FI57673B - MAGNETIC DOMAINING - Google Patents

Description

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Patent · och regictentyrelsen Anteion utisgdoch utUkriftm pubiictnd 30.05.80 "(32) (33) (31) hT * · *** ttuolkuui —Btglrd priority 29.08.72 USA (US) 28 ^ 513 Toteennäytetty-Styrkt" (71) International Business Machines Corporation, Armonk, NY 1050U, USA (72) Praveen Chaudhari, Briarcliff Manor, New York, Jerome John Cuomo, Bronx,

New York, Richard Joseph Gambino, Yorktown Heights, New York, USA (USM) 7M Oy Kolster Ah (5M Magnetic Domain Device - Magnetic domananordning

The present invention relates to an apparatus using mainly amorphous magnetic compositions having uniaxial magnetic anisotropy.

Amorphous substances are known in the art and can generally be classified as either metals or non-metals. The metals are described either according to the Bemal model (where dense arbitrary packing (prevhning) occurs) or according to microcrystalline models. Amorphous substances include Ρά-Si and

0 Mn alloys.

Non-metallic amorphous substances are generally covalently bonded and "ovonic" substances (which are built on the Ovshinsky effect) are an example of such a substance. Non-metallic amorphous materials include, for example, SiO 2, Si, Ge and Ce-Te alloys.

Non-metallic amorphous materials have been used for a variety of applications, including beam addressing information storage, as disclosed in U.S. Patent 3,530,441. However, this prior art technique does not use an amorphous magnetic material with uniaxial anisotropy for applications such as magneto-optical devices and bubble domain systems. bubble-range systems). The use of amorphous magnetic materials as a permanent magnet material is also not known in the art. Such agents would be valuable in many applications in this area. For example, an amorphous substance can be placed on any type of substrate and does not need to be compatible with the substrate with respect to the lattice. Furthermore, the inherent substrate effects are not detrimental to the properties of the later placed amorphous material.

Other advantages of an amorphous substance include the fact that the composition can be adjusted to optimize the properties without the limitations caused by the stoichiometry of the compound. This means that the »restrictions» arising from the phase diagrams of the substances »which must be combined» are not actual when preparing amorphous substances. Furthermore, amorphous materials can be prepared at low temperatures and by simple techniques such as evaporation, electrode evaporation, etc.

With regard to magnetic amorphous substances in particular, there are no structural defects in the amorphous substances that could hinder the transfer of magnetic domains (regions, islets) and the formation of the heart in the substance. Furthermore, these materials may have compositions that vary over large ranges to improve selected magnetic properties. The addition of interfering substances to the composition does not adversely affect the structural or magnetic properties of the layer and can be used to achieve greater flexibility in forming the compositions.

Amorphous films (films) containing a multicomponent system have been discussed in the literature. Thus, for example, Savatzky et al., In Journal of Applied Physics, 42, January 1, 1971, page 367, describe films of the type which are amorphous in electrode evaporation and subsequently crystalline after the curing process. In another article in the journal Science Research, Vol. 4 »1969, describes on page 493 by E. Giess et al. Gadolinium iron garnet films with a crystal size between 30 and 50 Å. A ferromagnetic amorphous film consisting of an Fe-C-P alloy is described by Duwez et al. In the Journal of Applied Physics, 38-10 September 1967, page 4096. The amorphous films described in the above publications do not have uniaxial magnetic anisotropy.

Amorphous magnetic films of compositions Fe Gd are described by J. Orehotsky x y in Journal of Applied Physics, 43, May 5, 1972, page 2413 * For the purpose of explaining non-saturation in these films, the author suggests the occurrence of perpendicular anisotropy, which is an isotropic stress at the film level.

In connection with the present invention, it has been found that uniaxial 3,5773 anisotropy can be exhibited in amorphous magnetic films and that anisotropy can be achieved independently of substrate limitations. This means that uniaxial anisotropy can be achieved by pairwise or shape-induced anisotropy. The actual amorphous compositions may consist of a single element or of several elements.

The use of these amorphous compositions in device applications eliminates many of the disadvantages of the prior art where a crystalline magnetic material had to be used.

It is therefore an object of the present invention to provide magnetic devices using predominantly amorphous magnetic compositions.

Another object of the invention is to provide devices in systems using mainly amorphous magnetic compositions, the properties of which can vary over a wide range. It is a further object of the invention to provide a magnetic bubble domain system using an amorphous magnetic material to carry magnetic bubble domains (regions).

Yet another object is to provide a magnetic bubble domain arrangement in which domains can be easily transferred regardless of structural defects or impurities in the material carrying the bubble domains.

It is an object of the invention to provide magneto-optical systems using an amorphous magnetic substance for modulating light rays.

Another object of the invention is to provide magnetic domains using devices that can be manufactured easily and at reduced cost.

Amorphous magnetic compositions are prepared in either pulp or thin film form. Furthermore, amorphous magnetic particles can be prepared for use in a binder on either strips or sheets. These compositions are formed from a single element or multicomponent system in which at least one component has an "odd spin". Thus, the compositions have a magnetic moment and are a magnetically ordered substance.

These amorphous substances have non-magnetic crystalline uniaxial magnetic anisotropy, which may be parallel or perpendicular to the plane of the films made from these compositions. Anisotropy occurs in one or a combination of the following ways: pairing, shape anisotropy, or exercise-induced anisotropy.

These amorphous compositions are in the microcrystalline range, where the atomic order, if any, exists in the order of 25 to 100 1. In addition, according to the invention, amorphous substances with a structure smaller than 25 A, regardless of the atomic order present, are present.

Binary and ternary compositions are particularly suitable for the practice of the present invention. This includes both compounds and alloys, and a suitable example is the state transitions in rare earth metal compositions. For example, Gd-Co alloys or Gd-Fe alloys are quite useful.

The magnetic properties of these substantially amorphous compositions can be altered during manufacture by altering the manufacturing process or the interrelationships of the ingredients in the composition. Furthermore, the magnetic properties of the compositions can be altered after manufacture and the films can be easily "doped" without adversely affecting the magnetic properties. For example, amorphous compositions of rare earth cobalt and rare earth iron can be easily doped with oxygen, nitrogen, carbon, etc. to intentionally affect the magnetic properties.

These magnetic compositions can be used in a variety of embodiments. For example, if the anisotropy forms a right angle with the layer plane, the films can be used in magneto-optical systems and magnetic bubble domain systems. It is to be understood that the present substantially amorphous magnetic films provide space for magnetic domains and then, in particular, magnetic bubble domains. Furthermore, these magnetic bubble domains can be transferred in the magnetic film in a manner identical to those known in the domain transfer technique-8a. Due to the fact that amorphous films do not have to be prepared on a precisely lattice-matched substrate and that defects and impurities in the film do not damage the domain transfer, the great advantages of a substantially amorphous bubble domain material are quite obvious. In addition, since the magnetic properties of these amorphous films can be altered, they can be used as a permanent magnetic bias voltage layer in connection with a magnetic bubble domain material of a previously known type, as well as in connection with an amorphous bubble domain material of the present invention.

Due to the fact that the present amorphous materials can be prepared as magnetic particles in a suitable binder, immediate use in tape or sheet applications may be required. Furthermore, amorphous films can be placed on a metallic or non-metallic substrate, including flexible substrates. Therefore, they can be used as storage media in any type of data processing systems.

The present amorphous substances can be used as light modulators in which the intensity of light passing through the amorphous film is affected by the presence or absence of a domain at the site where the light spot hits. The polarization of the polarized input light reverses according to the state of the amorphous substance at the point where the light beam strikes. The analyzer is used to detect whether or not the amorphous film has a magnetic domain at the light spot. By selectively producing a magnetic domain in the region of the point of impact of a polarized incident light beam in an amorphous film, the intensity of the beam received by the detector as it passes through the amorphous film can be varied, thus providing a light modulator.

