JP2007227847A - Magnetic shield material, method of manufacturing magnetic shield material, and magnetic shield case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To cope with such a problem that a magnetic sensor may be injured by a strong external magnetic field when the magnetic sensor is used in an electromagnetic environment, and it becomes impossible to detect any magnetic field to be detected when the magnetic sensor is shielded by a shield material. <P>SOLUTION: The magnetic sensor is contained in a magnetic shield case made of a material whose permeability rapidly increases at the time of exceeding a critical magnetic field strength. The material has a structure formed by laminating a ferromagnetism material and an antiferromagnetism material which have magnetic anisotropies in the mutually different directions. Laminations consisting of the ferromagnetism material and the antiferromagnetism material are further laminated through nonmagnetic materials. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic shield material for shielding magnetic devices such as a magnetic sensor and a magnetic head from a magnetic field in an electromagnetic environment.

  In electric equipment and electronic equipment, with miniaturization and higher performance of functions, electromagnetic fields of various directions and strengths due to electromagnetic phenomena are congested inside these equipment. Such an electromagnetic environment has various influences on a magnetic device made of a magnetic material such as a magnetic sensor or a magnetic head for detecting a weak magnetic field provided in these devices. In particular, a magnetic sensor such as a magneto-impedance element is a magnetic device for detecting a specific weak magnetic field in an electromagnetic environment, and therefore is configured to react to a weak magnetic field and is generated by a weak external magnetic field. Magnetic flux can be detected and output as an electrical signal. As described above, the magnetic field applied to the magnetic sensor from the electromagnetic environment causes noise in the electrical signal of the detection output of the magnetic sensor, thereby degrading the S / N ratio of the detection value and causing an error. Further, a particularly strong magnetic field not only causes an error in the detection value of the magnetic sensor, but also may cause an obstacle to the operation of the magnetic sensor and the magnetic sensor itself. To protect a magnetic device installed in an electronic device having a complicated electromagnetic environment from the electromagnetic environment and prevent damage due to magnetism, the magnetic device is surrounded by a magnetic shielding material to block a magnetic field entering the magnetic device. The shield method is known. In the magnetic shield method, a magnetic device is surrounded by a magnetic shield material having a high magnetic permeability, and a magnetic field entering the magnetic device due to an electromagnetic environment is guided to the magnetic shield material to block or reduce the magnetic field entering the inside. Known magnetic shield materials having high magnetic permeability include permalloy (NiFe), which is an alloy of nickel and iron, and an amorphous magnetic thin plate. As a magnetic shielding material having a particularly high magnetic permeability, a magnetic permeability of 200,000 is obtained by adding a small amount of manganese (Mn), silicon (Si), molybdenum (Mo) and copper (Cu) to Ni and Fe as main materials. Patent Document 1 discloses a high magnetic permeability magnetic material exceeding the above. It is said that a good shielding effect can be obtained in an example in which a magnetic head is housed in a shielding case for a magnetic head using this high permeability magnetic material.

  As another example of the magnetic shield material, Patent Document 2 discloses a laminated electrical steel sheet in which a plurality of directional electrical steel sheets having easy magnetization axes in one direction are stacked with the easy magnetization axes orthogonal to each other. This laminated electrical steel sheet is constructed by laminating directional electrical steel sheets with a thickness of 2 mm or less in which silicon (Si) is added to iron, and is good even for a strong DC field to a weak DC magnetic field. It is said that a shielding effect can be obtained.

