A magnetic core optical fiber, a probe applied to a magnetic scanning microscope and a preparation method thereof

Abstract

The application provides a magnetic core optical fiber probe applied to a magnetic scanning microscope and a preparation method thereof, and belongs to the technical field of scanning probe microscopes, in particular relates to a magnetic core optical fiber probe applied to a magnetic scanning microscope and a preparation method thereof. The magnetic core optical fiber probe is composed of silicon dioxide containing ferromagnetic substances. The magnetic substances in the probe are solid bodies made of iron, cobalt, nickel and their alloys and oxide crystals, and do not need to be plated, the probe is prepared by combining the methods of tensioning and etching, the probe tip can be adjusted, and therefore the resolution of the magnetic force microscope can be adjusted. The magnetic core optical fiber probe is fixed on a tuning fork to form a tuning fork feedback magnetic scanning microscope system. The system realizes the scanning and imaging of the magnetic information of a sample by using the tuning fork feedback and combining an atomic force microscope. The probe is a multifunctional probe which can obtain the magnetic information distribution image, the surface topography image and the optical image of the sample at the same time, and provides a technical means for the multi-angle analysis of the sample. Meanwhile, the probe has the advantages of simple preparation process, easy operation, low cost, long service life and wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of scanning probe microscopy technology, and in particular relates to a magnetic core fiber optic probe for use in magnetic scanning microscopes and its preparation method. Background Technology

[0002] With the development of nanomagnetism, people are increasingly interested in various novel, fine surface magnetic structures. The size of nanomagnetic material particles has gradually shrunk to the range of a few nanometers. Since there is a close correlation between the magnetic parameters and magnetic domain structure of ferromagnets, accurate detection of the surface magnetic structure of magnetic materials at the nanoscale is of great significance for understanding the performance and magnetic reversal behavior of nanomagnetic materials. However, traditional magnetic domain detection techniques, such as powder mapping, magneto-optical Kerr effect, Lorentz microscopy, and scanning electron microscopy with spin pole analysis (SEMPA), have some limitations, such as complex sample preparation, low resolution, and the need for a high vacuum environment. These techniques can no longer meet the needs of detecting nanoscale magnetic structures.

[0003] Scanning probe microscopy (SPM) is an important instrument with atomic-level resolution for surface morphology acquisition and electromagnetic property analysis, serving as a crucial characterization tool in surface science, nanotechnology, and other fields. Magnetic scanning probe microscopy, also known as magnetic force microscopy (MFM), is a member of the SPM family and a novel technique for measuring magnetic information, widely used in the study of the magnetic structure of various magnetic materials. The working principle of MFM is similar to that of atomic force microscopy, but the biggest difference lies in the fact that the probe used in MFM is magnetic, enabling the detection of long-range interactions between the magnetic tip and the stray magnetic field on the surface of the magnetic sample. Magnetic interaction is a long-range force; when the probe is ferromagnetic, scanning the surface of a magnetic sample within a certain height range allows the magnetic tip to sense the magnetic force generated by the stray magnetic field on the surface of the magnetic material. Therefore, by detecting the distribution of the magnetic gradient, information about the surface magnetic structure can be obtained. In recent years, with the continuous maturation and improvement of MFM technology, its application in materials research has become increasingly widespread, and its research focus has gradually shifted to the microscale. Since MFM involves the interaction between a magnetic tip and the stray field on the sample surface, the probe is crucial to the resolution and sensitivity of the magnetic force microscope. In addition, these probes are also one of the commonly used consumables of this equipment.

