) as a function of the electrode sputtering bias applied to the substrate during the deposition of an amorphous magnetic alloy according to the invention; 6 is a graph of deposition rate as a function of the applied high frequency energy for electrode sputtering of amorphous magnetic alloys, which curve shows the effect of the application of a magnetic field of approx. 500 during the marketing process, fig. Fig. 7 is a graph of the anisotropy Ku of an amorphous, uniaxial magnetic layer as a function of the thickness of the magnetic layer; Fig. 8 is a graph of deposition rate on a logarithmic scale as a function of inverse substrate temperature, illustrating the amorphous / crystalline transformation that occurs at certain deposition conditions; Fig. 9 shows a magnetic bubble domain apparatus in which the amorphous magnetic materials are used as the bubble domain material; 10 shows in detail a part of that in fig. 9 schematically shown, fig. Fig. 11 shows a magneto-optical light modulator in which the amorphous magnetic materials are used as light-modulating medium; Fig. 12 shows a magnetic bubble domain material with an adjacent layer of amorphous magnetic material acting as a bias layer for magnetic domains in the bubble domain material; and FIG. 13 shows a tape or disk information processing plant in which the amorphous magnetic material is used as the recording medium.

Amorphous magnetic materials with uniaxial anisotropy have been produced mainly, which materials are suitable for many magnetic applications. These materials can be made in bulk or thin film form, or they can be present as magnetic particles in a carrier binder. As this is amorphous material, the choice of substrate does not matter and factors such as lattice alignment can be disregarded. This simplifies the deposition on substrates of any type and greatly increases the achievable manufacturing speed when using materials of the present type.

These magnetic materials may consist of a single element or a combination of elements that occur in a multicomponent system. At least one of the components must have an unpaired electron spin so that the material has a magnetic moment. This means that it is a magnetically ordered material.

These amorphous magnetic materials have a uniaxial anisotropy that can be perpendicular to or parallel to the plane of a film containing these amorphous magnetic materials. The anisotropy results from combinations of the following phenomena or from any of them: A. Pair arrangement B. Formanisotropy C. Influence-induced anisotropy.

In the present invention, it is not essential that a uniaxial anisotropy be provided in a particular manner.

The above-mentioned three phenomena for producing uniaxial anisotropy in the substantially amorphous films of the invention are well known in the art and are therefore not described in detail here. It seems sufficient to point out that the pairing scheme includes combinations of two atoms whose magnetization is paired to form a magnetic dipole. The magnetic pair is oriented in certain directions, giving rise to the uniaxial anisotropy required for use in magnetic organs.

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Formanisotropy occurs due to the geometric shape of the magnetic regions. For example, an ordered group of atoms in an area of a substantially disordered material will have a magnetization which is directed along the longitudinal axis of the atomic group, since this axis is the preferred one for orienting magnetic moments. Along the short axis of the region defined by the atomic group, a strong demagnetization field appears.

Furthermore, compositional variations in the amorphous material provide phase separations, giving rise to this type of anisotropy. Phase separation includes both a state of distinct composition regions located near each other and a state of adjacent regions of the same composition but with different structural phases, i.e., one region is amorphous while another is more crystalline. .

An example of phase separation is an amorphous, magnetic Gd-Co alloy, which may consist of localized areas that are co-enriched and other localized areas that are Gd-enriched.

If these two regions are adjacent to each other, the phase separation will produce a uniaxial anisotropy.

Influence-induced anisotropy results from inequalities in the lattice parameters of the substrate and localized areas in the amorphous film, or it is due to inequalities in thermal coefficients of the amorphous film and its substrate. This type of influence can also be a contributing factor to uniaxial anisotropy in the substantially amorphous films of the invention.

Amorphous magnetic compositions of the invention have microcrystalline and / or substantially amorphous structure.

Both of these structures differ from polycrystalline and monocrystalline structures known in the art in magnetic materials. For example, the amorphous materials of the invention may have localized atomic arrangement. However, if this atomic arrangement occurs, it exists over stretches of between 25 and 100Å if the material is microcrystalline, or over stretches below 25Å if the material is essentially amorphous. It is, of course, understood that in the main case no nuclear system can also occur, in which file division it is a purely amorphous material.

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Amorphous materials according to the invention consist of single magnetic elements or multicomponent cysts. An example of a system of the latter kind are binary and ternary alloys and compounds. Particularly suitable materials consist of materials containing elements from the rare earths and metal elements with state transitions. These include Gd-Co, Gd-Fe, Y-Co and La-Co. These compositions can be varied within a wide range without the limitations of the stoichiometry of the compounds due to the phase diagram of the components. Therefore, the magnetic properties of the material can be designed specifically in accordance with each individual embodiment. For example, the composition ranges can be selected so that the atomic moments of a rare earth and the metal element almost equalize each other, whereby a material with low saturation magnetization is obtained, which material is particularly important as a bubble domain material.

These amorphous magnetic materials have a longitudinal magnetic arrangement and have uniaxial anisotropy. In their simplest form, they are composed of elements that have a magnetic moment. Examples are the 4f series or elements of rare earths, and the 5f series or actinide elements. Furthermore, the iron group of state transition metals is included, i.e. 3d series. In addition, elements that can have a magnetic moment when they are in a special state, e.g. such elements as Mn,

Cr, V and Pd.

For any amorphous material consisting of a single element, any non-magnetic element can be added in relatively small amounts without disturbing the magnetic properties. This means that a dilution can be made with non-magnetic elements, e.g. 0, C, P and N, without adversely affecting the magnetic properties. It can therefore be advantageous to add small amounts, generally approx. 2 atomic percent, of these non-magnetic elements in order to simplify the production of the amorphous film. If large amounts are added, there is of course an influence on the magnetic properties. Thus, e.g. larger quantities than approx.

50 atomic percent disturb the magnetic scheme.

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Binary materials including at least one of the previously disclosed elements may also be used to provide the amorphous magnetic materials of the invention.

Binary materials are generally easier to work with as they retain their amorphous structure over larger temperature ranges than amorphous, single-magnetic magnetic materials. As in the case of amorphous single element materials, small amounts of non-magnetic elements can also be added.

Another modification that can be performed on binary amorphous materials consists in the addition of a larger concentration, such as 2-50 atomic percent, of non-magnetic elements to vary the magnetic properties. For example, copper can be added to dilute the magnetic moment.