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

By changing the properties of the actual amorphous material, permanent magnetic granules can be obtained. These are useful as a prestressing layer in magnetic bubble dane systems as well as in areas where a permanent magnet material is required.

It has further been found that the amorphous compositions of the present invention can be used in beam-addressed amorphous compositions. Further features of the invention are given in the appended claims.

The foregoing and other objects, features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, taken in conjunction with the accompanying drawings.

Fig. 1A is an electron beam micrograph of a diffraction pattern of the amorphous magnetic composition of the present invention, while Fig. 1B is an electron beam pattern of a diffraction pattern of the same substance after the substance has been cured to intentionally crystallize it.

Figures 2A and 2B are photographs of the magnetic domains in the amorphous material of Figure 1A illustrating the motion of the magnetic domains when the magnetic field acts on the amorphous material.

Figure 3A is a graph of magnetization as a function of cobalt concentration

O

in an amorphous Gd-Co alloy.

Figure 3B is another plot of magnetization as a function of composition

B

in an amorphous Gd-Co alloy used to indicate the change in magnetization that occurs when dopants are added to an amorphous substance.

jr

Figure 4A is a plot of inverse specific length u as a function of * r (h cobalt concentration in an amorphous Gd-Co alloy.

Figure 4B is a plot of length L as a function of the thickness of the amorphous film of the present invention.

Figure 5 is a graph of domain boundary energy (4'Γδω) as a function of electrode vaporization bias voltage applied to a substrate when placing an amorphous magnetic alloy of the present invention.

Figure 6 is a graph of deposition rate as a function of large new energy in electrode vaporization of amorphous magnetic alloys, illustrating the effect of a magnetic field of about 50 örsteds during the deposition process.

Figure 7 is a graph of the anisotropy of the amorphous uniaxial magnetic layer as a function of the thickness of the magnetic layer.

Figure 8 is a plot of deposition rate (on a logarithmic scale) as a function of the inverse of the substrate temperature, illustrating the amorphous / crystalline change that occurs under certain deposition conditions.

Figure 9 is a view of a magnetic bubble domain system using an amorphous magnetic material as a bubble domain material.

Figure 10 is a detailed view of a portion of the circuit schematically shown in Figure 9. _

Figure 11 illustrates a magneto-optical light modulator in which the present amorphous magnetic material has been used as a light modulating agent.

Fig. 12 is a description of a magnetic bubble domain material with layers arranged therein as an amorphous magnetic material which acts as a bias layer for magnetic domains in the bubble domain material.

Figure 13 is a description of a tape or disk information processing system using amorphous magnetic materials of the present invention as a recording agent.

Substantially amorphous magnetic compositions with uniaxial anisotropy have been prepared and are useful in many magnetic applications. These compositions may be prepared in pulp and thin film form or may be present as magnetic particles in a carrier binder. Since these are amorphous materials, the choice of substrate is irrelevant and factors such as lattice matching can be disregarded. This simplifies the deposition of the composition on any type of substrate and greatly increases the manufacturing yield that is achievable when using materials of the present species.

These magnetic compositions may consist of a single element or a combination of elements present in a multicomponent system. At least one component must have an odd electron spin so that the composition receives a magnetic moment. This means that it is a magnetically arranged material.

These amorphous magnetic materials have uniaxial anisotropy, which may be at right angles or parallel to the plane of the film containing these amorphous magnetic compositions. Anisotropy is due to a combination or combination of the following phenomena: 7 57673 A. Pairing order B. Form anisotropy C. Exercise-induced anisotropy.

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

The above three phenomena for producing uniaxial anisotropy in the substantially amorphous films of the invention are well known in the art and will not be described in detail herein. Suffice it to say that the pair order comprises a combination of two atoms whose magnetization is paired to form a magnetic dipole. The magnetic pairs are oriented in certain directions, generating the uniaxial anisotropy required for use in magnetic devices.

Form anisotropy arises due to the geometric shape of the magnetic regions. For example, with an ordered condensation of atoms in a region with a predominantly disorganized substance, there will be magnetization directed along the longitudinal axis of the atomic condensation, because this axis is primary in the orientation of the magnetic moment. Along the short axis, strong demagnetization fields occur in the region defined by atomic density.

Furthermore, variations in composition in the amorphous substance cause phase separations which cause this type of anisotropy. Phase difference means both the space in different composition regions located close to each other and the space in regions close to the same composition when the composition has different structural phases (i.e., one region is amorphous while the other is more crystalline). An example of a phase difference is an amorphous magnetic Gd-Co alloy, which may consist of localized regions that are Co-rich and other localized regions that are Gd-rich. If these two regions are located close to each other, the phase difference will cause uniaxial anisotropy.

Stress-induced anisotropy is due to differences in lattice parameters in the substrate and localized regions in the amorphous film, or it also depends on differences in thermal coefficients in the amorphous film and its substrate. This type of stress can also become an adjunct to uniaxial anisotropy in the substantially amorphous membranes of the present invention.

The amorphous magnetic compositions of the present invention have microcrystallinity and / or a substantially amorphous structure. Both of these structures differ from the polycrystalline and monocrystalline structures known in the art for magnetic compositions. For example, the amorphous substances of the present invention may have a localized β 57673 atomic sequence. However, if this atomic order occurs »it exists on journeys 25-100 i, if the substance is microcrystalline, or on journeys less than 25 if the substance is substantially amorphous * It is, of course, understood that a question of a purely amorphous substance.

The amorphous substances of the present invention consist of simple magnetic elements or a multicomponent system. Examples of the latter systems are binary and temporal alloys and compounds. Particularly suitable substances are compositions containing rare earth metals and transition metal elements. Here __ can be mentioned Gd-Co »Gd-Fe, Y-Co and La-Co. These compositions can be varied over a wide range without limitations due to the stoichiometry of the compound due to the phase diagram of the ingredients. Therefore, the magnetic properties of the materials can be specifically tailored to each particular embodiment. For example, the composition ranges can be selected so that the atomic moment in a rare earth metal and a metal element is almost reversed, resulting in a substance with low saturation magnetization, which is likely to be of particular value as a bubble domain substance.

These amorphous magnetic compositions have a progressive magnetic order and have uniaxial anisotropy. In their simplest form, they consist of elements »with a magnetic moment. Examples of this are the 4f series (rare earth elements) and the 5f series (actinide elements). Further included is an iron group of transition metals (3d series). In addition to this, there are elements »which have a magnetic moment when they are located in a special state, for example elements such as Mn, Cr, V and Pd.

For each amorphous composition consisting of a single element, it is true that any non-magnetic element can be added to the composition in relatively small amounts without disturbing the magnetic properties. This means that attenuation (dilution) with non-magnetic elements (e.g., 0, C, P, and N) can be performed without adversely affecting the magnetic properties. Therefore, it may be advantageous to add small amounts (usually about 2 atomic percent) of these non-magnetic elements to simplify the preparation of the amorphous film. Of course, if large amounts are added, the magnetic properties are affected. Thus, for example, amounts greater than about 50 atomic percent destroy the magnetic order.

Binary compositions containing at least one of the aforementioned elements can also be used in the amorphous magnetic materials of the present invention. Binary compositions are generally easier to work with because they retain their amorphous structure over higher temperature ranges than amorphous monoelemental materials. As in the case of a monoelemental material, small amounts of non-magnetic elements can be added to the composition.

Another change that can be made with binary amorphous compositions is the addition of a higher concentration (2-50 atomic percent) of non-magnetic element to vary the magnetic properties. For example, copper can be added to reduce the magnetic moment.

