An insulating coated magnetic core for a GMI sensor probe and a preparation method thereof, and a sensor probe

Abstract

The present invention provides an insulating coated magnetic core for a GMI sensor probe and a preparation method thereof, and a sensor probe. A copper wire with a purity of 4N is used as a substrate, and the diameter of the copper wire is 20-140 μm; an Al2O3 insulating layer, a FeNi or Nb conductive metal layer and a FeNi conductive metal layer are sequentially wrapped on the copper wire from the inside to the outside. 20 Ni 80 Permalloy coating; wherein the thickness of the Al2O3 insulating layer is 100-500 nm, the thickness of the FeNi or Nb conductive metal layer is 100-500 nm, and the thickness of the Fe 20 Ni 80 The thickness of the Permalloy coating is 4-14 μm, and finally a direct current is used for annealing, the annealing current is 1.6-2 A, and the annealing time is 10-20 min to obtain an insulating coating magnetic core, which is then made into a sensor probe. The present invention introduces an insulating layer between the metal copper wire and the Permalloy coating soft magnetic material coating, and improves the noise performance, stability and anti-interference ability of the GMI sensor by effectively reducing the noise source, and has a wide range of application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of weak magnetic measurement elements, and in particular relates to an insulating coated magnetic core for a GMI sensor probe, a preparation method thereof, and a sensor probe. Background Art

[0002] Giant Magneto-Impedance (GMI) sensor is a highly sensitive magnetic field sensor widely used in biomedicine, military, aerospace and industrial automation. Its core principle is based on the impedance change caused by the change in the magnetic permeability of the material under AC excitation. The sensitivity and performance of the GMI sensor depend on the magnetic properties and structural design of the material. When the composite wire used for the GMI sensor is in direct contact with the soft magnetic material coating, the AC current will generate eddy currents in the wire. These eddy currents cause energy loss and heat generation, which not only reduces the sensitivity of the sensor, but also introduces additional noise. At the same time, electrical contact may occur between the wire and the soft magnetic material coating, resulting in electromagnetic coupling. This coupling may cause electrical noise and affect the signal quality of the sensor. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide an insulating coated magnetic core for a GMI sensor probe in view of the shortcomings of the prior art. The present invention comprises a metal copper wire, an insulating Al2O3 coating and Fe 20 Ni 80 The GMI sensor is composed of a layer of Permalloy soft magnetic material. First, a layer of insulating material is sputtered on the surface of the metal wire, then a conductive material is sputtered, and finally the Permalloy soft magnetic material is deposited by electrochemical deposition, which significantly reduces the noise level of the GMI sensor probe.

[0004] Another object of the present invention is to provide a method for preparing the above-mentioned insulating coated magnetic core for a GMI sensor probe.

[0005] Another object of the present invention is to provide the above-mentioned insulating coated magnetic core sensor probe for GMI sensor probe.

[0006] In order to solve the technical problem of the present invention, the following technical solution is adopted:

[0007] An insulating coated magnetic core for a GMI sensor probe, with a copper wire with a purity of 4N as a substrate, the copper wire having a diameter of 20-140 μm; an Al2O3 insulating layer, a FeNi or Nb conductive metal layer and a Fe 20 Ni 80 Permalloy coating; wherein the thickness of the Al2O3 insulating layer is 100-500 nm, the thickness of the FeNi or Nb conductive metal layer is 100-500 nm, and the thickness of the Fe20 Ni 80 The thickness of the Permalloy coating is 4-14 μm, and it is finally annealed with a direct current, the annealing current is 1.6-2 A, and the annealing time is 10-20 min; the insulating coating core used for the GMI sensor probe is U-shaped.

[0008] The Al2O3 insulating layer and the FeNi or Nb conductive metal layer are prepared by magnetron sputtering, and the vacuum degree of the magnetron sputtering is better than 3×10 -5 Pa, the sputtering gas pressure is 0.1-0.3 Pa, and argon gas with a purity of more than 99.99% is introduced.