Ternary combinations of the above-mentioned 3d, 4f and 5f elements can also be prepared to provide amorphous compositions with uniaxial magnetic anisotropy. As with the binary materials, higher concentrations of non-magnetic elements can be added in order to change the magnetic properties of these ternary combinations. Likewise, small amounts of non-magnetic material can be added to facilitate the formation of amorphous films without adversely affecting the magnetic properties. It is understood that the amount of non-magnetic material added is insufficient to destroy the magnetic arrangement in the amorphous film.

The amorphous magnetic materials of the invention have a longitudinal magnetic arrangement and are either ferromagnetic, ferrimagnetic or antiferromagnetic. Of course, it is this longitudinal magnetic arrangement which causes the provision of the uniaxial anisotropy in these materials which in turn makes them very suitable for apparatus applications.

The magnetic properties of these materials can be changed during manufacture or after manufacture to accommodate particular embodiments. It has been found that the magnetic properties are highly dependent on the composition range of the components and also on the deposition conditions that prevailed in the manufacture of the material. However, the dependence of the magnetic properties on the deposition parameters is less than the dependence associated with the composition ranges of the constituents.

Processes such as curing and ion implantation can be used to modify the magnetic properties after the production of these amorphous materials. Furthermore, these magnetic materials can be doped with dopants without adversely affecting the structural magnetic properties of the films. Therefore, the magnetic domain motion in the films is not affected, as is the case with conventional crystalline magnetic films. The following are examples of particularly suitable amorphous magnetic materials for multiple applications.

Depending on the exchange co-operation occurring in these materials, it should be possible to provide insulators, conductors and semiconductors which are substantially amorphous. In metals and semiconductors, the exchange interaction can be either directly due to overlap for the atomic orbits or indirectly due to the conduction electrons. These mechanisms make the amorphous material more suitable for magnetic applications. However, the exchange mechanism in insulators is based on "super-exchange", which is critically dependent on the bond angle and stretch. Since no longitudinal magnetic arrangement occurs in amorphous material, these "super-exchange conditions" cannot be met and no magnetic arrangement is observed.

Figures 1A and 1B show electron beam photomicrographs illustrating amorphous and crystalline material. The electron beam diffraction pattern of FIG. 1A is characteristic of an amorphous material, while the diffraction pattern of FIG. IB is characteristic of a crystalline material.

More specifically, FIG. 1A and 1B produced by electron diffraction from a Gd-Co alloy. The solid line L in FIG. 1A and 1B are used to block the incident electron beam in order to facilitate the production of these photographs. The diffraction pattern in FIG. 1A is characteristic of an amorphous material.

FIG. IB is a diffraction pattern of the material Gd-Co in FIG. 1A, after it has crystallized by the application of heat. In this case, the amorphous film of FIG. 1A in the electron beam microscope and heated to approx. 300 ° C. The diffraction pattern in FIG. IB is therefore characteristic of the diffraction from a crystalline material. FIG. 1A and IB are shown on the same scale. These figures illustrate the substantially amorphous nature of films made in accordance with the invention.

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FIG. 2A and 2B show the presence of magnetic edge domains in the amorphous material of FIG. ΙΑ. In FIG. 2A and 2B, a reference mark M is engraved in the film, which mark is used to determine the movement of the edge domains when a magnetic field is applied over the amorphous material.

In FIG. 2A, magnetic edge domains D are clearly visible over the amorphous magnetic material. These peripheral domains have boundaries that are mainly oriented in the vertical direction in this figure.

However, when a magnetic field is applied in the plane of the amorphous material, the edge domains D are imparted. This is seen when the position of the domains D relative to the reference mark M is examined in these two figures. Thus, FIG. 2A and 2B the presence of domains in the amorphous magnetic material and the motion of these domains due to an applied magnetic field. As shown below, the peripheral domains D can be caused to collapse into round bubble domains.

Amorphous films with a thickness of about 1 micron were deposited on NaCl, SiC> 2 and Al 2 O 2. These films showed uniaxial anisotropy and also had marginal domains. A magnetic field applied at a right angle to a few hundred earlobes was sufficient to cause the peripheral domains to collapse into round bubble domains. Furthermore, the bubble domains were moved when the outer magnetic field was moved. The domain pattern in the amorphous material was similar to the domain patterns observed in accurately made garnet films.

This suggests that the amorphous material lacks local inhomogeneities sufficient to provide local retention of domains, which would limit their movement. Of course, this is an advantage in an amorphous magnetic material, where per. definition does not exist crystal structure error. The nucleation and propagation of magnetic domains in such an amorphous material is not limited by this type of defect.

Depending on the particular application for which these amorphous magnetic materials are intended, the said magnetic properties are adjustable to obtain optimum performance. The regulation of the magnetic properties of these amorphous materials is readily accomplished by certain methods during the manufacture of the amorphous materials and by processes used after their manufacture. Unlike previously known crystalline magnetic materials, the magnetic properties of the amorphous films are generally easier to control than similar properties in crystalline materials. One reason for this is that the composition variations allowed in an amorphous material are much more far-reaching than the allowable variations in a crystalline material, because amorphous compositions are characterized by metastability, rather than thermodynamic equilibrium. Various magnetic properties are discussed below separately to illustrate the flexibility offered by amorphous materials.

Saturation magnetization Mg

The magnetization Mg can be easily changed in an amorphous magnetic material by adding a magnetic atom which is coupled to a normal magnetic atom in the amorphous material or an atom in the amorphous material which is magnetic in a certain state, e.g.

Mn, Cr, etc. In order to reduce the magnetization Mg, the material added to the amorphous composition is antiferromagnetically coupled with the magnetic atom of the amorphous material.

In order to reduce the magnetization in the amorphous Gd-Co alloy, for example, the Gd / Co ratio is regulated so that the magnetic moment of the material is almost equalized.

To increase the magnetization in the amorphous material, magnetic atoms are added to the composition which are ferromagnetically coupled to the magnetic atom in the amorphous composition. For example, an addition of Nd to an amorphous composition of Gd-Co provides an increase in the magnetization of the composition. As another example, it may be mentioned that the addition of Co to an amorphous composition of Y-Co increases the magnetization.

These additions are carried out during the manufacturing process and take place as follows: a mixture of the constituent elements is melted and cast into a disc-shaped plate used as a measure of electrode sputtering. The composition may be adjusted during the target manufacture, or the composition of the film may be varied during the sputtering process by adjusting the bias on the substrate for preferred re-sputtering of a portion of one or more of the components. Alternatively, another additive element may be provided in the atomizing system so that one of the additive elements is introduced into the deposited film.

When thin films are produced by vacuum evaporation, the concentration of the additive can be varied in the evaporation source, or an additional source of the additive element can be provided.

