Micro-magnetic field detection method and device based on magnetic / plasmonic core-shell nanoparticles-metal thin film

Abstract

This invention relates to a method and apparatus for detecting micromagnetic fields based on magnetic / plasma core-shell nanoparticles and a metal thin film. The method involves constructing a plasma nanolaser possessing both magnetic and plasma properties. The plasma nanolaser comprises a metal thin film layer, magnetic / plasma core-shell nanoparticles, and a liquid gain dye medium. The plasma nanolaser is placed in the external magnetic field to be measured, and the plasma nanolaser is excited. By observing the change in the wavelength of the plasma nanolaser, the change in distance between the magnetic / plasma core-shell nanoparticles and the metal thin film layer is determined, thereby detecting the intensity and intensity change of the external magnetic field. The magnetic field detection apparatus provided by this invention has the advantages of high sensitivity, stable performance, low noise, and low power consumption when detecting external magnetic field intensity, providing convenience for detecting micromagnetic fields.

Description

Technical Field

[0001] This invention relates to the field of micromagnetic field detection technology, specifically to a method and apparatus for micromagnetic field detection based on magnetic / plasma core-shell nanoparticles-metal thin films. Background Technology

[0002] Magnetic field detection technology has wide applications in military, resource exploration, and scientific research. As research in the field of magnetic fields becomes increasingly popular, research focus has gradually shifted from macroscopic Earth magnetic field detection to weak magnetic field detection. Classified by working principle, detection methods include total magnetic field strength detection systems and magnetic field vector detection systems, which compensate for the relatively backward technology in the field of small-scale magnetic field detection. Generally, micro-magnetic field detection involves measuring the magnetic field of a magnetic target. It mostly utilizes micro-magnetic detection technology to fabricate micro-magnetic detectors based on different structures and principles for detection, and then obtains relevant information through signal processing and analysis.

[0003] Previous studies have found that micromagnetic sensors manufactured using micromagnetic detection technology can detect external magnetic fields or the magnetism of objects. For example, in 2002, Besse et al. used a silicon Hall sensor made of metal-oxide-semiconductor (CMOS) to detect magnetic microspheres. By depositing a specific chemical coating, they used first or multiple harmonic detection methods to detect the target's magnetism. In 2009, Chong et al. used a three-dimensional electromagnetic coil and a magnetic core to form a micro fluxgate sensor. They read the harmonic detection signal output by the fluxgate sensor through a lock-in amplifier, obtained the amplitude and phase values ​​of the second harmonic signal, and calculated the micromagnetic field. However, current micromagnetic field detection methods or devices have limitations such as large size, high noise, low resolution, low sensitivity, and inability to withstand high temperatures. These limitations lead to errors when these traditional detection devices are used, thus restricting the further application of micromagnetic field detection technology. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention influences the gap between magnetic / plasmolytic core-shell nanoparticles and a metal thin film in a liquid gain material using an external micro-magnetic field. This alters the plasma resonance wavelength of the particle-film composite structure, thereby changing the wavelength of the Surface Plasmon Amplification by Stimulated Emission of Radiation (SPASER). By observing the change in the SPASER wavelength, the change in the distance between the magnetic / plasmolytic core-shell nanoparticles and the metal thin film can be deduced, leading to the inference of the strength and intensity variation of the external magnetic field. This solves the problem of the scale limitations of traditional micromagnetic detection devices and provides a new approach for the research of micromagnetic detection devices at the nanoscale.

[0005] To achieve the above objectives, the present invention employs the following technical solution: a method and apparatus for micro-magnetic field detection based on magnetic / plasma core-shell nanoparticles-metal thin films, which is carried out according to the following method:

[0006] A plasma nanolaser with both magnetic and plasma properties is constructed. The plasma nanolaser includes a substrate, a metal thin film layer and a liquid gain medium arranged from bottom to top. Magnetic / plasma core-shell nanoparticles are distributed in the liquid gain medium.

[0007] The plasma nanolaser is placed in the external magnetic field to be tested, and the plasma nanolaser is excited. By measuring the change in the wavelength of the plasma nanolaser, the change in the distance between the magnetic / plasma core-shell nanoparticles and the metal film is determined, thereby detecting the strength and intensity change of the external magnetic field.

[0008] Before each micro-magnetic field detection, the magnetic / plasma core-shell nanoparticles need to be reset using the external magnetic field coil assembly so that the distance between the single-layer nanoparticles and the metal thin film layer is 0, and then the magnetic field is adjusted to proceed to the next step.

