High-frequency magnetic field application device for diamond magnetic sensors

Abstract

To provide a high-frequency magnetic field application device capable of achieving a diamond magnetic sensor with performance better than before.SOLUTION: The high-frequency magnetic field application device includes a microstrip line (42) formed on a dielectric substrate. The microstrip line has an antenna line (423) that is formed of a first part (423a) and a second part (423b) arranged in a first direction perpendicular to the thickness direction of the dielectric substrate and a loop part (423c) that is a line leading from the first part to the second part and protrudes from the first part and the second part along a second direction in an element placement area (40) where diamond elements including diamond nitrogen-vacancy centers are placed. The electrical length of the line from the first part through the loop part to the second part is formed to be half the wavelength of a high-frequency magnetic field.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a high-frequency magnetic field application device for a diamond magnetic sensor. [Background technology]

[0002] Various types of so-called diamond magnetic sensors have been known in the past, which are magnetic sensors that utilize the electron spin quantum state of diamond nitrogen-vacancy centers (i.e., NV centers), which are lattice defects in nitrogen-doped synthetic diamond. Such diamond magnetic sensors include at least a diamond element having NV centers and a high-frequency magnetic field application device that applies a high-frequency magnetic field of around 2.87 GHz to the diamond element. Specifically, for example, Patent Document 1 discloses a configuration in which a diamond layer containing NV centers is provided on an integrated circuit having an inductor for generating a high-frequency magnetic field. This inductor is formed as a multiple-loop on-chip inductor or a metal wire array. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 10,962,610 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when detecting localized magnetic fields, such as those related to brain magnetism, the diamond element and the object to be measured must be located as close as possible to each other. Therefore, the high-frequency magnetic field must be generated parallel to the substrate. In contrast, when using a multi-loop on-chip inductor in the configuration described in Patent Document 1, the high-frequency magnetic field is generated perpendicular to the substrate, preventing the diamond element from being located close enough to the object to be measured. Furthermore, while the resonant structure provides high efficiency near the resonant frequency, the high-frequency magnetic field rapidly decreases when the frequency is outside the resonant frequency. Furthermore, fluctuations in the resonant frequency due to temperature fluctuations and aging can cause the sensor to deviate from the resonant frequency at which the sensor sensitivity is maximized. Furthermore, the sensor sensitivity of diamond NV is 28 MHz / mT, making resonant types unsuitable for sensors with a wide dynamic range. On the other hand, using a metal wire array in the configuration described in Patent Document 1 makes it possible to realize a sensor with a wide dynamic range. However, with this configuration, although a uniform magnetic field is formed in the in-plane direction of the substrate, the current is distributed to each wiring and flows into the GND, so the amount of magnetic field generated in response to the input current is the same as in the case of a single electric wire, and the high-frequency magnetic field generated is smaller than in the resonant type.

[0005] The present invention has been made in view of the above-mentioned circumstances, etc. That is, the present invention provides, for example, a high-frequency magnetic field application device for realizing a diamond magnetic sensor having better performance than conventional devices. [Means for solving the problem]