Ternary combinations of the aforementioned Jd, 4f and 5f elements can also be prepared to provide amorphous compositions with uniaxial magnetic anisotropy. As with binary compositions, higher concentrations of non-magnetic elements can be added to alter the magnetic properties of these binary compositions. Likewise, small amounts of non-magnetic material can be added to make it easier to form amorphous films without adversely affecting the magnetic properties. It will be appreciated that the amount of non-magnetic material added must be insufficient to lose the magnetic order in the amorphous film.

The amorphous materials of the present invention have a broad magnetic order and are either ferromagnetic, ferromagnetic or antiferromagnetic. Of course, the magnetic order that gives the uniaxial anisotropy present in these materials, in turn, makes the materials very useful for equipment applications.

The magnetic properties of these compositions can be altered during manufacture or after manufacture for application to specific embodiments. It has been found that the magnetic properties depend very much on the composition range for the ingredients and also on the deposition conditions that prevail during the preparation of the composition. However, the dependence of the magnetic properties on the deposition parameters is smaller than the dependence related to the composition ranges of the components. Processes such as curing and ion implantation can be used after the preparation of these amorphous compositions to modify the magnetic properties. Furthermore, these magnetic substances can be doped with interfering substances without adversely affecting the structural magnetic properties of the films. Therefore, the movement of magnetic domains in the films will not be affected, as is the case with conventional crystalline magnetic films. Examples of specific amorphous magnetic compositions suitable for a variety of applications are set forth below and tables of materials and their properties are provided at the end of the specification.

10 57673

Depending on the varying interaction that occurs in these materials, it is possible to provide insulators, conductors, and semiconductors that are substantially amorphous. In metals and semiconductors, the interaction can be either a direct consequence of the overlap of atomic orbits or indirectly dependent on conductor electrons. These are the mechanisms that make amorphous materials suitable for magnetic applications. However, the interaction mechanism in the insulators is critically dependent on the bond angle and distance. Since far-reaching magnetic order does not exist in amorphous materials, these interaction conditions cannot be satisfied and no magnetic order can be detected.

Figures 1A and 1B are electron beam images depicting amorphous and crystalline substances. The electron beam diffraction pattern in Figure 1A is characteristic of an amorphous substance, while the diffraction pattern in Figure 1B is characteristic of a crystalline substance. ~

More specifically, Figures IA and IB are made by electron diffraction from a Gd-Co alloy. The intact L line in Figures 1A and 1B is used to block the incoming electron beam to produce these photographs. The diffraction pattern in Figure 1A is characteristic of an amorphous substance.

Figure 1B is an electron diffraction pattern for the material of Figure 1A (Gd-Co) after it has been crystallized by heat transfer. In this case, the amorphous film of Figure 1A was left under an electron beam microscope and heated to about 300 ° C. The diffraction pattern in Fig. 1B is characteristic of this as a result of diffraction from a crystalline substance. Figures 1A and 1B are on the same scale.

These figures illustrate a substantially amorphous characteristic in films made in accordance with the present invention.

Figures 2A and 2B illustrate the presence of magnetic edge domains in the amorphous material of Figure 1A. In Figures 2A and 2B, the reference mark M is scratched on the film, this mark being used to determine the movement of the edge domains when the amorphous substance is exposed to the magnetic field. ___

In particular, in Figure 2A, the magnetic edge domains D are clearly visible with an amorphous magnetic substance. These edge domains have boundaries that are generally oriented in the vertical direction in this figure.

However, when the magnetic field is exposed to the plane of the amorphous substance, the slope of the edge domains D is caused. This becomes apparent when the position of the domains D relative to the reference label M is examined in these two figures. Thus, Figures 2A and 2B illustrate the presence of domains in an amorphous magnetic medium and the movement of these domains as a result of the acting magnetic field. As will become apparent later, the edge domains D can be made to decompose into round bubble domains.

11 57673

Amorphous films with a thickness of about 1 ψι were deposited on NaCl, SiO 2 and AlgO 2. These membranes had uniaxial anisotropy and also had edge domains. The rectangular magnetic field of a few hundred örsteds was sufficient to break down the edge domains into round bubble domains. Bubble domains were further transferred, the external magnetic field of the law was transferred. The domain model in the amorphous material resembled those of the domain models observed in carefully prepared garnet films. This means that the amorphous substance lacks local inhomogeneities that are sufficient to cause the domains to be held in place, which would limit their movement. Of course, this is an advantage in amorphous magnetic material, where crystal structure defects do not exist by definition. The formation and propagation of magnetic domains in such an amorphous material is not limited by errors of this class.

- 'Depending on the application for which the amorphous magnetic compositions are to be used, said magnetic properties are adjustable to achieve optimum performance. The control of the magnetic properties in these amorphous materials is readily accomplished by certain methods in the preparation of amorphous materials and by the processes used after the amorphous compositions have been prepared. Unlike previously known crystalline magnetic materials, the magnetic properties in amorphous films are generally easier to control than the corresponding properties in crystalline materials. One reason for this is that the compositional variations allowed in an amorphous substance are very much wider than the allowable variations in a crystalline substance because amorphous compositions are characterized by metastability rather than thermodynamic equilibrium. The various magnetic properties are discussed separately below to illustrate the flexibility provided by amorphous materials.

Saturation Magnetization Mg _ The magnetization Mg is easily changed in an amorphous magnetic substance by adding a magnetic atom normally coupled to a magnetic atom in the amorphous substance or to an atom of the amorphous substance magnetically in a certain state (e.g., Mh, Cr, etc.). To reduce the magnetization Mg, the substance added to the amorphous composition is coupled antiferromagnetically with a magnetic atom in the amorphous substance. To reduce the magnetization in the amorphous Gd-Co alloy, for example, the Gd / Co ratio is adjusted so that the magnetic moments of the substances are almost canceled.

To increase magnetization in the amorphous material, magnetic atoms are added to the composition, which atoms are ferromagnetically coupled to magnetic atoms in the amorphous composition. For example, the addition of Nd causes an increase in Gd-Co magnetization of the 12,576,73 amorphous composition. As another example, the addition of Co to the amorphous composition Y-Co increases the magnetization of the composition.

These additions are made during the manufacturing process and are implemented as follows; the mixture of elements is melted and cast into a disc-shaped plate which is used as a paint in electrode evaporation. The composition may be varied in the manufacture of the paint, or the composition of the film may also be varied during the vaporization process by adjusting the bias voltage in the substrate for the purpose of re-vaporizing some or more of the ingredients. Alternatively, a second paint of the additional element can be provided in the evaporation system so that one of the additional elements is introduced into the layered film.

When thin films are prepared by vacuum evaporation, the concentration of the addition in the evaporation source can be varied, or a supplement source of the additional element can also be provided. _

Figure 3A is a graph of magnetization at 4 »Mg at room temperature as a function of cobalt concentration in an amorphous Gd-Co alloy. This curve shows that the number of magnetic Co atoms in an amorphous alloy determines the magnetization of the alloy. Accordingly, the magnetization of the alloy is altered by the addition of substances to the amorphous alloy which changes the Gd / Co ratio and thus the degree to which the magnetic moments of the substances are canceled.

The composition range near the excitation minima is particularly suitable for materials with a low magnetic moment and a high Curie point. Due to the fact that the low excitation in compositions with close to 79 atomic percent cobalt is due to the erasure of Gd and Co moments rather than attenuation effects, the Curie point, which is largely determined by the Gd-Co interaction, is not affected. Thus, the excitation of the substance at room temperature can be changed by keeping T within the specified limits.

c

Another way to change the magnetization in an amorphous alloy is to add small amounts of N2 when the amorphous alloy is electrode vaporized. When, for example, GdCo ,. electrode vaporization in argon significantly reduces the size of the edge domains in the substance in small amounts of N2 (about 1% by volume in N2 argon gas). This in turn indicates an increase in 4 TMg. This means that the antiferromagnetic coupling of Gd and Co is affected in such a way that the excitation is increased without eliminating the uniaxial anisotropy of the amorphous substance. Nitrogen binds to Gdnn, which impairs the antiferromagnetic coupling between Gdsn and Cosn. The moment in the Co sublattice becomes less effectively canceled by the Gd sublattice moment, so that the magnetization increases.