[0004] In magnetic force microscopy (SPM), probes are typically fabricated using microelectromechanical systems (MEMS) technology to process materials such as silicon or silicon nitride, used to measure simple information such as sample morphology and mechanics. If the magnetic properties of the sample need to be observed, a magnetic metal layer (such as iron, cobalt, nickel, and their alloys) tens of nanometers thick, along with other reinforcing coatings (such as titanium, chromium, platinum, and iridium), is usually deposited on the surface of a standard probe tip to improve the adhesion of the coating. However, due to the extremely small size of the probe tip, preparing the coating only on the tip surface significantly increases the complexity and cost of the process. Furthermore, the presence of the magnetic coating reduces the sharpness of the tip, and as the coating wears off, the magnetism of the probe decreases, thus reducing the resolution of the magnetic force microscope. In addition, current probes often cover part or all of the probe cantilever surface with the magnetic coating, in addition to the probe tip surface. Since magnetic force microscopy (MFM) detects the long-range force interaction between the magnetic probe and the magnetic sample, the magnetic coatings at the probe tip and cantilever will interact with the magnetic sample, introducing some systematic errors. To address these issues, several techniques have been proposed, such as using carbon nanotube probes and developing probes with highly magnetic coatings, to reduce the thickness of the magnetic coating and thus improve the sharpness of the probe tip. However, the fabrication process of carbon nanotube probes is complex and unstable, and the coercivity and saturation magnetization of the Co-Cr magnetic layer tips used are insufficient. Therefore, these techniques cannot significantly improve the resolution of magnetic force microscopy. Thus, there is an urgent need to develop a novel magnetic force microscopy probe that is simple to fabricate, low in cost, and offers higher resolution. Summary of the Invention

[0005] To address the above-mentioned technical problems, the present invention aims to provide a magnetic core fiber optic probe for use in magnetic scanning microscopy, which has advantages such as high magnetic signal detection accuracy, simple fabrication process, low cost, and long service life. Using this probe, not only can the magnetic information of the sample be obtained, but also the surface morphology and optical images of the sample can be acquired simultaneously.

[0006] This invention is achieved through the following technical solution:

[0007] A magnetic core optical fiber includes a cladding and a core, characterized in that: the cladding further comprises a magnetic core parallel to the core, the magnetic core containing a magnetic material. The magnetic core contains a ferromagnetic material, the ferromagnetic material including one or more alloys of iron, cobalt, or nickel, and their oxide crystals.

[0008] The method for preparing optical fibers is as follows: axial holes are drilled in the optical fiber preform and magnetic material is inserted, and then the preform is drawn into an optical fiber.

[0009] A magnetic core fiber optic probe for a magnetic scanning microscope: A section of magnetic core fiber is cut, and one end is drawn into a tapered shape. The magnetic core fiber is then further drawn into a pointed cone using a tapering apparatus, and the shape of the pointed cone is then corrected using chemical etching. The cone angle, cone length, and tip diameter parameters can be adjusted using a suitable etchant.

[0010] A tuning fork feedback magnetic scanning microscopy system is formed by fixing a magnetic core fiber optic probe to a tuning fork. This system utilizes tuning fork feedback, combined with atomic force microscopy, to achieve magnetic information scanning imaging of the sample. The tuning fork probe is connected to a preamplifier and a scanning circuit feedback system. The combined operating modes of the tuning fork and probe include shear force mode and normal force mode. The scanning circuit feedback system, connected to the tuning fork probe sensor, demodulates the signal detected by the magnetic core fiber optic probe. This signal includes frequency, amplitude, and phase signals. Based on the demodulation result of the tuning fork signal, the scanning circuit feedback system controls the movement of the magnetic core fiber optic probe in three-dimensional space to control the distance between the magnetic core fiber optic probe and the test sample, thereby measuring the morphology of the sample. The magnetic information of the sample is tested, which can increase the spacing between the probe tip and the sample. This can be controlled in two ways: first, by raising the magnetic core probe stage while moving it, and second, by lowering the sample stage while moving it, and keeping the magnetic core probe stage stationary. The scanning circuit feedback system connected to the tuning fork probe has two driving modes: the first driving mode involves controlling the magnetic core probe stage to move while keeping the sample stage stationary; and the second driving mode involves controlling the sample stage to move while keeping the magnetic core probe stage stationary.

[0011] The advantages of this invention compared to the prior art are:

[0012] (1) In this invention, the probe is fixed on a tuning fork, and the probe tip is used to approach the sample to measure the sample's morphology, magnetic information, etc. The main component of the probe tip is ferromagnetic material, while the tuning fork is made of non-magnetic material and is not magnetic itself. This structural design can utilize the probe to detect the magnetic information characteristics of magnetic samples, while only the probe is magnetic and the other parts are not magnetic. This avoids the introduction of systematic errors due to the magnetic properties of other parts and enables accurate measurement of the sample's magnetic information.

[0013] (2) In this invention, the probe tip is made of ferromagnetic material. Ferromagnetic materials are widely available and can be flexibly selected or designed with high / low magnetic moment or high / low coercivity according to the needs of the test sample.

