JP4648876B2 - Magnetic circuit for radial magnetic field generation - Google Patents

Description

  The present invention provides a magnetic circuit for generating a radial magnetic field necessary for a film formation process, a heat treatment process, etc. of a substrate for manufacturing a magnetic disk device.

  As information recording in magnetic disk devices, a horizontal magnetic recording system in which magnetization is performed in a horizontal direction with respect to a track of a recording medium is widely used. In this method, since the micro magnets magnetized in the horizontal direction with respect to the recording film have a demagnetizing field relationship with the adjacent micro magnets, the magnetization decreases as the recording density increases and the micro magnets become smaller. Or degaussing occurs, making it impossible to read the recorded signal. A vertical recording method has been proposed as a method for solving such a limitation of the high density recording of the horizontal recording method. The recording medium of the perpendicular recording system has, for example, a two-layer structure in which a recording hard magnetic film magnetized in the vertical direction is laminated on a high magnetic permeability soft magnetic film. This high permeability soft magnetic film functions as a magnetic circuit that recirculates the recording magnetic field from the magnetic head to the magnetic head side during signal recording, and increases the strength of the recording magnetic field for recording and reproduction. Since it plays a role of improving efficiency, it is desired to have a higher magnetic permeability. In addition, if a stray magnetic field exists around the recording medium or the magnetic head, the stray magnetic field is concentrated on the magnetic pole of the magnetic head, and the magnetic wall of the soft magnetic film is moved by the concentrated magnetic field, thereby changing the reproduction output and recording magnetization. There was something to do.

  As one method for solving this problem, it has been proposed to give a circumferential or radial magnetic anisotropy to a substrate on which a soft magnetic film is formed. A soft magnetic film having magnetic anisotropy has improved magnetic permeability and improved magnetic efficiency during recording and writing. Further, as a magnetic field generation source for giving this magnetic anisotropy, a three-layer film structure in which a hard magnetic film (undercoat film) 112 is formed between a substrate 111 and a soft magnetic film (undercoat film) 113 as shown in FIG. For example, a recording medium 110 having a hard magnetic film (recording film) 114 provided thereon is proposed. Since the hard magnetic film 112 as the base film is magnetized in the radial direction and a magnetic field in the radial direction is always applied to the soft magnetic film 113, the movement of the domain wall due to the stray magnetic field is suppressed, Problems such as changes in reproduction output and demagnetization of recorded magnetization can be solved.

  In addition to this, in order to solve various problems, a method having a medium structure having a further multilayer structure is adopted, and a multilayer structure for solving the above-mentioned problem in high density is also proposed in the horizontal recording system. However, these multilayer films are increasingly required to have a step of uniformly magnetizing the substrate in the circumferential direction and the radial direction.

  As described above, in the manufacturing process of a magnetic disk medium substrate, the effectiveness of applying a circumferential or radial magnetic field to a soft magnetic film or a hard magnetic film, and the heat treatment process after the film formation In addition, the effectiveness of applying a magnetic field in the above direction to the substrate has been proposed. Film formation on a substrate is mainly performed by sputtering or plating, but a magnetic circuit for generating a magnetic field suitable for each is required.

  When a magnetic field is applied to the substrate in the radial direction or circumferential direction, these magnetic field directions must be parallel to the substrate surface. If the direction of the applied magnetic field is tilted with respect to the substrate surface, the magnetization direction of the hard magnetic film is similarly tilted, and the direction of magnetic anisotropy of the soft magnetic film is not uniform. It is disadvantageous in realizing.