The figure is a plot of magnetization in Mg arbitrary units as a function of composition in an amorphous Gd-Co alloy - also in arbitrary units. This is the minimum in magnetization with a given Gd-Co composition.

If the Gd-Co composition is normal with composition A and the composition is prepared in the presence of N 2, there will be a shift in magnetization as if there were an increase in the cobalt composition. Therefore, the magnetization becomes larger. If the other side of the source of the composition C, and the nitrogen-layer schemes, with the film will be produced by the excitation of a modified minimum. Therefore, the excitation Mg can be changed by simple additions of N 1 to the substance to change the interaction between the components of the composition towards a higher or lower excitation depending on where the excitation / composition curve of this substance is.

Coherence H

c

Coercivity in a magnetic material is a primary factor in determining the ease with which magnetic domains are transferred in a material. Coherence adjustments usually involve a change in the grain size of the magnetic material because coercivity is dependent on the grain size. In general, coercivity is at a maximum at a given grain size value and decreases at larger and smaller grain sizes than that which gives the highest coercivity. For example, coercivity is high in magnetic materials where the grain size approaches the domain boundary width.

Grain size can be affected by the addition of dopants, such as or Og * These additions change the magnetic order in the amorphous film so that it becomes second (or the same) as the domain boundary width (δ). If & is greater, H is low, while if δ is approximately

O

the same in said order is H maximum.

c

Ion implantation at a selected depth is normally suitable when it is not desired to heat the amorphous material. Heating above certain temperatures causes the amorphous substance to change to a crystalline state, which may not be a recoverable state. Curing of the amorphous film to crystallize in order to obtain grains of the desired size can also be used.

Other methods of influencing coherence include surface treatment such as vapor etching and ion scavenging to make the surface structure uneven. This in turn affects the transfer of domains in the amorphous magnetic medium.

Curie temperature T

c These amorphous magnetic materials are easy to alloy to change the Curie temperature without adversely affecting the structure of the materials. Accordingly, there is no limiting effect based on the phase diagram, as would be the case with crystalline substances. A wide range of alloys (about 50 atomic percent) can be used as long as uniaxial anisotropy in the material is not affected. In general, the Curie temperature follows the number of magnetic atoms present in a straight line. The Curie temperature in these amorphous materials is easier to control than in crystalline magnetic materials.

Alloy ratios are used to change the Curie temperature in an amorphous magnetic medium. For example, in an amorphous Gd-Co alloy, the addition of magnetic substances with a lower torque, e.g., Ni, Cr, Mn, or non-magnetic substances, e.g., Cu, Al, Ag, Pd, Ga, In, etc., decreases the Curie temperature when while an element such as e.g.

Adding Fri raises the Curie temperature. The intensity of the magnetic interaction (coupling) in the substance is changed by the added elements.

Praday rotation 0 ^,

The added Paraday rotation, or Kerr rotation in the light beam that hits the amorphous magnetic substance, is achieved by providing an amorphous substance with a high magnetic moment. Rare earth metal dopants, e.g. Tb, By, Ho, can be added to the amorphous substance or alloying additives can also be added to the substance. For example, in the case of an amorphous Gd-Co alloy, increasing the amount of Co will increase the Faraday rotation. Fe additions to the substance will also increase the Faraday rotation. With a large Faraday rotation, it is desirable for the magnetization to have the highest possible value of 4 TT "Mg (e.g., 8000 to 10,000 gauss).

Specific length (L parameter)

The parameter L is a quantity that is particularly useful in muddostetta sa magnetic bubble domain systems. A more detailed description of this parameter is given by A.A. Thiele in Journal of Applied Physics, no. 41 »s * 1139 (1970).

The parameter L is highly dependent on the dimension of the constituents in the amorphous alloy. Thus, for example, Figure 4A shows variations in the parameter

K

L (more specifically defined as u) as a function of the magnetic ion concentration 4 "Γ 1 (p in an amorphous magnetic alloy. In this special case the composition is Gd-Co and on the horizontal axis the concentration Co. This shows that the parameter L can be varied by changing the composition of the amorphous alloy. 4A is taken for different compositions Gd-Co when all preparation parameters were kept constant in each different experiment.When prepared with the same compositions under different conditions there are different values of parameter L. It follows that the composition range with amorphous substance can be easily varied within wide limits, which differs in the case of a crystalline magnetic material, it is relatively easy to vary the parameter L.

Figure 4B illustrates the dependence of the parameter L on the thickness Ξ of the amorphous magnetic layer. Below the critical thickness of each composition, it is not possible to achieve sufficient rectangular anisotropy to support the bubble domains, and therefore the curve is depicted by the dashed line below the critical thickness. The particular composition in question (Gd 20 atomic percent, Fe 80 atomic percent) gives a thickness of 0.2 ψη to favor the rectangular anisotropy bubble domains.

Domain boundary energy 6 ^

The domain boundary energy (wall energy) δ is related to the L-parameter of an amorphous substance. The domain boundary energy is also directly relative V ^ u »where A ^ is the interaction constant of the substance and K ^ is the uniaxial rectangular anisotropy constant of the substance.

2

Figure 5 is a plot of domain boundary energy at 4 δ ergs / cm, measured as a function of w from the substrate bias voltage used for electrode vaporization of an amorphous Gd-Co alloy containing 80 to 85 atomic percent Co.

This substrate bias voltage is the substrate voltage measured with respect to ground. In the DC electrode evaporator used to obtain the curve of Figure 5, about 2000 volts are connected between the anode and the cathode to effect deposition of the amorphous Gd-Co composition. The use of a substrate bias voltage allows the composition and magnetic properties of the deposited material to be controlled. In this way, the domain boundary energy can be varied over a wide range. The domain boundary energy can also be changed by varying the interaction constant A or the anisotropy K ^. The interaction constant A represents the intensity in the magnetic coupling in the substance and is relative to the Curie temperature T. As a result, the constant A varies from substance to substance. Changes in c r anisotropy are discussed later in this specification.

Anisotropy Ku

The anisotropy of the substance can be varied by altering the process used to prepare the amorphous composition. For example, the deposition rate is a decisive factor, as is the thickness of the deposited film. In general, K 1 is a function of material composition and construction conditions. These factors are discussed in more detail in the section of the specification dealing with manufacturing methods.

Domain size and domain boundary width δ

The domain boundary width is equal to 1T / K 2, where A is the interaction constant of the substance and is its anisotropy. As previously mentioned, ani-16 57C73 sotropia K? Depends on the thickness and deposition rate of the amorphous film. Therefore, the domain boundary width δ can be varied by varying the anisotropy K ^. This in turn is a function of the composition of the amorphous layer, the components of this range, and the deposition process used to make the amorphous material. In the part of the invention relating to the manufacturing methods, curves describing the variation of the anisotropy K i depending on the layer thickness and the deposition rate are discussed.

The domain size is a function of the specific length L and the film thickness * In general, the domain size is chosen so that the performance of the device becomes optimal. Magnetic bubble domain systems are given a length L by the following equations l - 4ί », 2 Accordingly, the specific length and thus the domain size can be changed by changing the magnetization M, the anisotropy K and the interaction constant A.

S u

The interaction constant is a quantity that represents the strength of the magnetic coupling in a given substance. It is relative to the Curie temperature and is higher for substances with a higher Curie temperature T. As previously explained, anisotropy is a function of the composition of the substance and other conditions used in the preparation of the substance. The magnetization M depends on the 8 magnetic spins and its direction (parallel or opposite). This quantity is temperature dependent and can be varied by changing the composition of the amorphous film and the parameters that are relevant in the preparation of the amorphous film. Therefore, the domain size can be easily changed over a wide range.

methods of Preparation

Amorphous magnetic materials can be made in bulk form or as thin films. In general, any known film-forming technique can be used, including electrode evaporation and evaporation.