[0014] (3) In this invention, the magnetic core fiber probe is prepared by a combination of tapering and chemical etching. Appropriate parameters such as cone angle, cone length, and tip diameter can be selected according to the needs of the test sample.

[0015] (4) In the prior art, magnetic probes require a magnetic coating, which limits the sharpness of the probe tip and reduces measurement resolution. In this invention, the magnetic core fiber optic probe tip is inherently magnetic, eliminating the need for a coating and allowing for sharper edges through chemical etching, thus achieving higher resolution. This method is simple to operate and low in cost.

[0016] (5) In the prior art, the magnetic coating on the probe tip is easily worn during use, which can lead to detection failure. In this invention, the probe tip does not require a coating and is made of ferromagnetic material that maintains uniform magnetism throughout. When testing samples, local wear of the tip will not cause a decrease in the probe's magnetism, thus ensuring the effectiveness and stability of the test and greatly increasing the probe's service life. It also saves materials and reduces costs.

[0017] (6) In this invention, the magnetic core fiber probe can be used as a multifunctional probe, which can detect the morphology and magnetic information of the sample, and can also be used as an optical probe. Attached Figure Description

[0018] The accompanying drawings are included to provide a further understanding of this application; they are incorporated into and constitute a part of this application. The drawings illustrate embodiments of this application and, together with this specification, serve to explain the principles of this application. In the drawings:

[0019] Figure 1 This is a schematic diagram of the end face of the magnetic core optical fiber in this invention;

[0020] Figure 2 This is a physical image of the end face of the magnetic core optical fiber in this invention;

[0021] Figure 3 This is a schematic diagram of the combined model of the magnetic core fiber probe and the tuning fork in this invention;

[0022] Figure 4 This is the present invention. Figure 3 Enlarged view of section I;

[0023] Figure 5 This is a schematic diagram of the system in which the present invention is applied.

[0024] In the figure: 1-Fiber core, 2-Fiber cladding, 3-Magnetic core, 4-Tuning fork, 5-Magnetic core fiber straight probe, 6-Magnetic core fiber bent probe, 7-Probe stage, 8-Preamplifier, 9-Circuit feedback system, 10-Sample stage, 11-CCD, 12-Objective lens. Detailed Implementation

[0025] The specific implementation method of the present invention will be described in further detail below, but the scope of protection of the present invention is not limited to the content described.

[0026] A magnetic core optical fiber includes a cladding and a core, characterized in that: the cladding further comprises a magnetic core parallel to the core, the magnetic core containing a magnetic material. The magnetic core contains a ferromagnetic material, the ferromagnetic material including one or more alloys of iron, cobalt, or nickel, and their oxide crystals.

[0027] The preparation method is as follows: A hole is drilled axially in the optical fiber preform and a magnetic material is inserted, then drawn into an optical fiber. A section of magnetic core optical fiber is cut, and one end is drawn into a tapered shape. The magnetic core optical fiber is further drawn into a pointed cone using a tapering machine, and then the shape of the pointed cone is corrected using chemical etching. The cone angle, cone length, and tip diameter parameters can be adjusted using a suitable etchant.

[0028] A magnetic core fiber optic probe for a magnetic scanning microscope: A tuning fork feedback magnetic scanning microscopy system is formed by fixing the magnetic core fiber optic probe onto a tuning fork. This system utilizes tuning fork feedback, combined with atomic force microscopy, to achieve magnetic information scanning imaging of the sample. The tuning fork probe is connected to a preamplifier and a scanning circuit feedback system. The combined operating modes of the tuning fork and probe include shear force mode and normal force mode. The scanning circuit feedback system, connected to a tuning fork probe sensor, demodulates the signal detected by the magnetic core fiber optic probe. The signal includes frequency, amplitude, and phase signals. The scanning circuit feedback system controls the movement of the magnetic core fiber probe in three-dimensional space based on the demodulation result of the tuning fork signal. This controls the distance between the magnetic core fiber probe and the test sample, thereby testing the sample's morphology and magnetic information. The distance between the probe tip and the sample can be increased through two control methods: first, raising the magnetic core probe stage while keeping the sample stage stationary; and second, lowering the sample stage while keeping the magnetic core probe stage stationary. The scanning circuit feedback system connects to the tuning fork probe in two driving modes: the first driving mode involves controlling the magnetic core probe stage to move while keeping the sample stage stationary; and the second driving mode involves controlling the sample stage to move while keeping the magnetic core probe stage stationary.