[0009] The FeNi or Nb conductive metal layer is formed by direct current sputtering with a power of 10-20 W and a sputtering time of 2500 s-5000 s; the Al2O3 insulating layer is formed by radio frequency sputtering with a power of 80-100 W and a sputtering time of 4000 s-8500 s.

[0010] During magnetron sputtering of the Al2O3 insulating layer and the FeNi or Nb conductive metal layer, the distance between the target and the substrate is 1-6 cm.

[0011] The Fe 20 Ni 80 The Permalloy coating is prepared by electrochemical deposition, specifically: the electrolyte composition is 0.01 M / L FeSO4·7H2O, 0.1 M / L NiSO4·7H2O, 0.3 M / L H3BO3, 5 g / L ascorbic acid, 1 g / L glycine, and 2 g / L saccharin; during electrochemical deposition, the electrolyte temperature is 45℃-65℃, the pH is 2-4, the deposition time is 2500-5000 s, and the deposition current density is 1.5-4A / dm 2 .

[0012] The method for preparing the insulating coated magnetic core for the GMI sensor probe has the following specific steps:

[0013] Step a: fold a copper wire substrate with a purity of 4N into a U shape, and the diameter of the copper wire is 20-140 μm;

[0014] Step b: pre-treating the copper wire substrate, specifically: washing with deionized water for 5-10 min → washing with 40-45 g / L sodium carbonate weak base solution for 10-15 min → washing with deionized water for 5-10 min → washing with 2 ml / 50 ml hydrochloric acid solution for 10-15 min → washing with deionized water for 5-10 min, taking out and drying with dry nitrogen;

[0015] Step c: The Al2O3 insulating layer and the FeNi or Nb conductive metal layer are sequentially plated on the pretreated copper wire substrate by magnetron sputtering. First, the Al2O3 target and the FeNi or Nb target are placed in the sputtering chamber and evacuated until the background vacuum reaches 3×10 -5 Pa or less; then the pretreated copper wire substrate is transferred from the injection chamber to the sputtering chamber, the distance between the target and the substrate is 1-6 cm, argon gas with a purity of more than 99.99% is introduced into the sputtering chamber, and the gas pressure is adjusted to 0.1-0.3 Pa, the conductive metal layer of FeNi or Nb is DC sputtered, the power is 10-20 W, the sputtering time is 1500 s-4000 s, and the thickness of the conductive metal layer of FeNi or Nb is 100-500 nm; the Al2O3 insulating layer is radio frequency sputtered, the power is 80-100 W, the sputtering time is 4500 s-9000 s, and the thickness of the Al2O3 insulating layer is 100-500 nm;

[0016] Step d: Prepare electrolyte to deposit Fe 20 Ni 80 Permalloy coating, the electrolyte composition of which is 0.01 M / L FeSO4·7H2O, 0.1 M / L NiSO4·7H2O, 0.3 M / L H3BO3, 5 g / L ascorbic acid, 1 g / L glycine, and 2 g / L saccharin;

[0017] Step e: Deposition by three-electrode method, during electrodeposition, pH value is 2-4, deposition current density is 1.5-4 A / dm 2 ; The electrolyte temperature is 45℃-65℃, the deposition time is 2500-5000 s, Fe 20 Ni 80 The thickness of the Permalloy coating is 4-14 μm;

[0018] Step f: After electrochemical deposition, take out the U-shaped insulating coated magnetic core for the GMI sensor probe, wipe off the surface solution, and then anneal with a direct current. The annealing current is 1.6-2 A and the annealing time is 10-20 min.