6A and 6B are graphs showing the relationship between magnetic field strength and magnetic permeability when a magnetic material having an easy magnetization axis in a certain direction is placed in a magnetic field. The magnetic material has a flat plate shape and has an easy magnetization axis in a predetermined direction M along the plane of the flat plate. When this magnetic material is placed in the magnetic field in the direction M and the strength of the magnetic field is changed, the magnetic permeability changes as shown in FIG. “+” And “−” on the horizontal axis in FIGS. 6A and 6B indicate directions opposite to each other in the magnetic field. When the strength of the magnetic field is zero or in the vicinity thereof, the magnetic permeability is zero or a small value close thereto. When the strength of the magnetic field is greater than zero in the “+” or “−” direction, the magnetic permeability increases and reaches the maximum value μ1. As the strength of the magnetic field increases further in the “+” or “−” direction, the magnetic permeability decreases and eventually becomes zero.
When the direction of the magnetic field is a direction (hard magnetic axis) perpendicular to the direction M along the plane of the flat plate, the magnetic field strengths are “+ R” and “+” as shown in FIG. In the range of “−R”, the magnetic permeability is the maximum value μ1. In the range where the strength of the magnetic field is larger than “+ R” and the range larger than “−R”, the magnetic permeability decreases and finally becomes zero. The following can be seen from the above magnetic characteristics. When the direction of the external magnetic field is the direction M, the magnetic field whose strength is zero or close to zero passes through the magnetic material. As the strength of the magnetic field increases in the “+” or “−” direction, the magnetic permeability increases and the magnetic field becomes difficult to pass through the magnetic material. On the other hand, when the direction of the external magnetic field is perpendicular to the direction M, a magnetic field having a strength smaller than + R and larger than −R does not pass through the magnetic material. Therefore, when a magnetic shield case is made of this magnetic material and a magnetic sensor is inserted therein, the magnetic sensor cannot detect an external magnetic field.
JP-A-11-354313 JP-A-8-264351

  In order to provide a sufficient magnetic shield for a magnetic device such as a magnetic sensor or a magnetic head using the magnetic shielding material having a high magnetic permeability disclosed in Patent Documents 1 and 2, the entire magnetic device is shielded from the magnetic shield. It is necessary to surround with material. However, if all of the magnetic device is surrounded by a high-permeability magnetic shield material, the magnetic field to be detected by the magnetic device (the magnetic field to be detected) cannot reach the magnetic device. It will not be possible. In order to allow the magnetic flux of the detected magnetic field to reach the magnetic device, it is necessary to provide an opening in a part of the magnetic shield material. From this opening, undesired magnetic flux due to the electromagnetic environment also enters along with the magnetic flux of the detected magnetic field, so that the SN ratio of the detection output of the detected magnetic field is deteriorated. When a magnetic field is generated by a particularly strong electromagnetic environment, the magnetic device and the electronic circuit connected thereto may be damaged.

  The present invention detects a desired external magnetic field when the strength of the external magnetic field is below a predetermined value even if the magnetic device for detecting the external magnetic field, such as a magnetic sensor or a magnetic head, is entirely covered with a magnetic shield material. An object of the present invention is to provide a magnetic shield material that can be used.

  In the magnetic shield material of the present invention, the nonmagnetic material layer is interposed between the ferromagnetic material layer and the antiferromagnetic material layer so that the directions indicating the respective magnetic anisotropies intersect at a predetermined angle. Are stacked.

  The magnetic shield material of the present invention is a first ferromagnetic film formed on the surface of a nonmagnetic substrate so as to have magnetic anisotropy in a predetermined direction along the surface of the substrate. A first antiferromagnetic film formed on the ferromagnetic film so as to have magnetic anisotropy in a direction different from the direction of magnetic anisotropy of the first ferromagnetic film by a predetermined angle; On the first antiferromagnetic film, on the second ferromagnetic film formed so as to have magnetic anisotropy in the same direction as the first ferromagnetic film, and on the second ferromagnetic film And a second antiferromagnetic film formed so that the direction of magnetic anisotropy is 180 degrees different from the direction of magnetic anisotropy of the first antiferromagnetic film.

  A magnetic shield material according to another aspect of the present invention is a first ferromagnetic film formed on a surface of a nonmagnetic substrate so as to have magnetic anisotropy in a predetermined direction along the surface of the substrate. A first anti-strength formed on the first ferromagnetic film so as to have a magnetic anisotropy in a direction different from the direction of the magnetic anisotropy of the first ferromagnetic film by a predetermined angle. A second ferromagnetic film formed on the magnetic film, the first antiferromagnetic film, and having a magnetic anisotropy in the same direction as the first ferromagnetic film; and the second ferromagnetic film A laminate having a second antiferromagnetic film formed on the film so that the direction of magnetic anisotropy is 180 degrees different from the direction of magnetic anisotropy of the first antiferromagnetic film A plurality of layers are laminated with a nonmagnetic film interposed.