[0029] A magnetic core fiber optic probe for use in a magnetic scanning microscopy system includes a tuning fork sensor for connecting the magnetic core fiber optic probe, the magnetic core fiber optic probe, and a tuning fork probe adapter plate. The tuning fork probe adapter plate is used to connect the tuning fork probe and a feedback circuit section. The two electrode pins of the tuning fork are used to connect a preamplifier and a scanning circuit feedback system section. The tuning fork sensor is suitable for sensing signals detected by the magnetic core fiber optic probe. The scanning circuit feedback system connects to the tuning fork probe sensor and demodulates the tuning fork sensing signal.

[0030] The magnetic core fiber optic probe is fixedly connected to the tuning fork sensor. The method of fixing is not limited, and the relative position of the probe on the cantilever of the tuning fork sensor is also not limited.

[0031] The magnetic core fiber optic probe is made of silicon dioxide containing ferromagnetic material.

[0032] The magnetic material is not limited to any particular material, including iron, cobalt, nickel and their alloys, as well as oxide crystals, etc.

[0033] The magnetic core fiber probe is drawn by a tapering machine, and parameters such as the taper angle, taper length, and tip diameter can be controlled.

[0034] The tip size is further reduced by chemical etching, which removes the silicon dioxide next to the magnetic material, allowing the magnetic material to be used as the primary probe tip for testing.

[0035] There are two ways to combine a magnetic core probe with a tuning fork: shear force mode and normal force mode.

[0036] The scanning circuit feedback system connected to the tuning fork probe has two driving modes. The first driving mode involves controlling the magnetic core probe stage to move while keeping the sample stage stationary. The second driving mode involves controlling the sample stage to move while keeping the magnetic core probe stage stationary.

[0037] The scanning circuit feedback system controls the movement of the magnetic core fiber probe in three-dimensional space based on the demodulation result of the tuning fork signal, thereby controlling the distance between the magnetic core fiber probe and the test sample and thus measuring the sample morphology. To measure the magnetic information of the sample, the distance between the probe tip and the sample needs to be increased. This can be controlled in two ways: first, by raising the magnetic core probe stage while moving it, and keeping the sample stage stationary; and second, by lowering the sample stage while keeping the magnetic core probe stage stationary.

[0038] The present invention also provides a method for preparing the magnetic core fiber probe, comprising the following steps:

[0039] Magnetic materials are added to optical fiber preforms, which are then melted and drawn to form magnetic core optical fibers.

[0040] A magnetic core fiber probe is drawn using a tapering apparatus. The parameters of the tapering apparatus are adjusted according to the needs of the test sample to draw appropriate parameters such as taper angle, taper length, and tip diameter. Chemical etching is then used to make the tip of the magnetic core fiber probe sharper.

[0041] The prepared magnetic core fiber probe is fixed on the tuning fork.

[0042] Example 1: Magnetic Core Optical Fiber

[0043] like Figure 1 , Figure 2As shown, the magnetic core optical fiber includes a core 1, a cladding 2, and a magnetic core 3. The main components of core 1 and cladding 2 are silicon dioxide, while the main component of magnetic core 3 is a ferromagnetic material. The diameter of the bare fiber in cladding 2 ranges from 125 μm, the diameter of core 1 ranges from 10 μm, and the diameter of magnetic core 3 ranges from 10 to 20 μm.

[0044] The method for preparing the magnetic core optical fiber is as follows: first, a preform of ordinary optical fiber is punched, then filled with ferromagnetic material, and then a magnetic core optical fiber sample is drawn out by a special optical fiber drawing machine.

[0045] Example 2: Fabrication of Magnetic Core Fiber Probe

[0046] 1. Take about 20cm of the nickel-core optical fiber prepared above and place it in a tapered drawing apparatus P2000. Set the parameters HEAT=490, VEL=85, DEL=115, PUL=140 to draw a tapered nickel-core optical fiber probe. Observe it under a scanning electron microscope. Its tip curvature radius is 60.7nm.

