RU2124755C1 - Method for reading and writing information - Google Patents

Abstract

FIELD: computer engineering, in particular, image recognition for hidden labels applied on arbitrary carriers (securities, bank notes, plastic cards, etc). SUBSTANCE: method involves storing information by affecting information carrier and reading information applied in this procedure. Goal of invention is achieved by application of magnetic film which is thinner than 50 A and which is later covered by protecting non-transparent coating. Information is read by means of measuring of distribution of magnetic field components generated by magnetic film using scanning SQUID magnetic detector. Authenticity of encoded information is judged by level and shape of measured distribution of magnetic field components. EFFECT: increased reliability and hidden capacities of stored information, possibility keep magnetic information after exposition to arbitrarily large magnetic field. 6 cl, 2 dwg

Description

 The invention relates to computer technology and can be used in pattern recognition systems and for covertly applying information to arbitrary media, such as securities, money, plastic cards, etc., of various configuration codes, thereby reducing the likelihood of its unauthorized reproduction and reading.

 A known data acquisition system (UK patent N 2137386, MKI G 06 K 7/08), containing a data carrier onto which encoded information is presented, represented by a specific combination of permanent magnets available on it. The read head available in the system contains several Hall effect readers that detect the magnets present on the storage medium when the medium and the head are in contact with each other. Information on the data carrier is read by scanning and processing the electrical signals received from readers using the Hall effect. The data carrier and the read head are held by the plates that are present on the read head and the data carrier, respectively.

The method of reading and writing implemented in this system has the following disadvantages:
- the impossibility of creating a hidden code of arbitrary configuration of various products and the high probability of its unauthorized reproduction and reading,
- low sensitivity, which requires relatively strong magnetic fields for reading information,
- low recording reliability.

 A known method of recording and reading encoded information (RF patent N 2022365, MKI G 06 K 1/12, 7/08, 7/10), which is the closest to the problem and the achieved effect, namely, that the specified code is applied to information carrier, changing the electrophysical properties in the material or on the inner surface of the information carrier, and the reading of the applied code is carried out by optical registration of the magnetization distribution using a sensitive film magneto-optical element mounted on the outer media surface.

The disadvantages of this method are
- low recording reliability, a relatively high possibility of unauthorized reading of encoded information,
- low sensitivity and resolution.

 Common essential features of the known method and the claimed are the recording of a given code on a storage medium and subsequent reading of the applied encoded information.

на которую затем наносят защитное, оптически непрозрачное покрытие, а считывание информации осуществляют путем измерения распределения компонент магнитного поля, создаваемого магнитной пленкой, сканирующим СКВИД-магнитометром, при этом о подлинности кодированной информации судят по величине и форме измеряемого распределения компонент магнитного поля.Distinctive essential features are: encoded information is recorded on a medium manufactured by applying a magnetic film with a thickness of less than 50 onto the information medium

on which a protective, optically opaque coating is then applied, and information is read by measuring the distribution of the magnetic field components generated by the magnetic film with a scanning SQUID magnetometer, and the authenticity of the encoded information is judged by the size and shape of the measured distribution of the magnetic field components.

 The sensitive element of a scanning SQUID magnetometer is a quantum interferometer made of a high-temperature superconducting material.

 The distribution of the components of the magnetic fields of scattering of the magnetic film is measured by a scanning SQUID magnetometer at a distance of not more than 400 μm from the surface of the information carrier.

Магнитную пленку изготавливают методом Ленгмюра-Блоджетт.The magnetic film is made of magnetic material, for example nickel, with a thickness of 25-50

The magnetic film is made by the Langmuir-Blodgett method.

 The protective coating is made of non-magnetic metals, for example silver, copper.

The technical result achieved by the implementation of the proposed method is
- high reliability of recording information using a new type of information carrier - a magnetic film protected by an optically opaque coating, which completely eliminates the possibility of falsification without knowledge of the manufacturing conditions of the material of the magnetic film, the location of the recorded encoded information.

- the use of a protective coating of the magnetic film, which excludes the possibility of detecting and reading information by any other methods, except for special equipment based on a scanning SQUID magnetometer, which has high sensitivity, which allows reading super-weak signals with an ultra-thin magnetic film that are not detected by other methods,
- preservation of "magnetic" information after an arbitrary, arbitrarily large, magnetic effect (equivalent to a permanent storage device),
- the possibility of identifying the authenticity of encoded information by the configuration of the magnetic field and its amplitude.

 The essence of the invention lies in the fact that information is recorded in a medium made by applying an ultrathin magnetic film onto a medium, onto which a protective, optically opaque coating is then applied, and information is read by measuring the distribution of the magnetic field components created by an ultrathin magnetic film with a scanning SQUID magnetometer .

