Magnetic particle detection system and method for detecting and measuring magnetic particles

Abstract

This device detects the size and concentration of magnetic particles mixed into powder products. [Solution] The present invention provides a system that can detect contamination levels of 0.5 ppm by setting the tip diameter of the sensor element 32 to 15 μm or less, which is comparable to the size of magnetic microparticles of 5 μm to 50 μm, fixing its tip position to the tip of the nT meter 321, and setting the distance between the magnetic microparticles 300 and the sensor tip to about 0.1 mm.

Description

Technical Field

[0001] In recent years, the mixing and contamination of magnetic microparticles have become a problem in food products and battery materials. These products are finished from raw materials into powder products and then processed into a predetermined shape. The powder products are manufactured using a pipe device with stainless steel equipment, but stainless steel magnetic microparticles are mixed in as foreign matter during pipe transportation. In particular, magnetic microparticles mixed in the positive electrode material of Li batteries can cause ignition even if they are微小, so strict management of about 1 ppm order of contamination degree is required. The size of magnetic microparticles is extremely small, ranging from 5 μm to 100 μm, and the development of detection methods for magnetic microparticles is currently underway.

[0002] Patent Document 1 discloses that a static magnetic field is formed by a permanent magnet, the magnetic field disturbed by a minute magnetic metal foreign object as the object to be measured is detected by a plurality of detection coils, and the signal is inspected by a SQUID magnetic sensor, and it was possible to measure using a metal sphere with a diameter of 0.2 mm. It can be said that it is difficult to detect metal foreign objects of 0.2 mm or less with a SQUID magnetic sensor having a large sensor element.

[0003] Patent Document 2 discloses a method for inspecting magnetic foreign objects present on an electrode sheet, and a method for measuring a magnetic field generated from a specific current distribution by supplying power to the electrode sheet, and discloses the identification of metal foreign objects of about several tens of μm, but it is not an invention that can detect foreign objects in the powder state targeted by the present invention. In addition, magnetic particles of 5 μm or less cannot be detected. Patent Document 3 discloses a method for magnetizing and detecting metal foreign objects mixed in a sheet-like inspection object, and a method for magnetizing metal foreign objects by transporting them on a plurality of permanent magnets and measuring the magnetic field with a magnetic sensor, and discloses the detection of metal foreign objects with a diameter of 100 μm at a distance of 10 mm or less between the magnet and the object to be measured, but it is not an invention that can detect foreign objects in the powder state targeted by the present invention.

[0004] Non-patent document 1 reports that a 50 μm magnetic particle was successfully detected using an element with a diameter of 30 μm and a length of 10 mm. Non-patent document 2 reports the successful detection of 40 μm magnetic particles using a sensor measuring 8 mm x 8 mm and 5 mm thick. This sensor incorporates improvements to the magnetic circuit and a bridge circuit with four elements, increasing the size of the magnetic sensor to enhance detection capabilities. However, the large surface area of ​​the magnetic sensor makes it difficult to detect particles smaller than 30 μm.

[0005] A single particle with a diameter of 5 μm weighs approximately 0.5 ng, and its contamination level, assuming a 1 mg sample, is 0.5 ppm. A contamination detection device must first be able to detect 5 μm diameter particles using a magnetic sensor, and then be able to detect the 0.5 ppm contamination level from a single 5 μm diameter particle present in a 1 mg sample taken from the product. Current development is far from achieving this goal. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2014-48170 [Patent Document 2] Japanese Patent Publication No. 2019-75290 [Patent Document 3] Japanese Patent Publication No. 2022-108554

[0007] [Non-Patent Document 1] Aichi Steel Corporation's website News Release, September 9, 2024 [Non-Patent Document 2] HP Sensor Solution by TDK Corporation [Overview of the project] [Problems that the invention aims to solve]

[0008] The first challenge is that, in order to develop a detection system for contamination levels on the order of 1 ppm, it is necessary to be able to detect the magnetic field of magnetic particles with a diameter of at least 5 μm under ideal conditions, when the magnetic particles and the sensor element are as close together as possible. Under these ideal conditions, detection of 0.5 μm magnetic particles is preferable. We first compared and evaluated various commercially available nT sensors (nT meters), namely FG sensors, MI sensors, GSR sensors, and tMR sensors.