[0019] The sensor probe made of the insulating coated magnetic core for the GMI sensor probe comprises a U-shaped insulating coated magnetic core for the GMI sensor probe, a voltage signal pickup coil, a second glass tube and a first glass tube, and a PCB printed circuit board; one side of the U-shaped insulating coated magnetic core for the GMI sensor probe penetrates into the second glass tube, the second glass tube is sleeved in the first glass tube, the other side of the U-shaped insulating coated magnetic core for the GMI sensor probe penetrates into the interlayer between the first glass tube and the second glass tube, and the U-shaped insulating coated magnetic core for the GMI sensor probe avoids mutual conduction by penetrating into different glass tubes; the voltage signal pickup coil is wound on the first glass tube, and the voltage signal pickup coil and the U-shaped insulating coated magnetic core for the GMI sensor probe are welded to the PCB printed circuit board.

[0020] The diameters of the first glass tube and the second glass tube are adapted to the diameter of a U-shaped insulating coated magnetic core for a GMI sensor probe.

[0021] The U-shaped bending part of the insulating coated magnetic core for the GMI sensor probe does not deposit Fe 20 Ni 80 Permalloy layer.

[0022] The permalloy-plated magnetic core with an insulating layer in the present invention has a high-purity copper wire as the inner core. When the insulating-plated magnetic core used for the GMI sensor probe is working, all the excitation current passes through the high-purity copper wire and does not pass through the coating. Therefore, the uneven rotation of the magnetic moment caused by the skin effect in the permalloy coating can be avoided. The insulating-plated magnetic core with an insulating layer for the GMI sensor probe is "U"-shaped, and has the advantage that two copper wires are electroplated at the same time, which not only avoids the problem of poor uniformity, but also offsets the interference caused by part of the current when the sensor is working. No permalloy is deposited at the bend of the insulating-plated magnetic core used for the GMI sensor probe, avoiding the noise caused by the stress caused by the bend. Because when the GMI sensor is working, the eddy current caused by the current will generate noise inside the metal wire, reducing the signal-to-noise ratio of the sensor, and the insulating coating can effectively suppress the generation of eddy currents, reduce the electromagnetic noise caused by eddy currents, and thus improve the sensitivity and accuracy of the sensor. At the same time, the insulating layer introduced between the metal copper wire and the Permalloy-plated soft magnetic material coating can effectively prevent the alternating current from forming eddy currents between the metal wire and the coating, because eddy currents will cause additional energy loss and heat, resulting in increased noise. The presence of the insulating layer limits the generation of eddy currents, thereby reducing the electromagnetic noise caused thereby. The insulating layer provides electrical isolation between the metal wire and the soft magnetic material coating. This isolation can prevent direct electrical contact between them, reduce electromagnetic coupling and interference, and thus reduce noise. The insulating layer can inhibit the movement of the magnetic domain wall between the metal wire and the coating, and reduce the noise caused by the hysteresis effect. The hysteresis phenomenon can cause signal instability. Through the isolation of the insulating layer, this phenomenon can be reduced and the signal stability can be improved. The insulating layer usually has a lower thermal conductivity and can suppress the thermal noise caused by temperature changes to a certain extent. This is particularly important for working environments with large temperature fluctuations, and helps to improve the temperature stability and signal quality of the sensor. In general, the present invention introduces an insulating layer between the metal copper wire and the Permalloy-plated soft magnetic material coating, and improves the noise performance, stability and anti-interference ability of the GMI sensor by effectively reducing the noise source, and has a wide range of application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of a composite structure magnetic core with an insulating layer of the present invention;

[0024] Figure 2 A schematic diagram of a GMI sensor probe having a composite structure magnetic core with an insulating layer according to the present invention;

[0025] Figure 3 The noise spectrum of a composite structure magnetic core with an insulating layer of the present invention when used in a GMI sensor probe;

[0026] Among them: copper wire-1, Al2O3 insulation layer-2, FeNi or Nb conductive metal layer-3, Fe 20 Ni80 Permalloy coating-4, second glass tube-5, first glass tube-6, voltage signal pickup coil-7. DETAILED DESCRIPTION

[0027] Embodiment 1: A method for preparing an insulating coated magnetic core for a GMI sensor probe, the specific steps are as follows:

[0028] Step a: Take a copper wire 1 with a purity of 4N and a length of 11 cm as a substrate and fold it in half to form a U shape, wherein the diameter of the copper wire 1 is 100 μm;

[0029] Step b: pre-treating the copper wire 1, specifically: washing with deionized water for 10 min → washing with 40 g / L sodium carbonate weak base for 10 min → washing with deionized water for 10 min → washing with 2 ml / 50 ml hydrochloric acid solution for 15 min → washing with deionized water for 10 min, taking out and drying with dry nitrogen for standby use;

[0030] Step c: Place the Al2O3 target and Nb target in the sputtering chamber of the magnetron sputtering machine and evacuate the chamber until the background vacuum reaches 2.8×10 -5 Pa; introducing argon gas with a purity of more than 99.99% into the sputtering chamber, and adjusting the gas pressure to 0.1 Pa, then transferring the pretreated copper wire 1 from the injection chamber to the sputtering chamber, the distance between the target and the substrate is 1 cm, the Nb conductive metal layer is DC sputtered, the power is 10 W, the sputtering time is 1800 s, the thickness of the Nb conductive metal layer is 100 nm, the Al2O3 insulating layer is radio frequency sputtered, the power is 100 W, the sputtering time is 7000 s, the thickness of the Al2O3 insulating layer is 500 nm, wherein the copper wire 1 surface is uniformly attached with a thin film, and needs to be turned over so that the thin film is evenly covered on the surface of the copper wire 1;

[0031] Step d: Prepare electrolyte to deposit Fe 20 Ni 80 Plating, the specific electrolyte composition is 0.01 M / L FeSO4·7H2O, 0.1 M / L NiSO4·7H2O, 0.3 M / L H3BO3, 5 g / L ascorbic acid, 1 g / L glycine, and 2 g / L saccharin;

[0032] Step e: Deposition by three-electrode method, during electrodeposition, pH value is 2-4, deposition current density is 2 A / dm 2 ; The electrolyte temperature is 45℃-65℃, the deposition time is 3000 s, Fe 20 Ni 80The thickness of the Permalloy coating is 8 μm. During electrochemical deposition, the U-shaped portion of the sputtered copper wire 1 is covered with a fixture so that Fe is not deposited on the U-shaped bending portion of the insulating coating core used for the GMI sensor probe. 20 Ni 80 Permalloy layer;

[0033] Step f: After electrochemical deposition, take out the U-shaped insulating coated magnetic core for the GMI sensor probe, wipe the surface solution with degreased cotton, and then anneal with a direct current. The annealing current is 2 A and the annealing time is 10 min. During annealing, a wire is used to keep the U-shaped composite structure magnetic core vertical to release stress and induce circumferential anisotropy.

[0034] Embodiment 2: A method for preparing an insulating coated magnetic core for a GMI sensor probe, the specific steps are as follows:

[0035] Step a: taking a copper wire 1 with a purity of 4N and a length of 11 cm as a substrate, and folding it in half to form a U shape, wherein the diameter of the copper wire 1 is 140 μm;

[0036] Step b: pre-treating the copper wire 1, specifically: washing with deionized water for 5 min → washing with 45 g / L sodium carbonate weak base for 10 min → washing with deionized water for 10 min → washing with 2 ml / 50 ml hydrochloric acid solution for 15 min → washing with deionized water for 5 min, taking out and drying with dry nitrogen for standby use;

[0037] Step c: Place the Al2O3 target and Nb target in the sputtering chamber of the magnetron sputtering machine and evacuate the chamber until the background vacuum reaches 2.0×10 -5 Pa; introducing argon gas with a purity of more than 99.99% into the sputtering chamber, and adjusting the gas pressure to 0.2 Pa, then transferring the pretreated copper wire 1 from the injection chamber to the sputtering chamber, the distance between the target and the substrate is 1 cm, the Nb conductive metal layer is DC sputtered, the power is 12 W, the sputtering time is 1500 s, the thickness of the Nb conductive metal layer is 100 nm, the Al2O3 insulating layer is radio frequency sputtered, the power is 85 W, the sputtering time is 9000 s, the thickness of the Al2O3 insulating layer is 500 nm, wherein the copper wire 1 surface is uniformly attached with a thin film, and needs to be turned over so that the thin film is evenly covered on the surface of the copper wire 1;