To provide a pulp film from an amorphous magnetic material, pour cooling may be a useful method. Here, the components of the film, in heated and flowable form, are allowed to hit a cold surface where the components solidify and form an amorphous mass film. This provides rapid cooling from the liquid phase (state).

it '57673

Uniaxial anisotropy can be applied to pulp films by subjecting them to atomic bombardment in a magnetic field or by curing them in a magnetic field at a temperature below the crystallization temperature of the films. Another method of obtaining pulp films is to continuously evaporate them using the procedure described above.

The fabrication of the thin amorphous film of the present invention may be based on vapor deposition, rapid cooling from the liquid phase, or ion implantation to control anisotropy. In general, these amorphous films depend on the rate at which the atoms are deposited on the substrate, the substrate temperature, and the angle of impact of the atoms deposited on the substrate.

If future atoms are unable to reach a certain equilibrium state, the tendency to form amorphous films increases. In this context, reference is made to S. Mader, "The Use of Thin Films in Physical Investigations," published by J.C. Anderson (Academic, New York, 1? 66) p. 455. See also U.S. Patent 3,427,154, which deals with the manufacture of amorphous thin films.

To promote pairing, the habit of inducing uniaxial anisotropy in these membranes appears to be essential for the deposition atoms to hit the substrate at an angle of impact other than straight. This means that the incoming atoms must have a certain velocity component parallel to the substrate surface in order to provide uniaxial anisotropy to the membrane. This "touch angle" provides atomic mobility parallel to the substrate, which in turn promotes pairing, as incoming atoms can move around (rotate) and select an atomic position that lowers energy in the system through the demagnetization field of matter. Phase separation is facilitated, leading to the formation of anisotropy due to the clustering of densities of similar atoms at one point where the energy of the system decreases. This in turn leads to compositional clusters which, as already mentioned above, lead to anisotropy in the membrane.

Another factor in achieving uniaxial anisotropy is the deposition rate of future atoms. If the deposition rate is too high, incoming atoms cannot rotate around the substrate on a large scale, which restricts mobility parallel to the substrate surface. In this context, reference is made to Figure 6, which is a plot of deposition rate in angstroms per second as a function of the high frequency energy used in an evaporation system to deposit an amorphous substance. In this case, the amorphous substance is Gd-Co. Figure 6 shows a critical deposition rate of four angstroms per second for a given substrate temperature and paint composition. This means that at a deposition rate of four angstroms per second, Gd-Co experiments showing domain patterns (containing about 80 atomic percent Co) were obtained, i.e. 57673, which were characteristic of uniaxial rectangular anisotropy in an amorphous magnetic Gd-Co alloy.

In the case of Fig. 6, the deposition was performed with a magnetic field (50?) At right angles to the substrate and in the absence of a magnetic field in order to determine the effect of the magnetic field during deposition. The effect of the magnetic field was not large, although it improved the evaporation efficiency to some extent.

As the substrate stress used in the evaporation system increases, the anisotropy generally increases. This is because the bias voltage causes the incoming atoms to detach from the surface of the deposition film by re-evaporation. As a result, the atoms have greater mobility parallel to the substrate surface, allowing it to reach priority locations, leading to composition grouping, or pairing.

Figure 7 is a graph of anisotropy K 2 (erg / cm 2) as a function of amorphous magnetic film thickness H ψι. This film of amorphous Gd-Co material requires critical anisotropy to promote domains of about 1.2 x 10 6 / erg / cm 2 as indicated by the stability state K> 2 μm.

IX 8 This critical anisotropy occurs at a film thickness of 0.2

For deposition of an amorphous magnetic material, the substrate temperature is kept relatively low. These films can be deposited at room temperature or below and are normally deposited at a temperature below that which would cause the substances to crystallize. For example, for amorphous Gd-Co ane, the upper limit of the substrate temperature is about 300 ° C, i.e. a crystallization temperature.

Figure 8 is a plot of deposition rate (on a logarithmic scale) as a function of substrate temperature for Gd-Co and Gd-Pe alloys. This curve shows that amorphous magnetic films can be made over a wide substrate-temperature range depending on the deposition rate. In general, the substrate temperature, regardless of the deposition rate used, must be lower than that at which crystallization occurs to provide the amorphous magnetic materials of the present invention.

Stress-produced anisotropy can also be used to provide the present magnetic agents. This type of anisotropy can be used in combination with other methods (pairing, etc.) to obtain anisotropy, or it can also be used alone. For stress-produced anisotropy, the substrate is selected in connection with the magnetostriction of the intended film so as to provide anisotropy to the amorphous film. More specifically, a film becomes if it is deposited at a temperature different from room temperature and the film and the substrate have different coefficients of thermal expansion, 19 57 67 3 subjected to a certain stress at room temperature.

As mentioned earlier, many platforms may come into question. Since there are no restrictions on the crystallographic fit in the production of amorphous films, the choice of substrate is completely free. These substrates can be any known material, such as metals and insulators, as well as semiconductors. Non-rigid substrates, e.g. plastics, can also be used. The following tables show a number of platforms.

Films with planar anisotropy can be converted to films with perpendicular anisotropy by curing the films. For example, curing Gd-Co films at about 300-400 ° C converts planar anthropropy to perpendicular anisotropy. As the film thickness increases, the probability of perpendicular anisotropy increases, of course. Thus, for example, Gd-Co films with a thickness of at least 2000 Å normally have perpendicular anisotropy.

The amorphous magnetic materials of the present invention can be used in a variety of applications, for example, bubble domain systems, beam address archives, light modulators, permanent magnets, and recorders for tape and disk. Each of these applications is discussed below along with the parameters of interest associated with them.

Kupladomeenijärjestelmät

In magnetic bubble domain systems, it is important that the 4 μM magnitude is low and that the material has uniaxial perpendicular anisotropy. Furthermore, the quality factor Q * H / 4 "M must be greater than one, d * 8 where H is the uniaxial anisotropy magnetic field and M is the saturation SL 8 excitation of the substance. Furthermore, the coercivity Hc of the substance must be low to facilitate bubble domain transfer Since the quality factor Q must be greater than one to obtain stable bubble domains, systems with low excitation are generally used because it is difficult to obtain very large induced anisotropy fields H. In ferromagnetic systems it is possible to calculate the excitation H by attenuating the non-magnetic element, but due to the fact that the magnetic Curie temperature follows the oin magnetization, sufficiently low 4 # M values can be obtained for alloys only 8 close to the Curie temperature »at aliquots at operating temperatures.

Low magnetic moments at the highest ordering temperatures so that amorphous materials become suitable for devices operating at room temperature are obtained in a ferromagnetic system containing two or more types of magnetic atoms with opposite spins. This type of order is obtained in amorphous alloys from rare earth metal elements - above all from transition metals. Amorphous alloys of rare earth elements - for example Gd Co with suitable x y compositions can be obtained * in which the atomic moments in the rare earth element and the metal element are almost canceled, resulting in a 'Ji' substance with a suitably low 4 '' 'M value. Suitable examples are 8

Gd-Co alloys with 70-90 Co and amorphous Gd-Fe alloys with 70-90 i Fe. In the thin film form, anisotropy is achieved by either stress, pairing, or shape anisotropy.

As previously mentioned, low coercivity is Ξ normally required for the bubble domain material. Accordingly, the δ of the bubble domain boundary-c should be such that, on average, the same mean potential prevails throughout the amorphous substance. The quantity δ should be approximately the same or somewhat larger than the type of atomic order found in the amorphous substance. If the local oscillations (phase separations, grain size, etc.) in the amorphous material are smaller than the boundary width δ, the effect of this on the domain boundary motion is insignificant. Furthermore, microcrystals of the order of 29-100 I are not necessarily detrimental to domain motion. Until the grain size in the amorphous material reaches the limiting width δ, the coercivity Ξ is low.