FIG. 3A shows a curve for the excitation 4! Mg at room temperature as a function of the concentration of cobalt in an amorphous Gd-Co alloy. From this curve it appears that the amount of magnetic atoms of Co in the amorphous alloy determines the magnetization of the alloy. Accordingly, the magnetization of the alloy changes with the addition of material to the amorphous alloy, which changes the Gd / Co ratio and there to the extent that the magnetic moment of the material is eliminated.

The composition areas in the vicinity of the minimum magnetization are particularly suitable for materials with low magnetic torque and high curie points. Since the low magnetization of compositions near 79 atomic percent cobalt results from the equalization of the Gd and Co moments, rather than from dilution effects, the curie point largely determined by the Gd-Co interaction is not affected. Consequently, the magnetization of the material at room temperature can be changed while maintaining Tc within specified limits.

Another way to change the magnetization of an amorphous alloy is to add small amounts of Nj when the amorphous alloy is electrode atomized. When e.g. GdCo2 is electrode atomized in argon, this is done by adding small amounts of N2, e.g. ca. 1% by volume of N2 in the argon gas, a significant reduction in the size of peripheral domains in the material. This again indicates an increase of 4) 7Mg. This means that the antiferromagnetic coupling of Gd and Co is affected so that the magnetization is increased without disturbing the uniaxial anisotropy of the amorphous material. The nitrogen is bound by Gd, which weakens the antiferromagnetic coupling between Gd and Co. The moment of the Co-lattice is less effectively eliminated by the Gd sub-lattice moment, so that the magnetization increases.

FIG. Fig. 3B shows a curve of the magnetization Mc in random b units as a function of the composition of an amorphous Gd-Co alloy, also expressed in random units · A minimal magnetization occurs at a certain composition of Gd-Co.

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If the Gd-Co composition is normal at the composition A, and the composition is prepared in the presence of N2 /, a shift of the magnetization occurs as if an increase of the cobalt composition occurred. Therefore, the magnetization becomes higher. If, on the other hand, they are started with a composition C and nitrogen is added to the deposition arrangement, the magnetization of the produced film will change to a minimum. Therefore, the magnetization Mg can be changed by simple additions of N2 to the material in order to change the interaction between the components of the composition to a higher or lower magnetization according to where one is on the magnetization / composition curve for the material in question.

Coercive force H _c

The coercive force in magnetic material is a primary factor in determining the ease with which magnetic domains move in the material. Adjustments regarding the coercive force usually include changing the grain size of the magnetic material, as the coercive force depends on the grain size. In general, the coercive force has a maximum for a certain value of the grain size and decreases at grain sizes smaller than and larger than the value which results in the largest coercive force. For example, the coercive force is large in magnetic material in which the grain size approaches the domain boundary width.

The grain size can be affected by the addition of dopants, such as e.g. ^ and These additions change the magnetic arrangement of the amorphous film so that it becomes different from or equal to the domain boundary widthS. If S is larger, Hc becomes small, but if S is approximately equal to said scheme, Hc is maximum.

Ion implantation to a selected depth is usually appropriate when it is not desirable to heat amorphous materials. Heating above certain temperatures causes amorphous materials to change to a crystalline state, which may not be a reversible state. A cure for crystallization of the amorphous film to provide grains of desired size can also be utilized.

Other methods of influencing the coercive force include a surface treatment, such as, for example, spray etching and ion etching, to make the surface structure uneven. This in turn affects the motion of the domains in the amorphous magnetic material.

Curie temperature Tc

These amorphous magnetic materials are easy to alloy in order to change the curie temperature without adversely affecting the structure of the material. Consequently, no limiting influence occurs due to a phase diagram, which would otherwise be the case for crystalline material. Alloy areas can be used to a large extent, such as 50 atomic percent, as long as the uniaxial anisotropy of the material is not affected. In general, the curie temperature linearly follows the amount of magnetic atoms present. The Curie temperature in these amorphous materials is easier to control than in crystalline magnetic materials.

The alloying conditions are used to change the curie temperature of the amorphous magnetic material. For an amorphous Gd-Co-alloy, the addition of lower atomic magnetic atoms, e.g. Ni, Cr, Mn or non-magnetic atoms, e.g. Cu, Al, Ag, Pd,

Ga, In, etc., for example, cause a lowering of the curie temperature, while the addition of such an element as e.g. Fe increases the curie temperature. The strength of the magnetic interaction or coupling in the material is changed by the added elements. Faraday rotation _Γ

An increased Faraday rotation or Kerr rotation of a light beam incident on the amorphous magnetic material is obtained by providing amorphous material with a high magnetic moment. Drugs in the form of rare earths, e.g. Tb, Dy, Ho, can be added to the amorphous material, or alloy additives can be added to the material. For example, in the case of the amorphous Gd-Co alloy, an increase in the Co amount will cause an increase in the Faraday rotation. Also, additions of Fe to the material will increase the Faraday rotation. For high Faraday rotation, it is desirable that the magnetization 4'TTMg carry as large a value as possible, e.g. 8000-10000 gauss.

Characteristic length (L-parameter)

The parameter L is a quantity which is especially useful in the design of magnetic bubble domain devices. A more detailed description of this parameter is given by A. A. Thiele, in "J.Appl.

Phys., ", No. 41, page 1139 of 1970.

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The parameter L is highly dependent on the extent of the constituents of the amorphous alloy. FIG. 4A thus shows, for example, the variation of parameter L, more specifically Ku / 4'TF (1 / L), as a function of the magnetion concentration in an amorphous magnetic alloy. In this particular case, the composition is Gd-Co and the horizontal axis shows the CO concentration. It can be seen that parameter L can be varied by changing the composition of the amorphous alloy. The curve in 4A has been determined for different compositions of Gd-Co, where all manufacturing parameters were kept constant for each sample. The same compositions produced under different conditions had different values of the parameter L. Depending on the fact that the composition range of an amorphous material can be easily varied within wide limits, which is in contrast to what is the case with a crystalline magnetic material, it is relatively easy to vary the parameter L.

FIG. 4B shows the dependence of parameter L on the thickness H of the amorphous magnetic layer. At a critical thickness for each composition, it is not possible to obtain sufficient right-angled anisotropy to support bubble domains, and the curve is therefore shown punctured below the critical thickness. At this particular special composition with 20 atomic percent Gd and 80 atomic percent Fe, a thickness of 0.2 microns provides a sufficient right-angled anisotropy to promote bubble domains.

Domain boundary energy

The domain boundary energy (f is related to the L parameter of the amorphous material. The domain boundary energy is also directly proportional to the VAKu, where A is the exchange constant of the material and Ku is the uniaxial perpendicular anisotropy constant of the material.