[0006] The high frequency magnetic field application device (1) for a diamond magnetic sensor having a diamond element (D) containing a diamond nitrogen-vacancy center according to claim 1, A dielectric substrate (41); a microstrip line (42) formed on the dielectric substrate; Equipped with The microstrip line is a first portion (423a) and a second portion (423b) arranged in a first direction perpendicular to the thickness direction of the dielectric substrate in an element placement region (40) where the diamond element is placed, and a loop portion (423c) which is a line extending from the first portion to the second portion and protrudes from the first portion and the second portion along a second direction perpendicular to the thickness direction and intersecting with the first direction, The instantaneous current flow state of the microstrip line is in the element placement area at phase 0 degrees and phase 180 degrees. The antenna line (423) is formed so as to generate a magnetic field in an in-plane direction perpendicular to the thickness direction, the first portion and the second portion are formed as linear wiring patterns having a predetermined width in the first direction and extending along the second direction, The line spacing of the microstrip line in the first direction is minimized between the first portion and the second portion, and is widened in the loop portion, thereby reducing the distance between the lines. configured to suppress mutual interference, The electrical length of the line extending from the first portion through the loop portion to the second portion is formed to be half the wavelength of the high frequency magnetic field applied to the diamond element. The high frequency magnetic field application device (1) for a diamond magnetic sensor having a diamond element (D) containing a diamond nitrogen-vacancy center according to claim 5, A dielectric substrate (41); a microstrip line (42) formed on the dielectric substrate; Equipped with The microstrip line is an antenna line (423) including a first portion (423a) and a second portion (423b) arranged in a first direction perpendicular to the thickness direction of the dielectric substrate in an element placement region (40) where the diamond element is placed, and a loop portion (423c) which is a line extending from the first portion to the second portion and protrudes from the first portion and the second portion along a second direction perpendicular to the thickness direction and intersecting with the first direction, and which is formed so that an instantaneous current flow state of the microstrip line generates a magnetic field in an in-plane direction perpendicular to the thickness direction in the element placement region at a phase of 0 degrees and a phase of 180 degrees; the first portion and the second portion are formed as linear wiring patterns having a predetermined width in the first direction and extending along the second direction, a line spacing of the microstrip line in the first direction is formed so that the line spacing between the first portion and the second portion is minimum and the line spacing is widened in the loop portion, thereby suppressing mutual interference between the lines; The electrical length of the line from the first portion through the loop portion to the second portion is formed to be half the wavelength of the high frequency magnetic field applied to the diamond element, The antenna further includes a line connected to the first portion, and a line having one end connected to the second portion and the other end provided as an open end, the line being configured so that the electrical length from the center position of the second portion in the second direction to the open end is one-fourth of the wavelength in the high-frequency magnetic field.

[0007] In addition, in each section of the application documents, each element may be assigned a reference symbol in parentheses. However, such reference symbol merely indicates an example of the correspondence between the element and the specific means described in the embodiment described below. Therefore, the present invention is not limited in any way by the above-mentioned reference symbols. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a perspective view showing a schematic configuration of a radio frequency magnetic field application device according to an embodiment of the present invention. [Figure 2] 2 is an enlarged plan view showing the antenna line and its surrounding area in the antenna substrate shown in FIG. 1. FIG. [Figure 3A] 3 is a plan view showing the state of instantaneous current in the antenna substrate shown in FIG. 2. FIG. [Figure 3B] 3 is a plan view showing the state of instantaneous current in the antenna substrate shown in FIG. 2. FIG. [Figure 3C] 3 is a plan view showing the state of instantaneous current in the antenna substrate shown in FIG. 2. FIG. [Figure 3D] 3 is a plan view showing the state of instantaneous current in the antenna substrate shown in FIG. 2. FIG. [Figure 4] 1. FIG. 4 is a plan view showing a modified example of the configuration of the antenna substrate shown in FIG. [Figure 5] FIG. 10 is a block diagram showing a schematic configuration of a radio frequency magnetic field application device according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Embodiment) Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that various modifications applicable to one embodiment may be inserted in the middle of a series of explanations relating to that embodiment, which may impede understanding of that embodiment. Therefore, the modifications will be described together after the series of explanations of the embodiment. As will be described later, FIG. 1 and the following explanation using these figures are simplified solely to explain the general configuration and functions of this embodiment, and do not necessarily correspond to the specific device configuration actually manufactured and sold. Furthermore, for convenience of illustration and explanation, an XYZ coordinate system is set in FIG. 1 and the like. The XYZ coordinate systems in each figure are assumed to be consistent with each other.

[0010] (composition) As shown in FIG. 1, a high-frequency magnetic field application device 1 for a diamond magnetic sensor equipped with a diamond element D containing a diamond nitrogen-vacancy center is configured to apply a high-frequency magnetic field to the diamond element D. Specifically, the high-frequency magnetic field application device 1 includes a housing frame 2, a high-frequency connector 3, and an antenna substrate 4. To simplify illustration and description, the operating principle of this type of diamond magnetic sensor and other components typically provided in this type of diamond magnetic sensor, such as excitation light generation and fluorescence detection for ODMR detection, are not shown or described in this specification. ODMR stands for Optically Detected Magnetic Resonance. For the operating principle of this type of diamond magnetic sensor and other components typically provided in this type of diamond magnetic sensor, please refer to Patent Document 1 mentioned above as well as Japanese Patent Laid-Open Publication No. 2020-38086, a prior application filed by the inventor of the present invention.