  In the magnetic shield material of the present invention, the magnetic permeability of the magnetic shield material changes depending on the strength of magnetism applied to the magnetic shield material. When the strength of the magnetic field applied to the magnetic shield material is equal to or less than a predetermined value (hereinafter referred to as critical magnetic field strength), the magnetic shield material has a low magnetic permeability, so that the detected magnetic field passes through the magnetic shield material. If the strength of the magnetic field exceeds the critical magnetic field strength, the magnetic shield material has a rapid increase in magnetic permeability, so that the magnetic field is blocked by the magnetic shield material. A magnetic shield container that covers the entire periphery of the magnetic device is configured with the magnetic shield material of the present invention, and the magnetic device is accommodated in the magnetic shield container.

  When the critical magnetic field strength is set to a value larger than the strength of the detected magnetic field to be detected by the magnetic device, when the strength of the magnetic field due to the electromagnetic environment is smaller than the strength of the detected magnetic field, Since the magnetic permeability is low, the magnetic flux of the detected magnetic field passes through the magnetic shield container and reaches the magnetic device and is detected.

  If the strength of the magnetic field due to the electromagnetic environment exceeds the critical magnetic field strength, the magnetic shielding material's permeability increases rapidly, so that the magnetic field to be detected and the magnetic field due to the electromagnetic environment are blocked by the magnetic shield container and do not reach the internal magnetic device. . For this reason, it is possible to avoid a strong magnetic field due to the electromagnetic environment from damaging the magnetic device.

  The method of manufacturing a magnetic shield material according to the present invention includes a step of forming a first ferromagnetic film on a surface of a nonmagnetic base material in a magnetic field in a first direction along the surface of the substrate, Forming a first antiferromagnetic film on the ferromagnetic film in a magnetic field in a second direction different from the first direction, and forming the first antiferromagnetic film on the first antiferromagnetic film. A step of forming a second ferromagnetic film in a magnetic field in one direction, and a magnetic field in a third direction that is 180 degrees different from the second direction on the second ferromagnetic film. And 2) forming a second antiferromagnetic film.

  According to the manufacturing method of the present invention, the first ferromagnetic film, the first antiferromagnetic film, the second ferromagnetic film, and the second antiferromagnetic film are formed in different magnetic fields. Since two types of films can be formed by a simple operation of changing the direction of the magnetic field, the manufacturing cost is low.

  According to the magnetic shield material of the present invention, when the strength of the external magnetic field is less than or equal to the critical magnetic field strength, the magnetic shield material has a low magnetic permeability and the external magnetic field passes through the magnetic shield material. Accordingly, the external magnetic field reaches the magnetic detection unit surrounded by the magnetic shield material. When there is a strong magnetic field that exceeds the critical magnetic field strength, the magnetic permeability of the magnetic shield material increases rapidly. Therefore, a strong external magnetic field that exceeds the critical magnetic field strength is not applied to the magnetic device shielded by the magnetic shield material. Therefore, there is no risk that the magnetic device will be damaged by the strong magnetic field in the electromagnetic environment.

  Hereinafter, preferred embodiments of the magnetic shield material and the manufacturing method thereof according to the present invention will be described with reference to FIGS.

<< First Example >>
A magnetic shield material and a manufacturing method thereof according to a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1A is a cross-sectional view of a magnetic shield material according to a first embodiment of the present invention, and FIG. 1B is an exploded perspective view of the magnetic shield material.
FIG. 2 is a graph showing the relationship between the magnetic field strength (horizontal axis) and the magnetic permeability (vertical axis) when the magnetic shield material of this example is placed in a magnetic field.