толщины пленки в магнитном поле.In FIG. 1 schematically shows an installation that implements the inventive method,
in FIG. 2 - magnetic image of 0.6x0.6 mm 26

film thickness in a magnetic field.

 The method of recording and reading encoded information is implemented as follows.

Толщина пленки может быть выбрана 25 - 50

и контролируется кварцмонитором. Таким образом, кодированную информацию в виде определенной конфигурации ультратонкой магнитной пленки записывают в носитель информации, которым может являться, например, пластиковая среда. После этого резистивная маска удалялась в ацетоне. Для защиты от несанкционированного доступа к кодированной информации на ультратонкую магнитную пленку наносится защитное, оптически непрозрачное покрытие, изготавливаемое из серебра, которое наносится сверху пленки со скоростью 15

сек толщиной 300

На фиг. 1 представлено схематическое изображение способа считывания кодированной информации. Форма образца - 600 х 600 мкм. Магнитное поле, создаваемое образцом - ультратонкой магнитной пленкой, считывалось сканирующим СКВИД-магнитометром.After applying the resistive mask to the storage medium, it is placed in the Leybold Z-400 spray system. After cleaning the carrier in a vacuum of 5 • 10 ^-6 mbar, a Ni nickel layer is applied to the carrier by thermal spraying at a rate of 1

Film thickness can be selected 25 - 50

and controlled by a quartz monitor. Thus, encoded information in the form of a specific configuration of an ultra-thin magnetic film is recorded in a storage medium, which may be, for example, a plastic medium. After that, the resistive mask was removed in acetone. To protect against unauthorized access to encoded information, a protective, optically opaque coating made of silver is applied to the ultra-thin magnetic film, which is applied on top of the film at a speed of 15

300 sec

In FIG. 1 is a schematic representation of a method for reading encoded information. The shape of the sample is 600 x 600 microns. The magnetic field created by the sample — an ultrathin magnetic film — was read by a scanning SQUID magnetometer.

The sensitive element of the scanning SQUID magnetometer is a quantum interferometer made of a high-temperature superconducting material - YBa ₂ Cu ₃ O ₇ .

 The distribution of the components of the scattering magnetic fields by an ultrathin magnetic film was measured with a scanning SQUID magnetometer at a distance of no more than 200 ... 300 μm from the surface of the information carrier.

 An ultra-thin magnetic film can be made by the Langmuir-Blodgett method in the form of an organic compound chemically bonded to metal ions, made in the form of a layered molecular structure of a Langmuir film with N> 1 ordered two-dimensional monolayers of magnetic metal ions included in it, while as a magnetic metal it can gadolinium, for example, can be used; to create an ultrathin magnetic film, amphiphilic compounds are used whose molecules form a Langmuir monolayer on the surface and aqueous phase. The classical substances for the formation of Langmuir monolayers at the water-air interface are fatty acids, especially stearic acid. A monolayer with ions adsorbed from the solution can then be transferred onto a solid-state substrate by the well-known Langmuir-Blodgett method.

Количество слоев магнитных ионов в многослойной ленгмюровской пленке на одной подложке может быть достаточно большим (от 1 до нескольких сотен и более ), при этом строго выдерживается параллельность слоев в структуре пленки. Для получения ультратонкой магнитной пленки был использован раствор стеариновой кислоты в хлороформе, который наносился на поверхность сверхчистой воды (полученной на установке MiLiQ фирмы Milipor), содержащей ионы Gd. Через 5 минут, необходимых для испарения хлороформа, монослой поджимался барьером до величины поверхностного давления P=30 мН/м со скоростью 3

молекулу•мин. Поверхностное давление в монослое измерялось с помощью весов Вильгельми. Затем после установления равновесия в системе методом Ленгмюра-Блоджетт монослой переносился на твердотельную подложку (полированный кремний) размером 3х30 мм. Последовательным повторением переноса монослоя с поверхности водной фазы на твердотельную подложку были получены образцы, содержащие 1, 10 и 25 слоев ионов гадолиния, инкорпорированных в слоистую структуру мультислойных пленок Ленгмюра-Блоджетт. Ультратонкая магнитная пленка, выполненная в виде слоистой молекулярной структуры ленгмюровской пленки с включенными в нее упорядоченными двумерными монослоями ионов магнитных металлов (конкретная реализация - гадолиний Gd), обладает магнитным упорядочением структуры уже при температуре ниже 500 К. Ультратонкая магнитная пленка обладает высокой стабильностью магнитных свойств. При этом пленка обладает также исключительно высокой стабильностью и однородностью структуры (в том числе высокой упорядоченностью и плотностью упаковки ионов гадолиния в плоскости слоя, среднее расстояние между ионами гадолиния 5

