METHOD FOR PRODUCING A HALBACH MAGNET ARRANGEMENT AND HALBACH MAGNET ARRANGEMENT

Abstract

The method for manufacturing the Halbach magnet assembly comprises a) magnetizing at least one first magnetic material piece and at least one second magnetic material piece in a direction parallel to a first direction, and b) magnetizing a third magnetic material piece in a direction parallel to a second direction, perpendicular to the first direction, in this order. The first magnetic material piece and the second magnetic material piece are arranged alternately in the second direction with the third magnetic material piece interposed therebetween. The first magnetic material piece adheres to the adjacent third magnetic material piece via a non-magnetic layer with a thickness t1, the second magnetic material piece adheres to the adjacent third magnetic material piece via a non-magnetic layer with a thickness t2, and t1 and t2 satisfy a formula t1 < t2.

Description

BACKGROUNDTechnical field

[0001] The present invention relates to a method for producing a Halbach magnet arrangement or Halbach magnet matrix and a Halbach magnet arrangement. State of the art

[0002] JP 2018-092988 A discloses a Halbach magnetic circuit comprising a plurality of permanent magnets having a plurality of regions magnetized in mutually different or different directions.

[0003] Furthermore, the document CN 105 280 324 B discloses a magnet unit and its manufacturing method from the prior art.

[0004] As in Fig.1, the Halbach magnetic circuit 120 generally includes a plurality of permanent magnets 101 arranged or aligned in one direction, and adjacent permanent magnets 101 have magnetized directions forming a predetermined angle (e.g., 90°). Such an arrangement or alignment provides a higher surface magnetic flux density on one surface (a front surface) of the Halbach magnetic circuit 120 and a lower surface magnetic flux density, or ideally, no surface magnetic flux density, on an opposite surface (a back surface) of the Halbach magnetic circuit 120. SUMMARY

[0005] When a Halbach magnetic circuit is manufactured by integrating a plurality of magnetized magnets together, repulsion between the magnets makes it difficult to precisely control the positions of the magnets, requiring a large external force. Therefore, such a manufacturing method is not suitable for mass production. Meanwhile, a Halbach magnetic circuit manufactured by integrating a plurality of non-magnetized materials together, followed by magnetizing each of the magnetic materials in a predetermined direction, or by forming a plurality of regions magnetized in mutually different directions in a permanent magnet, as shown in JP 2018-092988 A, tends to exhibit a small ratio of end face magnetic flux density.front surface to that of the back or rear surface.

[0006] Therefore, the present invention provides a method that enables easy manufacture of a Halbach magnet assembly having a large ratio of a magnetic flux density at a front side to a magnetic flux density at a back side, and a Halbach magnet assembly manufactured thereby.

[0007] According to one aspect of the present invention, there is provided a method of manufacturing a Halbach magnet assembly, the method comprising, in this order: a) magnetizing at least one first magnetic piece of material and at least one second magnetic piece of material in a direction parallel to a first direction, wherein the at least one first magnetic material piece and the at least one second magnetic material piece are arranged alternately in a second direction, perpendicular to the first direction, with a third magnetic material piece inserted therebetween, wherein each of the at least one first magnetic material piece adheres to the adjacent third magnetic material piece via a non-magnetic layer having a thickness t1, wherein each of the at least one second magnetic material piece adheres to the adjacent third magnetic material piece via a non-magnetic layer having a thickness t2, where the thickness t1 and the thickness t2 satisfy a formula t1 < t2, wherein the at least one first magnetic material piece and the at least one second magnetic material piece have easy and weak axes of magnetization and magnetization axes parallel to the first direction, wherein the third magnetic material piece has an easy or weak axis of magnetization or magnetization axis parallel to the second direction, and wherein the direction of magnetization of the at least one first magnetic material piece differs from the direction of magnetization of the at least one second magnetic material piece by 180°, and b) magnetizing the third magnetic piece of material in a direction parallel to the second direction such that the third magnetic piece of material has a south pole opposite the adjacent first magnetic piece of material and a north pole opposite the adjacent second magnetic piece of material.

