JP2001261433A - Nonmagnetic ceramics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain nonmagnetic ceramics which have a thermal thermal expansion coefficient near to that of a magnetic film and low saturation magnetic flux density and are excellent in sinterability and workability. SOLUTION: This nonmagnetic ceramics adopted consist essentially of CaO and Fe2O3, wherein the molar blending ratio of CaO to Fe2O3 (CaO/Fe2O3) is 15/85 to 44/56.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to non-magnetic ceramics, and more particularly to non-magnetic ceramics used for sliders, cores and the like of magnetic heads.

[0002]

2. Description of the Related Art In the field of magnetic recording, the track width and gap length of a magnetic head have been reduced as much as possible in order to improve the recording density. Recently, a magnetic head satisfying these conditions has been developed. Have been. As the above-described magnetic head, for example, a magnetic core formed of a magnetic film is sandwiched between substrates by forming a magnetic film on a substrate by sputtering or vapor deposition and bonding another substrate on the formed magnetic film. Such a thing is mentioned. In the above-described magnetic head, since the thickness of the formed magnetic film becomes the track width as it is, it is easy to narrow the track, and it is possible to improve the recording density and prevent interference with an adjacent track. . Further, since the magnetic circuit forming portion is a magnetic film having a thickness of several μm, the overcurrent loss is reduced, and the performance of the magnetic head in a high frequency band can be improved.

As the above-mentioned magnetic film, for example, Fe—S
i-Al alloy film, Fe-MC alloy film (M is T
i, Zr, Hf, V, Nb, Ta, Mo, and W), a Fe—X—M—Z alloy film (X
Is one of Si and Al, and T is Cr, Ti, M
o, W, V, Re, Ru, Rh, Ni, Co, Pd, P
t, at least one of Au, M is Zr, Hf, Nb,
At least one of Ta, Z represents at least one of C and N) and the like are used. As the substrate, nonmagnetic ceramics such as calcium titanate, barium titanate, zinc ferrite, manganese zinc ferrite, and calcium ferrite are used.

In particular, calcium ferrite-based non-magnetic ceramics are prepared by mixing CaO and Fe ₂ O ₃ ,
It is obtained by performing heat treatment such as hot isostatic pressure treatment, and has a coefficient of thermal expansion close to the coefficient of thermal expansion of the material of the magnetic film. Therefore, a magnetic head using a calcium ferrite-based non-magnetic ceramic as a base does not generate stress between the base and the magnetic film and does not generate residual strain even during cooling after a heating step in a manufacturing process. In addition, it is possible to prevent occurrence of a defect of the magnetic head.

[0005]

The calcium ferrite non-magnetic ceramic described above is obtained by mixing CaO and Fe ₂ O ₃ powder in a molar ratio of CaO / Fe ₂ O ₃ = 45 / 55-67.
/ 33 and obtained by heat-treating them. However, in the non-magnetic ceramics thus obtained, since a large number of pores are formed in the bulk at the time of sintering of the raw material powder, the density of the bulk is reduced, and the so-called sinterability is significantly reduced. There was a problem that it was inferior.

Therefore, in order to improve sinterability, several weight%
ZrO_Two, TiO_Two, MgO, Al _TwoO_ThreeAdd additives such as
Calcium ferrite based non-magnetic ceramics
Proposed. However, this non-magnetic ceramics
Therefore, it is necessary to mix additives uniformly,
When manufacturing costs of magnetic ceramics increase
There was a problem. In addition, the above-mentioned calcium ferrite-based
Non-magnetic ceramics have high hardness,
Manufacturing magnetic heads with complicated shapes that are difficult to process
There was a problem that it was difficult to do.

The present invention has been made to solve the above-mentioned problems, and has a thermal expansion coefficient close to that of a magnetic film, a low saturation magnetic flux density, and excellent sinterability and workability. An object is to provide a non-magnetic ceramic.

[0008]

In order to achieve the above object, the present invention employs the following constitution. The non-magnetic ceramic of the present invention is a non-magnetic ceramic containing CaO and Fe ₂ O ₃ as main components, wherein CaO / Fe ₂ O ₃
The molar ratio of CaO and Fe ₂ O _{3 represented} by
/ 85 or more and 44/56 or less. The mixing ratio (x) of CaO in the non-magnetic ceramic of the present invention is as follows:
15 mol% or more and 44 mol% or less, the compounding ratio (y) of Fe ₂ O ₃ is 56 mol% or more and 85 mol% or less, and x
It is preferable that + y = 100 mol%. The average thermal expansion coefficient of the nonmagnetic ceramic of the present invention at 100 ° C. to 600 ° C. is 115 × 10 ⁻⁷ / ° C. or more and 125 × 10 ⁻⁷ / ° C.
It is preferable that the temperature is not higher than ° C.