[0009] Preferably, the plasma nanolaser has a strip resonant cavity, the metal thin film layer is disposed at the bottom of the strip resonant cavity, the strip resonant cavity is filled with a liquid gain medium, and magnetic / plasma core-shell nanoparticles are distributed in the liquid gain medium.

[0010] Preferably, the doping concentration of the magnetic / plasma core-shell nanoparticles is 1×10⁻⁶. -8 g / ml - 2.4 × 10 - 5 g / ml.

[0011] Preferably, the magnetic / plasma core-shell nanoparticles are composite structures with a core-shell structure, which are magnetic nanoparticle cores coated with noble metal nanoshells, or noble metal nanoparticle cores coated with magnetic nanoshells.

[0012] The magnetic nanoparticle core or magnetic nanoshell is magnetic, and the noble metal nanoparticle core or noble metal nanoshell can generate localized surface plasmon effect (LSP); thus, the magnetic / plasma core-shell nanoparticles simultaneously possess magnetic and plasma properties.

[0013] More preferably, the magnetic nanoparticle core or magnetic nanoshell material in the magnetic / plasma core-shell nanoparticles is a magnetic compound.

[0014] More preferably, the magnetic compound is Fe3O4 or γ-Fe2O3; the noble metal is Au, Ag or Pt, which have localized surface plasmon effects.

[0015] More preferably, the liquid gain medium is a liquid gain medium made of a semiconductor laser material capable of emitting laser light, and the concentration of the semiconductor laser material is 1×10⁻⁶. -4 mg / ml - 0.1 mg / ml.

[0016] More preferably, the metal thin film layer material is a gold or silver film capable of generating surface plasmon resonance (SPP), with a thickness of 10 nm to 1 mm.

[0017] Based on the same inventive concept, the present invention also provides a magnetic field detection device, including a plasma nanolaser. The plasma nanolaser includes a substrate and a transparent substrate disposed on the substrate. A strip-shaped resonant cavity is formed in the transparent substrate. A metal thin film layer is disposed at the bottom of the strip-shaped resonant cavity. A liquid gain medium inlet and outlet channel connecting the two ends of the strip-shaped resonant cavity is also formed on the transparent substrate. The inlet and outlet channel and the strip-shaped resonant cavity together form a microfluidic channel. The microfluidic channel is filled with a liquid gain medium, and magnetic / plasma core-shell nanoparticles are distributed in the liquid gain medium.

[0018] Preferably, the transparent substrate includes an upper substrate and a lower substrate, the strip resonant cavity is recessed on the lower substrate, the liquid gain medium inlet / outlet channel is vertically opened on the upper substrate and communicates with the strip resonant cavity; the height of the strip resonant cavity is 5nm-1cm.

[0019] More preferably, the magnetic field detection device further includes an external magnetic field coil assembly, which includes three pairs of external magnetic field coils and external devices for controlling the three pairs of external magnetic field coils respectively. The three pairs of external magnetic field coils are respectively arranged along the top and bottom, front and back, and left and right sides of the plasma nanolaser.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This invention is based on a magnetic / plasma core-shell nanoparticle structure. By applying a micromagnetic field to the magnetic / plasma core-shell nanoparticles, the distance between them and a metal thin film is altered, changing the plasma characteristics. The strength and intensity changes of the external magnetic field are inferred by observing the changes in the SPASER wavelength. Compared with existing methods, the method provided by this invention has the following advantages: First, this invention provides a non-contact control method, which will not affect or damage the structure after repeated use and has the advantage of long lifespan; second, when using the magnetic field detection device provided by this invention to detect the external magnetic field strength, it has the advantages of high sensitivity, stable performance, low noise, and low power consumption; third, this magnetic field detection device is at the nanoscale, with a smaller volume, providing convenience for detecting micromagnetic fields. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the micro magnetic field detection device provided in an embodiment of the present invention;

[0023] Figure 2 This is a top view schematic diagram of the micro magnetic field detection device provided in an embodiment of the present invention;

[0024] Figure 3 This is a cross-sectional view of the micro-magnetic field detection provided in an embodiment of the present invention;

[0025] Figure 4 The variation of SPASER emission wavelength under different spacing h between Fe3O4@Ag (diameter@thickness, 30@10nm) nanoparticles and silver films. Detailed Implementation

[0026] The following specific embodiments further illustrate the implementation of the present invention and its beneficial effects, with the aim of helping to better understand the essence and spirit of the present invention, and should not be construed as limiting the scope of the present invention.