[0038] Step d: Prepare electrolyte to deposit Fe 20 Ni 80 Plating, the specific electrolyte composition is 0.01 M / L FeSO4·7H2O, 0.1 M / L NiSO4·7H2O, 0.3 M / L H3BO3, 5 g / L ascorbic acid, 1 g / L glycine, and 2 g / L saccharin;

[0039] Step e: Deposition by three-electrode method, during electrodeposition, pH value is 4, deposition current density is 1.5 A / dm 2 ; the electrolyte temperature is 65℃, the deposition time is 5000 s, Fe 20 Ni 80 The thickness of the Permalloy coating is 14 μm. During electrochemical deposition, the U-shaped portion of the sputtered copper wire 1 is covered with a fixture so that Fe is not deposited on the U-shaped bending portion of the insulating coating core used for the GMI sensor probe. 20 Ni 80 Permalloy layer;

[0040] Step f: After electrochemical deposition, take out the U-shaped insulating coated magnetic core for the GMI sensor probe, wipe the surface solution with degreased cotton, and then anneal with a direct current. The annealing current is 1.6 A and the annealing time is 20 min. During annealing, a wire is used to keep the U-shaped composite structure magnetic core vertical to release stress and induce circumferential anisotropy.

[0041] Embodiment 3: A method for preparing an insulating coated magnetic core for a GMI sensor probe, the specific steps are as follows:

[0042] Step a: Take a copper wire 1 with a purity of 4N and a length of 11 cm as a substrate, and fold it in half to form a U shape, wherein the diameter of the copper wire 1 is 20 μm;

[0043] Step b: pre-treating the copper wire 1, specifically: washing with deionized water for 10 min → washing with 40 g / L sodium carbonate weak base for 15 min → washing with deionized water for 5 min → washing with 2 ml / 50 ml hydrochloric acid solution for 10 min → washing with deionized water for 10 min, taking out and drying with dry nitrogen;

[0044] Step c: Place the Al2O3 target and FeNi target in the sputtering chamber of the magnetron sputtering machine and evacuate the chamber until the background vacuum reaches 2.0×10 -5 Pa; introducing argon gas with a purity of more than 99.99% into the sputtering chamber, and adjusting the gas pressure to 0.2 Pa, then transferring the pretreated copper wire 1 from the injection chamber to the sputtering chamber, the distance between the target and the substrate is 6 cm, the conductive metal layer of FeNi is DC sputtered, the power is 20 W, the sputtering time is 4000 s, the thickness of the conductive metal layer of FeNi is 500 nm, the Al2O3 insulating layer is radio frequency sputtered, the power is 80 W, the sputtering time is 4500 s, the thickness of the Al2O3 insulating layer is 100 nm, wherein the thin film is evenly attached to the surface of the copper wire 1, and it needs to be turned over so that the thin film is evenly covered on the surface of the copper wire 1;

[0045] Step d: Prepare electrolyte to deposit Fe 20Ni 80 Plating, the specific electrolyte composition is 0.01 M / L FeSO4·7H2O, 0.1 M / L NiSO4·7H2O, 0.3 M / L H3BO3, 5 g / L ascorbic acid, 1 g / L glycine, and 2 g / L saccharin;

[0046] Step e: Deposition by three-electrode method, during electrodeposition, pH value is 2, deposition current density is 4 A / dm 2 ; the electrolyte temperature is 45℃, the deposition time is 2500 s, Fe 20 Ni 80 The thickness of the Permalloy coating is 5 μm. During electrochemical deposition, the U-shaped portion of the sputtered copper wire 1 is covered with a fixture so that Fe is not deposited on the U-shaped bending portion of the insulating coating core used for the GMI sensor probe. 20 Ni 80 Permalloy layer;

[0047] Step f: After electrochemical deposition, take out the U-shaped insulating coated magnetic core for the GMI sensor probe, wipe the surface solution with degreased cotton, and anneal it with a direct current. The annealing current is 2 A and the annealing time is 10 min. During annealing, a wire is used to keep the U-shaped composite structure magnetic core vertical to release stress and induce circumferential anisotropy.