[0009] As a result, the FG sensor type had a large element (magnetic wire) with a diameter of 3 mm and a length of 30 mm, and was unable to detect magnetic particles as small as 100 μm. Next, the MI sensor type had a relatively small element with a diameter of 30 μm and a length of 10 mm, which seemed capable of detecting magnetic particles with a diameter of 30 μm, but its length of 10 mm was too large, limiting its detection to magnetic particles with a diameter of 50 μm. Finally, the GSR sensor type had a small element with a diameter of 10 mm and a length of 2 mm, and was able to detect magnetic particles with a diameter of 10 μm. Furthermore, because the tMR sensor type utilizes a wide, flat detection area that contributes to its magnetic collection effect, it was not possible to design the distance between the sensor element body and the magnetic particles to the absolute minimum, limiting detection to magnetic particles with a diameter of 40 μm. The inventors decided to improve upon the commercially available GSR sensor type nT meter, which was the best available at the time, for this purpose.

[0010] The second challenge is to develop a detection device that can identify and detect samples containing minute magnetic foreign matter mixed into the positive electrode powder material of lithium-ion batteries, with contamination levels of 10 ppm or less. This involves inventing a system that takes a sample from a contaminated powder product, places a predetermined amount in a container, magnetizes the magnetic particles, measures the magnetic field emitted from it using an improved nT sensor, and determines the degree of contamination from the resulting value. [Means for solving the problem]

[0011] The inventors fabricated a GSR sensor type nT meter and measured the magnetic field emitted from magnetic nanoparticles ranging from 1 μm to 100 μm. As a result, as shown in Figure 1, they discovered that the smaller the element, the smaller the diameter of the nanoparticles that could be detected. Here, GSR-5 in Figure 1 is an example of a GSR sensor with an element diameter (magnetic wire-based magnetometer) of 5 μm, and GSR-10 is an example of a GSR sensor with an element diameter of 10 μm. For comparison, the MI sensor has an element diameter of 30 μm. In particular, it is preferable that the diameter of the element is close to the diameter of the magnetic nanoparticles. The magnetic wire, which is the detection element, needs to have an aspect ratio of 200 or more. Increasing the diameter increases the length, and thus the volume of the magnetic wire increases.

[0012] Figure 2 shows the results of measuring the magnetic field emitted from magnetic nanoparticles with a diameter of 10 μm. As the volume of the element increases, the detected magnetic field decreases significantly from 26 μm to 2 μm. The nT meters used have similar detection power when measuring uniform magnetic fields, but it was revealed for the first time that the size of the magnetic wire is important when measuring minute spatial magnetic fields emitted by magnetic nanoparticles. In this invention, regarding the performance of the nT meter, the size of the magnetic sensor element of the sensor element with a detection power of 1 nT or less was set to a diameter of 15 μm or less and a length of 2 mm or less.

[0013] Next, we investigated the effect of the distance between the tip of the GSR sensor element and the magnetic microparticles. As shown in Figure 3, it was found that reducing the distance from 0.9 mm to 0.1 mm improved the diameter of the measurement limit for magnetic nanoparticles from 10 μm to 0.5 μm. Therefore, in this invention, as shown in Figure 7, the tip of the magnetic wire (sensor element) is positioned at the tip of the nT meter so that the tip of the nT meter is the tip of the sensor element. In other words, the end of the GSR element is made to be the end of the wire. Next, the design of the electronic circuit board is modified so that the sensor element is installed at the tip of the board.

[0014] A predetermined amount of the contaminated powder base material, consisting of magnetic microparticles, is collected and placed in a dedicated container. To minimize the distance between the magnetic microparticles and the sensor tip, the thickness of the container's bottom is set to 0.1 mm or less. Furthermore, magnetic nanoparticles were magnetized, ultrasonic vibrations were applied to cause them to accumulate at the bottom of the container, and then they were fixed with wax to create a measurement sample in which the magnetic nanoparticles were fixed to the bottom of the container (Figures 5 and 6).