[0047] 2. Take the drawn fiber optic tapered probe and immerse it in HF solution to etch away the quartz portion of the tip. Nickel will be the main component of the tip, with a tip curvature radius of 27.2 nm. For a smaller tip, use a solution that reacts with nickel to etch the nickel tip.

[0048] 3. Fix the prepared magnetic fiber probe to the side arm of the tuning fork with epoxy resin to form a tuning fork probe.

[0049] Example 3: Magnetic Core Fiber Optic Probe Working System

[0050] like Figure 5 The diagram shows a magnetic core fiber optic probe system. The magnetic core fiber optic probe is fixed to a tuning fork, operating in either shear force or normal force mode. The tuning fork is connected to a preamplifier 8, which in turn is connected to a scanning circuit feedback system 9. The relative distance between the probe tip and the sample is observed through a side objective lens 12 and a CCD 11. By moving the probe stage 7 or the sample stage 10, the relative position of the probe and sample can be changed. The morphology of the sample can be obtained based on the feedback of the atomic forces between the tuning fork probe and the sample surface. At this point, the entire system is equivalent to an atomic force microscope system. Then, by controlling the sample stage or the probe stage, the distance between the probe tip and the sample can be separated by a distance of approximately tens of nanometers, allowing the magnetic force to dominate. At this point, a magnetic information map of the sample can be scanned.

Claims

1. A magnetic core fiber optic probe for use in a magnetic scanning microscope, characterized in that: A section of magnetic core optical fiber is cut and one end is drawn into a tapered shape. The magnetic core optical fiber includes a cladding and a core. There is also a magnetic core parallel to the core in the cladding, and the magnetic core contains magnetic material.

2. The magnetic core fiber optic probe for use in a magnetic scanning microscope according to claim 1, characterized in that: The magnetic core contains ferromagnetic materials, which include one or more alloys of iron, cobalt, or nickel, as well as their oxide crystals.

3. The magnetic core fiber optic probe for use in a magnetic scanning microscope according to claim 1, characterized in that... The preparation method is as follows: axial holes are drilled in the optical fiber preform and magnetic material is inserted, and then drawn into an optical fiber.

4. The magnetic core fiber optic probe for use in a magnetic scanning microscope as described in claim 1, characterized in that... The method for preparing magnetic core fiber probes is to first draw magnetic core fiber into a pointed cone using a tapering device, and then use chemical etching to correct the shape of the pointed cone.

5. The magnetic core fiber optic probe for use in a magnetic scanning microscope as described in claim 4, characterized in that... The cone angle, cone length, and tip diameter parameters are adjusted using a suitable etchant.

6. The magnetic core fiber optic probe for use in a magnetic scanning microscope as described in any one of claims 1-5, characterized in that: A tuning fork feedback magnetic scanning microscopy system is formed by fixing a magnetic core fiber probe onto a tuning fork. This system utilizes tuning fork feedback and combines it with an atomic force microscope to achieve magnetic information scanning imaging of the sample.

7. The magnetic core fiber optic probe for use in a magnetic scanning microscope as described in claim 6, characterized in that... The tuning fork probe is connected to the preamplifier and the scanning circuit feedback system. The combined working modes of the tuning fork and probe include shear force mode and normal force mode.

8. The magnetic core fiber optic probe for use in a magnetic scanning microscope as described in claim 7, characterized in that... Tuning forks are suitable for sensing signals detected by fiber optic probes in magnetic cores. The scanning circuit feedback system is connected to a tuning fork probe sensor and demodulates the tuning fork sensing signal, which includes frequency, amplitude, and phase signals.

9. The magnetic core fiber optic probe for use in a magnetic scanning microscope as described in claim 8, characterized in that... The scanning circuit feedback system controls the movement of the magnetic core fiber probe in three-dimensional space based on the demodulation result of the tuning fork sensing signal. This controls the distance between the magnetic core fiber probe and the test sample, thereby measuring the sample's morphology and magnetic information. The distance between the probe tip and the sample is controlled in two ways: first, the magnetic core probe is raised while the sample remains stationary; second, the sample is lowered while the magnetic core probe remains stationary. The scanning circuit feedback system connects to the tuning fork probe in two driving modes: the first driving mode involves controlling the magnetic core probe to move while the sample remains stationary; the second driving mode involves controlling the sample to move while the magnetic core probe remains stationary.

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