[0048] Embodiment 4: A method for preparing an insulating coated magnetic core for a GMI sensor probe, the specific steps are as follows:

[0049] Step a: Take a copper wire 1 with a purity of 4N and a length of 11 cm as a substrate, and fold it in half to form a U shape, wherein the diameter of the copper wire 1 is 20 μm;

[0050] Step b: pre-treating the copper wire 1, specifically: washing with deionized water for 10 min → washing with 40 g / L sodium carbonate weak base for 15 min → washing with deionized water for 5 min → washing with 2 ml / 50 ml hydrochloric acid solution for 10 min → washing with deionized water for 10 min, taking out and drying with dry nitrogen;

[0051] Step c: Place the Al2O3 target and FeNi target in the sputtering chamber of the magnetron sputtering machine, adjust the distance between the target and the substrate to 3 cm, and then start to evacuate. -5Pa, the pretreated copper wire 1 is transferred from the sample feeding chamber to the sputtering chamber, and then argon gas with a purity of more than 99.99% is introduced into the sputtering chamber, and the gas pressure is adjusted to 0.1 Pa. The conductive metal layer FeNi is DC sputtered with a power of 20 W, a sputtering time of 4000 s, and a thickness of 500 nm. The Al2O3 insulating layer is RF sputtered with a power of 80 W, a sputtering time of 4500 s, and a thickness of 100 nm. In order to ensure that the surface of the copper wire 1 is evenly attached to the film, the copper wire 1 needs to be turned over so that the film is evenly covered on its surface.

[0052] Step d: Prepare electrolyte to deposit Fe 20 Ni 80 Plating, the specific electrolyte composition is 0.01 M / L FeSO4·7H2O, 0.1 M / L NiSO4·7H2O, 0.3 M / L H3BO3, 5 g / L ascorbic acid, 1 g / L glycine, and 2 g / L saccharin;

[0053] Step e: Deposition by three-electrode method, during electrodeposition, pH value is 2, deposition current density is 4 A / dm 2 ; the electrolyte temperature is 45℃, the deposition time is 2000 s, Fe 20 Ni 80 The thickness of the Permalloy coating is 4 μm. During electrochemical deposition, the U-shaped portion of the sputtered copper wire 1 is covered with a fixture so that Fe is not deposited on the U-shaped bending portion of the insulating coating core used for the GMI sensor probe. 20 Ni 80 Permalloy layer;

[0054] Step f: After electrochemical deposition, take out the U-shaped insulating coated magnetic core for the GMI sensor probe, wipe the surface solution with degreased cotton, and anneal it with a direct current. The annealing current is 2 A and the annealing time is 10 min. During annealing, a wire is used to keep the U-shaped composite structure magnetic core vertical to release stress and induce circumferential anisotropy.