[0015] A powder foreign matter sample for measurement is fixed to a powder container fixing stand, and an nT meter mounting stand is placed below it. After attaching the nT meter to the nT meter mounting stand, the nT meter mounting stand is tilted so that the tip of the GSR element is perpendicular to the bottom surface of the container. The XY axes are then adjusted so that the tip of the element is in the center of the container, and the Z axis is adjusted so that the tip of the element contacts the bottom of the container, so that the distance between the tip of the element and the magnetic particles is 0.1 mm or less. A micromagnetic field measuring device with the above functions (Figure 7) was fabricated.

[0016] Under the above conditions, 1 mg of powder was taken from samples with contamination concentrations ranging from 0.5 ppm to 100 ppm, and powder foreign matter samples were prepared using the method described above. Magnetic field measurements were then performed, and as shown in Figure 4, it was found that a contamination level of 0.5 ppm could be detected when the distance was reduced to 0.1 mm. Since the weight of one magnetic particle with a diameter of 10 μm is 4 ng, this corresponds to 4 ppm. A magnetic particle with a diameter of 5 μm weighs 0.5 ng, which corresponds to 0.5 ppm. This device can handle magnetic particles with a diameter of up to 0.5 μm, and it is clear that it is sufficiently capable of determining a contamination level of 0.5 ppm.

[0017] This invention was realized by setting the diameter of the GSR element to 15 μm or less and the length to 2 mm, aligning the end of the magnetic wire with the end of the sensor, and setting the thickness of the bottom of the container to 0.1 mm or less, thereby minimizing the distance between the magnetic particles and the end of the sensor element. At the same time, the system was realized by combining a mechanism that causes magnetic particles to accumulate at the bottom of the container with a precision positioning device that ensures the tip of the sensor element is in contact with the bottom of the container and is located in the center. [Effects of the Invention]

[0018] According to the present invention, it becomes possible to inspect powder products with a contamination level of about 0.5 ppm to 100 ppm due to magnetic fine particles mixed during powder production, and it becomes possible to identify and take countermeasures for the mixing process and to guarantee the quality of the products. Particularly in lithium batteries, the mixing of magnetic fine particles is a cause of ignition, and this product plays an important role in guaranteeing its quality.

Brief Description of the Drawings

[0019] [Figure 1] It is a diagram showing the influence of the size of magnetic fine particles on the magnetic field. [Figure 2] It is a diagram showing the influence of the volume of the element on the magnetic field. [Figure 3] It is a diagram showing the influence of the size of magnetic fine particles and the distance between the magnetic fine particles and the sensor element on the magnetic field. [Figure 4] It is a diagram showing the influence of the concentration of magnetic fine particles and the distance between the magnetic fine particles and the sensor element on the magnetic field. [Figure 5] It is a diagram showing a sample preparation device. [Figure 6] It is a diagram showing a measurement sample composed of magnetic fine particles accumulated at the bottom of the container [Figure 7] It is a diagram showing a micro magnetic field measurement device.