[0027] This invention provides a method for detecting micromagnetic fields based on magnetic / plasma core-shell nanoparticles-metal thin films, which is carried out according to the following method:

[0028] A plasma nanolaser with both magnetic and plasma properties was constructed. The plasma nanolaser comprises, from bottom to top, a substrate, a metal thin film layer, and a liquid gain medium, in which magnetic / plasmotropic core-shell nanoparticles are distributed. The metal thin film layer can generate a surface plasmon polarization (SPP) effect, the magnetic nanoparticle core or magnetic nanoshell is magnetic, and the noble metal nanoparticle core or noble metal nanoshell can generate a local surface plasmon (LSP) effect. Therefore, the composite magnetic / plasmotropic core-shell nanoparticles have both magnetic and plasma properties, and their displacement can be controlled by an external magnetic field.

[0029] It should be noted that before each micro-magnetic field detection, the magnetic / plasma core-shell nanoparticles need to be reset using the external magnetic field coil assembly to ensure that the spacing between the monolayer nanoparticles and the metal thin film layer is 0, and then the magnetic field is adjusted to proceed to the next step.

[0030] The reset plasma nanolaser is placed in the external magnetic field to be measured. The plasma nanolaser is excited by optical pumping. Since the external magnetic field can affect the distance between the magnetic / plasma core-shell nanoparticles and the metal film, and change the plasma properties, the change in the distance between the magnetic / plasma core-shell nanoparticles and the metal film can be determined by observing the change in the wavelength of the plasma nanolaser. Thus, the strength and intensity change of the external magnetic field can be detected.

[0031] It should be noted that the aforementioned metal thin film material is a metallic material capable of generating surface plasmon resonance (SPP), such as a gold or silver film, with a thickness of 10 nm to 1 mm, which can match the magnetic / plasmotropic core-shell nanoparticles to form coupled plasma. The magnetic / plasmotropic core-shell nanoparticles are composite structures with a core-shell structure. They can be either a noble metal nanoshell encapsulating a magnetic nanoparticle core, or a magnetic nanoshell encapsulating a noble metal nanoparticle core. The magnetic nanoparticle core or magnetic nanoshell possesses magnetism, while the noble metal nanoparticle core or noble metal nanoshell can generate localized surface plasmon resonance (LSP). This gives the magnetic / plasmotropic core-shell nanoparticles both magnetic and plasmotropic properties, resulting in high sensitivity, high precision, and easy controllability when detecting micro-magnetic fields. The doping concentration of these magnetic / plasmotropic core-shell nanoparticles in the liquid gain dye medium is controlled at 1 × 10⁻⁶. -8 g / ml - 2.4 × 10 -5 Within the g / ml range, this concentration range is set to control the number of nanoparticles and ensure that the nanoparticles are arranged in a single layer in the liquid gain medium, so as to better realize the detection of micro magnetic fields.

[0032] It should be further clarified that the magnetic nanoparticle core or magnetic nanoshell material in the aforementioned magnetic / plasma core-shell nanoparticles is a magnetic compound, such as Fe3O4 or γ-Fe2O3; the noble metal can be Au, Ag, or Pt, which exhibit localized surface plasmon effects. The liquid gain medium is a liquid gain medium made of a semiconductor laser material capable of emitting laser light. The liquid gain medium consists of the semiconductor laser material and a solvent capable of dissolving the semiconductor laser material, wherein the concentration of the semiconductor laser material is 1 × 10⁻⁶. -4 mg / ml-0.1mg / ml; These semiconductor laser materials, whether red, green, blue, or other colored dyes, can be used for micro-magnetic field detection and are not limited to a certain type or color of material.

[0033] It should be further explained that before each magnetic field detection, the magnetic / plasma core-shell nanoparticles need to be reset so that the spacing between the single-layered nanoparticles and the metal film layer is 0. To do this, we also need to set up a magnetic field coil assembly around the plasma nanolaser. The magnetic field generated by the magnetic field coil assembly is used to adjust the displacement of the magnetic / plasma core-shell nanoparticles and reset them.