O

The domain boundary width δ follows the Curie temperature T because the exchange constant A

c

Follow Tq (δδν = A). If large domain boundary widths are desired, it is necessary to achieve large alternation constants. However, the limit width δ must not be too large as the anisotropy energy increases, which has an adverse effect on mobility. For amorphous bubble domain material, it is normally desirable to provide a low cut-off energy, which means that materials with a low Curie point T must be used. As previously mentioned, amorphous magnetic materials can be easily alloyed to change the T.

O

The restrictions on the Curie temperature T for amorphous bubble domain materials v are essentially the same as for crystalline bubble domain materials. However, it is simpler to adjust the Curie temperature T in the amorphous magnetic material c than in the crystalline one.

The choice of substrate is free when amorphous magnetic bubble domain materials become available. Suitable substrates include semiconductors, insulators and metals, for example NaCl, glass, SiO 2 * S 4, Ge, GaAs and AlgO 2. A particularly suitable amorphous magnetic film consisted of GdCl 2, which is electrode vapor deposited on a NaCl support. This electrode evaporation took place from the arc-forming paint Gd-Co 2, where the substrate was water-cooled (about 20 ° C) and had a gallium coating to ensure thermal contact with the cooling body. Ser-pentin domains were detected by electron microscopy in a film about 790 L thick. The presence of a ferromagnetic sequence was detected by heating a sample of n 57673 to a compensation point to disrupt the Gd sequence at which planar domains were detected. Perpendicular domains were again generated by cooling to room temperature. The electron diffraction pattern was typical of an amorphous substance. These magnetic serpentine domains with perpendicular excitation could be detected in the free membrane removed from the NaCl support, indicating that the anisotropy was not induced by stress but probably of the pairwise type.

Films with a thickness of about one ψη were deposited on different substrates but under the same manufacturing conditions on NaCl, SiO 2 and A 1 O 0 substrates. Z Z 3 in these membranes also had serpentine domains when detected by the Bitter model and the Kerr effect.

A perpendicular magnetic field of a few örsteds was sufficient to cause the sepentin domains to collapse into circular domains. By transferring an external magnetic field, it is possible to transfer domains in an amorphous magnetic film. This domain pattern resembles that observed in carefully prepared garnet films, which means that the amorphous material lacks local inhomogeneities that would be sufficient to cause local adhesion of the domains. Of course, this is an advantage in an amorphous material where crystal structure defects do not occur. Magnetic bubble domains and their transfer are not limited by errors in this class.

Figure 9 illustrates a magnetic bubble domain system in which amorphous magnetic material 10 is used as the agent that promotes magnetic bubble domains therein. Fig. 10 is a diagram of a part of the circuit in the decoders of Fig. 1. The sole function of the embodiment shown in Figures 9 and 10 is to describe a bubble domain arrangement in which the present amorphous magnetic materials can be used, for which reason the system itself will not be explained in detail. The following is a brief explanation of this bubble domain system using an amorphous material as a magnetic material 10.

Figure 9 is a block diagram of a memory system using cylindrical magnetic domains (bubble domains) that provides write, storage, decoding, decryption, and retrieval. The amorphous magnetic sheet 10 consists of one of the aforementioned compositions. A suitable example is an amorphous Gd-Co alloy or a Gd-Fe alloy. The properties of the amorphous film required for use in a bubble domain system have already been described above. The sheet 10 has a front voltage magnetic field at right angles to its plane to maintain the diameter in the cylindrical magnetic domains in the magnetic sheet 10.

The bias field is provided by a bias field source 12, which may be an external winding. If desired, the bias field may be provided by a permeable magnetic layer or a second magnetic sheet 22 57673 interchanged with the magnetic sheet 10.

When domains have to be transferred by magnetic poles created from soft magnetic elements placed close to the magnetic sheet 10, a transfer field H is provided by a transfer field source 14 · The transfer field H is a reorientation magnetic field elements close to the magnetic sheet 10. The transfer field source 14 consists of external windings arranged around the magnetic sheet 10 and to which pulses are alternately applied to produce a magnetic field in an arbitrary desired direction. Figure 9 shows a transfer field H a rotating magnetic field which can be directed in one of the directions 1, 2, 3 and 4 ·

Although bubble domain conditions will be explained with particular reference to transfer means comprising soft magnetic elements, it will be appreciated that other transfer means, e.g., conductor loops, may equally well be used. The bias field source 12 and the transfer field source 14 are activated by a field control circuit 16 which supplies current to the sources 12 and 14 to provide a bias field H and a transfer field H. Domains move closed

Z N

lines in each of the 2 shift registers. Domains represent binary information, with the presence of the domain indicating binary 1 while the domain

OF

absence indicates binary 0. For each shift register 1, 2 ... 2, a bone domain generator 18-1, 18-2, ... 18-2 was heard. These generators write information to the shift register with input signals produced by the write

OF

with pulse sources 20 to lines W1, W2, ... W2. If desired, the write transducer opener can be used in conjunction with domain generators 18-1, etc. to intentionally apply induction to selected shift registers.

The read transducer opener 22 is associated with the shift registers.

The read transducer receives 2N input signals produced from the transducer pulse source 24 · Depending on the input signals produced

OF

to the read transducer 22, any of the 2 shift registers can be selected for reading the information.

After selection, the read transducer 22 passes information to the selected register via clearing means 26 which are activated by source 28. Source 28, transducer pulse source 24 and write pulse sources 20 are selectively controlled from control circuit 30 which produces input signals to each of these sources at the correct time. The clearing means 26 sends the domains in the selected shift register to one of the two paths depending on whether the information is read destructive or non-destructive.

If a destructive number is to be used, the domains of the selected register are fed directly to the detector 32, which may be a magnetoresistive identification element, an inductive loop, a magneto-optical identification device, or some other detector. The detector includes a domain destroyer that causes the doipenes to collapse. The output signal from the detector 32 goes to a drive member 34 »which may be an arbitrary external circuit that utilizes the binary information contained in the selected shift register.

In the case of a non-destructive number, the clearing means 26 will direct the domains from the selected register to the domain diameter 36-1, 36-2, ...

36-2. The diameter divides the input domains into two parts, one of which goes to the detector 32 for the destructive number while the other goes back to the selected shift register for continuous rotation in this shift register loop. Figure 9 shows the shift registers, read / write transducers 22 and clearing means 26 as separate components for simplicity, but it should be understood that a transducer with clearing means is integrated in the shift register. As a result, the wires 46 and 44 represent shift register loops 1, 2, ... 2 intersected by the transducer 22, which includes the clearing means 26.

The block diagram of Figure 9 shows a complete, cylinder domain type

OF

a memory system where the induction is selectively written to 2 weather shift registers for storage. The information content of the shift registers can be selectively addressed by input signals from the read transducer 22. Depending on the activation of the clearing means 26, the domains from the selected registers will be read as destructive or non-destructive. If the clearing means indicates a destructive reading, the domains in the selected registers become destructively read by the detector 32. In the destructive reading, the control circuit 30 activates the write pulse source 20, which in turn activates the domain generators.

OF

18-1, 18-2, ... 18-2, which belong to the register that will be destroyed. Thus, new information is written to the destructively read transfer register.

If the clearing means indicates that the information needs to be read from a non-destructively selected shift register, the domains from this shift register are directed to the domain diameter, where they are divided into two new domains. One of the new domains goes to detector 32 for destructive reading while the other is taken back to the selected shift register to continuously rotate in this shift register.

Selection of some or all of the shift registers for destructive or non-destructive reading is possible according to the binary input signals input to the read transducer. Figure 10 shows a part of the shift register (SR14) to describe the code change and clear functions. The magnetic sheet is not shown.