A method of solving this problem and applying a radial magnetic field to the substrate is proposed in Patent Document 1. As shown in FIG. 16, a plane including the ring-shaped substrate 111 is defined as an arrangement plane (a plane passing through XX and perpendicular to the central axis 123 of the substrate), and has a symmetrical shape with respect to the arrangement plane. A pair of ring-shaped permanent magnets 121 is installed. The center of each ring-shaped permanent magnet 121 is disposed on the center axis 123 of the ring-shaped substrate. The magnetization direction 124 of each ring-shaped permanent magnet is perpendicular to the arrangement surface and is symmetric with respect to the arrangement surface. When the permanent magnets are arranged in this way, the permanent magnets form a magnetic field schematically shown by the magnetic lines of force 125 as a whole, and the magnetic lines of force 125 are radial, that is, radially directed on the arrangement surface. Furthermore, since the magnet is in a symmetrical position with respect to the substrate, the direction of the lines of magnetic force on the substrate is completely parallel to the substrate.
However, although this method can cope with processing with one substrate, a problem arises when processing a plurality of substrates. For example, when processing two substrates at the same time, if two of the magnetic circuits shown in Patent Document 1 are used side by side so that the arrangement surfaces of the ring-shaped substrates are on the same plane, the magnetic field generated by one magnetic circuit is changed to the other substrate. Therefore, the magnetic field on the substrate is not correctly directed in the radial direction as shown in FIG. As can be seen from FIG. 17, the direction of the magnetic field is greatly deviated from the radial direction in a region close to the adjacent magnetic circuit.

Recently, small-diameter substrates having a diameter of 1 inch or less have been used, and the number is expected to increase. On the other hand, these small-diameter substrates are eagerly desired to reduce costs and increase productivity, and for that purpose, it is necessary to process a plurality of substrates at a time.
JP 2005-209326 A

When processing a plurality of substrates simultaneously in the manufacturing process of a magnetic disk medium substrate, the direction of the magnetic field applied to the soft magnetic film and the hard magnetic film formed on the circular substrate is in the radial direction of the substrate and on the substrate surface. there is provided a magnetic circuits as magnetic source to be parallel for.

The present invention is a magnetic circuit unit comprising a pair of ring-shaped permanent magnets provided on both sides of the arrangement surface of a ring-shaped substrate to be processed, and when the ring-shaped substrate is arranged, At least two magnetic circuit units that generate a magnetic field in the radial direction of the ring-shaped substrate are combined so that the arrangement surfaces of the ring-shaped substrates of all the magnetic circuit units are on the same plane, and the pair of ring-shaped permanent magnets Provided is a magnetic circuit for generating a radial magnetic field having a shape having different volumes in a portion close to and a portion far from adjacent magnetic circuit units.
An integrated magnet may be used as the ring-shaped permanent magnet, but it is preferably a combination of two or more segment magnets, and segment magnets close to adjacent magnetic circuit units are more than other segment magnets. Also has a small volume. In addition, the ring-shaped permanent magnet preferably has a shape that is small at a portion close to an adjacent magnetic circuit unit and large at a distant portion. The ring-shaped permanent magnet may preferably have a shape having a gap in the portion closest to the adjacent magnetic circuit unit. The pair of ring-shaped permanent magnets are preferably provided at positions symmetrical to each other with respect to the arrangement surface of the ring-shaped substrate, and have a symmetrical shape and a magnetization direction with respect to the arrangement surface. The ring-shaped permanent magnet may have a magnetization direction perpendicular to the arrangement surface of the ring-shaped substrate or a magnetization direction inclined from the direction perpendicular to the arrangement surface.
Further, the present invention is a magnetic circuit unit comprising a pair of ring-shaped permanent magnets provided outside the arrangement surface of the ring-shaped substrate to be processed, and the arrangement surface when the ring-shaped substrate is arranged. In which at least two magnetic circuit units that generate a magnetic field in the radial direction of the ring-shaped substrate are combined so that the arrangement surfaces of the ring-shaped substrates of all the magnetic circuit units are on the same plane, The volume of each ring-shaped magnet within an angle range of ± θ (where θ is 0 <θ <90 degrees) from the line connecting the centers of adjacent ring-shaped permanent magnets is 180 degrees ± of the same ring-shaped permanent magnet. A magnetic circuit for generating a radial magnetic field that is smaller than the volume of the same permanent magnet in the range of the angle θ is provided .