[0055] Embodiment 5: A sensor probe made of an insulating coated magnetic core for a GMI sensor probe, comprising a U-shaped insulating coated magnetic core for a GMI sensor probe, a voltage signal pickup coil 7, a second glass tube 5 and a first glass tube 6, and a PCB printed circuit board; wherein the U-shaped bending portion of the U-shaped insulating coated magnetic core for the GMI sensor probe is not deposited with Fe 20 Ni 80 Permalloy layer. A copper wire 1 with a purity of 4N is used as a substrate, and the diameter of the copper wire 1 is 20-140 μm; an Al2O3 insulating layer 2, a FeNi or Nb conductive metal layer 3 and a Fe20 Ni 80 Permalloy coating 4; wherein the thickness of Al2O3 insulating layer 2 is 100-500 nm, the thickness of FeNi or Nb conductive metal layer 3 is 100-500 nm, Fe 20 Ni 80 The thickness of the Permalloy coating 4 is 4-14 μm. One side of the U-shaped insulating coated magnetic core for the GMI sensor probe penetrates into the second glass tube 5, and the second glass tube 5 is sleeved in the first glass tube 6. The other side of the U-shaped insulating coated magnetic core for the GMI sensor probe penetrates into the interlayer between the first glass tube 6 and the second glass tube 5. The U-shaped insulating coated magnetic core for the GMI sensor probe avoids mutual conduction by penetrating different glass tubes; the diameters of the first glass tube 6 and the second glass tube 5 are adapted to the diameter of the U-shaped insulating coated magnetic core for the GMI sensor probe. The voltage signal pickup coil 7 is wound on the first glass tube 6, and the voltage signal pickup coil 7 and the U-shaped insulating coated magnetic core for the GMI sensor probe are welded to the PCB printed circuit board.

[0056] The sensor noise of the GMI sensor probe of the present invention is significantly reduced at 1 Hz when AC excitation and DC bias are applied to the sensor probe, compared with the composite structure magnetic core without an insulating layer. Figure 3 The noise power spectral density shows that at a frequency of 1 Hz, the noise value drops from 59 pT / √Hz to 42 pT / √Hz.

Claims

1. An insulating coated magnetic core for a GMI sensor probe, characterized in that: A copper wire (1) with a purity of 4N is used as a substrate, wherein the diameter of the copper wire (1) is 20-140 μm; an Al2O3 insulating layer (2), a FeNi or Nb conductive metal layer (3) and a Fe 20 Ni 80 Permalloy coating (4); wherein the thickness of the Al2O3 insulating layer is 100-500 nm, the thickness of the FeNi or Nb conductive metal layer is 100-500 nm, and the Fe 20 Ni 80 The thickness of the Permalloy coating is 4-14 μm, and it is finally annealed with a direct current, the annealing current is 1.6-2 A, and the annealing time is 10-20 min; the insulating coating core used for the GMI sensor probe is U-shaped.

2. The insulating coated magnetic core for a GMI sensor probe according to claim 1, characterized in that: The Al2O3 insulating layer (2) and the FeNi or Nb conductive metal layer (3) are prepared by a magnetron sputtering method, wherein the vacuum degree of the magnetron sputtering is better than 3×10 -5 Pa, the sputtering gas pressure is 0.1-0.3 Pa, and argon gas with a purity of more than 99.99% is introduced.

3. The insulating coated magnetic core for a GMI sensor probe according to claim 2, characterized in that: The FeNi or Nb conductive metal layer is formed by direct current sputtering with a power of 10-20 W and a sputtering time of 1500 s-4000 s; the Al2O3 insulating layer is formed by radio frequency sputtering with a power of 80-100 W and a sputtering time of 4500 s-9000 s.

4. The insulating coated magnetic core for a GMI sensor probe according to claim 3, characterized in that: During magnetron sputtering of the Al2O3 insulating layer and the FeNi or Nb conductive metal layer, the distance between the target and the substrate is 1-6 cm.

5. The insulating coated magnetic core for a GMI sensor probe according to claim 4, characterized in that: The Fe 20 Ni 80 The Permalloy coating (4) is prepared by electrochemical deposition, specifically: the electrolyte composition is 0.01 M / L FeSO4·7H2O, 0.1 M / L NiSO4·7H2O, 0.3 M / L H3BO3, 5 g / L ascorbic acid, 1 g / L glycine, and 2 g / L saccharin; during electrochemical deposition, the electrolyte temperature is 45°C-65°C, the pH is 2-4, the deposition time is 2500 s-5000 s, and the deposition current density is 1.5-4A / dm 2 .