[0008] According to one aspect of the present invention, there is provided a Halbach magnet assembly comprising: at least a first magnetic piece of material having a magnetization in a direction parallel to a first direction; at least one second magnetic material piece having a magnetization in a direction that differs by 180° from the direction of magnetization of the first magnetic material piece; and at least a third magnetic piece of material having a magnetization in a direction parallel to a second direction perpendicular to the first direction, wherein the at least one first magnetic material piece and the at least one second magnetic material piece are arranged alternately in the second direction with the third magnetic material piece being inserted therebetween, wherein the third magnetic material piece has a south pole opposite the adjacent first magnetic material piece and a north pole opposite the adjacent second magnetic material piece, wherein each of the at least one first magnetic material piece adheres to the adjacent third magnetic material piece via a non-magnetic layer having a thickness t1, wherein each of the at least one second magnetic material piece adheres to the adjacent third magnetic material piece via a non-magnetic layer having a thickness t2, and where the thickness t1 and the thickness t2 satisfy a formula t1 < t2.

[0009] A manufacturing method according to the present invention enables easy manufacture of a Halbach magnet arrangement having a large proportion or ratio of a magnetic flux density at a front side to a magnetic flux density at a back side. SHORT DESCRIPTION OF THE DRAWING Fig. 1 is a drawing schematically illustrating a conventional exemplary Halbach magnetic circuit; Fig. 2 is a flow diagram of a manufacturing process according to one embodiment; Fig. 3 is a drawing schematically illustrating an exemplary assembly which has undergone a step of magnetizing a first piece of magnetic material; Fig. 4 is a drawing schematically illustrating an exemplary Halbach magnet assembly manufactured by the manufacturing method according to the embodiment; and Fig.5 is a drawing showing a proportion of a magnetic flux at a front side and a proportion of a magnetic flux at a back side for summing the magnetic fluxes at the front side and the back side of a tested object in each of Examples 1 and 2 and Comparative Examples 1 to 4. DETAILED DESCRIPTION

[0010] The following describes embodiments with reference to the drawings, where appropriate. The present invention is not limited to the following embodiments. Note that in the drawings referred to in the following description, the same reference numerals denote the same elements or elements with similar functions, and repeated descriptions are omitted in some cases. The drawings have dimensional ratios or scales, which may differ from the actual ratios or scales for the sake of explanation, and parts of an element may be omitted from the drawings. In the application, a numerical range represented using a "-" sign includes respective numerical values ​​written before and after the "-" sign as a lower limit and an upper limit.In the application, “perpendicular” includes substantially perpendicular, and “parallel” includes substantially parallel.

[0011] A method for manufacturing a Halbach magnet arrangement comprises, as in Fig. 2, a step (S1) of magnetizing a first magnetic material piece and a second magnetic material piece, and a step (S2) of magnetizing a third magnetic material piece. a) Magnetization of the first magnetic material piece and the second magnetic material piece