  The present invention provides a magnetic circuit for generating a radial magnetic field required in the simultaneous film formation process and the simultaneous heat treatment process of a plurality of substrates in the manufacture of a magnetic disk device, and is suitable for the entire substrate in the radial direction. A radial magnetic field can be generated.

  FIG. 18 shows how the magnetic fields from adjacent magnetic circuits influence when the two magnetic circuit units of FIG. 16 are used by arranging the arrangement surfaces of the ring-shaped substrates so as to be the same plane. It is shown. As seen in FIG. 17, the direction of the magnetic field is tilted to the right in the region near the adjacent magnetic circuit unit located on the right side. This is a result of the right radial magnetic field superimposed on the original radial magnetic field. That is, a rightward magnetic field acts from the adjacent magnetic circuit unit. Referring to FIG. 18, magnetic field lines 125 as shown in the figure are generated from adjacent magnetic circuit units, and as a result, a magnetic field vector 126 facing right is applied on the substrate. The magnitude of the applied magnetic field is larger as it is closer to the adjacent magnetic circuit unit. As a result, the total magnetic field tends to increase in inclination as it is closer to the adjacent magnetic circuit unit.

  As described above, it can be seen that the influence of the adjacent magnetic circuit unit gives a rightward magnetic field on the substrate, but at the same time, the portion shown in the region P of FIG. It can be seen from the 16 lines of magnetic force. The magnetic field distribution by the region P is also closer to the region P and has a magnetic field distribution similar to the magnetic field exerted by the adjacent magnetic circuit unit. As a matter of course, if the same magnetic field is not applied to the left and right substrates, the substrates have different performances. Therefore, the two magnetic circuits are basically mirror-symmetrical. As a result of considering these together, if the magnetic force of the region P and the region Q that is mirror-symmetrical with the region P is weakened by the same amount, the correct radial direction is corrected by correcting the magnetic field inclined to the right side on the left substrate. At the same time, the right-side substrate also has a mirror-symmetric magnetic field, so that it can be directed correctly in the radial direction. In order to form an accurate radial magnetic field, it was thought that a radial magnetic field distribution could be obtained by dividing the magnet into several regions and applying different magnetic forces to each.

  There are several ways to reduce the magnetic force, but one is to reduce the volume of the magnet, and the other is to use a magnet with weak magnetic force, that is, a magnet with low residual magnetization Br. Here, a method of obtaining a radial magnetic field by reducing the magnet volume will be described in detail.

An example of a magnetic circuit for generating a radial magnetic field of the present invention is shown in FIG. In FIG. 1, when the magnetic circuit is viewed in plan, the two magnetic circuit units are arranged on the same plane with each ring-shaped substrate arrangement surface (the plane passing through XX and perpendicular to the central axes 23 and 33 of the substrate). The magnetic circuit combined as follows is shown. A pair of ring-shaped permanent magnets 21 (21A and 21B) and a pair of ring-shaped permanent magnets 31 (31A and 31B) for generating radial magnetic fields on the substrates 11 and 12 are arranged so as to sandwich each substrate. In FIG. 1, A is attached to the permanent magnet above the substrate, and B is attached below the same. In order to give exactly the same magnetic field distribution to the two substrates, the ring-shaped permanent magnets 21 and 31 have a mirror-symmetric shape with respect to the symmetry plane σ ₁ perpendicular to the arrangement plane and defining each magnetic circuit unit. Yes. Of course, in order to generate a magnetic field in the radial direction correctly on the substrate, the magnetic field is also symmetric with respect to a symmetry plane σ ₂ perpendicular to the arrangement plane and perpendicular to the symmetry plane σ ₁ , and is ring-shaped. The permanent magnet has a mirror-symmetric shape with respect to the symmetry plane σ ₂ . In addition, by making the ring-shaped permanent magnet (magnetic circuit) symmetrical with respect to the arrangement surface, the magnetic field on the substrate placed on the same plane as the arrangement surface can always be parallel to the substrate surface. In that case, the magnetization direction of the magnet is made symmetrical with respect to the arrangement plane.