FIG. 5 shows a curve for the domain boundary energy 4P 6 in 2 W erg / cm as a function of the substrate bias used during the electrode sputtering of amorphous Gd-Co alloys containing 80-85 atomic percent Co. This substrate prestress is the substrate tension measured in relation to soil. In the DC electrode sputtering apparatus used to provide the curve of FIG. 5, approx. 2000 volts between the anode and the cathode to provide deposition of the amorphous Gd-Co composition. The use of substrate prestress allows control of the composition and the magnetic properties of the deposited, amorphous material.

18 144153 In this way, the domain boundary energy can be varied within a wide range. The domain boundary energy can also be changed by varying the exchange constant A or the anisotropy Ku · The exchange constant A represents the strength of the magnetic coupling in the material and is proportional to the curie temperature T. Consequently, the constant A varies from one material to another. Changes in the anisotropy are discussed in a later part of the description. Anisotropy Ku

The anisotropy of the material can be varied by changing the process used in the production of the amorphous material. For example, the rate of deposition is a decisive factor, as is the thickness of the deposited film. In general, a function of the material composition and construction conditions.

These factors are described in more detail in the part of the description which relates to manufacturing methods.

Domain size and domain boundary width

The domain boundary width is equal to VA / ^ u, where A is the exchange constant of the material and is its anisotropy. As mentioned earlier, the anisotropy Ku depends on the thickness of the amorphous film and the rate of deposition. Therefore, the domain boundary width S 'can be varied by changing the anisotropy Ku. This in turn is a function of the composition of the amorphous layer, its range of constituents and the deposition process used in the manufacture of the amorphous material. In the part of the description which relates to manufacturing methods, there are curves which illustrate the variation of the anisotropy K 2 with the layer thickness and the rate of deposition.

The domain size is a function of the characteristic length L and the thickness of the film. In general, the domain size is chosen so that the performance of the device is optimal. For magnetic bubble doomers, the characteristic length L is determined by the following equation

L = <T / 4TTm w S

4 ^ MS2 19 144153 Consequently, the characteristic length and thus the domain size can be changed by varying the magnetization Mg, the anisotropy Ku and the exchange constant A.

The gear constant is a quantity that represents the strength of magnetic coupling in a given material. It is proportional to the curie temperature and is greater for materials that have higher curie temperature T. As explained earlier, the anisotropy Ku is a function of the material composition and other conditions used in the manufacture of the material. The magnetization M

S

derives from magnetic spins and their orientation, i.e. whether they are parallel or antiparallel. This size is temperature dependent and can be varied by changing the composition of the amorphous film and the parameters used in the manufacture of the amorphous film. Therefore, the domain size can be easily changed within large areas.

Manufacturing methods

The amorphous magnetic materials can be made in bulk or as thin films. In general, any known film deposition technique, including electrode sputtering and vapor deposition, can be used.

To provide a mass film of amorphous magnetic material, splash cooling can be a useful method. In this method, the film constituents in heated and liquid form are brought to hit a cold surface, where the constituents solidify and form an amorphous mass film. This results in a rapid cooling from the liquid phase.

A uniaxial anisotropy can be provided in bulk films by subjecting them to atomic bombardment in a printed magnetic field or by curing them in a magnetic field at a temperature below the crystallization temperature of the films. Another method of producing bulk films consists in continuously evaporating them using the method described below.

The production of thin amorphous films of the present invention may be based on the deposition of a vapor, a rapid cooling of a liquid phase or an ion implantation to control the anisotropy. In general, these amorphous films depend on the rate of deposition of atoms on the substrate, the temperature of the substrate and the angle of incidence of atoms deposited on the substrate. If the incoming atoms are not able to achieve a certain equilibrium position, the tendency to form amorphous films increases. In this connection, reference is made to S. Mader: "The Use of Thin Films in Physical Investigations", published by J.C. Anderson, Academic, New York, 1966, page 433. At the same time, reference is made to U.S. Patent No. 3,427,154, which relates to the manufacture of amorphous thin films.

In order to promote the pairing arrangement as a way of providing uniaxial anisotropy in these films, it seems to be essential that the deposition atoms strike the substrate at an angle of incidence other than a right angle. This means that the incoming atoms must have a certain velocity component parallel to the substrate surface to achieve uniaxial anisotropy in the film.

This "gravitational angle" causes an atomic motion parallel to the substrate, which in turn promotes the pairing arrangement, as the incoming atoms can move around and select an atomic position that reduces the energy of the arrangement via the demagnetization field of the material. The phase separation is promoted, leading to the formation of anisotropy, because groups of uniform atoms are grouped together in a place where the energy of the system is lowered. This in turn leads to composition groupings which, as previously stated, result in anisotropy in the film.

Another factor associated with achieving uniaxial anisotropy is the rate of deposition of incoming atoms. If the rate of deposition is too great, incoming atoms cannot move around to such an extent on the substrate surface, limiting the motion parallel to the substrate. In this connection, reference is made to FIG. 6, which shows a curve for the rate of deposition in steam flow per second as a function of the high frequency energy used in a sputtering arrangement for depositing the amorphous material. In this case, the amorphous magnetic material is Gd-Co. In FIG. 6, a critical deposition rate of 4 angstroms per second at a given substrate temperature and target composition.

This means that at a sales rate of 4 angstroms per second for a Gd-Co sample containing approx. 80 atomic percent Co, a domain pattern is obtained which is characteristic of uniaxial, right-angled anisotropy in the amorphous magnetic alloy of Gd-Co.

In FIG. 6, the deposition is performed with a magnetic field of 500 perpendicular to the substrate and without the presence of the magnetic field in order to determine the effect of the magnetic field during the deposition. The effect of the magnetic field was not great, although it did to some extent improve the efficiency of the atomization.

2i 144153 As the substrate bias used in the atomizing arrangement increases, the anisotropy generally increases.

This is because the bias causes incoming atoms to be released from the surface of the deposition film by sputtering.

Consequently, the atoms have greater motion parallel to the substrate surface so that they can reach preferred positions, resulting in a composition grouping or pairing arrangement.

FIG. 7 shows a curve for the anisotropy Ku in erg / cm3 as a function of the thickness H of the amorphous magnetic film, measured in microns. This film of amorphous Gd-Fe material requires a critical anisotropy of approx. 1.2 x 10 erg / cm to promote domains therein, which is expressed by the stability state K V 2TfM.

This critical anisotropy occurs at a film thickness of 0.2 microns.