“’ 57673 24

The domains, for example, 55 »shifted to the right of the arrow 36 direction in the shift register (SRI4) · It should be understood that much of this transfer rekisterisilmukasta is not shown and that the loop extends further to the left in order to accommodate koodinmuuttajasilmukat D1-D2 '(Figure 9) and to provide sufficient storage space . in accordance with principles known in the art to produce the transfer field rotation (rotation) withdrawing terminals T and I shaped permalloyelement the transfer of 54-domains in the direction of the arrow 46. Conductors are placed on the magnetic sheet 10 and on top of the selected permalloymagnets, which are used for the transducer loops D3 »D3 '> D4 and D4'. A discharge loop CL, which is also a conductive loop (for example of copper), is further arranged on the magnetic sheet 10 and on the suitable permalloy elements 54. This shows that the transducer loops D3 and D4 'have wider sections in the areas where they intersect the T-shaped elements on road 46, while the transducer loops S3' and D4 do not have wider sections where they bypass the T-elements on road 46. This means that currents in transducer loops D3 * and D4 do not affect the passage of domains along the road 46 ·

The magnetic sheet 10 is further provided with permalloy domain splitters 36-14 », which in this case comprise an upper permalloy layer and a lower permalloy layer, indicated by broken lines.

When using the binary input signals 10100110 to the transducer inputs D1, D1 ,, ... D4 * for a selective reading from this shift register, no current is present in the transducer loops D3 and D4 '. As a result, transfer domains 53 of the arrow 46 in the direction of the pole-position two T-element 56. This is followed by a domain 53 either to follow the path indicated by the arrow 38 ', or the path represented by arrow 40. If tyhjennyssilmukka CL is activated by the current pulse, there is no tractive the magnetic pole ^ is produced in the pole position 3 'for the element 56. Therefore, the domains located in the pole position 2 by the element 56 are pulled up to the pole position 4 by the element 56 when the transfer field H has a direction 4. The domains then move to the pole position 1 ” T-element 58, when the transfer field H is in the direction of the arrow 1. transfer 38 continues in the direction it rotates according to the H, which takes 32 domains destructive detector for reading.

The detector 32 is described as a magnetoresistive detector associated with the element 60. The magnetoresistive detection detector 32 consists of a magnetoresistive detection element 62 and a constant current source 64. The excitation vector of the detection element 62 rotates when the leakage magnetic field of domain 53 interacts with it. V. Element 60 includes

O

57673 an elongated permallom model 66 for moving domains 53 to pole position 4 by element 66. As H rotates, domains 53 move to the corner of element 66 and are closed here even though H rotates in directions 2 and 3 because pole position 5 is far from the corner of element 66 . When H is in position 3, the local field in the corner becomes repulsive, and the domains collapse.

If there is no current pulse in the discharge loop CL when the domains are located in the pole position 2 of the element 56, these domains will be shifted along the path indicated by the arrow 40 as the transfer field H rotates. Thus, the domains are introduced into domain diameters 36-14 · As previously mentioned, this diameter includes the upper permalloy layer, indicated by solid T-elements and 1 elements, and the lower permalloy layer, iote, is indicated by dashed elements. Under the influence of the rotating transfer field H, the domains 53 *, which become diameters 36-14 *, are divided into two parts. Part passes towards the detector 32 via the lower layer, and the driving of the terminals a-b-c (arrow 42 suvultaan). These domains then follow a path to 38 detectors.

The other part of the split domain goes to successive pole positions a’-b’-c ’by element 68 as the transfer field H rotates. These domains follow the path indicated by arrows 44 »for recirculation in the non-volatile register 14 · As a result, this bubble domain system provides memory and logic functions on a single sheet of amorphous magnetic material.

The various components that can be used in the previously known bubble domain materials can also be used here. In the present case, amorphous magnetic materials are easy to provide for all types of substrates and can have selected thicknesses and side dimensions.

Also, although permallom models have been described for domain transfer, it is to be understood that the yonde loop model can also be used as well as the band model. Furthermore, the writing and recognition devices can be varied without going beyond the scope of the invention.

Valomodulaatio

Due to the fact that the amorphous magnetic substances according to the present invention favor magnetic domains, it is possible to provide a light modulator which modulates the intensity in the incident light beam. in the present

In the case of Cf, a high magnetic moment 4 ^ M * low coercivity 6, a high Curie temperature T and an anisotropy field H which is c c p- 'a is greater than the magnetic moment 4 ^ M · is desirable.

S

amorphous substances such as Y-Co, La-Co, Ce-Co, Nd-Co and Pr-Co.

26 57673

Since the magnetization of the magnetic domains on the sheet of amorphous magnetic material is either parallel or antiparallel to the direction of the incoming light beam, the light beam is affected differently depending on the direction of magnetization in the region of the magnetic sheet where the beam hits. With input polarized light, the rotation of the polarization becomes different depending on the direction of magnetization in these domains, as a result of which the intensity in the light beam passing through the amorphous magnetic substance can be changed by varying the direction in the magnetization of the domains.

Figure 11 illustrates a light modulator in which a laser 70 produces a beam of light passing through a polarizing element 72 before it impinges on an amorphous magnetic material 74 · Near the film 74 are domain transfer members 76.

In this case, the transfer members 76 include T- and I-shaped elements that provide pulling magnetic poles for transferring the domain 78 on the sheet 74 according to the orientation of the transfer magnetic field H produced by the transfer source BO. After passing through the amorphous sheet 74, a light beam strikes the analyzer 82 before being detected by the photocell 84 ·

Depending on the presence or absence of domain 78 where the light beam hits the amorphous sheet 74, the polarization of the light beam will rotate differently. With a certain rotation of the polarization, the light beam is able to pass through the analyzer 82 and hit the photocell 84, which gives a current through the resistor R. In the second case, the rotation of the polarization of the light beam is such that the beam does not pass through the analyzer 82 and as a result no voltage is detected in the resistor R. Thus, a light modulator with a suitable sheet of amorphous magnetic material containing domains is provided.

In connection with Figure 11, it is to be understood that light may be reflected from the amorphous sheet 74 instead of passing through the sheet. In both cases, the effect is the same, namely that the polarization of the light is affected differently depending on the magnetization of the domains at the point of impact of the light beam.

Permanenttimagneetti

The amorphous magnetic materials of the present invention can be used as permanent magnets. In this case, it is desirable that the magnets have a high coercivity force H, a high magnetic moment f.y c 4JtM, and a high Curie temperature T. Suitable compositions include Y-Co, which is

8 C

doped with oxygen, nitrogen or carbon.

A particularly suitable embodiment for a permanent magnetic layer using an amorphous material is a bias layer associated with a magnetic sheet having bubble domains. The magnetic sheet that favors bubble domains may be a crystalline magnetic sheet or an amorphous magnetic sheet according to the present invention. Unlike crystalline permanent magnets, which are dependent on crystal properties for high bias fields, the present amorphous permanent magnets are easy to fabricate with selected properties according to the explanations given above.

Figure 12 illustrates the use of an amorphous permanent magnet layer 86, which layer is used to bias the magnetic bubble domain sheet 88. The transfer field source 90 and control / logic circuits 92 are arranged to act on domains in the bubble domain material 88. This material may be a known substance having a garnet structure (e.g. ^ (Ga, Fe) ^) ^) or an amorphous substance according to the present invention. In preparing the embodiment of Figure 12, it is not critical that the crystal properties be maintained because the amorphous material does not follow the rules that apply to the preparation of crystalline compositions.

A general structure comprising an amorphous magnetic layer on an arbitrary quality substrate is also illustrated in Figure 12. In this general case, the structure may have arbitrary use, and layer 86 is an amorphous magnetic layer according to the present invention. Layer 88 is an arbitrary suitable substrate, e.g., a semiconductor, insulator, or metal. Furthermore, the substrate may be flexible or rigid, and means may be used to move the combination of amorphous magnet film and substrate.

