CN115340088B - Temperature-independent linear magneto-resistance material and preparation method and application thereof - Google Patents
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- 238000002360 preparation method Methods 0.000 title abstract description 17
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- 229910002804 graphite Inorganic materials 0.000 claims abstract description 39
- 239000010439 graphite Substances 0.000 claims abstract description 39
- 239000011259 mixed solution Substances 0.000 claims description 59
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 39
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- IKDUDTNKRLTJSI-UHFFFAOYSA-N hydrazine monohydrate Substances O.NN IKDUDTNKRLTJSI-UHFFFAOYSA-N 0.000 claims description 12
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 11
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
- G01R33/09—Magnetoresistive devices
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Abstract
The invention discloses a temperature-independent linear magneto-resistance material, a preparation method and application thereof. The Magnetic Resistance (MR) of the graphite film material is 96% at 2K and the MR at 300K is 118% under the condition that the magnetic field is 9T. Based on the characteristics, the graphite film obtained by the invention can be widely applied to the preparation of various magnetic sensors, and the prepared graphite film magnetic sensor can realize the measurement of high precision and wide temperature range based on the linear response of the magnetic resistance independent of temperature, and is particularly suitable for the measurement of a strong magnetic field.
Description
Technical Field
The invention belongs to the technical field of magnetoresistive materials, and particularly relates to a temperature-independent linear magnetoresistive material, a preparation method and application thereof.
Background
In 1833, the american scientist kelvin first found that the resistance of the conductor changed under the influence of the magnetic field. Subsequently, it was found that the resistivity of some metals or semiconductors increases with increasing magnetic field, and this phenomenon is called magnetoresistance effect. Semiconductor magnetoresistance effects are classified into two types, one of which is the magnetoresistance effect of the material itself, referred to as physical magnetoresistance effect; the other is that the semiconductor has different shape and structure, and the resistance increase rate is different under the action of the same magnetic field, and the magnetic resistance effect related to the shape and size of the semiconductor is called geometric magnetic resistance effect. We define the change in resistance asWherein R (H) is the resistance under the external magnetic field H, and R (0) is the resistance under the external magnetic field of 0.
The application of the magneto-resistance effect is very wide, and the common magneto-resistance effect is divided into four types: giant magnetoresistance effect (GMR), super giant magnetoresistance effect (CMR), tunnel magnetoresistance effect (TMR), anisotropic magnetoresistance effect (AMR). The giant magnetoresistance effect is a characteristic in which the magnetoresistance R of some magnetic or alloy materials is drastically reduced by a certain magnetic field, and Δr/R is drastically increased, and generally the increase is about 10 times higher than that of a general magnetic or alloy material. The sensor made by this effect is called GMR sensor. GMR effect is a quantum mechanical and aggregate physical phenomenon that can be observed in thin film layer (a few nanometers thick) structures where magnetic and non-magnetic materials are alternating. The GMR effect has wide application in high density read heads, magnetic storage elements. However, the saturated magnetic field of the common GMR material is smaller and can be used for detecting weak magnetic field generally. The super giant magneto-resistance effect is a physical phenomenon of aggregate, which means that the resistance of a material in a magnetic field is significantly reduced. The magneto-resistance of the super giant magneto-resistance effect varies by orders of magnitude with the variation of the applied magnetic field. Because of the low phase transition temperature, unlike giant magneto-resistive materials, which can exhibit their properties at room temperature, there is a distance from practical applications.
The measurement/detection of magnetic fields is of great technical importance, and various types of magnetic field sensors have been developed. It is clear that the magneto-resistive effect is just useful for this purpose, and magneto-resistive sensors based on the AMR effect have been widely used for measuring or detecting magnetic fields for decades. In today's hard disk drives, the read head almost entirely uses the giant magnetoresistive principle, utilizing a so-called spin valve structure. The introduction in 1997 made it possible to further maintain a high rate of increase in magnetic storage density, and GMR performance guaranteed that this trend could continue even in the future. MR is expected to have great application potential in magnetic field measurement, magnetoresistive sensors and magnetic storage. There have been studies to find giant magnetoresistance effects in graphite and graphite-based materials.
In general, MR in conventional metals is less than a few percent, negligible, and reaches saturation under high magnetic fields. Over the last several decades, linear dependent magnetoresistance (LMR), i.e. a linear increase in resistance with increasing magnetic field, was observed in zero bandgap semiconductors such as Ag 2±δSe、Ag2±δ Te, inSb, multi-layer graphene, topologically crystalline insulators, topologically insulating insulators and dirac material Cd 3As2. The magnetoresistance of most of these materials is relatively large at different temperatures: the magnetic resistance is large at low temperature, and the resistance value is small from high Wen Duanci. If the material is applied to some magnetic sensors, the accuracy of the sensor is reduced due to the high temperature environment.