Best Mode for Carrying Out the Invention

[0020] The magnetic fine particle detection system according to the first embodiment of the present invention is as follows. In a magnetic fine particle detection system comprising a sample preparation device, a measurement sample, a micro magnetic field measurement device, and a magnetic field signal processing device, the sample preparation device includes a non-magnetic container, a container fixing portion for fixing the container, and a sample adjusting portion installed at the upper and lower portions of the container, the container is a cylindrical or mortar-shaped container, the tip of the container has a diameter of 2 mm or less, and the bottom thickness is 0.1 mm or less, The sample preparation unit includes a powder insertion device for inserting powder into the upper part of the container and a wax insertion device for inserting wax, The container comprises a magnetic field generating device that applies a magnetic field to the magnetic particles contained in the powder at its lower part, and a vibration generating device that accumulates the magnetic particles in the magnetic field at the bottom of the container. The aforementioned measurement sample is a sample prepared by the sample preparation device and accumulated at the bottom of the container, and consists of magnetic nanoparticles which are the object to be measured by the micromagnetic field measuring device. The aforementioned micromagnetic field measuring device comprises a powder container containing the sample for measurement, a powder container fixing part for fixing the powder container, a sensor element installed below the powder container, and a position adjustment part for adjusting the position of the sensor element and the powder container. The sensor element consists of an nT meter having a detection force of 1 nT or less, and the nT meter is fixed to an nT meter mounting stand. The size of the magnetic element of the aforementioned sensor element is 15 μm or less in diameter and 2 mm or less in length, and the tip of the magnetic element is positioned at the tip of the nT meter. The position adjustment unit comprises a parallelism (tilt) adjustment mechanism for adjusting the parallelism between the sensor element of the nT meter fixed to the nT meter mounting base and the bottom surface of the powder container, and a position adjustment mechanism for adjusting the position of the sensor element along the XY axis (center) and Z axis (distance). The magnetic field signal processing device comprises a sensor signal processing device that calculates the size and / or content of magnetic particles from the magnetic signal measured by the minute magnetic field measuring device. It is characterized by the following:

[0021] Furthermore, in the apparatus of the first embodiment, each device is characterized by being made of a non-magnetic material.

[0022] This invention makes it possible to detect contamination concentrations of magnetic fine particles mixed in powder ranging from 0.5 ppm to 1 ppm.

[0023] The detection and measurement method of the second embodiment is as follows: In a method for detecting and measuring magnetic fine particles mixed in powder, (1) The first step consists of the process of preparing the sample for measurement, Step a) Set the container in the sample preparation device, Step b) Take a sample of 20 mg or less from the powder base material and place it in a container. Step c) Apply a magnetic field to the sample and vibrate it ultrasonically to accumulate the magnetic particles at the bottom of the container. Step d) The liquid wax is poured into the container and solidified to prepare it. Step e) Remove the powder container containing the prepared measurement sample from the sample preparation device. (2) The second step consists of detecting and measuring the minute magnetic field of the sample for measurement, Step f) The powder container is fixed to the fixing device of the powder container fixing part for magnetic field measurement. Step g) Using the parallelism (tilt) adjustment mechanism, the bottom surface of the powder container and the sensor element at the tip of the nT meter are made parallel. Step h) The position adjustment mechanism is used to align the XY axis (center) of the sensor element with the center of the powder container. Step i) The Z-axis (distance) of the sensor element is adjusted by adjusting the distance from the bottom surface of the powder container. Step j) Using the nT meter, measure the minute magnetic field of the magnetic nanoparticles to obtain a measurement signal. Step k) Using a calibration curve prepared in advance, detect and measure the size and / or content of the magnetic fine particles mixed in the powder. It is characterized by the following: Furthermore, the order of steps a) and b) described above can be reversed. That is, the powder sample is inserted into the container after it has been set up.

[0024] This invention enables the detection of highly accurate size of magnetic nanoparticles and the measurement of their content through a simple process, and further allows for the detection and measurement of both size and content.

[0025] Next, embodiments will be described using Figures 3 to 7. The system for detecting magnetic microparticles mixed into powder as foreign matter first prepares a measurement sample by accumulating and fixing the magnetic microparticles in the powder at a predetermined position in a container in order to measure the magnetic field of the magnetic microparticles in the powder. Next, the system measures the minute magnetic field of this measurement sample and processes the magnetic signal using a pre-prepared calibration curve to obtain the contamination concentration of the powder, which is determined by the size and content of the magnetic microparticles. The details are explained below.

[0026] <Sample preparation device 1> As shown in Figure 5, the sample preparation device 1 consists of a non-magnetic container 11, a container fixing part 110, and sample preparation parts (12, 13, 14, 15). This device makes it possible to prepare measurement samples in which magnetic nanoparticles in powder can be measured using a micromagnetic field measuring device.