  With reference to FIG. 1, the structure of the magnetic shielding material of a present Example is demonstrated. 1 (a) and 1 (b), the first ferromagnetic film 1 is formed on the main surface of the nonmagnetic substrate 4 by sputtering of NiFe in a magnetic field in the direction indicated by the arrow Ma1 (hereinafter referred to as the magnetic field Ma1). Film. The thickness of the ferromagnetic film 1 is 5 to 100 nm. When the thickness is thinner than 5 nm or thicker than 100 nm, the magnetic properties are greatly deteriorated. As a material of the substrate 4, polyester resin, polyimide resin, nonmagnetic metal, glass, nonmagnetic ceramic, or the like is used. The thickness of the substrate 4 is 0.5 mm, for example. Next, the first antiferromagnetic film 2 is formed on the ferromagnetic film 1 by sputtering of FeMn or the like in the magnetic field in the direction indicated by the arrow Ma2 (hereinafter referred to as the magnetic field Ma2). The thickness of the antiferromagnetic film 2 is 0.5 to 50 nm. If the thickness of the diamagnetic layer 2 is less than 0.5 nm, the exchange force at the interface with the ferromagnetic film is weakened and the characteristics are deteriorated. On the other hand, if it is thicker than 50 nm, the magnetic interaction between the ferromagnetic films is weakened, causing a decrease in output. As a material of the antiferromagnetic film 2, IrMn, PtMn, NiMn, NiO, etc. can be used in addition to the FeMn. The direction of the magnetic field Ma2 is 90 degrees different from the direction of the magnetic field Ma1.

  A nonmagnetic film 3 is formed on the antiferromagnetic film 2. The nonmagnetic film 3 is formed by sputtering of Ta and has a thickness of 2 nm, for example.

  A second ferromagnetic film 1a is formed on the nonmagnetic film 3 by sputtering of NiFe in a magnetic field in the direction indicated by the arrow Ma3 (hereinafter referred to as magnetic field Ma3). The direction of the magnetic field Ma3 is the same as that of the magnetic field Ma1. The thickness of the ferromagnetic film 1a is substantially the same as that of the ferromagnetic film 1.

  A second antiferromagnetic film 5 is formed on the ferromagnetic film 1a by sputtering of FeMn or the like in a magnetic field in the direction indicated by an arrow Ma4 (hereinafter referred to as a magnetic field Ma4). The direction of the magnetic field Ma4 is opposite to the magnetic field Ma2 (180 degrees). Finally, the insulating film 3 is formed on the second antiferromagnetic film 5 to obtain a plate-like magnetic shield material. As a means for generating the magnetic fields Ma1, Ma2, Ma3 and Ma4, permanent magnets or DC electromagnets are used, and the strength of the magnetic field is, for example, 500 Oe. As the sputtering apparatus, a ternary magnetron sputtering apparatus was used, and the sputtering process was performed in a continuous process in a vacuum.

  By the above treatment, magnetic anisotropies in different directions are imparted to the ferromagnetic films 1 and 1a and the antiferromagnetic films 2 and 5, respectively. The ferromagnetic films 1 and 1a exhibit soft magnetic properties.

  The critical magnetic field strength of the magnetic shield material of this example is about 1 Oe. That is, the magnetic shielding material of the present example has a magnetic permeability almost close to zero when the magnetic field strength of the external magnetic field is 1 Oe or less. When the magnetic field strength exceeds 1 Oe, the magnetic permeability of the magnetic shield material increases rapidly, and a magnetic shielding function as a magnetic shield material is generated.

  The magnetic characteristics of the magnetic shield material according to the first embodiment of the present invention will be described with reference to FIGS. For example, the magnetic shield material of the present embodiment has a flat plate shape and has an easy axis of magnetization in a predetermined direction M along the plane of the flat plate. The hard axis of magnetization is in a direction perpendicular to the direction M of the easy axis of magnetization along the plane of the flat plate.

  FIG. 2A shows the relationship between the external magnetic field strength and the magnetic permeability measured by applying an external magnetic field in the direction of the hard axis of magnetization to the plate-like magnetic shield material of this example. ) Shows the relationship between the permeability and the strength of the external magnetic field when an external magnetic field is applied in the direction of the easy axis. 2A and 2B, the horizontal axis indicates the magnetic field strength (Oe), and “+” and “−” indicate external magnetic fields in opposite directions. Both vertical axes represent magnetic permeability (μ).

  In FIG. 2A, the magnetic permeability is close to zero when the strength of the external magnetic field is in the range of zero to about ± 0.5 Oe. The magnetic permeability is about 600 when the strength of the external magnetic field ranges from zero to about ± 1 Oe. When the strength of the external magnetic field increases beyond 1 Oe (absolute value), the magnetic permeability increases and becomes maximum at about 10 Oe.