[0012] First, at least one non-magnetized first magnetic material piece, at least one non-magnetized second magnetic material piece, and at least one non-magnetized third magnetic material piece are prepared. The first magnetic material piece, the second magnetic material piece, and the third magnetic material piece each comprise a permanent magnet material. Examples of the permanent magnet material include an Nd-Fe-B-based magnet material, an Sm-Co-based magnet material, an Sm-Fe-N-based magnet material, a ferrite-based magnet material, and an Al-Ni-Co-based magnet material. The first magnetic material piece, the second magnetic material piece, and the third magnetic material piece have magnetic anisotropy. That is, the first magnetic material piece, the second magnetic material piece, and the third magnetic material piece each have a slight or slight magnetic anisotropy.weak axis and a hard or strong axis of magnetization. The first magnetic material piece, the second magnetic material piece, and the third magnetic material piece can have any shape. For example, each material piece can have a columnar shape with an approximately rectangular base (in particular an approximately square base) or an approximately partially circular ring-shaped base. Furthermore, the first magnetic material piece, the second magnetic material piece, and the third magnetic material piece can have the same shape and dimension. If the first magnetic material piece, the second magnetic material piece, and the third magnetic material piece have a columnar shape with an approximately rectangular base (i.e., a cubic shape) of the same dimension, the light or strong axis of magnetization can beweak axes of the first magnetic material piece and the second magnetic material piece may be perpendicular to a pair of surfaces which are parallel to each other among the surfaces perpendicular to the base surface, and the easy or weak axis of the third magnetic material piece may be perpendicular to another pair of surfaces which are parallel to each other among the surfaces perpendicular to the base surface. When the first magnetic material piece, the second magnetic material piece, and the third magnetic material piece have a columnar shape with an approximately partially circular ring-shaped base surface of the same dimension, the easy or weak axes of the first magnetic material piece and the second magnetic material piece may be parallel to a radial direction of the partially circular ring, and the easy or weak axisThe weak axis of the third magnetic material piece may be parallel to a circumferential direction of the partially circular ring. The first magnetic material piece, the second magnetic material piece, and the third magnetic material piece can be manufactured using a well-known manufacturing method. Commercially available material pieces can be used as the first magnetic material piece, the second magnetic material piece, and the third magnetic material piece.

[0013] As in Fig. 3, first magnetic material pieces 1, a second magnetic material piece 2 and third magnetic material pieces 3 are arranged in a predetermined direction (X direction in Fig. 3) arranged or aligned to form an array 10. While a linear array 10 in Fig.3, when the first magnetic material pieces 1, the second magnetic material piece 2, and the third magnetic material pieces 3 have a columnar shape with an approximately partially circular annular base, a predetermined number of the first magnetic material pieces 1, the second magnetic material piece 2, and the third magnetic material piece 3 may be arranged in a circumferential direction to form a circular annular array 10. In the array 10, the first magnetic material pieces 1 and the second magnetic material piece 2 are arranged alternately with the third magnetic material piece 3 being sandwiched between the first magnetic material piece 1 and the second magnetic material piece 2.Each of the first magnetic material pieces 1 adheres to the adjacent third magnetic material piece 3 via a non-magnetic layer 5 with a thickness t1. The second magnetic material piece 2 adheres to the adjacent third magnetic material pieces 3 via non-magnetic layers 5 with thicknesses t2, and a formula t1 < t2 is satisfied. The non-magnetic layers 5 may include an adhesive (for example, an epoxy resin-based adhesive and an acrylic resin-based adhesive).

[0014] The non-magnetic layers 5 may have thermal conductivities of 0.5 W / m·K or less, particularly 0.2 W / m·K or less. When the first magnetic material pieces 1 and the second magnetic material piece 2 are magnetized under a condition in which the first magnetic material pieces 1 and the second magnetic material piece 2 have temperatures higher than those of the third magnetic material pieces 3, the non-magnetic layers 5 having the above-described thermal conductivities reduce heat transfer from the first magnetic material pieces 1 and the second magnetic material piece 2 to the third magnetic material pieces 3. This results in effective control of the magnetization of the third magnetic material pieces 3 by the magnetic field for magnetizing the first magnetic material pieces 1 and the second magnetic material piece 2.Similarly, in the subsequent step of magnetizing the third magnetic material pieces 3, when the third magnetic material pieces 3 are magnetized under a condition in which the third magnetic material pieces 3 have higher temperatures than those of the first magnetic material pieces 1 and the second magnetic material piece 2, the non-magnetic layers 5 having the above-described thermal conductivities reduce heat transfer from the third magnetic material pieces 3 to the first magnetic material pieces 1 and the second magnetic material piece 2. This leads to effective control of the effect of a magnetic field for magnetizing the third magnetic material pieces 3 on residual magnetizations (remanence).Residual magnetism) of the first magnetic material pieces 1 and the second magnetic material piece 2 during the magnetization of the third magnetic material pieces 3. Furthermore, the non-magnetic layers 5 typically have thermal conductivities of 0.01 W / m·K or more, but the thermal conductivities are not limited to this.