[0027] The container 11 is made of a non-magnetic metal, such as SUS304 non-magnetic stainless steel. Alternatively, it can be made of a non-magnetic plastic or vinyl-based resin. The shapes include cylindrical, mortar-shaped, cylindrical-mortar-shaped (for example, the container in Figure 6), and pyramidal-mortar-shaped, with the tip (bottom) of the container having a diameter of 2 mm or less and the thickness of the bottom being 0.1 mm or less. For magnetic nanoparticles to accumulate on a small-diameter sensor element, a diameter of 2 mm at the tip of the container is sufficient. Furthermore, the thickness of the bottom should be 0.1 mm or less, as detection power decreases as the distance from the tip of the sensor element to the magnetic nanoparticles increases. The container fixing section 110 stabilizes the container 11 with a fixing device to prevent it from moving or tipping over while powder or the like is being inserted into the container 11 to prepare the sample for measurement.

[0028] The sample preparation section has a powder insertion device 12 for inserting powder (10, 100) into the container and a wax insertion device 13 for inserting wax, both located at the top of the container 11. The powder to be inserted into container 11 shall be taken from the powder base material in an amount of 20 mg or less. The amount can be determined considering the size and content (concentration) of the magnetic particles. The wax to be inserted into container 11 is heated and poured in as a liquid, and then solidified by cooling. For simplicity, wax or similar material can be used.

[0029] A magnetic field generator 14 and a vibration generator 15 are installed at the bottom of the container 11. The magnetic field generator 14 is a device that generates a magnetic field 141 and applies it to the magnetic nanoparticles 100, which are foreign substances mixed in the powder 10. The magnitude of the applied magnetic field is 0.1T to 0.5T. The vibration generator is a device that applies vibration to the powder 10 to accumulate the magnetized magnetic particles 100 in the powder at the bottom of the container 11. The vibration can be ultrasonic vibration or the like. The positional relationship between the magnetic field generator 14 and the vibration generator 15 and the container 11 is not limited to the lower part of the container 11, but may also be in the position shown in Figure 5.

[0030] <200 samples for measurement> As shown in Figure 6, the measurement sample 200 prepared by the sample preparation device 1 is separated from the powder 20 and accumulated at the bottom of the container 21 of the powder container 2, forming an aggregate of magnetic nanoparticles which are the object to be measured by the micromagnetic field measuring device. This aggregate of magnetic nanoparticles, which is the measurement sample 200, is solidified with wax 201 along with powder 20 to prevent it from moving during preparation for the measurement procedure and during the measurement itself.

[0031] <Micromagnetic field measuring device 3> As shown in Figure 7, the micromagnetic field measuring device 3 consists of a powder container 31 containing a measurement sample 300, a powder container fixing part 310 for fixing the powder container 31, a sensor element 32, and a position adjustment part 33. This device makes it possible to detect magnetic fields of less than 1 nT in magnetic nanoparticles of a measurement sample.

[0032] The powder container 31 contains a sample 300 of magnetic fine particles separated from the powder and accumulated inside the container, which is solidified with wax at the bottom of the container. The thickness of the bottom of the container is 0.1 μm. The powder container 31 is fixed to the powder container fixing part 310 to prevent it from moving during measurement preparation or measurement.

[0033] The sensor element 32 is a sensor element of an nT meter 321 having a detection force of 1 nT or less. The nT meter 321 is fixed to the mounting base 3210. In this invention, the sensor element 32 uses a magnetic wire as its magnetosensitive element, with a diameter of 15 μm or less and a length of 2 mm or less. The tip of this magnetosensitive element (the end of the magnetic wire) is positioned at the tip of the nT meter 321, as shown in Figure 7, and is in contact with the lower surface of the bottom of the powder container 31, which is 0.1 mm or less thick. This allows the distance between the measurement sample 300 (magnetic microparticles) and the sensor element to be 0.1 mm or less, ensuring detection capability (Figures 3 and 4).