Patent CN112938961A, "a device and a method for preparing graphite by an on-line catalytic reduction method", adopts the most common H 2/Fe catalytic reduction method to prepare a graphitizing device for on-line catalytic water samples. The device abandons the traditional method of utilizing a vacuum system to extract CO 2 in a sample, adopts helium to purge and acidify the sample in a designed closed gas path, and enters a catalytic reduction tube after purifying and removing impurities from the purged CO 2 gas, and reduces the CO 2 gas into graphite carbon under the action of H 2 and iron powder. The method can effectively avoid atmospheric leakage, pollute graphitized samples, and purify volatile impurity gas generated by water samples, thereby avoiding the failure of catalysts and reducing agents. The progress of graphitization reaction is controlled by controlling the flow rate of H 2, the flow rate of He, the acidification temperature of the reaction, the iron powder content and the temperature of the reaction furnace. And judging the completion progress of the graphitization reaction by detecting the contents of CO 2 and CH 4 in the exhausted gas. However, the reaction apparatus is complicated and difficult to operate, thus limiting the yield; the reaction needs to be carried out under high temperature, the required time is long, and the reaction condition is very high, so that the production cost is relatively high, and the method is not suitable for large-scale production and application.
Disclosure of Invention
In order to solve the problems existing in the existing materials, the invention provides a temperature-independent linear magneto-resistance material, and a preparation method and application thereof. The material is composed of a graphite film, and the magnetic resistance effect of the material has good linearity at low temperature and normal temperature and basically does not change with temperature.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a preparation method of a temperature independent linear magneto-resistance material comprises the following steps:
S1: adding the non-spar ink into concentrated sulfuric acid, and stirring to obtain a mixed solution; adding KMnO 4, stirring, and carrying out all stirring processes under ice bath conditions; transferring the mixed solution into a water bath, slowly adding KNO 3 into the mixed solution, and stirring; adding deionized water into the mixed solution continuously, transferring the mixed solution into an oil bath, and stirring;
S2: adding H 2O2 into the mixed solution obtained in the step S1, and continuing the reaction until the solution turns from dark brown to bright yellow; adding a mixed solution of hydrazine hydrate and polyvinylpyrrolidone (PVP) into the bright yellow mixed solution for reaction; adding a reducing agent into the mixed solution after the reaction to obtain black powder, sequentially washing the powder with water and ethanol, centrifuging and drying;
s3: and adding the dried powder into a mould, and performing mould pressing to obtain a graphite film, namely the temperature-independent linear magneto-resistance material.
Further, in the step S1, the purity of the amorphous graphite is 99%, and the mass-volume ratio of the amorphous graphite to the concentrated sulfuric acid is 0.005-0.1 g/mL; the non-spar ink is added into the concentrated sulfuric acid and stirred for 20 to 40 minutes.
Further, in the step S1, the mass ratio of KMnO 4 to amorphous graphite is 4-8; adding KMnO 4 and stirring for 20-40 min.
Further, in the step S1, the mass ratio of KNO 3 to amorphous graphite is 6-10; adding KNO 3 into the mixed solution, stirring for 40-80 min, and heating in water bath at 10-30deg.C.
Further, in the step S1, the mass volume ratio of the non-spar ink to the deionized water is 0.01-0.017 g/mL; transferring the mixed solution into an oil bath and stirring for 20-40 min, wherein the temperature of the oil bath is 60-100 ℃.
Further, in the step S2, the mass-volume ratio of the amorphous graphite to the H 2O2 is 0.1-0.125 g/mL; the reaction is continued for 40-80 min.
Further, in the step S2, the volume ratio of the hydrazine hydrate to the PVP mixed solution is V Hydrated nitriles ∶VPVp = 2:1, wherein the mass concentration of PVP is 1-15 wt%; the mixed solution of hydrazine hydrate and PVP is added into the bright yellow mixed solution for reaction for 30-120 min at 40-80 ℃.
Further, in step S2, the reducing agent is acetic acid or hydroiodic acid; the addition amount was 20mL.
Further, in the step S2, the drying temperature is 40-60 ℃ and the drying time is 12-36 h.
Further, in step S3, the molding conditions are as follows: the pressure is 1-10 Mpa, the temperature is 800-950 ℃, and the vacuum degree is less than 0.1Mpa.
The invention also provides a temperature independent linear magneto-resistance material prepared by the preparation method.