The non-magnetic ceramic of the present invention is the above-described non-magnetic ceramic, wherein the non-magnetic ceramic is ground by the grindstone while the non-magnetic ceramic and the grindstone are relatively moved. When forming a groove in the ceramic, when the depth of the groove formed in the non-magnetic ceramic at the start of grinding is a, and the depth of the groove formed in the non-magnetic ceramic at the end of the grinding is b The shape change rate represented by the following formula is 35% or less. Shape processing rate (%) = (ab) / a × 100 Further, the saturation magnetic flux density of the non-magnetic ceramic of the present invention is 7
It is preferably at most 10 ^{3 -3} T.

[0010]

Embodiments of the present invention will be described below in detail. Nonmagnetic ceramic of the present invention contains as main components, CaO and Fe ₂ O _3, was mixed with CaO and Fe ₂ O ₃ at a predetermined ratio, which is obtained by heat treatment, at least CaFe ₂ The O ₄ phase and the Fe ₂ O ₃ phase are deposited. In the non-magnetic ceramic of the present invention, the mixing ratio of CaO and Fe ₂ O ₃ is CaO / Fe
_{When represented by 2} O ₃ , the molar ratio is 15/85 or more and 44/5.
6 or less, preferably 40/60 or more and 44/5.
More preferably, it is 6 or less.

As the amount of CaO increases, the coefficient of thermal expansion of the nonmagnetic ceramic increases, but the CaO phase precipitates and the sinterability decreases. On the other hand, as the amount of Fe ₂ O ₃ increases, the sinterability improves, and the addition of additives and the like becomes unnecessary. When the amount of Fe ₂ O ₃ increases, the coefficient of thermal expansion of the nonmagnetic ceramic slightly decreases, but the hardness decreases and the workability improves. Therefore, CaO / Fe
_{When the} molar ratio represented by ₂ O ₃ is in the above range, the generation of voids is prevented during sintering of the raw material powder, and the sinterability is improved, and the workability is improved. The non-magnetic ceramic of the present invention is suitable as a material for a base of a magnetic head.

If the molar ratio of CaO to Fe ₂ O ₃ is less than 15/85, the amount of Fe ₂ O ₃ is increased, and the amount of the Fe ₂ O ₃ phase, which is a ferromagnetic material, is increased. Is easily magnetized, which is not preferable. On the other hand, if the molar ratio of CaO to Fe ₂ O ₃ exceeds 44/56, the amount of CaO increases and the CaO phase precipitates, so that the size of the pores increases and the sinterability decreases. Is not preferred. Further, in order to improve sinterability, ZrO ₂ , T
Additives such as iO ₂ , MgO, and Al ₂ O ₃ need to be added, and these additives need to be uniformly mixed, which increases the production cost of nonmagnetic ceramics, which is not preferable. Furthermore, the blending amount of Fe ₂ O ₃ is relatively reduced, and the hardness of the non-magnetic ceramic is increased.

In the non-magnetic ceramic of the present invention, when the molar ratio of the mixture of CaO and Fe ₂ O ₃ is in the above-mentioned range, the sinterability is improved and the addition of additives is not required.
It is obtained by mixing and heat-treating only e ₂ O ₃ .
Here, the compounding ratio (x) of CaO is preferably 15 mol% or more and 44 mol% or less, more preferably 40 mol% or more and 44 mol% or less, and the mixing ratio (y) of Fe ₂ O ₃ is preferably Non-magnetic ceramics excellent in sinterability can be obtained by setting the molar ratio to 56 mol% to 85 mol%, more preferably 56 mol% to 60 mol%, and x + y = 100 mol%.