  In FIG. 2B, the magnetic permeability is close to zero when the strength of the external magnetic field is in the range from zero to about ± 0.5 Oe. Therefore, since the detected magnetic field and the external magnetic field are transmitted through the magnetic shield material, the detected magnetic field reaches the magnetic detection element surrounded by the magnetic shield material and can be detected. The magnetic permeability is about 500 when the strength of the external magnetic field is in the range of zero to about ± 1 Oe. If the magnetic permeability is about 500 or less, the magnetic field is transmitted through the magnetic shield material of the invention, so that the detected magnetic field can be detected. When the strength of the external magnetic field increases beyond 1 Oe (absolute value), the magnetic permeability increases almost linearly and reaches a maximum value at about 5 Oe. When the magnetic permeability exceeds 500, the magnetic field transmitted through the magnetic shield material starts to decrease. When the strength of the external magnetic field exceeds 5 Oe, the magnetic permeability decreases and becomes zero at about 10 Oe. When an external magnetic field of ± 2 Oe or more is applied to the magnetic shield material of this embodiment, the transmitted magnetic field is greatly reduced, and the magnetic shield effect can be obtained.

<< Second Embodiment >>
A magnetic shield material according to a second embodiment of the present invention will be described with reference to FIG. In the figure, the magnetic shield material of the present embodiment is provided with a first magnetic body 10 on the main surface of a non-magnetic substrate 4. The first magnetic body 10 has a high magnetic permeability, and a magnetic material provided with magnetic anisotropy in a predetermined direction by stretching a member that is a raw material of the magnetic body 10 by machining or placing it in a strong magnetic field. It is a ribbon. A first antiferromagnetic film 2 similar to that in the first embodiment is formed on the first magnetic body 10 by sputtering of FeMn in a magnetic field in a predetermined direction.
Next, a nonmagnetic film 3 is formed on the first antiferromagnetic film 2. The nonmagnetic film 3 is formed by sputtering of Ta.
The second magnetic body 10a is provided on the nonmagnetic film 3 so that the direction showing the magnetic anisotropy is the same as the direction showing the magnetic anisotropy of the first magnetic body 10.

A second antiferromagnetic film 5 is formed on the second magnetic body 10a by sputtering in a magnetic field opposite to the direction of the magnetic field when the first antiferromagnetic film 2 is formed.
A nonmagnetic film 3 is formed on the second antiferromagnetic film 5, and a first magnetic body 10 is further provided thereon. Thereafter, the antiferromagnetic film 2, the nonmagnetic film 3, the second magnetic body 10a, the second antiferromagnetic film 5, and the nonmagnetic film 3 are sequentially stacked in the same process as described above.
In this embodiment, when the first and second magnetic bodies 10 and 10a are provided, a ready-made magnetic ribbon is used instead of sputtering, so that the processing steps are simplified as compared with the first embodiment and the processing time is increased. Is shortened.
Also in the magnetic shield material of the present embodiment, the characteristics shown in FIGS. 4A and 4B are obtained, and the same magnetic shield effect is obtained.

<< Third embodiment >>
The third embodiment of the present invention relates to a magnetic shield case constructed using the magnetic shield material according to the first and second embodiments of the present invention. FIG. 5 is a cross-sectional view of the magnetic shield case 20 of this embodiment. In the figure, the magnetic shield case 20 is formed using the magnetic shield material of the first or second embodiment, and is substantially a sealed container. A magnetic sensor 21 such as a magnetic head, which is an object to be magnetically shielded, is supported by a support 22 in the magnetic shield case 20.

  When the strength of the magnetic field outside the magnetic shield case 20 is less than or equal to the critical magnetic field strength, the magnetic field to be detected to be detected by the magnetic sensor 21 and the other magnetic field due to the electromagnetic environment are magnetized with low magnetic permeability of the magnetic shield case 20. It is detected by the magnetic sensor 21 through the shield material.

  When the strength of the external magnetic field exceeds the critical magnetic field strength, the magnetic permeability of the magnetic shield material of the shield case 20 increases. As a result, the magnetic flux that attempts to enter the magnetic shield case 20 by an external magnetic field passes through the magnetic shield material having a high magnetic permeability. Therefore, it does not enter the magnetic shield case 20. That is, the magnetic flux is blocked by the magnetic shield case 20 from the external magnetic field. As a result, even when the external magnetic field is extremely large, such as a discharge or a lightning strike, the influence of the magnetic field on the magnetic sensor 21 in the magnetic shield case 20 is prevented from damaging the magnetic sensor 21 and the electronic circuit connected thereto. can do.