For the deposition of amorphous magnetic materials, the substrate temperature is kept relatively low. These films can be deposited at room temperature or lower temperature and are usually deposited at a temperature lower than the temperature that would cause a crystallization of the materials. For example, for amorphous Gd-Co materials, an upper limit of the substrate temperature of approx. 300 ° C, i.e. crystallization temperature.

FIG. 8 shows a curve for the logarithmic scale deposition rate as a function of the substrate temperature for Gd-Co alloys and Gd-Fe alloys. This curve shows that amorphous magnetic films can be produced over a wide range of substrate temperatures depending on the rate of deposition. In general, the substrate temperature, regardless of the rate of deposition used, must be less than the temperature at which crystallization occurs, in order to produce amorphous magnetic materials in accordance with the invention.

Exposed anisotropy can also be used to provide the available magnetic materials. This type of anisotropy can be used with the other methods, such as pairing, etc., to obtain anisotropy, or it can be used alone. For impact-generated anisotropy, the substrate is selected in connection with the magnetostriction of the deposited film so as to provide anisotropy in the amorphous film. More specifically, if the film is deposited at a temperature deviating from room temperature, and the film and the substrate have different coefficients of thermal expansion, they are subject to a certain influence at room temperature.

22 144153

As previously mentioned, many different substrates can be considered. Since there are no restrictions on crystallographic adaptation in the production of amorphous films, the substrate can be chosen completely freely. These substrates can consist of any known materials, such as metals and insulators, as well as semiconductors. Non-rigid substrates can also be used, e.g. plastic materials.

Films with in-plane anisotropy can be changed to films with perpendicular anisotropy by curing. For example, a curing of Gd-Co films at approx. 300-400 ° C a change from an in-plane anisotropy to a right-angled anisotropy. With increasing thickness, there is, of course, an increase in the probability of perpendicular anisotropy. Thus, for example, Gd-Co films with a thickness of at least 2000 Å usually have perpendicular anisotropy.

The amorphous magnetic materials according to the invention can be used for many different applications, e.g. in bubble domain monitors, beam addressable archives, light modulators, permanent magnets and recording media on tapes and plates. Each of these uses is discussed below along with associated parameters of interest.

Bubble domain device

In the case of magnetic bubble domain devices, it is important that the size 4TTm is small and that the material has a uniaxial, perpendicular s 3 anisotropy. Furthermore, the quality factor or the goodness number Q = Η / 4ΤΓμ should be greater than 1, where H & is the uniaxial anisotropy magnetic field and Mg is the saturation magnetization of the material. Furthermore, the coercive force Hc of the material must be small in order to facilitate the movement, nucleation and collapse of the bubble domains within the amorphous magnetic material. Since the goodness number Q should be greater than 1 to provide stable bubble domains, low magnetization arrangements are generally used, as it is difficult to provide very large induced anisotropy fields Η. In ferromagnetic arrangements it is possible to reduce the magnetization Mg by dilution with a non-magnetic element, but since the magnetic curie temperature follows the magnetization, only small 4 ^ Ms values can be obtained in alloys with working temperatures close to the curie temperature. .

23 146153

Low magnetic moments with high system temperatures, so that the amorphous materials become suitable for devices working at room temperature, are obtained in a ferrimagnetic arrangement containing two or more types of magnet atoms with opposite spins. This type of scheme is achieved in amorphous alloys of rare earths, primarily metals, at state transitions. Amorphous alloys of rare earths can be provided, e.g. Gd Co, with suitable x y composition, at which the atomic moments in the rare earth and metal element almost cancel each other out, leading to a material with suitably small 4'lj'M value. A suitable example are Gd-Co alloys with 70-90% Co and amorphous Gd-Fe alloys with 70-90% Fe. In the thin film form, the anisotropy is produced either by influence, pairing or formanisotropy.

As previously mentioned, small coercive force Hc is usually required for bubble domain materials. Accordingly, the bubble domain boundary width £ should be such that on average the same mean potential occurs throughout the amorphous material. The size 6 should be approximately equal to or slightly larger than the type of atomic arrangement that occurs in the amorphous material. If local fluctuations, such as phase separations, grain sizes, etc., in the amorphous material are less than the boundary width S, their effect on the domain boundary movement is negligible. Furthermore, microcrystals of the order of 25-100Å are not necessarily harmful to the domain movement. Until the grain size of the amorphous material reaches the limit width S, the coercive force Hc is small.

The domain boundary width <f follows the curie temperature, as the exchange constant A follows Tc (Scf ^ A). Consequently, if large domain boundaries are desired, it is necessary to provide large exchange constants. However, the limit width $ should not be too large as the anisotropy increases, which has an adverse effect on mobility. In the case of amorphous bubble domain materials, it is usually desirable to provide a low cut-off energy cf, which means that materials with w low curie points Tc should be used. As pointed out earlier, amorphous magnetic materials can be easily alloyed to alter T. The limitations regarding the curie temperature Tc for amorphous bubble domain materials are essentially the same as for crystalline bubble domain materials. However, it is simpler to control the curie temperature Tc in an amorphous magnetic material than in a crystalline material.

The substrate selection is free when using amorphous magnetic bubble domain materials. Suitable substrates include semiconductors, insulators and metals, e.g. NaCl, glass materials,

SiO2, Si, Ge, GaAs, and Α1203 · A particularly suitable amorphous magnetic film consists of GdCo2, which is electrode atomized on a NaCl substrate.

This electrode atomization has been performed from an arc forming measure of Gd-Co 2, where the substrate was water cooled to approx. 20 ° C and had a gallium coating to ensure thermal contact with the cooling block. Serpentine domains were observed by electron microscopy in a film with a thickness of approx. 750Å. The presence of ferrimagnetic scheme was confirmed by heating the sample to the compensation point to interfere with the Gd scheme at which point in-plane domains were observed. Perpendicular domains were restored by cooling to room temperature. The electron diffraction pattern was typical of an amorphous material. These right-angled magnetic serpentine domains could be observed in the free-standing film removed from the NaCl substrate, indicating that the anisotropy was not impact generated but was probably of the pairing type.

Film with a thickness of approx. 1 micron was deposited at a separate course, but under the same manufacturing conditions, on a support of NaCl, SiO 2 and Al 2 O 3 · These films also showed serpentine domains when observed by Bitter patterns and by the Kerr effect. A perpendicular magnetic field of a few hundred earlobes was sufficient to cause the serpentine domains to collapse into round domains. By moving the outer magnetic field, it is possible to move the domains in the amorphous magnetic film. This domain pattern is similar to that observed in accurately made garnet films, suggesting that the amorphous material lacks local inhomogeneities sufficient to cause local retention of the domains. Of course, this is an advantage for amorphous materials where no crystal structure defects occur. Magnetic bubble domains and their motion are not limited by this type of error.