[0011] The housing frame 2 includes a connector mounting portion 21 and a board support portion 22. The connector mounting portion 21 has a thickness direction in the X-axis direction in the figure and is formed as a rectangular flat plate in the YZ plane. The high-frequency connector 3 is attached to one surface in the thickness direction, i.e., the outer surface. The board support portion 22 extends in the X-axis direction from the other surface in the thickness direction, i.e., the inner surface, of the connector mounting portion 21. The board support portion 22 has a thickness direction in the Z-axis direction in the figure and is formed as a substantially rectangular flat plate in the XY plane. In this embodiment, the housing frame 2 is seamlessly formed as a single unit using a metal material such as copper that has excellent electrical and thermal conductivity. Specifically, the housing frame 2 has a shape as a substantially L-shaped plate member in side view, with the board support portion 22 extending in a cantilevered manner from the lower end of the connector mounting portion 21 in the figure.

[0012] The substrate support portion 22 has a protrusion 22a and a substrate accommodating portion 22b. The protrusion 22a protrudes in the positive direction of the Z axis in the figure from one end side in the X axis direction of the planar substrate accommodating portion 22b, i.e., the tip side, and the end portion in the Y axis direction. The upper surface of the protrusion 22a, i.e., the surface exposed in the positive direction of the Z axis, is formed in a flat shape. The substrate accommodating portion 22b is a recess formed in the substrate support portion 22 relatively by providing the protrusion 22a, and has a substantially L-shaped planar shape that substantially matches the planar shape of the antenna substrate 4.

[0013] A pair of high-frequency connectors 3, i.e., an input connector 31 and an output connector 32, are attached to the connector attachment portion 21 of the housing frame 2. The input connector 31 and the output connector 32 are arranged in the Y-axis direction in the figure. The input connector 31 and the output connector 32 are electrically connected to the antenna board 4.

[0014] The antenna substrate 4 is configured to fixedly support the diamond element D in the element placement region 40. In other words, the antenna substrate 4 is configured to apply a high-frequency magnetic field to the diamond element D placed in the element placement region 40 by high-frequency power input to the high-frequency connector 3. Specifically, the antenna substrate 4 includes a dielectric substrate 41, a microstrip line 42, and a heat dissipation layer 43.

[0015] The dielectric substrate 41 is formed in the shape of a thin plate with its thickness oriented in the Z-axis direction from a material with a higher dielectric constant than FR-4, which has a dielectric constant of approximately 4.3 to 5.0, for example, an alumina substrate with a dielectric constant of 9.6. FR-4 stands for Flame Retardant Type 4. Specifically, the dielectric substrate 41 has a pattern formation surface 411 and a back surface 412. A microstrip line 42 is formed on the pattern formation surface 411. The back surface 412, on which a grounding conductor film (not shown) is formed, is joined to the surface of the substrate accommodating portion 22b of the substrate support portion 22.

[0016] The microstrip line 42 formed on the dielectric substrate 41 has an input line 421, an output line 422, and an antenna line 423. The input line 421 is a feed line connected to one end of the antenna line 423, and is electrically connected to the input connector 31. That is, the input line 421 is provided to connect the input connector 31 and the antenna line 423. The output line 422 is a line connected to the other end of the antenna line 423, and is provided to connect the antenna line 423 and the output connector 32.

[0017] As shown in FIG. 2, the antenna line 423 is formed by a first portion 423a, a second portion 423b, and a loop portion 423c. The first portion 423a and the second portion 423b have a predetermined width in the Y-axis direction (i.e., the first direction) in the figure and are formed as linear wiring patterns extending along the X-axis direction (i.e., the second direction) in the figure. The first portion 423a and the second portion 423b are arranged in the Y-axis direction (i.e., the first direction) in the element placement area 40. The loop portion 423c, which is a line extending from the first portion 423a to the second portion 423b, has the same wiring width as the first portion 423a and the second portion 423b and protrudes from the first portion 423a and the second portion 423b along the X-axis direction in the figure. The wiring width of the antenna line 423 is set so that the characteristic impedance matches the system impedance (i.e., typically 50Ω, for example). The transmission line extending from first portion 423a through loop portion 423c to second portion 423b is hereinafter referred to as unit antenna line 423d. Microstrip line 42 is formed so that the electrical length of unit antenna line 423d is half the wavelength in the high-frequency magnetic field.

[0018] In this embodiment, in order to suppress mutual interference between the wires, the microstrip line 42 is formed so that the wire spacing is smallest in the element placement region 40 and wider in other areas. That is, the microstrip line 42 is formed so that the line spacing in the Y-axis direction of the loop portion 423c is wider than the line spacing between the first portion 423a and the second portion 423b.