[0015] In Fig.3, two first magnetic material pieces 1 and a second magnetic material piece 2 are arranged alternately with the third magnetic material piece 3, which is inserted between the first magnetic material piece 1 and the second magnetic material piece 2. As long as the first magnetic material piece(s) 1 and the second magnetic material piece(s) 2 can be arranged alternately, the number of the first magnetic material piece(s) 1 contained in the arrangement 10 can be more than two or less than two, however, the number of the second magnetic material piece(s) 2 contained in the arrangement 10 can be more than one, and / or the number of the third magnetic material piece(s) 3 and the second magnetic material piece(s) 2 can beof the third magnetic material pieces 3 contained in the arrangement 10 may be more than two or less than two.

[0016] In the arrangement 10, the easy and weak axes of the first magnetic material pieces 1 and the second magnetic material piece 2 (represented by hollow arrows in Fig. 3) parallel to a first direction (Z-direction in Fig. 3), and the easy and weak axes of the third magnetic material pieces 3 (represented by hollow arrows in Fig. 3) are parallel to a second direction (X-direction in Fig. 3). The first direction and the second direction are perpendicular to each other. The second direction is parallel to the arrangement direction of the first magnetic material pieces 1, the second magnetic material piece 2, and the third magnetic material pieces 3.

[0017] Next, the first magnetic material pieces 1 and the second magnetic material piece 2 in the array or matrix 10 are magnetized in a direction parallel to the first direction. The magnetization directions of the first magnetic material pieces 1 differ from the magnetization direction of the second magnetic material piece 2 by 180°.

[0018] The first magnetic material pieces 1 and the second magnetic material piece 2 can be magnetized using any magnetizer. For example, the first magnetic material pieces 1 and the second magnetic material piece 2 can be magnetized by placing the first magnetic material pieces 1 and the second magnetic material piece 2 in a magnetic field (an external magnetic field) generated by a magnetizing yoke or a magnetizing fork, respectively.

[0019] The first magnetic material pieces 1 and the second magnetic material piece 2 can be magnetized under a condition in which the first magnetic material pieces 1 and the second magnetic material piece 2 have higher temperatures than the third magnetic material pieces 3. This makes it possible to provide sufficiently large residual magnetizations on the first magnetic material pieces 1 and the second magnetic material piece 2, while the magnetization of the third magnetic material pieces 3 is controlled or prevented by the magnetic field for magnetizing the first magnetic material pieces 1 and the second magnetic material piece 2.This is because the higher the temperature of the magnetic material piece when magnetized, the higher the residual magnetization ratio (i.e., the ratio of residual magnetization to saturated residual magnetization) of the magnetic material piece generally becomes. The temperature dependence of the residual magnetization ratio of the magnetic material piece generally depends on the type of magnetic material contained as the main component in the magnetic material piece, the presence or absence of element substitution and the type of a substitution element in the magnetic material, the structure (e.g., crystal grain size) of the magnetic material piece, and the like.

[0020] For example, the first magnetic material pieces 1 and the second magnetic material piece 2 can be magnetized while the first magnetic material pieces 1 and the second magnetic material piece 2 are heated. Additionally or instead, the first magnetic material pieces 1 and the second magnetic material piece 2 can be magnetized while the third magnetic material pieces 3 are cooled. The first magnetic material pieces 1 and the second magnetic material piece 2 can be heated using any heating devices (for example, a resistance heating plate and a rubber heater). The first magnetic material pieces 1 and the second magnetic material piece 2 can be heated and magnetized using a magnetizing yoke with a heating device.The third magnetic material pieces 3 can be cooled using any cooling devices (for example, a water cooling block). b) Magnetization of the third magnetic piece of material

[0021] Next, the third magnetic material pieces 3 are magnetized such that the third magnetic material pieces 3 each have a south pole (S pole) opposite to the adjacent first magnetic material piece 1 and a north pole (N pole) opposite to the adjacent second magnetic material piece 2.