Writing down subsystem

It is possible to deposit the present amorphous magnetic material as a recording agent on a substrate, e.g. a semiconductor, an insulator or a metal. The substrate can be tapes or plates. Furthermore, this amorphous magnetic material can be prepared as magnetic particles in a binder (e.g., a conventional resin-type binder) for use on an arbitrary substrate.

Fig. 13 shows a tape or disk recording medium 94 »containing an amorphous magnetic film according to the present invention on which a read / write main memory 96 is placed. The converter 96 is used to record information on magnetic domains on a tape or disk 94 and to read stored information in a known manner. For this purpose, electrical signals read from the recording medium 94 are sent to an identification amplifier 98 and then to a drive circuit 100, which may be an arbitrary circuit used in conventional data technology.

The use of the amorphous film of Figure 13 has many advantages.

Disc or tape substrates can be either flexible or rigid. Furthermore, the amorphous material is easy to deposit (place) on all types of substrates evenly, so that uniform magnetic properties are obtained everywhere.

28 57673

Example

Amorphous magnetic compositions with uniaxial anisotropy have been prepared using electrode evaporation (DC and high frequency) and electron beam evaporation. In general, films have been prepared which have amorphous properties as determined e.g. elektronisädediffraktio technology. Magnetic anisotropies have been obtained that were parallel to the plane of the membrane and perpendicular to the plane of the membrane.

I. Electron Beam Vaporized Films In this method for producing a film, a polycrystalline paint is first obtained using a conventional technique. For example, small pieces of the materials used in the paint are melted in an inert gas atmosphere using, for example, argon. Smelting takes place in a water-cooled copper stove in a standard arc furnace available on the market. The temperature is raised to the melting temperature of the ingredients in order to provide an arc molten ingot. Usually this is polycrystalline paint. In the laboratory, test specimens have been prepared from arc-melted GdCl 2 paint.

The paint is then placed in an ultra-high vacuum evaporator where the -9 base pressure is about 10 torr. The ingot is placed in a water-cooled copper slurry and heated with electron beams obtained from the electronic cannon of the evaporator. Accelerating voltages of about 10 kV are used in conjunction with beam currents of about 100 mA.

The substrates used to deposit these films are arbitrarily selected and substrates such as glass, polished hardened quartz, rock salt and sapphire have been used successfully. The substrates are cooled with liquid nitrogen and have a temperature of about 100 ° K during evaporation. The deposition rate was generally about 30 k per second.

In one case, films have been made in thicknesses of 400 l and 4000 l. These films were Gd-Co alloys that proved to become amorphous by electron beam diffraction. The atoms in the deposition agents that hit the substrate approached at an oblique angle (anywhere that deviated from a 90 ° angle to the plane of the substrate) in order to produce uniaxial anisotropy as described above. Rectangular domains are observed in this membrane.

In another film deposition, the substrate temperature was 273 ° K. The same substrate was used, in addition to the BaTiO 2 substrate and the split quartz substrate. The cabbage composition (GdCo,.) Was the same as that used in the 400 a and 4000 k films of the previous paragraph. Only the substrate temperature was changed in this composition. In the present case, there were crystals locally in the film in a generally amorphous matrix, indicating that the substrate temperature is critical in the electron beam deposition process. In order to obtain substantially amorphous films, the substrate temperature must be lowered from 273 ° K.

Another electron beam layer contained GdCOg as the paint composition and the substrate was cooled with liquid nitrogen. The fabricated film was amorphous and had uniaxial excitation in the plane of the film. It seemed as if the excitation M in this composition was too large, so that the ratio cf ® E / 4 M was not exactly correct to favor the a s domains with perpendicular excitation.

Electrode vaporized films

Many amorphous films have been fabricated by direct current or high frequency electrode evaporation with varying evaporation parameter values. These films had perpendicular magnetic anisotropy and parallel magnetic anisotropy and were uniaxial. Many values for magnetization and other magnetic parameters were obtained according to the principles outlined above in this specification.

Various arrangements have been described above in which magnetic compositions having uniaxial magnetic anisotropy with substantially amorphous structural properties have been introduced. These compositions can be made in pulp or thin film form and the magnetic properties can be controlled over a wide range.

Furthermore, many applications other than those disclosed herein for these films can be readily contemplated, particularly in view of the ease of varying properties and wide range of compositions. Because the stringent substrate requirements that normally exist in crystal fabrication do not apply here, these films can be used in all types of environments with all types of substrates.

It will be appreciated that the magnetic and / or structural properties of these films may vary to a significant extent and methods other than those described herein may be used. Furthermore, a different method of preparation can be used according to principles known in the art.

Claims (32)

1. A magnetic domain device, characterized by a magnetic medium, in which said domains exist, which medium is an amorphous magnetic material down non-magnetocrystalline uniaxial anisotropy, and of means for effecting said domains in said amorphous magnetic medium. Device according to claim 1, characterized in that said amorphous magnetic material exists in a microcrystalline structure with localized atomic arrangement over a distance of approx. 100 Å and less. Device according to claim 1, characterized in that said amorphous material has a localized atomic arrangement over a distance of approx. 25. and less. 1+. Device according to claim 1, characterized in that said uniaxial anisotropy is substantially perpendicular to the plane of said amorphous magnetic material. Device according to claim 1, characterized in that said amorphous magnetic material consists of a single element with a magnetic torque. 6. Apparatus according to claim 5, characterized in that said elements come from any of the UF, 5F or 3D element series in the periodic system. Device according to claim 1, characterized in that said amorphous magnetic medium contains a plurality of elements, at least one of which has an unpaired magnetic spin. 3. Device according to claim 7, characterized in that said amorphous medium is an amorphous alloy of rare earth and transition metals. 9. Device according to claim 8, characterized in that said alloy is a Gd-Co alloy. 10. Device according to claim 8, characterized in that said alloy is a Gd-Fe alloy. 11. Device according to claim 7, characterized in that said amorphous magnetic medium contains an additive, corn is coupled anti-ferromagnetically to a magnetic atom in said amorphous medium. Device according to claim 7, characterized in that said amorphous magnetic medium contains an additive which is coupled ferromagnetically to a magnetic atom in said amorphous medium. 57673 Device according to claim 7, characterized in that said araorphic magnetic medium contains an additive which undermines the atomic order of said amorphous magnetic medium relative to the width of the domain borders therein. k. Device according to claim 7, characterized in that said araorphic medium is a ternary alloy which is magnetically arranged. Device according to claim 1, characterized in that said amorphous magnetic material contains an additive element of 0, N, C or P. Device according to claim 1, characterized in that said amorphous magnetic material is doped with elements which occur in a range up to 50 atomic percent. Device according to claim 1, characterized in that said uniaxial anisotropy is paired anisotropy. Device according to claim 1, characterized in that said amorphous medium is a sheet which is arranged on a substrate. An apparatus according to claim 13, characterized in that said substrate is a semiconductor. Device according to claim 19, characterized in that said semiconductor is silicon. 21. Apparatus according to claim 11, characterized in that said substrate is an insulator. Apparatus according to claim 1, characterized by sensing means for detecting the magnetization state of said doraans. Device according to claim 22, characterized in that said domains are magnetic bubble domains. 2h. Device according to claim 22, characterized in that the amorphous medium is a sheet arranged on a substrate. 25. Device according to claim 2U, characterized in that said substrate is a flexible medium. 2u. Device according to claim 2> 4, characterized in that said substrate is a rigid medium. Device according to claim 2, characterized in that said substrate is an insulator. 28. Device according to claim 2U, characterized in that said substrate is silicon. Device according to claim 2U, characterized in that said substrate is a metal. Device according to claim 22, characterized by means for moving said amorphous magnetic medium.