The linear magneto-resistance material independent of temperature can be widely applied to the preparation of various magnetic sensors. Based on the linear response of the magnetic resistance independent of temperature, the prepared magnetic sensor can realize measurement in high precision and wide temperature range, and is particularly suitable for measurement of strong magnetic fields.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) Compared with the preparation of other magnetic resistance materials, the preparation method has the advantages of lower cost, simple required equipment and more convenient preparation process.
(2) The magnetic resistance of the material prepared by the invention is hardly affected by temperature, and has better linear response from 2K to 300K. The material has a Magnetic Resistance (MR) of 96% at 2K and an MR of 118% at 300K under a magnetic field of 9T.
(3) The resistivity of the carbon film prepared by the invention is about 0.05mΩ cm, the linear magnetic resistance can be measured when the current is 100 mu A, the power is about 5 multiplied by 10 -9 W, and the device prepared by the invention has small power consumption and is more energy-saving.
Drawings
FIG. 1 is a schematic diagram of devices of different shapes and sizes made of the magnetoresistive material prepared in accordance with the invention, the dimensions being in cm.
FIG. 2 is a Raman spectrum of graphite films of different thicknesses obtained in example 1.
Figure 3 shows XRD diffractograms of graphite films of different thicknesses obtained in example 1.
FIG. 4 shows MR curves of 0.1mm graphite films obtained in example 1 at different temperatures, with a scan interval of-9T to 9T.
FIG. 5 shows MR curves of 0.01mm graphite films obtained in example 1 at different temperatures, with a scan interval of the magnetic field of-9T to 9T.
Detailed Description
The following describes the embodiments of the present invention further with reference to specific examples and drawings, but the embodiments of the present invention are not limited thereto.
Example 1
A preparation method of a temperature independent linear magneto-resistance material comprises the following steps:
S1: 2g of non-spar ink with the purity of 99% is added into 50mL of concentrated sulfuric acid and stirred for 20min, and the whole stirring process is carried out under the ice bath condition; adding 8g KMnO 4 into the mixed solution, stirring for 20min, and stirring under ice bath condition; transferring the mixed solution into a water bath at 10 ℃, adding 12g KNO 3 into the mixed solution, and stirring for 40min; 200mL of deionized water was continuously added to the above mixture, the mixture was transferred to an 80℃oil bath and stirred for 30min;
s2: dropwise adding 20mL of H 2O2 into the mixed solution obtained in the step S1, and continuing to react for 50min until the solution turns from dark brown to bright yellow; 10mL of a mixed solution of hydrazine hydrate and PVP (10 wt% PVP, V Hydrated nitriles ∶VPVP =2:1) is added into the bright yellow mixed solution to react for 1h at 40 ℃; adding 20mL of acetic acid into the mixed solution obtained in the previous step to obtain black powder, washing the powder with water, centrifuging for several times, washing with ethanol once, and drying at 50 ℃ for 24 hours;
S3: 1.5g of the dried powder was put into a mold, and the graphite film was obtained by molding under a pressure of 5MPa, a temperature of 850℃and a vacuum of 0.05MPa for 30 minutes.
As shown in FIG. 1, the magneto-resistive material prepared by the invention can be prepared into devices with different sizes and shapes, and (a) in FIG. 1 is a hall-bar made of a graphite film obtained in example 1, the resistivity of the bar is about 0.05mΩ & cm, the linear magneto-resistance can be detected at a current of 100 μA, and the power is about 5×10 -9 W. Fig. 1 (b) is a schematic view of another device made of the material, and is circular.
FIG. 2 is a Raman spectrum obtained at three different thicknesses of 0.03mm, 0.05mm and 0.1mm of the graphite film obtained in example 1, and it can be seen that characteristic peaks of carbon are obvious, indicating that the purity of the sample is relatively high. The D peak in the raman spectrum represents a defect in the lattice of C atoms and the G peak represents in-plane stretching vibration of sp2 hybridization of C atoms. That is, the relative intensity of the D peak reflects the degree of disorder of the crystal structure, the G peak represents the sp2 bond structure of C, and the D/G intensity ratio can be used to characterize the disorder degree of graphite, and the disorder degree of the graphite film obtained in example 1 can be judged to be low by Raman analysis. FIG. 3 shows XRD diffraction patterns of the graphite film obtained in example 1 at three different thicknesses of 0.03mm, 0.05mm and 0.1mm, and a weak broad peak located at about 23℃in addition to the diffraction peaks of the two crystal planes (002) and (004), which may be caused by nanocrystals in the sample. Figures 2 and 3 show that the graphite flake produced by the process of the present invention is a polycrystalline material having a very high degree of orientation.