[0022] The third magnetic material pieces 3 can be magnetized using any magnetizer. For example, the third magnetic material pieces 3 can be magnetized by placing the third magnetic material pieces 3 in a magnetic field generated by a magnetizing yoke or a magnetizing fork (an external magnetic field).

[0023] The third magnetic material pieces 3 can be magnetized under a condition in which the third magnetic material pieces 3 have higher temperatures than those of the first magnetic material pieces 1 and the second magnetic material piece 2. This makes it possible to provide sufficiently large residual magnetizations to the third magnetic material pieces 3 while controlling the effect of the magnetic field for magnetizing the third magnetic material pieces 3 on the residual magnetizations of the first magnetic material pieces 1 and the second magnetic material piece 2. For example, the third magnetic material pieces 3 can be magnetized while the third magnetic material pieces 3 are being heated. Additionally or instead, the third magnetic material pieces 3 can be magnetized while the first magnetic material pieces 3 and the second magnetic material piece 2 are being cooled.The third magnetic material pieces 3 can be heated using any heating device (for example, a resistance heating plate and a rubber heater). The third magnetic material pieces 3 can be heated and magnetized using a magnetizing yoke with a heating device. The first magnetic material pieces 1 and the second magnetic material piece 2 can be cooled using any cooling device (for example, a water cooling block).

[0024] As described above, a Halbach magnet arrangement 20 as shown in Fig. 4. The Halbach magnet arrangement 20 comprises the first magnetic material pieces 1 with a magnetization in a direction parallel to a first direction (Z direction in Fig.4), the second magnetic material piece 2 with a magnetization in a direction which differs by 180° from the magnetized direction of the first magnetic material pieces 1, and the third magnetic material pieces 3 with a magnetization in a direction parallel to a second direction (X-direction in Fig.4) perpendicular to the first direction. The first magnetic material pieces 1 and the second magnetic material piece 2 are arranged alternately in the second direction, with the third magnetic material piece 3 being sandwiched between the first magnetic material piece 1 and the second magnetic material piece 2. The third magnetic material pieces 3 each have an S pole opposite to the adjacent first magnetic material piece 1 and an N pole opposite to the adjacent second magnetic material piece 2. Each of the first magnetic material pieces 1 adheres to an adjacent third magnetic material piece 3 via the non-magnetic layer 5 with the thickness t1, the second magnetic material piece 2 adheres to the adjacent third magnetic material pieces 3 via the non-magnetic layers 5 with the thickness t2, and the thickness t1 and the thickness t2 satisfy a formula t1 < t2.

[0025] In the Halbach magnet assembly 20 obtained by the manufacturing method according to the embodiment, the thickness t2 of the non-magnetic layer 5 between the second magnetic material piece 2 and the third magnetic material piece 3, which are adjacent to each other, is greater than the thickness t1 of the non-magnetic layer 5 between the first magnetic material piece 1 and the third magnetic material piece 3, which are adjacent to each other. The non-magnetic layers 5 having such thicknesses result in a higher ratio of a magnetic flux density at the front surface to a magnetic flux density at the back surface of the Halbach magnet assembly 20, as in the example described below.Furthermore, in the manufacturing method of the embodiment, the integration of the magnetic material pieces does not suffer from any repulsive force between the magnetic material pieces, since the integration of a plurality of non-magnetized magnetic material pieces subsequently magnetizes each of the magnetic material pieces in a predetermined direction. Therefore, the integration of the magnetic material pieces does not require a large external force to achieve or overcome the repulsive force between the magnetic material pieces, and enables easier control of the arrangement of the magnetic material pieces. EXAMPLES

[0026] While the following specifically describes the present invention using examples, the present invention is not limited to these examples. Examples 1 and 2, and Comparative Examples 1 to 3

[0027] Five magnetic material pieces (neodymium magnet sintered bodies) with a rectangular, parallelepiped, or parallelepiped shape, measuring 5 mm × 5 mm × 7 mm, and with an easy or weak axis perpendicular to a surface of 5 mm × 7 mm, were prepared. Among the five magnetic material pieces, two were designated as the first magnetic material pieces, one as the second magnetic material piece, and two as the third magnetic material pieces.