[0034] Based on the same inventive concept described above, the present invention also provides a magnetic field detection device, which is a plasma nanolaser, such as... Figure 1-3 As shown, the system specifically includes a substrate 7 and a transparent substrate disposed on the substrate 7. A strip-shaped resonant cavity is formed within the transparent substrate, and a metal thin film layer 5 is disposed at the bottom of the strip-shaped resonant cavity. A liquid gain medium inlet / outlet channel 1 connecting the two ends of the strip-shaped resonant cavity is also formed on the transparent substrate. The inlet / outlet channel 1 and the strip-shaped resonant cavity together form a microfluidic channel. A liquid gain medium 4 is injected into the microfluidic channel, and magnetic / plasma core-shell nanoparticles 6 are distributed within the liquid gain medium 4. Since the magnetic / plasma core-shell nanoparticles 6 possess both magnetic and plasma properties, their displacement can be controlled by an external magnetic field. Therefore, they can be used to detect the existence of a micro-magnetic field in the external environment, as well as the strength and changes in magnetic field strength. The purpose of selecting a transparent substrate is to facilitate the introduction of light from the optical pump source for optical pumping. A polymer material is preferably used for the transparent substrate.

[0035] It should be noted that, for ease of processing, the above-mentioned transparent substrate includes an upper substrate 2 and a lower substrate 3. The strip resonant cavity is recessed on the lower substrate 3, and the height of the strip resonant cavity is 5nm-1cm. The liquid gain medium 4 inlet / outlet channel 1 is vertically opened on the upper substrate 2 and communicates with the strip resonant cavity.

[0036] It should be further explained that the magnetic field detection device also includes an external magnetic field coil assembly 8. The external magnetic field coil assembly 8 includes three pairs of external magnetic field coils and external devices for controlling each pair of external magnetic field coils. The three pairs of external magnetic field coils are respectively arranged along the top and bottom, front and back, and left and right sides of the plasma nanolaser. The top and bottom sets of magnetic field coils are mainly used to adjust the height of the magnetic / plasma core-shell nanoparticles 6, while the left and right, front and back sets of coils are responsible for adjusting the position of the magnetic / plasma core-shell nanoparticles 6 to prevent aggregation or to adjust them to the ideal position. Therefore, the purpose of the external magnetic field coil assembly 8 is to reset the magnetic-plasma core-shell nanoparticles 6 before each magnetic field detection, so that the distance between the single-layer nanoparticles and the metal thin film layer is 0, and then the magnetic field is adjusted for the next operation.

[0037] The present invention will now be described in more detail and with specific examples.

[0038] Example 1

[0039] This embodiment provides a magnetic field detection device, which is a plasma nanolaser. The device includes a substrate 7 and a transparent substrate disposed on the substrate 7. A strip-shaped resonant cavity is formed within the transparent substrate. A metal thin film layer 5, i.e., an Ag film, is disposed at the bottom of the strip-shaped resonant cavity. A liquid gain medium inlet / outlet channel 1 connecting the two ends of the strip-shaped resonant cavity is also formed on the transparent substrate. The inlet / outlet channel 1 and the strip-shaped resonant cavity together form a microfluidic channel. The microfluidic channel is filled with a semiconductor laser material with a doping concentration of 1×10⁻⁶. -2 Liquid gain medium 4 with a doping concentration of 1×10 mg / ml. -8 The magnetic / plasma core-shell nanoparticles 6, with a density of g / ml, possess both magnetic and plasma properties. Their displacement can be controlled by an external magnetic field, thus enabling them to detect the presence and strength of micro-magnetic fields in the external environment.

[0040] An external magnetic field coil assembly 8 is also disposed around the periphery of the plasma nanolaser. The external magnetic field coil assembly 8 includes three pairs of external magnetic field coils and external devices for controlling the three pairs of external magnetic field coils respectively. The three pairs of external magnetic field coils are respectively arranged along the top and bottom, front and back, and left and right sides of the plasma nanolaser. Before each magnetic field detection, the magnetic-plasma core-shell nanoparticles 6 are reset using the external magnetic field coil assembly 8, so that the distance between the monolayer nanoparticles and the metal thin film layer is 0, and then the magnetic field is adjusted for the next operation.

[0041] Specifically, in this embodiment, the magnetic / plasma core-shell nanoparticle 6 is a composite structure with a core-shell structure, specifically a magnetic nanoparticle core coated with a noble metal nanoshell, the magnetic nanoparticle core being Fe3O4 nanoparticles, and the noble metal nanoshell material being Ag nanolayers.