FIG. 9 shows a magnetic bubble domain apparatus in which an amorphous magnetic material 10 is used as the medium promoting magnetic bubble domains therein. FIG. 10 is a diagram of a portion of the circuit of the decoders of FIG. 9. The device shown in FIG. 9 and 10 are merely intended to illustrate a bubble domain arrangement, in which the present amorphous magnetic material may be utilized, and the apparatus itself is therefore not described in detail. In the following, a brief explanation of this bubble domain apparatus is given, in which an amorphous material is used as the magnetic medium 10.

In FIG. 9 shows a block diagram of a storage device in which cylindrical, magnetic domains or bubble domains are utilized, which device causes writing, storage, decoding, emptying and sensing. The amorphous magnetic sheet 10 consists of one of the above compositions. A suitable example is an amorphous Gd-Co alloy or an amorphous Gd-Fe alloy. The properties of the amorphous film required for use in a bubbledo detector have already been discussed. The sheet 10 has a bias field H_ perpendicular to its plane to preserve the diameter of the cylindrical magnetic domains in the magnetic sheet 10. The bias field Hz is provided by a bias field source 12, which may consist of an outer coil. If desired, the bias field can be provided by a permanent magnetic layer or by another magnetic sheet which is exchange coupled to the magnetic sheet 10.

When domains are to be moved by means of attractive magnetic poles formed by soft magnetic means located near the magnetic sheet 10, a propagation field H is provided by a propagation field source 14. The propagation field H is a reorientation magnetic field in the plane of the magnetic sheet 10. which field produces attractive and repulsive magnetic poles along the soft magnetic means located near the magnetic sheet 10. The propagation field source 14 consists of outer coils arranged around the magnetic sheet 10 and which are alternately provided with pulses to provide a magnetic field in an arbitrary, desired direction. In FIG. 9, the propagation field H is a rotating magnetic field which can be directed in any of the directions 1, 2, 3 and 4.

Although the bubble domain conditions are described specifically with reference to a propagating agent which includes soft magnetic means, it is to be understood that other propagating agents may just as well be used, e.g. wire loops. The bias field source 12 and the propagation field source 14 are activated by a field control circuit 16 which supplies current to the sources 12 and 14 for providing the bias field Hz and the propagation field H.

26 144153

N

The domains move in closed lanes in each of the 2 shift registers. The domains are representative of binary information, with the presence of a domain indicating a binary 1 value, while the absence of a domain indicates a binary O value. To

N

each shift register 1, 2, ...., 2 there is a domain generator 18-1, 18-2, ... 18-2N. These generators enter information in the shift registers in accordance with input signals provided by

d N

veres from write impulse sources 20 on lines W1, W2, ... W2.

If desired, a write decoder can be used together with the domain generators 18-1 etc. for the purpose of entering information in selected shift registers.

The shift registers include a read decoder 22. The read decoder receives 2N input signals output from a decoder pulse source 24. Depending on the input signals output to the read decoder 22, any or all of the 211 shift registers may be selected for information reading.

After selection by the reader decoder 22, the information in the selected register passes through an emptying means 26 activated by a source 28. The source 28, the decoder pulse source 24 and the write pulse sources 20 are selectively controlled by a control circuit 30 which outputs input signals to each of these sources. to activate them at a correct time. The emptying means 26 sends the domains in the selected shift register to one of two lanes depending on whether the information is to be read out destructively or non-destructively. If destructive readout is to be used, the domains in the selected register are fed directly to the detector 32, which may be a magnetoresistive sensing element, an inductive loop, a magneto-optical sensing means or any other detecting means. The detector includes a domain interfering means which causes the domains to collapse. The output signal from the detector 32 proceeds to an utilization means 34, which may be constituted by any external circuit which utilizes the binary information contained in the selected shift register.

If a non-destructive readout is to occur, the emptying means 26 will carry the domains from a selected register to a domain splitter 36-1, 36-2, .... 36-2 ^. The splitting means divides the input domains into two parts, one of which is fed to the detector 32 for destructive readout, while the other is returned to the selected shift register for continued circulation in this shift register loop. FIG. 9 shows, for convenience 27 UA153, the shift registers, the read / write decoder 22 and the emptying means 26 as separate components, but it is understood that the decoder, which has an emptying means, is integrated in the shift registers. Accordingly, lines 46 and 44 represent the shift register loops 1, 2, ...

2, cut by the decoder 22, which includes the emptying means 26.

The block diagram in FIG. 9 shows a complete storage arrangement of the cylinder domain type, where the information selectively N

entered in 2 probate registers for storage purposes. The information content of the shift registers can be selectively addressed by means of input signals to the read decoder 22. Depending on the activation of the emptying means 26, domains in selected registers are read out destructively or non-destructively. If destructive readout of the emptying agent is indicated, the domains in the selected register are destructively read out by a detector 32. Upon destructive readout, a control circuit 30 activates write write pulse.

Vf source 20, which in turn activates domain generators 18-1, 18-2, ..., 18-2 belonging to the register which is being destructively read out. Thus, new information is entered in the destructively read shift register.

If the emptying means indicates that the information is to be read out non-destructively from the selected probate register, the domains from this probate register are transferred to a domain splitting body, where they are divided into two new domains. One of the new domains is fed to the detector 32 for destructive readout, while the other is returned to the selected shift register for continued circulation in this shift register.

The selection of one or all of the shift registers for destructive or non-destructive readout is possible in accordance with the binary input signals which are fed to the read decoder. In FIG. 10, a part of a shift register SR14 is shown to illustrate the decoding and emptying functions. The magnetic sheet is not shown.

Domains, e.g. 53, moves to the right in the direction of the arrow 46 in this shift register S14. It is understood that the majority of this shift register loop is not shown and that the loop extends further to the left to be able to include the decoding loops D1-D2 ', see fig. 9, and to provide sufficient storage space. In accordance with well known principles, the rotation of the propagation field produces attractive poles in T-shaped and Ι-shaped per-malloy means 54 for moving the domains in the direction 144153 28 of the arrow 46. On the magnetic sheet 10 and above the selected permalloy means 54, conductors are deposited, which is utilized for the decoder loops D3, D3 ', D4 and D4'. Furthermore, on the magnetic sheet 10 and on suitable permalloy means 54, the emptying loop SL is deposited, which loop is also constituted by a conductor loop, e.g. of copper. It can be seen that the decoding loops D3 and 041 have wider portions within the areas where they intersect the T-shaped members in the path 46, while the decoding loops Ds' and D4 do not have wider portions where they pass the T-members in path 46. This causes currents in the decoder loops D3 'and D4 not to affect the passage of the domains along path 46.