When combining two magnetic circuit units, the distance between adjacent ring-shaped permanent magnet centers varies depending on the size of the ring-shaped substrate to be processed and the magnetic characteristics, but not more than three times the outer diameter of one magnetic circuit. The outer diameter is preferably larger than the length. The object whose volume is changed adjusts a region having at least one of the units in which the distance between the centers of adjacent magnet units is three times or less of the outer diameter.
The fixture 41 of the ring-shaped permanent magnets 21 and 31 is not particularly limited as long as it is a non-magnetic material that does not obstruct the passage of sputtered particles from between the ring-shaped permanent magnets to the substrate in the case of sputtering, but is shown in FIG. As described above, a plate (nonmagnetic) fixed to a wall or the like can be used. This plate has a hole so as not to prevent the necessary exposure of the ring-shaped permanent magnet to the substrate, and a magnetic circuit can be placed on this plate. Although FIG. 2 shows two ring-shaped permanent magnets, for three or more ring-shaped permanent magnets, the number of holes may be increased so as to correspond to the number of magnets.
The fixture 51 of the ring-shaped substrates 11 and 12 is not particularly limited as long as it is a non-magnetic material that does not shield the substrate from the magnetic circuit. For example, as shown in FIG. 2, a substrate fixed to a wall or the like is used. A nonmagnetic fixture having a support portion to be sandwiched is preferred. FIG. 2 shows two ring-shaped substrates. For three or more ring substrates, the number of supporting portions may be increased so as to correspond to the number of substrates. It is preferable to provide a movement support function so that the substrate can be taken out and moved.
Each of the magnetic circuit units includes a support bar on which a ring-shaped permanent magnet fixture and a substrate fixture can be installed independently, and a plurality of substrates can be easily connected by connecting the support rods of a desired number of magnetic circuit units. A magnetic field circuit capable of processing

In FIG. 1, the ring-shaped permanent magnet has a region A, and other regions than the region A are formed of segment magnets. FIG. 1 shows that in the same magnetic circuit unit, the magnet volumes facing the region A (opposite 180 ^° ) are different. The number of regions in which the volume is changed is not limited as long as it is one or more, but at least the volume of the magnet near the adjacent magnetic circuit unit among the ring-shaped permanent magnets is basically changed more than the remaining magnets. It is. Furthermore, although the volume is reduced by reducing the magnet height in the region of FIG. 1, the volume may be changed by changing the outer diameter or the inner diameter.

In addition, as shown in FIG. 3, the volume of each ring-shaped magnet in the range of an angle of ± θ (where θ is 0 <θ <90 degrees) from the line connecting the centers of adjacent ring-shaped permanent magnets is the same. It is preferable that the volume of the ring-shaped permanent magnet is smaller than the volume of the same permanent magnet in the range of 180 ° ± θ. When the ring-shaped permanent magnet is a combination of two or more segment magnets, for example, if the sector-shaped central angle 2θ connecting one segment magnet and the center of the ring-shaped magnet is set, the volume of the segment magnet is the ring-shaped magnet. It is preferable that the volume is smaller than the volume of the segment magnet portion included in the sector having a central angle 2θ rotated 180 degrees around the center of the axis.
In addition, each magnetic circuit unit is combined so that the arrangement surface of each ring-shaped board | substrate may become the same plane. The term “adjacent” means that the magnet units are located adjacent to each other at a distance equal to or less than three times the outer diameter, and preferably have a rotationally symmetric axis and are adjacent in the rotational direction. This means that when the ring substrate has an arrangement surface on the rotation axis, the arrangement adjacent to the ring substrate means an arrangement surface located radially from the center of the arrangement surface.