[0042] The fabrication process of this magnetic field detection device is as follows:

[0043] A 100 nm thick Ag film was deposited in a prepared micro / nano container. A liquid gain medium containing the aforementioned magnetic / plasma core-shell nanoparticles was then introduced into the micro / nano container to form a plasma nanolaser. The magnetic / plasma core-shell nanoparticles (6) are a composite structure with a core-shell structure, i.e., a noble metal nanoshell encapsulating a magnetic nanoparticle core, which possesses magnetism. The noble metal nanoshell can generate a localized surface plasmon (LSP) effect. The magnetic / plasma core-shell nanoparticles simultaneously possess magnetic and plasmonic properties, and their displacement can be controlled by an external magnetic field. Therefore, they can be used to detect the presence and strength of a micro-magnetic field in the external environment.

[0044] Example 2

[0045] This embodiment provides a magnetic field detection device, the specific structure of which is the same as that of Embodiment 1, except that: the magnetic / plasma core-shell nanoparticle 6 is a magnetic nanoshell coating a noble metal nanoparticle core; the magnetic nanoshell is an Fe3O4 nanolayer, and the noble metal nanoparticle core material is Ag nanoparticles.

[0046] Example 3

[0047] This embodiment provides a method for micro-magnetic field detection based on the magnetic field detection device provided in Embodiments 1-2. Specifically, the plasma nanolaser provided in Embodiment 1 or Embodiment 2 is placed in the external magnetic field to be measured. The magnetic field detection device is excited by an external pump light source. The external magnetic field affects the movement of the magnetic / plasma core-shell nanoparticles 6 in the magnetic field detection device. By observing the change in the wavelength of the plasma nanolaser, the distance or distance change between the magnetic / plasma core-shell nanoparticles 6 and the metal thin film layer 5 is determined, thereby detecting the intensity and intensity change of the external magnetic field.

[0048] Taking the magnetic field detection device provided in Embodiment 1 of the present invention as an example, when using this device to perform micro-magnetic field detection, we simulate it by utilizing an existing external micro-magnetic field. When the magnetic field detection device is placed in a micro-magnetic field, the distance between the Fe3O4@Ag core-shell nanoparticles and the Ag film... h This will cause changes, which we can observe. The SPASER wavelength is correlated with the strength of the external micro-magnetic field, and can be observed through... Figure 4 It was found that the SPASER wavelength is related to the particle-film gap distance; when the gap... h As the wavelength increased from 2 to 50 nm, the SPASER peak changed from 589 nm to 528 nm. Therefore, further calculations revealed the intensity and variation of the detected micro-magnetic field.

[0049] To further verify the magnetic field detection device's ability to detect the strength and changes in external micro-magnetic fields, we constructed an integrated microfluidic control platform based on a micro-magnetic field detector. This platform includes a magnetic bead trapping system and a micro-magnetic field detection device. The magnetic bead trapping system comprises a microchannel, a micro-helical coil disposed within the microchannel, and magnetic beads. The core of the micro-helical coil in the microchannel is made of magnetic material, which generates different field intensities when energized, enabling it to trap various types of magnetic beads within the microchannel. Under the influence of magnetic force, the trapping coil reduces the velocity of the magnetic beads, ultimately effectively trapping them on the surface of the planar micro-helical coil excited by an external current. The magnetic microbeads exhibit superparamagnetism, displaying magnetism in the presence of a magnetic field, which rapidly disappears when the magnetic field is removed.

[0050] The micromagnetic field detection device in the integrated microfluidic control platform of this micromagnetic field detector can be used to detect the magnetic field strength of the captured magnetic microbeads. Since the magnetic beads generate a weak stray magnetic field under the magnetization of the external magnetic field, the change in the spacing between the magnetic / plasma core-shell nanoparticles 6 and the metal thin film layer 5 can be obtained by changing the SPASER wavelength in the micromagnetic detection device of this invention. The properties of the magnetic field of the magnetic beads themselves can be calculated, and the magnetic beads can be effectively screened.