The graphite film obtained in example 1 is cut into rectangular graphite sheets with the length of 5mm being 10mm being 0.1mm by using a diamond knife, magnetic resistance of the graphite film under the conditions of 2K, 10K, 100K, 200K and 300K is measured by using a four-electrode method, a scanning interval of a magnetic field is-9T, the electrode spacing is 3mm, and a magnetic resistance MR curve of the material is obtained, and as shown in a result of fig. 4, the magnetic resistance of the material hardly changes along with temperature, the magnetic resistance can reach 118% at room temperature and is in linear relation with the magnetic field, the sensitivity to magnetic field change is high, and the material can be used for high-precision magnetic field measurement. The graphite film obtained in example 1 was cut into rectangular graphite sheets of 5mm by 10mm by a diamond knife, and the magnetic resistance was measured by the same method as described above, and as a result, as shown in fig. 5, the MR of the vacuum hot-pressed 300K sintered magnetoresistive material could reach 118% at room temperature, 96% at 2K, and a good linear response of MR to external magnetic field H could be maintained over several temperature periods, substantially without temperature change.
Example 2
A preparation method of a temperature independent linear magneto-resistance material comprises the following steps:
S1: 2g of non-spar ink with the purity of 99% is added into 100mL of concentrated sulfuric acid and stirred for 30min, and the whole stirring process is carried out under the ice bath condition; adding 10g of KMnO 4 into the mixed solution, stirring for 30min, wherein the whole stirring process is carried out under ice bath condition; transferring the mixed solution into a water bath at 20 ℃, adding 20g KNO 3 into the mixed solution, and stirring for 60min; 200mL of deionized water was continuously added to the above mixture, the mixture was transferred to an 80℃oil bath and stirred for 20min;
S2: dropwise adding 20mL of H 2O2 into the mixed solution obtained in the step S1, and continuing the reaction for 60min until the solution turns from dark brown to bright yellow; 20mL of a mixed solution of hydrazine hydrate and PVP (10 wt% PVP, V Hydrated nitriles ∶VPVP =2:1) is added into the bright yellow mixed solution to react for 30min at 60 ℃; 20mL of acetic acid was added to the mixture after the previous reaction to obtain a black powder, and the powder was washed with water, centrifuged several times, washed once with ethanol, and dried at 50℃for 24 hours.
S3: 1g of the dried powder was put into a mold, and the mold was pressed under a pressure of 10MPa, a temperature of 850℃and a vacuum of 0.05MPa for 10 minutes to obtain a graphite film.
Example 3
A preparation method of a temperature independent linear magneto-resistance material comprises the following steps:
S1: 2g of non-spar ink with the purity of 99% is added into 200mL of concentrated sulfuric acid and stirred for 40min, and the whole stirring process is carried out under the ice bath condition; adding 14g KMnO 4 into the mixed solution, stirring for 40min, and stirring under ice bath condition; transferring the mixed solution into a water bath at 30 ℃, adding 20g KNO 3 into the mixed solution, and stirring for 80min; 120mL of deionized water was continuously added to the above mixture, and the mixture was transferred to a 100deg.C oil bath and stirred for 40min.
S2: dropwise adding 16mL of H 2O2 into the mixed solution obtained in the step S1, and continuing the reaction for 80min until the solution turns from dark brown to bright yellow; 40mL of a mixed solution of hydrazine hydrate and PVP (10 wt% PVP, V Hydrated nitriles ∶VPVP =2:1) is added into the bright yellow mixed solution to react for 2 hours at 80 ℃;20 mL of hydroiodic acid was added to the mixture after the previous reaction to obtain a black powder, and the powder was washed with water, centrifuged several times, washed with ethanol once, and dried at 50℃for 24 hours.
S3: 1g of the dried powder was put into a mold, and the graphite film was obtained by molding under a pressure of 10MPa, a temperature of 950℃and a vacuum of 0.05MPa for 20 minutes.
Example 4
A preparation method of a temperature independent linear magneto-resistance material comprises the following steps:
S1: 2g of non-spar ink with the purity of 99% is added into 100mL of concentrated sulfuric acid and stirred for 40min, and the whole stirring process is carried out under the ice bath condition; adding 16g KMnO 4 into the mixed solution, stirring for 30min, and stirring under ice bath condition; transferring the mixed solution into a water bath at 20 ℃, adding 15g KNO 3 into the mixed solution, and stirring for 60min; 200mL of deionized water was continuously added to the above mixture, the mixture was transferred to an 80℃oil bath and stirred for 20min;
S2: dropwise adding 20mL of H 2O2 into the mixed solution obtained in the step S1, and continuing the reaction for 60min until the solution turns from dark brown to bright yellow; 20mL of a mixed solution of hydrazine hydrate and PVP (10 wt% PVP, V Hydrated nitriles ∶VPVP =2:1) is added into the bright yellow mixed solution to react for 30min at 60 ℃;20 mL of acetic acid was added to the mixture after the previous reaction to obtain a black powder, and the powder was washed with water, centrifuged several times, washed once with ethanol, and dried at 60℃for 36 hours.