As shown in FIG. 4, the volume change between adjacent magnets may be a shape having a region without a volume, that is, a shape in which a part of a ring-shaped magnet is interrupted. The magnet may have a shape with a hole or a slit.
The gap without the magnet may be left as it is, but a non-magnetic or magnetic material such as Al, SUS, or resin may be inserted. Furthermore, a non-magnetic material such as Al, SUS, or resin or a magnetic material may be disposed on the magnet portion (uneven portion) having a volume change for the sake of stability as a magnetic circuit.

The ring-shaped permanent magnet of the present invention may be composed of an integrated magnet or a segment magnet (divided permanent magnet piece), but an integrated magnet with a changed volume is very difficult to manufacture. It is preferable to use a material whose volume and characteristics are changed. For segmented magnets, how much the volume of each region can be reduced to obtain a radial magnetic field on the substrate, the inner and outer diameters and height of the magnet, the value of residual magnetization, the distance between symmetrically placed magnets, etc. Therefore, the inner diameter and outer diameter of the ring-shaped permanent magnet are selected according to the size of the substrate and the space in which the ring-shaped permanent magnet can be arranged.
The increase / decrease of the volume is controlled at 20% or more and less than 100% based on a magnet that is not affected by the adjacent magnetic circuit unit (a magnet far from the adjacent magnetic circuit unit).

  5 and 11 show the magnetic field gradients at the positions corresponding to the seven lines indicated by 0 deg. To 180 deg. On the left substrate of FIG. 1 when the inclinations coincide with each other as zero degrees. ing. The horizontal axis r represents the radial distance from the center of the ring on the substrate. In the case of a magnet shape in which the magnet volume is not changed between a portion close to and far from a conventional adjacent magnetic circuit unit, the magnetic fields on the seven evaluation lines are greatly inclined as shown in FIG. The only magnetic field above 0deg. Has a zero slope because the magnet is symmetrical with respect to the 0deg. Line. On the other hand, when the magnet volume is changed, the magnetic field gradient on each line is almost zero as shown in FIG.

  Moreover, the structure of the ring-shaped magnet by arranging the magnet in the substrate center hole as shown in Patent Document 1 and arranging the divided magnets can be used in combination with the present invention.

The magnetization direction of the permanent magnet unit is not limited to being perpendicular to the substrate, but may be inclined to some extent from the perpendicular to the substrate.
This is because even if the magnetization direction is inclined, only a radial magnetic field can be generated on the arrangement surface as long as it is symmetrical with respect to the arrangement surface. In some cases, it is possible to increase the strength of the radial magnetic field by giving an inclination to the magnetization direction. This is based on the fact that the inclination of the magnetic field lines formed on the arrangement surface becomes more parallel to the arrangement surface.
FIG. 6 shows the inclination of the magnetization direction from the perpendicular magnetization direction to the outward direction of each magnetic circuit unit by t, where the perpendicular magnetization direction perpendicular to the arrangement surface and opposite to the arrangement surface is zero. The inclination t is not particularly limited, but is preferably 0 ≦ t <90 ° or 180 ≦ t <270 °, more preferably 0 ≦ t ≦ 60 ° or 180 ≦ t <240 °. preferable.