The magnetic head using the non-magnetic ceramic of the present invention can be formed, for example, by depositing an Fe-Si-Al-based alloy or an Fe-XMZ-based alloy film (X is Si , Al, T is Cr, T
i, Mo, W, V, Re, Ru, Rh, Ni, Co, P
d, Pt, at least one of Au, M is Zr, Hf,
At least one of Nb and Ta and Z represents at least one of C and N) are sandwiched therebetween, and the manufacturing process includes a heating process. Therefore, if the thermal expansion coefficient of the magnetic film is extremely different from that of the magnetic film, a stress is generated between the magnetic film and the magnetic film, resulting in residual distortion, and a magnetic head failure. Therefore, the coefficient of thermal expansion of the non-magnetic ceramic is preferably a value close to the coefficient of thermal expansion of the magnetic film. In particular, 100% of Fe—X—M—Z alloys
The average coefficient of thermal expansion between 115 ° C and 600 ° C is 115 × 10 ^-7 to 1
Since it is in the range of 45 × 10 ⁻⁷ / ° C., the thermal expansion coefficient of the non-magnetic ceramic of the present invention is preferably substantially equal to or slightly smaller than this value. Therefore, the nonmagnetic ceramic of the present invention has an average coefficient of thermal expansion at 100 ° C. to 600 ° C. of 115 × 10 ⁻⁷ / ° C. or more and 125 × 10 ⁻⁷ / ° C.
C. or lower, more preferably 120 × 10 ⁻⁷ / ° C. or higher and 123 × 10 ⁻⁷ / ° C. or lower.

[0015] The shape change rate of the nonmagnetic ceramic of the present invention is preferably 35% or less, more preferably 33% or less. As shown in FIGS. 3A and 3B, the shape change rate of the nonmagnetic ceramic is determined by relatively moving the nonmagnetic ceramic block 40 and the grindstone 41.
When the nonmagnetic ceramic block 40 is ground with the grindstone 41 to form the groove 42 in the nonmagnetic ceramic, the depth of the starting end 43 of the groove 42 formed at the start of grinding is defined as a, and the depth is formed at the end of grinding. When the depth of the end portion 44 of the groove 42 is set to b (FIG. 3C), it is represented by the following equation (1). Shape processing rate (%) = (ab) / a × 100 (1)

The grindstone 41 is a disc-shaped grindstone having a diameter of 70 mm and a thickness of 0.297 mm. The grindstone 41 is rotated at a rotation speed of 24000 rpm to grind the nonmagnetic ceramic block 40 to form a groove 42. To form The relative speed between the grindstone 41 and the nonmagnetic ceramic block 40 is 0.5 mm / s. The grindstone 41 has a ground surface having a roughness of # 3000. The width of the groove 42 to be formed is 0.35 mm, the length of the groove 42 is 260 mm, and the depth (a) of the groove at the start of grinding is 0.2 mm. Shape change rate is 3
If it exceeds 5%, the hardness of the non-magnetic ceramic increases, and it becomes difficult to process the non-magnetic ceramic into a complicated shape. For example, when this non-magnetic ceramic is used as a base for a magnetic head, It is not preferable because the production becomes difficult and the production cost increases.

Furthermore, the saturation magnetic flux density of the non-magnetic ceramic of the present invention is preferably 7 × 10 ⁻³ T or less, more preferably 6.7 × 10 ⁻³ T or less.
If the saturation magnetic flux density exceeds 7 × 10 ⁻³ T, the nonmagnetic ceramics are easily magnetized, which is not preferable. In particular, when this non-magnetic ceramic is used as a base material of a magnetic head, the base itself is magnetized and the track width of the magnetic head is undesirably widened.

The non-magnetic ceramic of the present invention is manufactured, for example, as follows. First, a powder of CaO and Fe
A powder of ₂ O ₃ is prepared. The average particle size of the CaO powder is 0.
The average particle size of the powder of Fe ₂ O ₃ is preferably in the range of 0.1 to 0.5 μm. These powders are mixed at a predetermined mixing ratio to obtain a raw material. If necessary, this raw material is heated at 700 to 1000 ° C. in the atmosphere for 3 to 10 hours.
It may be calcined by heating for a time. This raw material is finely pulverized with alumina balls, zirconia balls or the like until the average particle size becomes 1 to 3 μm. Add a binder to this raw material and granulate,
It is molded into a predetermined shape to obtain a molded body. Next, heat treatment of the molded body is performed. First, the molded body is heated from room temperature to 1100 ° C. to 1200 ° C. in an oxidizing atmosphere such as the atmosphere or oxygen, held for a certain period of time, and then cooled to room temperature to obtain a fired body. Next, hot isostatic pressure treatment is performed for the purpose of increasing the density of the obtained fired body and eliminating voids. Hot isostatic pressure treatment is performed in an inert gas atmosphere such as argon or nitrogen.
It is carried out at 100 to 1150 ° C. under 100 to 120 MPa. In this way, a non-magnetic ceramic is manufactured.