[0028] The first magnetic material pieces and the second magnetic material piece were alternately arranged in a second direction perpendicular to a first direction, while the easy and weak axes of the first magnetic material pieces and the second magnetic material piece were parallel to the first direction. The third magnetic material pieces were each arranged between the first magnetic material piece and the second magnetic material piece, which are adjacent to each other, while the easy and weak axes of the third magnetic material pieces were parallel to the second direction. The first magnetic material pieces, the second magnetic material piece, and the third magnetic material pieces were arranged such that the 5 mm × 5 mm surfaces of each of the material pieces were parallel to both the first direction and the second direction.A non-magnetic adhesive with a thermal conductivity of 0.2 W / m·K was used to attach the first magnetic material piece to the adjacent third magnetic material piece and the second magnetic material piece to the adjacent third magnetic material piece. The adhesive layers between the first magnetic material pieces and the third magnetic material pieces had the thicknesses t1 described in Table 1, and the adhesive layers between the second magnetic material piece and the third magnetic material pieces had the thicknesses t2 described in Table 1. In Table 1, a formula S < M < L is satisfied.

[0029] While the first magnetic material pieces and the second magnetic material piece were heated to 65°C, the first magnetic material pieces and the second magnetic material piece were magnetized by an external magnetic field parallel to the first direction. At this time, the magnetization direction of the first magnetic material pieces differed by 180° from the magnetization direction of the second magnetic material piece.

[0030] Next, while heating the third magnetic material pieces at 65 °C, the third magnetic material pieces were magnetized by an external magnetic field parallel to the second direction such that the third magnetic material pieces had an S pole opposite to an adjacent first magnetic material piece and an N pole opposite to an adjacent second magnetic material piece.

[0031] This resulted in a test piece with a Halbach magnet matrix arrangement as shown in Fig. 4 shown, preserved. Comparison example 4

[0032] Five magnetic material pieces (neodymium magnet sintered body) with magnetic anisotropy were prepared similarly to Example 1. Each of the magnetic material pieces was magnetized in a direction of its easy and weak axes, respectively. Next, among the five magnetic material pieces, two were designated as the first magnetic material pieces, one was designated as the second magnetic material piece, and two were designated as the third magnetic material piece. The five magnetic material pieces were arranged similarly to Example 1. The non-magnetic adhesive was used to attach the first magnetic material piece to the adjacent third magnetic material piece and the second magnetic material piece to the adjacent third magnetic material piece.Layers of the adhesive between the first magnetic material pieces and the third magnetic material pieces had the thicknesses t1 described in Table 1, and layers of the adhesive between the second magnetic material piece and the third magnetic material pieces had the thicknesses t2 described in Table 1. This produced a test piece having a Halbach magnet matrix arrangement shown in . Fig. 4 is shown. Table 1 t1 t2 Comparison example 1 S S Example 1 S M Example 2 S L Comparison example 2 M S Comparison example 3 L L Comparison example 4 S S Evaluation

[0033] The magnetic fluxes on two surfaces perpendicular to the first direction of each of the test pieces were measured by a flux meter. Among the two surfaces, a surface with a larger magnetic flux was defined as a front surface, and a surface with a smaller magnetic flux was defined as a back surface. A ratio of the magnetic flux at each of the front and back surfaces was calculated to sum the magnetic fluxes at the front and back surfaces. The results are shown in Fig. 5 shown.