[0034] The position adjustment unit 33 is the part that adjusts the position between the sensor element 32, which is installed below the powder container 31, and the powder container, and consists of a parallelism (tilt) adjustment mechanism and a center distance position adjustment mechanism. The adjustment method involves first adjusting the parallelism (tilt) between the tip of the sensor element 32 of the nT meter 321, which is fixed to the nT meter mounting base 3210, and the bottom surface of the powder container 31 using the parallelism (tilt) adjustment mechanism. This adjustment allows the bottom surface of the powder container 31 containing the measurement sample (magnetic nanoparticles) 300 and the tip of the sensor element 32 to be in parallel contact without any gaps. Next, the position of the tip of the sensor element 32 is adjusted to the center of the XY axis using the center-distance position adjustment mechanism, and the distance along the Z axis, i.e., the distance between the bottom surface and the tip of the sensor element 32, is adjusted.

[0035] <Magnetic field signal processing device> The magnetic field signal processing device (figures omitted) can obtain the size and content (concentration) of magnetic nanoparticles 300 from the magnetic signal obtained by measuring the minute magnetic field of the measurement sample (magnetic nanoparticles) 300 using a pre-prepared calibration curve (Figures 3 and 4) via a magnetic signal obtained by the nT meter 321 of the minute magnetic field measuring device 3. [Examples]

[0036] [Example 1] A 15 mg sample is taken from the powder base material and inserted into a 0.5 mm thick cylindrical mortar-shaped plastic container 11 using a powder insertion device 12. The diameter of the container 11 is 8 mm, and the length to the tip of the mortar is 15 mm. The diameter of the tip of the container 11 is 1.5 mm, and the thickness of the bottom of the mortar container is 0.07 mm. The container 11 containing the powder is set in the sample preparation device and fixed to the container fixing part 110. This container 11 contains a sample in which magnetic microparticles 100 are mixed in as foreign matter with the powder 10.

[0037] A 0.2T magnetic field 141 generated by a magnetic field generator 14 located at the bottom of the container 11 is applied to the sample (consisting of 10 and 100), and ultrasonic vibration is generated by a vibration generator 15. As a result, only the magnetized magnetic particles from the powder in the sample accumulate at the bottom of the container. Next, the wax insertion device 13 injects the liquid wax, which is then cooled and solidified. In this way, a powder container 2 containing a measurement sample 200 capable of detecting and measuring magnetic microparticles is created. The powder container 2 has the measurement sample 200 (an aggregate of magnetic microparticles) at the bottom of the container 21, and the upper part consists only of powder 20, both of which are solidified with wax 201.

[0038] Next, the measurement sample 200 prepared by the sample preparation device 1 is used to detect and measure a minute magnetic field using the minute magnetic field measuring device 3, and the size and content of magnetic particles are determined from the measurement signal. The nT meter provided in the micromagnetic field measuring device 3 has a detection force of 0.3 nT, and the size of the magnetic sensor element (magnetic wire) is 10 μm in diameter and 2 mm in length.

[0039] The powder container 31 containing the measurement sample 300 is fixed to the fixing device of the powder container fixing part 310 of the micromagnetic field measuring device 3. The parallelism (tilt) adjustment mechanism of the position adjustment unit 33 ensures that the bottom surface of the powder container 31 and the tip surface of the sensor element at the tip of the nT meter are parallel. Next, the position adjustment mechanism aligns the XY axis (center) of the sensor element with the center of the powder container 31. The Z axis (distance) of the sensor element is adjusted so that the distance between the tip of the sensor element and the bottom surface of the powder container 31 is zero. As a result, the distance between the magnetic nanoparticles of the measurement sample and the tip of the sensor element becomes 0.07 mm, improving and ensuring detection power.

[0040] The nT meter 321 measures the minute magnetic field of the magnetic nanoparticles 300 to detect a magnetic signal. This magnetic signal is then used by a magnetic field signal processing device to detect and measure the size and content (concentration) of the magnetic nanoparticles using a pre-prepared calibration curve (Figures 3 and 4).