Next, a method of manufacturing a magnetic head using the non-magnetic ceramic of the present invention will be described. First, as shown in FIG. 1A, a magnetic film 20 is formed on one surface of a block-shaped substrate 26 made of non-magnetic ceramics by an evaporation method. The magnetic film 20 is made of, for example, Fe _73.5 Al _3.3 Si _13.6 Hf _3.1 C
An alloy film having a composition of _4.6 Ru _1.5 is preferable. Next, a laminated glass 24 is formed on the magnetic film 20, and another substrate 26 'is bonded on the laminated glass 24 (FIG. 1B). At this time, the laminated glass 24 is formed on one surface of the base 26 '. Bonded substrate 2
By heating 6, 26 ', the laminated glass 2
4 and 24 are melted, and the bases 26 and 26 'and the magnetic film 20 are pressed. Then, after cooling to room temperature to solidify the laminated glass, this block is cut and subjected to processing such as grinding and polishing to form two cores of a predetermined shape. A magnetic head is manufactured by aligning the two cores so that the magnetic films 20 sandwiched therebetween are continuous, and welding and integrating the cores with nonmagnetic glass or the like. At this time, the non-magnetic glass sandwiched between the cores forms a magnetic gap.

When a magnetic film is formed on a substrate, a plurality of magnetic films and insulating films such as SiO ₂ are alternately laminated to form a pair of substrates 28, 28 as shown in FIG. A plurality of magnetic films 32, 32, an insulating film 34,
It is also possible to form a magnetic core 33 composed of.
In FIG. 2, reference numeral 24 denotes a magnetic core 33 and a base 28.
And reference numeral 30 denotes a magnetic gap.

The above nonmagnetic ceramics are made of CaO and F
containing and e ₂ O ₃ as a main component, which is obtained by heat treating a mixture of the CaO and Fe ₂ O ₃ at a predetermined ratio,
Since the molar ratio of CaO to Fe ₂ O ₃ is 15/85 or more and 44/56 or less when represented by CaO / Fe ₂ O ₃ , precipitation of the CaO phase during sintering is prevented. The generation of vacancies is prevented and the sinterability is improved, and the workability is improved without the hardness of the non-magnetic ceramics becoming too high without the content of Fe ₂ O ₃ being relatively reduced. It can be suitably used as a material for a base of a magnetic head. Further, in the above-mentioned nonmagnetic ceramics, the mixing ratio (x) of CaO is 15 mol% or more and 44 mol% or less, and Fe ₂
Since the compounding ratio (y) of O ₃ is not less than 56 mol% and not more than 85 mol%, and x + y = 100 mol%, the precipitation of CaO phase is prevented, the generation of voids is prevented, and the sinterability is improved. By the improvement, there is no need to add an additive or the like, and the manufacturing cost of the nonmagnetic ceramic can be reduced.

The above-mentioned nonmagnetic ceramic has a coefficient of thermal expansion of 115 × 10 ⁻⁷ / ° C. or higher and 125 × 10 ⁻⁷ / ° C.
° C or less, for example, Fe-Si-Al alloy, Fe
-MC-based alloy film (M is Ti, Zr, Hf, V, N
b, Ta, Mo, W, etc.) is close to the thermal expansion coefficient of a magnetic film made of such a material. Therefore, when manufacturing a magnetic head in which these magnetic films are sandwiched by the above-mentioned non-magnetic ceramics, Has no residual strain,
It is possible to prevent occurrence of a defect of the magnetic head.

Further, the above nonmagnetic ceramic has a shape change rate of 35% or less and a low hardness, so that it can be processed into a complicated shape. Furthermore, since the above-mentioned non-magnetic ceramic has a saturation magnetic flux density of 7 × 10 ⁻³ T or less, the non-magnetic ceramic itself is not magnetized.