  The present invention can be used as a shielding material for a magnetic sensor used in an electromagnetic environment in which magnetic fields of various directions and strengths are congested.

(A) is sectional drawing of the magnetic shielding material of 1st Example of this invention, (b) is the same exploded perspective view (A) is a graph showing the relationship between magnetic field strength and permeability when an external magnetic field is applied to the magnetic shielding material of the first embodiment of the present invention in the direction of its hard axis, and (b) is the same magnetization easy. Graph when an external magnetic field is applied in the direction of the axis Sectional drawing of the magnetic shielding material of 2nd Example of this invention (A) is a graph showing the relationship between magnetic field strength and magnetic permeability when an external magnetic field is applied to the magnetic shield material of the second embodiment of the present invention in the direction of the easy magnetization axis, and (b) is the same magnetization difficulty. Graph when an external magnetic field is applied in the direction of the axis Sectional drawing of the magnetic shielding case as 3rd Example manufactured with the magnetic shielding core of 1st or 2nd Example of this invention (A) And (b) is a graph which shows the relationship between the magnetic field of a conventional magnetic shielding material, and magnetic permeability.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a Ferromagnetic film 2, 5 Antiferromagnetic film 3 Nonmagnetic film 4 Substrate 10, 10a Magnetic body 20 Magnetic shield case 21 Magnetic sensor 22 Support body

Claims (8)

A first ferromagnetic film formed on the surface of the nonmagnetic substrate so as to have magnetic anisotropy in a predetermined direction along the surface of the substrate;
A first anti-strength formed on the first ferromagnetic film so as to have a magnetic anisotropy in a direction different from the direction of the magnetic anisotropy of the first ferromagnetic film by a predetermined angle. Magnetic film,
A second ferromagnetic film formed on the first antiferromagnetic film so as to have magnetic anisotropy in the same direction as the first ferromagnetic film; and A second antiferromagnetic film formed so that a direction of magnetic anisotropy is 180 degrees different from a direction of magnetic anisotropy of the first antiferromagnetic film;
Magnetic shielding material having A first ferromagnetic film formed on the surface of the nonmagnetic substrate so as to have magnetic anisotropy in a predetermined direction along the surface of the substrate;
A first anti-strength formed on the first ferromagnetic film so as to have a magnetic anisotropy in a direction different from the direction of the magnetic anisotropy of the first ferromagnetic film by a predetermined angle. Magnetic film,
A second ferromagnetic film formed on the first antiferromagnetic film so as to have magnetic anisotropy in the same direction as the first ferromagnetic film; and A second antiferromagnetic film formed so that a direction of magnetic anisotropy is 180 degrees different from a direction of magnetic anisotropy of the first antiferromagnetic film;
A magnetic shielding material comprising a plurality of laminated bodies each having a nonmagnetic film interposed therebetween.   3. The magnetic shield material according to claim 1, further comprising a nonmagnetic film between the first antiferromagnetic film and the second ferromagnetic film.   The magnetic shield material according to claim 1 or 2, wherein the base material is at least one selected from the group consisting of a resin film, a metal plate, a glass plate, and a ceramic plate.   3. The magnetic shield material according to claim 1, wherein the ferromagnetic film is an alloy of nickel and iron (NiFe).   The antiferromagnetic film is at least one selected from the group consisting of iron manganese (FeMn), iridium manganese (IrMn), platinum manganese (PtMn), nickel manganese (NiMn), and nickel oxide (NiO). The magnetic shielding material according to claim 1 or 2. Forming a first ferromagnetic film on a nonmagnetic base material in a magnetic field in a first direction along the surface of the substrate;
Depositing a first antiferromagnetic film on the first ferromagnetic film in a magnetic field in a second direction different from the first direction;
Forming a second ferromagnetic film on the first antiferromagnetic film in a magnetic field in the first direction, and forming the second ferromagnetic film on the second ferromagnetic film. Forming a second antiferromagnetic film in a magnetic field in a third direction that is 180 degrees different from the direction;
The manufacturing method of the magnetic-shielding material which has. A magnetic shield case for a magnetic sensor, comprising the magnetic shield material according to claim 1.

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