[0019] In this embodiment, the antenna line 423 has a plurality of loop portions 423c (i.e., three in the example shown in FIG. 2) protruding in opposite directions, and is thus formed into a meandering wiring shape that snakes along the Y-axis direction. Specifically, in the example shown in FIG. 2, unit antenna lines 423d extending from a first position P1 to a second position P2, unit antenna lines 423d extending from the second position P2 to a third position P3, and unit antenna lines 423d extending from the third position P3 to a fourth position P4 are provided alternately. The first position P1, second position P2, third position P3, and fourth position P4 are arranged in this order in the Y-axis direction on center line L, which is an imaginary line that passes through the center of element placement region 40 in a plan view and is parallel to the Y-axis.

[0020] The heat dissipation layer 43 is formed of a ceramic material (e.g., aluminum nitride, silicon nitride, alumina zirconia, etc.) that has excellent electrical insulation and heat dissipation properties. The heat dissipation layer 43 is provided so as to dissipate heat from the diamond element D to the substrate support part 22 by bonding to the protrusions 22a of the substrate support part 22.

[0021] (effect) Hereinafter, an outline of the operation of the high frequency magnetic field application device 1 according to this embodiment having the above-described configuration will be described together with the effects of such a configuration with reference to the drawings.

[0022] 3A to 3D show the instantaneous current flow state in the antenna line 423 shown in FIG. 2. That is, FIGS. 3A, 3B, 3C, and 3D show phases of 0 degrees, 90 degrees, 180 degrees, and 270 degrees, respectively. In FIGS. 3A to 3D, the short solid arrows indicate only the direction of the current, not the magnitude of the current. The dashed arrows in FIGS. 3A and 3C indicate the magnetic field generated by the current. As shown in these figures, at phases of 0 degrees and 180 degrees, the instantaneous current is at its maximum in the element placement region 40 where the diamond element D is arranged. In this state, the instantaneous currents are directed in the same direction, and therefore a high-frequency magnetic field is generated in the direction indicated by the dashed arrows in the figures. In contrast, at phases of 90 degrees and 270 degrees, the instantaneous current is at its minimum in the element placement region 40 where the diamond element D is arranged, and because they are directed in opposite directions, the instantaneous high-frequency magnetic field in the element placement region 40 is also at its minimum. Furthermore, it was confirmed by computer simulation that the configuration according to this embodiment can generate a wide band high frequency magnetic field from 1.6 GHz to 3.6 GHz, although the design center is 2.87 GHz.

[0023] As described above, in this embodiment, multiple wirings (i.e., four in the specific example shown in FIG. 2) run through the element placement region 40, and signals flow from the first position P1 to the second position P2 to the third position P3 to the fourth position P4 in this order. The electrical lengths (i.e., wavelengths at a specific frequency) between the first position P1 and the second position P2, between the second position P2 and the third position P3, and between the third position P3 and the fourth position P4 are half wavelengths, and the instantaneous current flows in the same direction. A high-frequency magnetic field is generated in a direction parallel to the antenna substrate 4. Therefore, this embodiment allows the diamond element D to be placed sufficiently close to the object being measured, making it suitable for use in localized magnetic field detection, such as magnetoencephalography. Furthermore, while the multiple-loop on-chip inductor configuration in Patent Document 1 has a problem of a narrow usable frequency range due to its resonant structure, this embodiment maintains a relatively high-frequency magnetic field strength even when the frequency deviates from the design center. Furthermore, due to the effect of folding back the wiring, a magnetic field strength that is more than twice as strong (i.e., four times as strong in the specific example shown in Fig. 2) as that of the metal wire array configuration in Patent Document 1 can be expected. Therefore, according to this embodiment, it is possible to provide a high-frequency magnetic field application device 1 that realizes a diamond magnetic sensor with better performance than conventional ones.

[0024] (Variation) The present invention is not limited to the above-described embodiment. Therefore, the above-described embodiment can be modified as appropriate. Representative modifications will be described below. In the following description of the modifications, differences from the above-described embodiment will be mainly described. Furthermore, the same reference numerals are used for parts that are identical or equivalent to each other in the above-described embodiment and the modifications. Therefore, in the following description of the modifications, the description of the above-described embodiment can be used as appropriate for components that have the same reference numerals as the above-described embodiment, unless there is a technical contradiction or special additional explanation.