In the present invention, it is desirable to configure a plurality of magnetic circuit units, and when two or more magnetic circuit units are arranged in parallel or when there are three or more magnetic circuit units, the same concept (reducing the volume of adjacent magnet segments) is used. A radial magnetic field can be created.
FIG. 7 shows a magnetic circuit having four magnetic circuit units combined so that the arrangement surface of the ring-shaped substrate is the same plane and has a rotational symmetry axis perpendicular to the plane. From the same concept as in the case of the two magnetic circuit units described above, the two magnetic circuit units are symmetrical with respect to the symmetry planes σ ₁ and σ ₂ , and the magnets are arranged so that both symmetry planes intersect each other. By rotating 90 degrees about an axis parallel to the central axis of the substrate to form four magnets, the same magnetic field distribution can be formed on each substrate.
The distance between adjacent ring-shaped permanent magnets is the same as when two or more magnetic circuit units are combined, even when three or more magnetic circuit units are combined.
FIG. 8 shows a magnetic circuit having three magnetic circuit units combined so that the planes of arrangement of the ring-shaped substrates are on the same plane and have a rotational symmetry axis perpendicular to the plane. In FIG. 8, the rotational symmetry axis and the center of the arrangement surface of one ring substrate are arranged so as to overlap each other, and the arrangement surfaces of the remaining two ring substrates are rotated 180 degrees around the rotational symmetry axis. Shows what was placed. Although not shown, it is also possible to adopt a mode in which three ring substrates are arranged at the vertices of an equilateral triangle, that is, a mode in which the three ring substrates are arranged at a position rotated 120 degrees around the rotational symmetry axis.
FIG. 9 shows a magnetic circuit in which the ring-shaped substrate is disposed on the same plane and has four magnetic circuit units. FIG. 9 is different from FIG. 7 in that four ring substrates are not arranged at positions rotated by 90 degrees around the rotational symmetry axis, but four are arranged every 90 degrees so as to draw an ellipse. is there. The arrangement surface of the ring substrate does not need to be regularly arranged as long as the amount of magnet reduction can be adjusted. However, the arrangement of the ring substrate can make the entire radial magnetic field generating magnetic circuit more compact. Further, it is preferable that the gaps between the magnetic circuit units are regularly arranged so as to be the same, because the amount of magnets can be easily adjusted.
FIG. 10 shows a magnetic circuit having seven magnetic circuit units combined such that the arrangement surface of the ring-shaped substrate is the same plane and has a rotational symmetry axis perpendicular to the plane. In FIG. 10, the rotational symmetry axis and the center of the arrangement surface of one ring substrate are arranged so as to overlap each other, and the arrangement surfaces of the remaining six ring substrates are arranged at positions rotated by 60 degrees around the rotational symmetry axis. It shows what was done.

The ring-shaped permanent magnet used in the magnetic circuit of the present invention is not particularly limited, and any permanent magnet such as an Nd-based, Sm-based rare earth magnet, alnico-based magnet, or ferrite-based magnet is preferable. .
The outer diameter of the ring-shaped permanent magnet is larger than the outer diameter of the ring-shaped substrate to be processed, and the ring-shaped permanent magnets are installed so that the central axes of the respective rings are the same.