[0041] In this example, a contamination concentration of 0.5 ppm due to magnetic microparticles was measured. [Industrial applicability]

[0042] Removing magnetic microparticles that become mixed into positive electrode material powders, such as those found in lithium-ion batteries, is an urgent issue. This invention, which allows for the measurement of contamination levels and quality assurance, is expected to have industrial applications. Furthermore, it enables the identification of the generation process and the implementation of countermeasures, highlighting its significant industrial importance. [Explanation of Symbols]

[0043] 1: Sample preparation device 10: Powder 100:Magnetic fine particles 11: Container 110: Container fixing stand 12: Powder insertion device 13: Wax (liquid) insertion device 14: Magnetic field generator 141: Magnetic field 15. Vibration Generator 2: Powder container 20: Powder 200: Sample for measurement (magnetic microparticles) 201: Wax 21: Container 3: Micromagnetic field measuring device 300: Sample for measurement (magnetic microparticles) 31: Powder container 310: Powder container fixing stand 32: Sensor element 321: nT meter 3210: nT meter mounting stand 33:Position adjustment section

Claims

1. In a magnetic particle detection system consisting of a sample preparation device, a measurement sample, a micromagnetic field measuring device, and a magnetic field signal processing device, The sample preparation apparatus comprises a non-magnetic container, a container fixing part for securing the container, and sample preparation parts installed on the top and bottom of the container. The container is cylindrical or mortar-shaped, with a diameter of 2 mm or less at the tip and a thickness of 0.1 mm or less at the bottom. The sample preparation unit includes a powder insertion device for inserting powder into the upper part of the container and a wax insertion device for inserting wax, The container comprises a magnetic field generating device that applies a magnetic field to the magnetic particles contained in the powder at its lower part, and a vibration generating device that accumulates the magnetic particles in the magnetic field at the bottom of the container. The aforementioned measurement sample is a sample prepared by the sample preparation device and accumulated at the bottom of the container, and consists of magnetic nanoparticles which are the object to be measured by the micromagnetic field measuring device. The aforementioned micromagnetic field measuring device comprises a powder container containing the sample for measurement, a powder container fixing part for fixing the powder container, a sensor element installed below the powder container, and a position adjustment part for adjusting the position of the sensor element and the powder container. The sensor element consists of an nT meter having a detection force of 1 nT or less, and the nT meter is fixed to an nT meter mounting stand. The size of the magnetic element of the aforementioned sensor element is 15 μm or less in diameter and 2 mm or less in length, and the tip of the magnetic element is positioned at the tip of the nT meter. The position adjustment unit comprises a parallelism (tilt) adjustment mechanism for adjusting the parallelism between the sensor element of the nT meter, which is fixed to the nT meter mounting base, and the bottom surface of the powder container, and a position adjustment mechanism for adjusting the position of the sensor element along the XY axis (center) and the Z axis (distance). The magnetic field signal processing device comprises a sensor signal processing device that calculates the size and / or content of magnetic particles from the magnetic signal measured by the minute magnetic field measuring device. A magnetic particle detection system characterized by the following features.

2. In a method for detecting and measuring magnetic fine particles mixed in powder, (1) The first step consists of the process of preparing the sample for measurement, Step a) Set the container in the sample preparation device, Step b) Take a sample of 20 mg or less from the powder base material and put it into a container. Step c) Apply a magnetic field to the sample and vibrate it ultrasonically to accumulate the magnetic particles at the bottom of the container. Step d) The liquid wax is poured into the container and solidified to prepare it. Step e) Remove the powder container containing the prepared measurement sample from the sample preparation device. (2) The second step consists of detecting and measuring the minute magnetic field of the sample for measurement, Step f) The powder container is fixed to the fixing device of the powder container fixing part for magnetic field measurement. Step g) Using the parallelism (tilt) adjustment mechanism, the bottom surface of the powder container and the sensor element at the tip of the nT meter are made parallel. Step h) The position adjustment mechanism is used to align the XY axis (center) of the sensor element with the center of the powder container. Step i) The Z-axis (distance) of the sensor element is adjusted by adjusting the distance from the bottom surface of the powder container. Step j) Using the nT meter, measure the minute magnetic field of the magnetic nanoparticles to obtain a measurement signal. Step k) Using a calibration curve prepared in advance, detect and measure the size and / or content of the magnetic fine particles mixed in the powder. A detection and measurement method characterized by the following.

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