[0024]

EXAMPLES (Experimental Example 1) A CaO powder having a particle diameter of 0.2 μm and a Fe ₂ O ₃ powder having a particle diameter of 0.3 μm were mixed at a predetermined mixing ratio to obtain a raw material. This raw material was heated at 1000 ° C. for 6 hours in the atmosphere and calcined. The calcined raw material was finely pulverized with alumina balls until the average particle size became 2 μm. An acrylic binder was added to the raw material, and the mixture was granulated and formed into a predetermined shape to obtain a molded body. The molded body was fired in the air under the conditions shown in Table 1 to obtain a fired body. . Further, the obtained fired body was heated at a temperature of 1050 in an argon atmosphere.
By performing hot isostatic pressure treatment at a temperature of 104 ° C. and a pressure of 104 MPa, compacts of Examples 1 to 27 were obtained.

The fired product was measured for shrinkage, density, crystal grain size (Gs) and Vickers hardness (Hv) due to firing. Table 2 shows the results. The density, crystal grain size (Gs), Vickers hardness (H
v), the coefficient of thermal expansion (α), the real value of magnetic permeability (μ), and the saturation magnetic flux density (Bs) were measured. The crystal structure was examined by X-ray diffraction. The results are shown in Tables 3 and 4. Further, as Comparative Example 1, 52.6 mol% of CuO and 47.2 mol of Fe ₂ O ₃ were used.
A sample of a commercial product consisting of 4 mol% is similarly shown.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

As shown in Table 4, Examples 1 to 3 after the heat treatment were performed.
The 27 compact has a coefficient of thermal expansion of 123.4 × 10 ^-7 to 1
23.9 × 10 ⁻⁷ / ° C., and Fe—Si—Al
Alloy, Fe-MC alloy film (M is Ti, Zr, H
f, V, Nb, Ta, Mo, W, etc.). Further, as shown in Table 3, it was found that each of the examples was fired at a higher density than that of Comparative Example 1. Further, as shown in Table 4, Examples 1-27 after the heat treatment were performed.
Has an effective value (μ) of magnetic permeability of 1 to 30 at 10 MHz and a saturation magnetic flux density of 3.1 × 10 ⁻³ to
6.7 × 10 ⁻³ T, which proved to be hardly magnetized.

(Experimental Example 2) A molded body was heated from room temperature to 800 ° C.
Temperature at a rate of 240 ° C / hr to 800 ° C
Performed in the same manner as in Experimental Example 1 except that the temperature was raised to 100 ° C. at a rate of 25 ° C./hr, held for 7.5 hours, then lowered at a rate of 180 ° C./hr, cooled to room temperature, and fired. The compacts of Examples 28 and 29 and Comparative Example 2 were obtained. Next, while relatively moving the obtained compact and the grindstone, grinding the compact with the grindstone to form a groove, the depth of the groove formed at the start of grinding and the depth of the groove formed at the end of grinding. From the amount of change in the height, the shape change rate was measured. The whetstone here has a diameter of 70
A disc-shaped grindstone having a thickness of 0.297 mm and a thickness of 0.297 mm was formed, and the disc-shaped grindstone was rotated at a rotation speed of 24000 rpm to grind the compact to form grooves. The relative speed between the grindstone and the compact was 0.5 mm / s. The grindstone had a ground surface having a roughness of # 3000. The width of the groove to be formed was 0.35 mm, the length of the groove was 260 mm, and the depth (a) of the groove at the start of grinding was 0.2 mm. Table 5 shows the results.

As shown in Table 5, it was found that the samples of Examples 28 and 29 had a smaller shape change rate than the sample of Comparative Example 2.

[0033]

[Table 5]

[0034]

As described in detail above, the present invention
Nonmagnetic ceramics consist of CaO and Fe _TwoO_ThreeAnd the main component
CaO and Fe_TwoO_ThreeCompounding ratio with
Is CaO / Fe_TwoO_ThreeWhen represented by the formula, a molar ratio of 15 /
Since it is 85 or more and 44/56 or less, the precipitation of the CaO phase
This prevents porosity and improves sinterability.
Fe_TwoO_ThreeWithout a relative decrease in the amount of
Workability without increasing the hardness of magnetic ceramics
Good, suitable for use as a base material for magnetic heads
Can be

Further, the non-magnetic ceramic of the present invention comprises C
mixing ratio of aO-(x) is not more than 44 mol% to 15 mol%, the blending ratio of Fe ₂ O ₃ (y) is not less 56 mol% 85 mol% or less, a x + y = 100 mol%, baked Since the bonding property is good, there is no need to add an additive or the like, and the production cost of the nonmagnetic ceramic can be reduced.