[0034] As in Fig.5, each of the test pieces of Examples 1 and 2 satisfying the formula t1 < t2 had a larger proportion of the magnetic flux at the end face than those of the test pieces of Comparative Examples 1 and 3 satisfying the formula t1 = t2 and the test piece of Comparative Example 2 satisfying the formula t1 > t2.

[0035] Although the ratios of the magnetic fluxes at the end faces of the test pieces of Examples 1 and 2 were smaller than the ratio of the magnetic flux at the end face of the test piece of Comparative Example 4, the method for manufacturing the test piece of Comparative Example 4 involved integrating the pre-magnetized material pieces together, which is not suitable for mass production. DESCRIPTION OF REFERENCE SYMBOLS 1 First piece of magnetic material 2 Second piece of magnetic material 3 Third piece of magnetic material 5 Non-magnetic layer 10 Arrangement or matrix 20 Halbach magnet arrangement

Claims

[1] A method of manufacturing a Halbach magnet assembly (20), the method comprising, in this order: a) magnetizing at least one first magnetic material piece (1) and at least one second magnetic material piece (2) in a direction parallel to a first direction, wherein the at least one first magnetic material piece (1) and the at least one second magnetic material piece (2) are arranged alternately in a second direction perpendicular to the first direction with a third magnetic material piece (3) inserted therebetween, wherein each of the at least one first magnetic material piece (1) adheres to the adjacent third magnetic material piece (3) via a non-magnetic layer (5) having a thickness t1, wherein each of the at least one second magnetic material piece (2) adheres to the adjacent third magnetic material piece (3) via a non-magnetic layer (5) having a thickness t2, where the thickness t1 and the thickness t2 satisfy a formula t1 < t2, wherein the at least one first magnetic material piece (1) and the at least one second magnetic material piece (2) have weak axes of magnetization parallel to the first direction, wherein the third magnetic material piece (3) has a weak axis of magnetization parallel to the second direction, and wherein the direction of magnetization of the at least one first magnetic material piece (1) differs from the direction of magnetization of the at least one second magnetic material piece (2) by 180°, and b) magnetizing the third magnetic material piece (3) in a direction parallel to the second direction, so that the third magnetic material piece (3) has a south pole opposite the adjacent first magnetic material piece (1) and a north pole opposite the adjacent second magnetic material piece (2). [2] The method according to claim 1, wherein the non-magnetic layer (5) has a thermal conductivity of 0.5 W / m·K or less. [3] A method according to claim 1 or 2, wherein the non-magnetic layer (5) comprises an adhesive. [4] Halbach magnet arrangement (20), comprising: at least one first magnetic material piece (1) having a magnetization in a direction parallel to a first direction; at least one second magnetic material piece (2) which has a magnetization in a direction which differs by 180° from the direction of magnetization of the first magnetic material piece (1); and at least one third magnetic piece of material (3) which has a magnetization in a direction parallel to a second direction, perpendicular to the first direction, wherein the at least one first magnetic material piece (1) and the at least one second magnetic material piece (2) are arranged alternately in the second direction with the third magnetic material piece (3) inserted therebetween, wherein the third magnetic material piece (3) has a south pole, opposite the adjacent first magnetic material piece (1), and a north pole, opposite the adjacent second magnetic material piece (2), wherein each of the at least one first magnetic material piece (1) adheres to the adjacent third magnetic material piece (3) via a non-magnetic layer (5) having a thickness t1, wherein each of the at least one second magnetic material piece (2) adheres to the adjacent third magnetic material piece (3) via a non-magnetic layer (5) having a thickness t2, and where the thickness t1 and the thickness t2 satisfy a formula t1 < t2. [5] Halbach magnet assembly (20) according to claim 4, wherein the non-magnetic layer (5) has a thermal conductivity of 0.5 W / m·K or less. [6] Halbach magnet assembly (20) according to claim 4 or 5, wherein the non-magnetic layer (5) comprises an adhesive.

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