6. A method for preparing an insulating coated magnetic core for a GMI sensor probe according to any one of claims 1 to 5, characterized in that The specific steps are as follows: Step a: folding a copper wire substrate with a purity of 4N into a U shape, wherein the diameter of the copper wire (1) is 20-140 μm; Step b: pre-treating the copper wire substrate, specifically: washing with deionized water for 5-10 min → washing with 40-45 g / L sodium carbonate weak base solution for 10-15 min → washing with deionized water for 5-10 min → washing with 2 ml / 50 ml hydrochloric acid solution for 10-15 min → washing with deionized water for 5-10 min, taking out and drying with dry nitrogen; Step c: Using magnetron sputtering, the Al2O3 insulating layer (2) and the FeNi or Nb conductive metal layer (3) are sequentially plated on the pretreated copper wire substrate. First, the Al2O3 target and the FeNi or Nb target are placed in a sputtering chamber and evacuated until the background vacuum reaches 3×10 -5 Pa or less; then the pretreated copper wire substrate is transferred from the injection chamber to the sputtering chamber, the distance between the target and the substrate is 1-6 cm, argon gas with a purity of more than 99.99% is introduced into the sputtering chamber, and the gas pressure is adjusted to 0.1-0.3 Pa, the conductive metal layer of FeNi or Nb is DC sputtered, the power is 10-20 W, the sputtering time is 1500 s-4000 s, and the thickness of the conductive metal layer of FeNi or Nb is 100-500 nm; the Al2O3 insulating layer is radio frequency sputtered, the power is 80-100 W, the sputtering time is 4500 s-9000 s, and the thickness of the Al2O3 insulating layer is 100-500 nm; Step d: Prepare electrolyte to deposit Fe 20 Ni 80 Permalloy coating, the electrolyte composition of which is 0.01 M / L FeSO4·7H2O, 0.1 M / L NiSO4·7H2O, 0.3 M / L H3BO3, 5 g / L ascorbic acid, 1 g / L glycine, and 2 g / L saccharin; Step e: Deposition by three-electrode method, during electrodeposition, pH value is 2-4, deposition current density is 1.5-4 A / dm 2 ; The electrolyte temperature is 45℃-65℃, the deposition time is 2500 s-5000 s, Fe 20 Ni 80 The thickness of the Permalloy coating is 4-14 μm; Step f: After electrochemical deposition, take out the U-shaped insulating coated magnetic core for the GMI sensor probe, wipe off the surface solution, and then anneal with a direct current. The annealing current is 1.6-2 A and the annealing time is 10-20 min.

7. A sensor probe made of an insulating coated magnetic core for a GMI sensor probe according to any one of claims 1 to 5, characterized in that: The invention comprises a U-shaped insulating coated magnetic core for a GMI sensor probe, a voltage signal pickup coil (7), a second glass tube (5), a first glass tube (6), and a PCB printed circuit board; one side of the U-shaped insulating coated magnetic core for a GMI sensor probe is inserted into the second glass tube (5), the second glass tube (5) is sleeved in the first glass tube (6), the other side of the U-shaped insulating coated magnetic core for a GMI sensor probe is inserted into the interlayer between the first glass tube (6) and the second glass tube (5), and the U-shaped insulating coated magnetic core for a GMI sensor probe is prevented from being connected to each other by being inserted into different glass tubes; the voltage signal pickup coil (7) is wound on the first glass tube (6), and the voltage signal pickup coil (7) and the U-shaped insulating coated magnetic core for a GMI sensor probe are welded to the PCB printed circuit board.

8. The sensor probe made of an insulating coated magnetic core for a GMI sensor probe according to claim 7, characterized in that: The diameters of the first glass tube (6) and the second glass tube (5) are adapted to the diameter of a U-shaped insulating coated magnetic core for a GMI sensor probe.

9. The sensor probe made of an insulating coated magnetic core for a GMI sensor probe according to claim 8, characterized in that: The U-shaped bending part of the insulating coated magnetic core for the GMI sensor probe does not deposit Fe 20 Ni 80 Permalloy layer.

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