The non-magnetic ceramic of the present invention has a coefficient of thermal expansion of 115 × 10 ⁻⁷ / ° C. or more and 125 × 10 ^−7.
/ ° C or lower, for example, Fe—Si—Al alloy, F
e-MC-based alloy film (M is Ti, Zr, Hf, V, N
b, Ta, Mo, or W)
Fe—X—M—Z alloy film (X is one of Si and Al, T is Cr, Ti, Mo, W, V, Re, R
at least one of u, Rh, Ni, Co, Pd, Pt, and Au; M represents at least one of Zr, Hf, Nb, and Ta; and Z represents at least one of C and N). When manufacturing a magnetic head in which these magnetic films are sandwiched by the non-magnetic ceramic of the present invention, since the thermal expansion coefficients of the magnetic films are close to each other, it is necessary to prevent the occurrence of defects in the magnetic head without generating residual strain. Can be.

Further, the nonmagnetic ceramic of the present invention has a shape change rate of 35% or less, has a low hardness, and can be processed into a complicated shape, so that, for example, the manufacturing cost of a magnetic head can be reduced. . Further, since the non-magnetic ceramic of the present invention has a saturation magnetic flux density of 7 × 10 ⁻³ T or less, the non-magnetic ceramic itself is not magnetized, and the track of the magnetic head can be narrowed.

The non-magnetic ceramic of the present invention can be suitably used as a material for a slider of a thin head used for a hard disk or the like, or as a material for a core of a laminated magnetic head used for a VTR or a tape recorder.

[Brief description of the drawings]

FIG. 1 is a process diagram for explaining a method of manufacturing a magnetic head using a non-magnetic ceramic according to an embodiment of the present invention, wherein A is a diagram showing a state before a block-shaped substrate is joined; FIG. 4 is a view showing a state after bonding.

FIG. 2 is an enlarged view of a magnetic gap peripheral portion of a magnetic head using nonmagnetic ceramics according to an embodiment of the present invention.

3A and 3B are diagrams for explaining a method of measuring a shape change rate of a non-magnetic ceramic according to an embodiment of the present invention, in which A is a diagram showing the start of formation of a groove, and B is a diagram showing the start of formation of the groove. It is a figure which shows the time of completion | finish of formation, C is a front view of the block of non-magnetic ceramics.

[Explanation of symbols]

 Reference Signs List 20 magnetic film (magnetic core) 24 laminated glass 26 base 26 'base 28 base 32 magnetic film 33 magnetic core 34 insulating film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takashi Hatanai 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. F-term (reference) 4G002 AA08 AB01 AE05 4G018 AA08 5D042 SA01 5D093 HC07 JB03 JC01 JC06

Claims (5)

[Claims] A non-magnetic ceramic containing CaO and Fe ₂ O ₃ as main components, wherein CaO / Fe ₂ O ₃
The molar ratio of CaO and Fe ₂ O _{3 represented} by
Non-magnetic ceramics having a ratio of not less than / 85 and not more than 44/56. 2. The compounding ratio (x) of CaO is 15 mol% or more and 44 mol% or less, and the mixing ratio (y) of Fe ₂ O ₃ is 5 mol% or less.
2. The non-magnetic ceramic according to claim 1, wherein x is not less than 85 mol% and x + y is 100 mol%. 3. The method according to claim 1, wherein the average thermal expansion coefficient at 100 ° C. to 600 ° C. is 115 × 10 ⁻⁷ / ° C. or more and 125 × 10 ⁻⁷ / ° C. or less. Non-magnetic ceramics. 4. When the grindstone grinds the nonmagnetic ceramic to form a groove in the nonmagnetic ceramic while relatively moving the nonmagnetic ceramic and the grindstone, the grindstone is formed on the nonmagnetic ceramic at the start of grinding. Assuming that the depth of the groove formed is a and the depth of the groove formed in the non-magnetic ceramic at the end of grinding is b, the shape change rate represented by the following equation is 35% or less. The non-magnetic ceramic according to any one of claims 1 to 3, wherein Shape change rate (%) = (ab) / a × 100 5. The non-magnetic ceramic according to claim 1, wherein a saturation magnetic flux density is 7 × 10 ⁻³ T or less.