Also deposited on the magnetic sheet 10 is a parmalloy domain splitting means 36-14, which in this case includes an upper permalloy layer and a lower permalloy layer, which are shown in dotted lines.

When using binary input signals 10100110 to the decoder inputs D1, D1 '..., D4' for selective reading of this shift register, no current occurs in the decoder loops Dj3 and D4 *. As previously mentioned, currents in the decoder loops D3 * and D4 do not affect the function of the shift register 14. Accordingly, the domains 53 are propagated in the direction of the arrow 46 to pole position 2 of the T-member 56. Thereafter, the domain 53 will either follow the path indicated by the arrow 38 or the path represented by the arrow 40. If the drain loop CL is activated by a current pulse , no attractive magnetic pole will be generated at pole position 3 'of the member 56. Domains located at pole position 2 of the member 56 will therefore be attracted upward to pole position 4 of the member 56 when the propagation field H has the direction 4. Thereafter, the domains move to pole position 1 "on the T-member 58 when the propagation field H has the direction 1. The movement in the direction of the arrow 38 continues as H is rotated, leading the domains to the detector 32 for destructive readout.

The detector 32 is shown in the form of a magnetoresistive detector adjacent to a means 60. The magnetoresistive sensing detector 32 consists of a magnetoresistive sensing means 62 and a constant current source 64. The magnetizing vector of the sensing means 62 is rotated when a leakage magnetic field of a domain 53 cooperates therewith.

This causes a change in resistance in the sensing element 62, which is expressed in a voltage signal v. The means 60 includes an elongate permalloy pattern 66 to which domains 53 move after sensing as H rotates to the direction 4, whereby the domains 53 move to pole position 4 on the means 66. As H rotates, the domains 53 move to the corner of the means 66 and is trapped here, even when H rotates to the directions 2 and 3, the pole position 3 being far away from the corner of the member 66. When H is in position 3, the located field at the corner becomes repulsive and the domains collapse.

If no current pulse occurs in the drain loop CL when the domains 53 are at the pole position 2 of the element 56, these domains will move along the path indicated by the arrow 40 when the propagation field H rotates. The domains are thus passed to the domain splitter 36-14. As previously mentioned, this cleavage means includes an upper permalloyl layer shown by the solid T and I members and a lower permalloyl layer indicated by punctured means. Under the influence of the rotating propagation field H, the domains 53 entering the splitting means 36-14 are divided into two parts. One part moves towards the detector 32 via the lower layer and follows attractive poles a-b-c in the direction of the arrow 42. Thereafter, these domains follow the path 38 to the detector.

The second part of the split domains is fed to successive pole positions a'-b'-c 'on the member 68 when the propagation field H rotates. These domains follow the path indicated by arrows 44 for recirculation to the shift register 14.

Accordingly, this bubble domain apparatus provides storage functions and logic functions on a single sheet of amorphous magnetic material. The various components that can be used in prior art bubble domain materials can also be used in the present case. In the present case, the amorphous magnetic materials are easy to manufacture on any type of substrate and can be formed with selected thicknesses and side dimensions.

Although permalloy patterns are shown for propagation of the domains, it is understood that wire loop femoral patterns or wedge patterns may also be used. Furthermore, the writing and sensing means can be varied without this falling outside the scope of the invention.

30 1U153

Light modulation

Since the amorphous magnetic materials of the invention promote magnetic domains, it is possible to provide a light modulator which modulates the intensity of an input light beam. In the present case, it is desirable to provide a high magnetic moment a small coercive force Hc, a high curie temperature Tc as well as an anisotropy field Ha, which should be larger than the magnetic moment 4 M. This can be conveniently fulfilled in such amorphous materials. such as Y-Co, La-Co, Ce-Co, Nd-Co, and Pr-Co.

Since the magnetization of magnetic domains in sheets of amorphous magnetic material is either parallel to or antiparallel to the direction of the input light beam, the light beam will be affected differently depending on the direction of magnetization in the area of the magnetic sheet struck by the beam. With input polarized light, the rotation of the polarization becomes different depending on the direction of magnetization of these domains, and the intensity of the light beam passing through the amorphous magnetic material can therefore be changed by varying the direction of magnetization of the domains.

Pig. 11 shows a light modulator in which a laser 70 produces a light beam which passes through a polarizing means 72 before it hits the amorphous magnetic material 74. In the vicinity of the film 74 there is a domain propagating means which is designated as a whole by 76. In this case the propagating means 76 includes T- and I-shaped means which provide attractive magnetic poles for moving a domain 78 in the sheet 74 in accordance with the orientation of the propagating field H generated by the propagating source 80. After passing through the amorphous sheet 74, the light beam strikes an analyzer. 82 before being detected by a photocell 84.

Depending on the presence or absence of a domain 78 at the location where the light beam hits the amorphous sheet 74, the polarization of the light beam will be rotated differently. At a certain rotation of the polarization, the light beam will be able to pass through the analyzer 82 and strike the photocell 84, causing a current through a resistor R. Otherwise, the rotation of the light beam polarization is of such a nature that the beam does not pass through the analyzer 82, and consequently no voltage across the resistor R is detected. Thus, a light modulator is provided by means of a suitable sheet of amorphous magnetic material containing domains.

In connection with FIG. 11, it is noted that the light can be caused to be reflected from the amorphous sheet 74 instead of propagating through it. In both cases the effect is the same, namely that the polarization of light is affected differently depending on the direction of magnetization of the domains at the point where the light beam is incident.

Permanent magnet

The amorphous magnetic material according to the invention can be used as permanent magnets. In this case, it is desirable that the magnets have high coercive force Hc, high magnetic moment M and high curie temperature T. Suitable compositions are S o Y-Co which are doped with oxygen, nitrogen or carbon.

A particularly suitable embodiment of a permanent magnetic layer to which an amorphous material is used is a bias field associated with a magnetic sheet in which bubble domains occur. The magnetic sheet promoting the bubble domains may be a crystalline magnetic sheet or an amorphous magnetic sheet in accordance with the invention. In contrast to crystalline, permanent magnetic materials, which depend on the crystal properties to obtain large bias fields, the present amorphous, permanent magnets are easy to manufacture with selected properties in accordance with the above.

FIG. 12 shows the use of an amorphous, permanent magnetic layer 86 used to provide biasing of a magnetic bubble domain sheet 88. A propagation field source 90 and control / logic circuit 92 are provided which are adapted to influence the domains of the bubble domain material 88. This material can be made of a known material with a garnet structure, e.g.