The ring-shaped substrate on which the magnetic field is formed by the magnetic circuit may be any substrate such as glass, Al, or Si. The ring-shaped substrate referred to in the present invention means a substrate itself or a substrate subjected to surface treatment for forming a soft magnetic or hard magnetic thin film on the substrate, unless otherwise specified in the drawings.
Forming a thin film of magnetic material on the substrate by arranging the substrate itself in the magnetic circuit and generating a magnetic field in the radial direction without generating a magnetic field substantially in the circumferential direction in combination with a sputtering device etc. Processing or processing can be suitably performed. A magnetic field can be generated by arranging a substrate on which a thin film of soft magnetism or hard magnet is formed in a magnetic circuit. Further, when heat treatment is performed in the magnetic circuit, the substrate can be heated preferably at 100 to 500 ° C. in the magnetic circuit.
The substrate having the thin film thus obtained can be applied to a magnetic recording medium.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these.
Example 1
A magnetic circuit for generating a radial magnetic field was used on two substrates as shown in FIG. As the permanent magnet, an Nd—Fe—B sintered magnet (N32Z manufactured by Shin-Etsu Chemical Co., Ltd., Br = 1.12T, Hcj = 2480 kA / m) was used. The dimensions of each magnet were an inner diameter of 38 mm, an outer diameter of 46 mm, and a height of 8 mm. The distance between the centers of the two magnetic circuits was 48 mm, and the magnetization direction of the magnet was perpendicular to the substrate surface. Further, the magnet height in the region close to the adjacent magnetic circuit (2θ: inner angle 60 °) was set to 3 mm, 4 mm, and 5 mm. In addition, the magnet of the adjacent area | region was arrange | positioned in the symmetrical position with the magnet (2 (theta): internal angle 60 degrees, height 8mm) facing an adjacent area | region.
At this time, the magnetic field gradients (Gauss meter measurement) on the seven lines of the substrate shown in FIG. 1 are shown in FIG. 11 (magnet height 4 mm), FIG. 12 (magnet height 3 mm), and FIG. 13 (magnet height 5 mm). It was shown to. 11 to 13 use an Si ring-shaped substrate having an outer diameter of 21.6 mm and an inner diameter of 6 mm, the horizontal axis is the distance from the substrate center, and the vertical axis is the inclination angle from the radial direction to the circumferential direction. As can be seen from FIG. 11, when the magnet height is 4 mm, the inclination angle from the radial direction to the circumferential direction is suppressed to 2 degrees or less on the substrate, which shows the effect of the present invention. The tilt angle from the radial direction can be separated into the tilt angle from the radial direction in the ring-shaped substrate plane to the circumferential direction and the tilt angle from the ring-shaped substrate plane in the axial direction from the radial direction in the vertical direction. it can. According to the present invention, a radial magnetic field oriented in the radial direction can be generated on the entire substrate, and both the inclination angle from the radial direction to the circumferential direction and the inclination angle from the radial direction to the axial direction are both The angle is preferably 20 degrees or less, more preferably 10 degrees or less, still more preferably 5 degrees or less, particularly preferably 2 degrees or less, and may be as close to zero as possible.

Example 2
A case with four substrates is shown. A magnetic circuit is arranged as shown in FIG. 7 using a Nd—Fe—B sintered magnet (above) having an inner diameter of 38 mm, an outer diameter of 44 mm, and a height of 8 mm, the distance between the magnetic circuit centers is 48 mm, and the magnetization direction of the magnet Was perpendicular to the substrate surface. The height of the magnet near the adjacent magnetic circuit was 4 mm. At this time, the magnetic field generated on the substrate surface is as shown in FIG. 14 , and it was found that the tilt angle from the radial direction to the circumferential direction can be suppressed to a considerably small value.

  Thus, in the magnetic circuit of the present invention, a magnetic field oriented in the radial direction can be generated over a plurality of substrates.

It is sectional drawing which shows an example of the magnetic circuit of this invention, and a back | latter stage shows sectional drawing of XX direction of a front | former stage. It is sectional drawing which shows an example of the magnetic circuit of this invention, and a back | latter stage shows sectional drawing of XX direction of a front | former stage. A permanent magnet having an angle range of ± θ from a line connecting the centers of adjacent ring-shaped permanent magnets and a permanent magnet having an angle range of 180 ° ± θ of the same ring-shaped permanent magnet are shown. The magnetic circuit using the ring-shaped permanent magnet unit which has a notch part is shown. The inclination angle of the magnetic field on seven evaluation lines in the case of the magnet shape which does not change the conventional magnet volume is shown. The magnetic circuit which showed inclination-angle t is shown. 2 shows a magnetic circuit having four magnetic circuit units. 2 shows a magnetic circuit having three magnetic circuit units. 2 shows a magnetic circuit having four magnetic circuit units. 2 shows a magnetic circuit having seven magnetic circuit units. Using the magnetic circuit obtained in Example 1, the relationship between the distance from the substrate center and the tilt angle from the radial direction when the height of the magnet is 4 mm is shown. Using the magnetic circuit obtained in Example 1, the relationship between the distance from the center of the substrate and the tilt angle from the radial direction when the height of the magnet is 3 mm is shown. Using the magnetic circuit obtained in Example 1, the relationship between the distance from the center of the substrate and the tilt angle from the radial direction when the height of the magnet is 5 mm is shown. The relationship between the distance from the substrate center and the tilt angle from the radial direction using the magnetic circuit obtained in Example 2 is shown. It is sectional drawing of a recording medium. A known method for applying a radial magnetic field to a substrate is shown. It is a figure which shows that when two well-known magnetic circuits are used side by side, the magnetic field on a board | substrate will not turn to a radial direction correctly. It is a figure which shows the influence of the magnetic field from an adjacent magnetic circuit.