[0051] The above embodiments are merely illustrative examples of the present invention and do not constitute a limitation on the scope of protection of the present invention. Any designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A method for detecting micromagnetic fields based on magnetic / plasma core-shell nanoparticles-metal thin films, characterized in that, Follow these steps: A plasma nanolaser with both magnetic and plasma properties is constructed. The plasma nanolaser comprises, from bottom to top, a substrate, a metal thin film layer, and a liquid gain medium. Magnetic / plasmotropic core-shell nanoparticles are distributed within the liquid gain medium. The magnetic / plasmotropic core-shell nanoparticles are composite structures with a core-shell structure, consisting of a noble metal nanoshell encapsulating a magnetic nanoparticle core, or a magnetic nanoshell encapsulating a noble metal nanoparticle core. The magnetic nanoparticle core or magnetic nanoshell is magnetic, and the noble metal nanoparticle core or noble metal nanoshell can generate a localized surface plasmon effect (LSP). This allows the magnetic / plasmotropic core-shell nanoparticles to possess both magnetic and plasma properties. The plasma nanolaser is placed in the external magnetic field to be tested, and the plasma nanolaser is excited. By measuring the change in the wavelength of the plasma nanolaser, the change in the distance between the magnetic / plasma core-shell nanoparticles and the metal film is determined, thereby detecting the strength and intensity change of the external magnetic field. Before each micro-magnetic field detection, the magnetic / plasma core-shell nanoparticles need to be reset using an external magnetic field coil assembly to ensure that the spacing between the monolayer nanoparticles and the metal thin film layer is 0, and then the magnetic field is adjusted to proceed to the next step.

2. The method for micromagnetic field detection based on magnetic / plasma core-shell nanoparticles-metal thin films according to claim 1, characterized in that, The plasma nanolaser has a strip-shaped resonant cavity, the metal thin film layer is disposed at the bottom of the strip-shaped resonant cavity, the strip-shaped resonant cavity is filled with a liquid gain medium, and magnetic / plasma core-shell nanoparticles are distributed in the liquid gain medium.

3. The method for micromagnetic field detection based on magnetic / plasma core-shell nanoparticles-metal thin films according to claim 1, characterized in that, The doping concentration of the magnetic / plasma core-shell nanoparticles is 1×10⁻⁶. -8 g / ml - 2.4 × 10 -5 g / ml.

4. The method for micromagnetic field detection based on magnetic / plasma core-shell nanoparticles-metal thin films according to claim 1, characterized in that, The magnetic nanoparticle core or magnetic nanoshell material in the magnetic / plasma core-shell nanoparticles is a magnetic compound. The magnetic compound is Fe3O4 or γ-Fe2O3; the noble metal is Au, Ag or Pt, which have localized surface plasmon effects.

5. The method for micromagnetic field detection based on magnetic / plasma core-shell nanoparticles-metal thin films according to claim 1, characterized in that, The liquid gain medium is a liquid gain medium made of a semiconductor laser material capable of emitting laser light, and the concentration of the semiconductor laser material is 1×10⁻⁶. -4 mg / ml - 0.1 mg / ml.

6. The method for micromagnetic field detection based on magnetic / plasma core-shell nanoparticles-metal thin films according to claim 1, characterized in that, The metal thin film layer material is a gold or silver film capable of generating surface plasmon resonance (SPP), with a thickness of 10 nm to 1 mm.

7. A magnetic field detection device, characterized in that, The invention includes a plasma nanolaser, comprising a substrate and a transparent substrate disposed on the substrate. A strip-shaped resonant cavity is formed within the transparent substrate, and a metal thin film layer is disposed at the bottom of the strip-shaped resonant cavity. A liquid gain medium inlet / outlet channel is also formed on the transparent substrate, connecting the two ends of the strip-shaped resonant cavity. The inlet / outlet channel and the strip-shaped resonant cavity together form a microfluidic channel, and a liquid gain medium is injected into the microfluidic channel. Magnetic / plasma core-shell nanoparticles are distributed in the liquid gain medium. The magnetic / plasma core-shell nanoparticles are composite structures with a core-shell structure, consisting of a noble metal nanoshell coating a magnetic nanoparticle core, or a magnetic nanoshell coating a noble metal nanoparticle core. The magnetic nanoparticle core or magnetic nanoshell is magnetic, and the noble metal nanoparticle core or noble metal nanoshell can generate a localized surface plasmon effect (LSP). This allows the magnetic / plasma core-shell nanoparticles to possess both magnetic and plasmonic properties.

8. The magnetic field detection device according to claim 7, characterized in that, The transparent substrate includes an upper substrate and a lower substrate. The strip resonant cavity is recessed on the lower substrate. The liquid gain medium inlet / outlet channel is vertically opened on the upper substrate and communicates with the strip resonant cavity. The height of the strip resonant cavity is 5nm-1cm.

9. The magnetic field detection device according to claim 7, characterized in that, It also includes an external magnetic field coil assembly, which includes three pairs of external magnetic field coils and external devices for controlling the three pairs of external magnetic field coils respectively. The three pairs of external magnetic field coils are respectively arranged along the top and bottom, front and back, and left and right sides of the plasma nanolaser.

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