а также регулярностью слоистой структуры.In addition to the introduced rare-earth metal ions, other ions may be present in the solution that can be adsorbed onto the monolayer and also be included in the structure of the ultrathin film. As a result, a strictly two-dimensional planar metal-containing Langmuir film is formed on the surface of the substrate. The high degree of ordering of the molecular structure of the film and the two-dimensional layered character of the arrangement of magnetic ions in it ensure the appearance of new useful properties in such films that substantially differ from the properties of the corresponding metals and other ionic compounds, in particular, the appearance of magnetic ordering at relatively high temperatures. A significant advantage of an ultrathin magnetic film is the fundamental possibility of obtaining it in the form of even one ideally ordered two-dimensional monolayer of magnetic ions included in the layered molecular structure of the Langmuir film, which is unattainable by other methods, including the most advanced methods of molecular beam zitaxy. The inclusion of rare earth metals in the structure of films of trivalent magnetic ions provides extremely high stability of the material. Thus, the obtained films of gadolinium stearate upon heating to 650 K with subsequent cooling to room temperature almost did not change their magnetic properties. An ultrathin magnetic film can be obtained on an atomically smooth solid-state substrate, which ensures the formation of flat layers of rare-earth metal ions in the structure of Langmuir films deposited on a substrate. The distance between the layers of magnetic ions in multilayer films is strictly equal to the distance between the regions of the polar heads, which in the case of Langmuir films of fatty acids (Y-type structures) is 50

The number of layers of magnetic ions in a multilayer Langmuir film on one substrate can be quite large (from 1 to several hundred or more), while the parallelism of the layers in the film structure is strictly maintained. To obtain an ultrathin magnetic film, a solution of stearic acid in chloroform was used, which was deposited on the surface of ultrapure water (obtained on a MiLiQ installation by Milipor) containing Gd ions. After 5 minutes, necessary for the evaporation of chloroform, the monolayer was pressed by the barrier to a surface pressure of P = 30 mN / m at a speed of 3

molecule • min. The surface pressure in the monolayer was measured using a Wilhelmy scale. Then, after equilibrium in the system was established by the Langmuir-Blodgett method, the monolayer was transferred onto a solid-state substrate (polished silicon) of size 3 × 30 mm. By successive repetition of the transfer of a monolayer from the surface of the aqueous phase to a solid-state substrate, samples were obtained containing 1, 10, and 25 layers of gadolinium ions incorporated into the layered structure of Langmuir-Blodgett multilayer films. An ultra-thin magnetic film made in the form of a layered molecular structure of a Langmuir film with ordered two-dimensional monolayers of magnetic metal ions included in it (a specific implementation is gadolinium Gd) has a magnetic ordering of the structure even at temperatures below 500 K. The ultra-thin magnetic film has a high stability of magnetic properties. Moreover, the film also has extremely high stability and homogeneity of the structure (including high ordering and packing density of gadolinium ions in the plane of the layer, the average distance between gadolinium ions 5

as well as the regularity of the layered structure.

The scanning SQUID magnetometer includes a sensitive element, which is a quantum interferometer made of high-temperature superconducting material YBa ₂ Cu ₃ O ₇ , standard SQUID flux-blocking electronics, which measures the magnetic field component perpendicular to the SQUID plane, the information carrier moving system, and the test magnetic task system fields. In the measurement, the interferometer was placed in a nitrogen dewar, which, in turn, was located inside a magnetic screen made of two layers of μ-metal. When measuring the magnetic field distribution of an ultrathin magnetic film, the distance between the film and SQUID was from 100 to 400 μm. The measurements were carried out after cooling in a zero magnetic field from T = 400 K to the temperature of liquid nitrogen.

давала слабый магнитный сигнал. Когда намагничивающее поле 4000

было приложено в плоскости пленки, то появлялся "хороший" магнитный "образ" пленки (фиг. 2). Можно видеть острые max и min B_z компоненты, локализованные около противоположных краев, помеченные на фиг. 2 пунктирной линией.After cooling, a film of thickness 26

gave a weak magnetic signal. When the magnetizing field is 4000

was applied in the plane of the film, a "good" magnetic "image" of the film appeared (Fig. 2). You can see the sharp max and min B _z components located near opposite edges, labeled in FIG. 2 dashed line.

Это значение почти в три раза меньше, чем в объемном никеле.The symmetry of FIG. 2 indicates that the magnetic moment of the film is oriented in the plane. The existence of only two peaks in FIG. 2 proves that ordering is single-domain. In this case, the spatial resolution of SQUID is at least an order of magnitude larger than the film size, and the signal-to-noise ratio of SQUID is more than 100. It was found that the saturation magnetization value is 0.17 MA / m and is reached at 2500

This value is almost three times less than in bulk nickel.