Explanation of symbols

11, 12, 111 Ring-shaped substrates 21A, 21B, 31A, 31B, 121 Ring-shaped permanent magnets 23, 33 Central axis 24 Magnetization direction 41 Fixing tool 51 Fixing tool 125 Magnetic field line 126 Magnetic field vector 110 Magnetic medium 112 Hard magnetic film (underlayer film) )
113 Soft magnetic film (underlayer)
114 Hard magnetic film (recording film)

Claims (7)

A pair of ring-shaped permanent magnets provided on both sides of the arrangement surface across a plane including the arrangement surface of the ring-shaped substrate to be processed, and the ring on the arrangement surface when the ring-shaped substrate is arranged Combining at least two magnetic circuit units that generate a magnetic field in the radial direction of the cylindrical substrates so that the arrangement surfaces of the ring-shaped substrates of all the magnetic circuit units are on the same plane, adjacent rings of adjacent magnetic circuit units The volume of the portion close to the adjacent magnetic circuit unit of each ring-shaped permanent magnet in an angle range of ± θ ₁ (where θ ₁ is 0 <θ ₁ <90 degrees) from the line connecting the centers of the shaped permanent magnets A magnetic circuit for generating a radial magnetic field that is smaller than the volume of a distant part of the same ring-shaped permanent magnet in the same angle range .   The radial magnetic field according to claim 1, wherein the ring-shaped permanent magnet is a combination of two or more segment magnets, and the segment magnet close to the adjacent magnetic circuit unit has a smaller volume than other segment magnets. Magnetic circuit for generation. The ring-shaped permanent magnet is smaller in a portion near the magnetic circuit unit adjacent said, so a not large volume distant portion, the height, according to claim 1 or claim outside diameter or a shape of varying internal diameter 3. A magnetic circuit for generating a radial magnetic field according to 2. The ring-shaped permanent magnet, so that a small volume in the near have partial magnetic circuit unit adjacent the shapes are broken part, or claims 1 to 3 which is a shape having a void containing the holes or slits A magnetic circuit for generating a radial magnetic field according to any one of the above.   The pair of ring-shaped permanent magnets are provided at positions symmetrical to each other with respect to the arrangement surface of the ring-shaped substrate, and have a symmetrical shape and a magnetization direction with respect to the arrangement surface. A magnetic circuit for generating a radial magnetic field as described.   The diameter according to claim 5, wherein the ring-shaped permanent magnet has a magnetization direction perpendicular to the arrangement surface of the ring-shaped substrate, or has a magnetization direction inclined from a direction perpendicular to the arrangement surface. Magnetic circuit for directional magnetic field generation. A pair of ring-shaped permanent magnets provided on both sides of the arrangement surface across a plane including the arrangement surface of the ring-shaped substrate to be processed, and the ring on the arrangement surface when the ring-shaped substrate is arranged Combining at least two magnetic circuit units that generate a magnetic field in the radial direction of the cylindrical substrates so that the arrangement surfaces of the ring-shaped substrates of all the magnetic circuit units are on the same plane, adjacent rings of adjacent magnetic circuit units The volume of each ring magnet in the range of ± θ (where θ is 0 <θ <90 degrees) from the line connecting the centers of the ring-shaped permanent magnets is an angle of 180 degrees ± θ of the same ring-shaped permanent magnet Magnetic circuit for generating a radial magnetic field that is smaller than the volume of the same permanent magnet in the range.

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