[0025] The present invention is not limited to the specific device configurations shown in the above-described embodiments. That is, as described above, the description of the above-described embodiments is within the scope of what is technically necessary and sufficient for the present invention, and other details have been omitted. Specifically, for example, in the above-described embodiments, details of the configuration required for mounting the high-frequency connector 3 on the copper housing frame 2 and electrically connecting the high-frequency connector 3 to the antenna substrate 4 (e.g., insulating means between the housing frame 2 and the signal input / output terminals of the high-frequency connector 3) are obvious in light of the common technical knowledge at the time of filing of this application, and therefore are not shown or described in this specification. The same applies to an impedance-matched terminator provided at the end of the output line 422. Furthermore, Figures 1 and 2 and the above description using them are simplified solely to explain the general configuration and function of this embodiment, and may not necessarily match the specific device configuration that will actually be manufactured and sold.

[0026] The heat dissipation layer 43 may be thin or thick. This is because each has its own advantages. That is, when the heat dissipation layer 43 is thin, the strength of the high-frequency magnetic field applied to the diamond element D is stronger. In this case, by using a thin diamond element D, the difference in high-frequency magnetic field strength between the surface close to the antenna line 423 and the surface far from the antenna line 423 in the diamond element D can be reduced. This is suitable for measuring magnetic fields that rapidly weaken with distance from the magnetic field source, such as brain magnetism. In contrast, when the heat dissipation layer 43 is thick, the difference in high-frequency magnetic field strength between the surface close to the antenna line 423 and the surface far from the antenna line 423 in the diamond element D is reduced. Therefore, a thick diamond element D can be used. A weakened high-frequency magnetic field can be addressed by increasing the current, and heat generated by the line is quickly dissipated by the thick heat dissipation layer 43. This is suitable for measuring uniform yet weak magnetic fields, such as geomagnetism and weak magnetic field fluctuations in bedrock.

[0027] The above embodiment is characterized by a two-port transmission line configuration and the ability to generate a high-frequency magnetic field over a wide bandwidth. Alternatively, as shown in FIG. 4, the output line 422 may be provided as an open end. Note that "open end" refers to neither a power feed point nor a ground point. In this case, if the fourth position P4 shown in FIG. 4 and beyond are defined as the output line 422, the output line 422 can be formed so that its electrical length is one-fourth the wavelength of the high-frequency magnetic field. With an open-tip structure as shown in FIG. 4, a standing wave is generated at the position of the diamond element D, and a high-frequency magnetic field strength twice that of the above embodiment can be obtained with the same input power.

[0028] In the above embodiment, most of the input power is lost to the output, which is a problem of poor efficiency. For this reason, a method for improving power utilization efficiency when configuring a sensor system is shown in Figure 5. In other words, in the configuration shown in Figure 5, the power lost to the output terminal is normally absorbed by a non-reflective termination and converted into heat, but this is input to a rectifier circuit to be converted into direct current, and then regenerated by converting it into the same voltage as the power supply voltage of the high-frequency magnetic field application device 1 using a DC-DC converter.

[0029] 5 , this modification includes a DC power supply 71, a radio-frequency signal generating unit 72, a converting unit 73, and a step-up / step-down converter 74. The radio-frequency signal generating unit 72 is driven by the DC power supply 71 and is electrically connected to an input line 421 so as to input radio-frequency power to an antenna line 423. The converting unit 73 is electrically connected to an output line 422 and is configured to convert the radio-frequency power output from the output line 422 into DC. The step-up / step-down converter 74 is a DC-DC converter and is configured to convert the voltage output from the converting unit 73 to the same voltage as the power supply voltage of the DC power supply 71. For example, at 2.87 GHz, the converting unit 73 achieves an RF / DC conversion efficiency of about 80%, and if the efficiency of the step-up / step-down converter 74 is 80%, 64% of power regeneration is possible.

[0030] In the above description, multiple components that were formed seamlessly and integrally with each other may be formed by bonding separate members together. Similarly, multiple components that were formed by bonding separate members together may be formed seamlessly and integrally with each other. Furthermore, in the above description, multiple components that were formed from the same material may be formed from different materials. Similarly, multiple components that were formed from different materials may be formed from the same material.