а остаточная намагниченность - 0,028 MA/м. Попытки измерить пленки толщиной 15 и 8

в перпендикулярном и параллельном магнитных полях при расстоянии между СКВИДом и пленкой 100 мкм не дали результата. В области толщин пленки 15 - 26

значение объемной намагниченности уменьшается более чем на два порядка величины, что и определяет оптимальное значение толщины ультратонкой магнитной пленки - 25 - 50

Магнетизм ультратонких магнитных пленок интересен с практической точки зрения, так как ультратонкие магнитные пленки могут быть использованы в приборах для магнитной записи с высокой плотностью. Свойства ультратонких магнитных пленок (точка Кюри - температура Tc, намагниченность M, ориентация магнитного момента) очень сильно зависят от толщины пленки и способа ее изготовления. Измерения намагниченности, то есть считывание записанной на пленку информации, требуют высокочувствительного прибора. Известные в настоящее время приборы: вибрационный магнитометр, торсионный магнитометр, магнитный силовой микроскоп, магнитооптический эффект Керра, электронный микроскоп не обладают необходимыми свойствами: чувствительностью, разрешающей способностью и т.д. Недавнее создание прибора нового вида - сканирующего СКВИД-магнитометра - позволило решить задачу по измерению намагниченности ультратонких пленок с высокой чувствительностью, а также запоминать распределение магнитной структуры с пространственным разрешением до нескольких микрометров, что позволило создать способ записи и считывания информации с использованием ультратонкой магнитной пленки.A study of hysteresis indicates the presence of a ferromagnetic order in the studied film with a Curie temperature above 77 K. The coercive force was 35

and the residual magnetization is 0.028 MA / m. Attempts to measure films of thickness 15 and 8

in perpendicular and parallel magnetic fields at a distance between SQUID and a film of 100 μm, they failed. In the range of film thicknesses 15 - 26

the value of the volume magnetization decreases by more than two orders of magnitude, which determines the optimal value of the thickness of an ultrathin magnetic film - 25 - 50

The magnetism of ultrathin magnetic films is interesting from a practical point of view, since ultrathin magnetic films can be used in high-density magnetic recording devices. The properties of ultrathin magnetic films (Curie point — temperature Tc, magnetization M, orientation of the magnetic moment) depend very much on the film thickness and the method of its manufacture. Magnetization measurements, that is, reading the information recorded on film, require a highly sensitive instrument. Currently known devices: a vibration magnetometer, a torsion magnetometer, a magnetic force microscope, the Kerr magneto-optical effect, and an electron microscope do not possess the necessary properties: sensitivity, resolution, etc. The recent creation of a new type of instrument - a scanning SQUID magnetometer - made it possible to solve the problem of measuring the magnetization of ultrathin films with high sensitivity, as well as remembering the distribution of the magnetic structure with a spatial resolution of up to several micrometers, which made it possible to create a method of recording and reading information using an ultrathin magnetic film.

 The method of recording and reading information has high reliability of recording information using a new type of information carrier - an ultrathin magnetic film protected by an optically opaque coating, which completely eliminates the possibility of counterfeiting without knowledge of the manufacturing conditions, the material of the ultrathin magnetic film, the location of the recorded information, as well as storage " magnetic "information after arbitrary magnetic exposure - the equivalent of a permanent storage device, the possibility of identification and the authenticity of the encoded information on the configuration of the magnetic field and its amplitude, which is of great interest for its widespread use, for example, to protect the encoded information printed on securities, money, plastic cards, etc.

Claims (5)

1. The method of recording and reading encoded information, which includes writing the specified information by acting on the information carrier and then reading the printed information, characterized in that the encoded information is recorded on the information medium by applying a magnetic film with a thickness of less than 50 to the information medium

onto which a protective, optically opaque coating is then applied, and the reading of the encoded information is carried out by measuring the distribution of the magnetic field components generated by the magnetic film, a scanning SQUID magnetometer, and the authenticity of the encoded information is judged by the size and shape of the measured distribution of the magnetic field components.  2. The method according to claim 1, characterized in that the sensitive element of the scanning SQUID magnetometer is made in the form of an interferometer made of a high-temperature superconducting material.  3. The method according to claim 1, characterized in that the distribution of the components of the magnetic field of the magnetic film is scanned by a SQUID magnetometer at a distance of not more than 400 microns from the surface of the information carrier. 4. The method according to claim 1, characterized in that the magnetic film is made of magnetic material, for example nickel, with a thickness of 25-50

5. The method according to claim 1, characterized in that the magnetic film is made by the Langmuir-Blodgett method.  6. The method according to claim 1, characterized in that the protective coating is made of non-magnetic metals, for example silver, copper.

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