(Eu, Y) 3 (Ga, Fe) 5012, or an amorphous material according to the invention. In the manufacture of the device shown in FIG. 12, it is not critical that the crystal properties be preserved, since the amorphous material does not follow the rules applicable to the preparation of crystalline compositions.

U4153 32

The general structure, which includes an amorphous magnetic layer on a substrate of any type, is also shown in FIG. 12.

In this general case, the structure can find any application, and the layer 86 is an amorphous magnetic layer in accordance with the invention. Layer 88 has an arbitrarily suitable substrate, e.g. a semiconductor, an insulator or a metal. Furthermore, the substrate may be flexible or rigid, and means may be provided for moving the combination of the amorphous magnetic film and the substrate.

Regis treringsunderan1æg

It is possible to deposit the present amorphous magnetic materials as a recording material on a substrate, e.g. a semiconductor, an insulator, or a metal. The substrate can be made of tape or sheets. Furthermore, this amorphous magnetic material can be produced as magnetic particles in a binder, e.g. a conventional resin-type binder, for use on any substrate.

FIG. 13 shows a tape or plate shaped recording medium 94 containing an amorphous magnetic film according to the invention over which a read / write head 96 is placed. The converter 96 is used for writing information into magnetic domains of the tape or plate 94 and for reading. of the information stored therein in a known manner. To this end, the electrical signals read from the recording medium 94 are sent to the sense amplifier 98 and then to the utilizing circuit 100, which may be any circuit used in conventional computer technology.

The use of an amorphous film in accordance with FIG. 13 has many benefits. The plate or strip substrates can be either flexible or rigid. This enables the use in all types of information processing facilities. Furthermore, the amorphous material is easy to deposit on any type of substrate in a uniform manner so that uniform magnetic properties are obtained everywhere.

Examples

Amorphous magnetic materials with uniaxial anisotropy have been produced by using electrode atomization at direct current and high frequency, as well as by electron beam evaporation.

In general, films have been produced which exhibit amorphous properties, determined i.a. by the electron beam diffraction technique.

Magnetic anisotropies are provided which were located parallel to the plane of the film and perpendicular to the film plane.

I. Electron Beam Evaporated Films

In this film-making process, a polycrystalline target is first provided using conventional techniques. For example, small pieces of constituents to be used in the target are melted in an inert gas atmosphere, e.g. argon can be used. The smelting takes place on a water-cooled copper arc in a commercially available standard arc furnace. The temperature is raised to the melting point of the ingredients to provide an arc-melted block. In general, this is a polycrystalline target. In the laboratory, a sample of a measure of the arc melt GdCo2 has been prepared.

Then the target is placed in an ultra-high vacuum evaporator -9 with a basic pressure of approx. 10 torr. The block is placed on a water-cooled copper bed and heated by means of an electron beam from an electron gun in the evaporator. Acceleration voltages of approx. 10 kV together with radiant currents of approx. 100 milliamp.

The substrates used for depositing these films have been randomly selected, and glass, polished, hardened quartz, rock salt and sapphire substrates have been advantageously used. The substrate is cooled with liquid nitrogen and has a temperature of approx. 100 ° K during evaporation. The sales rate was generally approx. 30Å pr. second.

In one case, films with thicknesses of 400Å and 4000Å have been produced. These films consisted of Gd-Co alloys that were found to be amorphous by electron beam diffraction. The atoms in the depositional materials that hit the substrate approached at an angulation angle, i.e. any angle other than 90 ° with respect to the substrate plane, in order to provide uniaxial anisotropy in accordance with the foregoing. Perpendicular domains were observed in this film.

At another film deposition, the substrate temperature was 273 ° K. The same substrate was used, and in addition a BaTi03 substrate and a substrate of cleaved quartz. The target composition, 34 U4153

GdCo 2 was the sairane used for the above-mentioned films having thicknesses of 400 Å and 4000 Å. Only the substrate temperature was changed by this composition. In the present case, the film had crystals located in a generally amorphous matrix, indicating that the substrate temperature is critical in an electron beam deposition process. In order to provide substantially amorphous films, the substrate temperature must be reduced from 273 ° K.

At another electron beam deposition, the target composition was GdCo 2, and the substrate was cooled with liquid nitrogen.

The film produced was amorphous with a uniaxial magnetization in the plane of the film. It seemed as if the magnetization Ms of this composition was too large, so that the ratio Η3 / 4ΤΓμξ was not exactly correct to promote domains with perpendicular magnetization.

II. Electrode atomized films

Many amorphous films have been produced by direct current and high frequency electrode sputtering with varying values of the sputtering parameters. These films exhibited perpendicular magnetic anisotropy and parallel magnetic anisotropy, and they were uniaxial.

Many different values of the magnetization and other magnetic parameters are obtained in accordance with the principles outlined above.

Claims (12)

35 UA 153 Patent claims. Magnetic bubble domain apparatus comprising a magnetic medium in which said domains occur, means for controlling the magnetization state of said magnetic medium and means for detecting the magnetization state of said magnetic medium, characterized in that the magnetic medium is an amorphous material without far-reaching atomic arrangement. with far-reaching magnetic arrangement in the form of uniaxial magnetic anisotropy. Apparatus according to claim 1, characterized in that the amorphous magnetic material appears in microcrystalline structure with localized atomic arrangement within areas with an extent of approx. 100Å and less. Apparatus according to claim 2, characterized in that the amorphous material has localized atomic arrangement within areas with an extent of approx. 25Å and less. Apparatus according to claim 1, characterized in that the uniaxial direction of anisotropy forms a substantially right angle with the plane of the amorphous magnetic material. Apparatus according to claim 1, characterized in that the amorphous magnetic material consists of a single element with a net magnetic moment. Apparatus according to claim 5, characterized in that the element belongs to one of the 4f, 5f or 3d element series in the periodic table. Apparatus according to claim 1, characterized in that the amorphous magnetic medium contains a plurality of elements, at least one of which has an unpaired magnetic spin. Apparatus according to claim 7, characterized in that the amorphous medium is constituted by an amorphous alloy of a rare earth and a metal with state transition. Apparatus according to claim 8, characterized in that said alloy is a Gd-Co alloy. Apparatus according to claim 8, characterized in that said alloy is a Gd-Fe alloy. Apparatus according to claim 7, characterized in that the amorphous magnetic medium contains an additive which is coupled antiferromagnetically to a magnetic atom in said amorphous medium. Apparatus according to claim 7, characterized in that