[0031] It goes without saying that the elements constituting the above-described embodiments are not necessarily essential unless expressly stated as essential or clearly considered essential in principle. Furthermore, when numerical values ​​such as the number, amount, range, etc. of components are mentioned, the present invention is not limited to those specific numerical values ​​unless expressly stated as essential or clearly limited to specific numerical values ​​in principle. Similarly, when the shape, direction, positional relationship, etc. of components are mentioned, the present invention is not limited to those shapes, directions, positional relationship, etc. unless expressly stated as essential or clearly limited to specific shapes, directions, positional relationship, etc. in principle.

[0032] The modified examples are not limited to the above examples, and for example, multiple modified examples may be combined with each other. [Explanation of symbols]

[0033] 1. High-frequency magnetic field application device 4 Antenna board 40 Element placement area 41 Dielectric substrate 42 Microstrip Line 423 Antenna Line 423a First part 423b Second part 423c Loop part D Diamond element

Claims

1. A high-frequency magnetic field application device (1) for a diamond magnetic sensor having a diamond element (D) containing a diamond nitrogen-vacancy center, A dielectric substrate (41); a microstrip line (42) formed on the dielectric substrate; Equipped with The microstrip line is an antenna line (423) including a first portion (423a) and a second portion (423b) arranged in a first direction perpendicular to the thickness direction of the dielectric substrate in an element placement region (40) where the diamond element is placed, and a loop portion (423c) which is a line extending from the first portion to the second portion and protrudes from the first portion and the second portion along a second direction perpendicular to the thickness direction and intersecting with the first direction, and which is formed so that an instantaneous current flow state of the microstrip line generates a magnetic field in an in-plane direction perpendicular to the thickness direction in the element placement region at a phase of 0 degrees and a phase of 180 degrees; the first portion and the second portion are formed as linear wiring patterns having a predetermined width in the first direction and extending along the second direction, a line spacing of the microstrip line in the first direction is formed so that the line spacing between the first portion and the second portion is minimum and the line spacing is widened in the loop portion, thereby suppressing mutual interference between the lines; The electrical length of the line from the first portion through the loop portion to the second portion is formed to be half the wavelength of the high frequency magnetic field applied to the diamond element. High frequency magnetic field application device.

2. The antenna line is formed in a meander wiring shape by having a plurality of the loop portions protruding in opposite directions.

2. The high frequency magnetic field application device according to claim 1.

3. The microstrip line is An input line (421) which is a feed line connected to one end of the antenna line; an output line (422) connected to the other end of the antenna line; further comprising 3. The high frequency magnetic field application device according to claim 1 or 2.

4. a high-frequency signal generating unit (72) driven by a DC power supply (71) and electrically connected to the input line so as to input high-frequency power to the antenna line; a conversion unit (73) electrically connected to the output line and configured to convert the high frequency power output from the output line into direct current; a step-up / step-down converter (74) configured to convert the voltage at the output from the conversion unit into a voltage identical to the power supply voltage of the DC power supply; Furthermore, 4. The high frequency magnetic field application device according to claim 3.

5. A high-frequency magnetic field application device (1) for a diamond magnetic sensor having a diamond element (D) containing a diamond nitrogen-vacancy center, A dielectric substrate (41); a microstrip line (42) formed on the dielectric substrate; Equipped with The microstrip line is an antenna line (423) including a first portion (423a) and a second portion (423b) arranged in a first direction perpendicular to the thickness direction of the dielectric substrate in an element placement region (40) where the diamond element is placed, and a loop portion (423c) which is a line extending from the first portion to the second portion and protrudes from the first portion and the second portion along a second direction perpendicular to the thickness direction and intersecting with the first direction, and which is formed so that an instantaneous current flow state of the microstrip line generates a magnetic field in an in-plane direction perpendicular to the thickness direction in the element placement region at a phase of 0 degrees and a phase of 180 degrees; the first portion and the second portion are formed as linear wiring patterns having a predetermined width in the first direction and extending along the second direction, a line spacing of the microstrip line in the first direction is formed so that the line spacing between the first portion and the second portion is minimum and the line spacing is widened in the loop portion, thereby suppressing mutual interference between the lines; The electrical length of the line from the first portion through the loop portion to the second portion is formed to be half the wavelength of the high frequency magnetic field applied to the diamond element, The line further includes: a line connected to the first portion; and a line having one end connected to the second portion and the other end provided as an open end, the line being formed so that the electrical length from a center position of the second portion in the second direction to the open end is one-fourth of the wavelength of the high frequency magnetic field. High frequency magnetic field application device.

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