S3: 1g of the dried powder was put into a mold, and the mold was pressed under a pressure of 10MPa, a temperature of 850℃and a vacuum of 0.05MPa for 10 minutes to obtain a graphite film.
Example 5
A preparation method of a temperature independent linear magneto-resistance material comprises the following steps:
S1: 2g of non-spar ink with the purity of 99% is added into 400mL of concentrated sulfuric acid and stirred for 20min, and the whole stirring process is carried out under the ice bath condition; adding 16g KMnO 4 into the mixed solution, stirring for 30min, and stirring under ice bath condition; transferring the mixed solution into a water bath at 30 ℃, adding 18g KNO 3 into the mixed solution, and stirring for 60min; 200mL of deionized water was continuously added to the above mixture, and the mixture was transferred to a 60℃oil bath and stirred for 20min;
S2: dropwise adding 20mL of H 2O2 into the mixed solution obtained in the step S1, and continuing the reaction for 60min until the solution turns from dark brown to bright yellow; 20mL of a mixed solution of hydrazine hydrate and PVP (10 wt% PVP, V Hydrated nitriles ∶VPVP =2:1) is added into the bright yellow mixed solution to react for 30min at 60 ℃; 20mL of acetic acid was added to the mixture after the previous reaction to obtain a black powder, and the powder was washed with water, centrifuged several times, washed once with ethanol, and dried at 40℃for 12 hours.
S3: 1g of the dried powder was put into a mold, and the mold was pressed under a pressure of 10MPa, a temperature of 850℃and a vacuum of 0.05MPa for 10 minutes to obtain a graphite film.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (2)
1. A method for preparing a temperature independent linear magnetoresistive material, comprising the steps of:
S1: adding the non-spar ink into concentrated sulfuric acid, and stirring to obtain a mixed solution; adding KMnO 4, stirring, and carrying out all stirring processes under ice bath conditions; transferring the mixed solution into a water bath, adding KNO 3 into the mixed solution, and stirring; adding deionized water into the mixed solution continuously, transferring the mixed solution into an oil bath, and stirring;
S2: adding H 2O2 into the mixed solution obtained in the step S1, and continuing the reaction until the solution turns from dark brown to bright yellow; adding the mixed solution of hydrazine hydrate and PVP into the bright yellow mixed solution for reaction; adding a reducing agent into the mixed solution after the reaction to obtain black powder, sequentially washing the powder with water and ethanol, centrifuging and drying;
S3: adding the dried powder into a mould, and performing mould pressing to obtain a graphite film, namely the linear magneto-resistance material independent of temperature;
In the step S1, the mass volume ratio of the amorphous graphite to the concentrated sulfuric acid is 0.005-0.1 g/mL; adding the non-spar ink into concentrated sulfuric acid and stirring for 20-40 min; the mass ratio of KMnO 4 to amorphous graphite is 4-8; adding KMnO 4 and stirring for 20-40 min;
In the step S1, the mass ratio of KNO 3 to amorphous graphite is 6-10; adding KNO 3 into the mixed solution, stirring for 40-80 min, and heating in water bath at 10-30deg.C; the mass volume ratio of the non-spar ink to the deionized water is 0.01-0.017 g/mL; transferring the mixed solution into an oil bath and stirring for 20-40 min, wherein the temperature of the oil bath is 60-100 ℃;
In the step S2, the mass volume ratio of the amorphous graphite to the H 2O2 is 0.1-0.125 g/mL; the continuous reaction time is 40-80 min;
In step S2, the volume ratio of the hydrazine hydrate to PVP mixed solution is V Hydrazine hydrate ：VPVP =2: 1, wherein the mass concentration of PVP is 1-15 wt%; adding the hydrazine hydrate and PVP mixed solution into the bright yellow mixed solution for reaction for 30-120 min at 40-80 ℃;
In step S3, the molding conditions are as follows: the pressure is 1-10 Mpa, the temperature is 800-950 ℃, and the vacuum degree is less than 0.1Mpa;
in the step S2, the reducing agent is acetic acid or hydroiodic acid;
In the step S2, the drying temperature is 40-60 ℃, and the drying time is 12-36 h.
2. Use of a temperature independent linear magnetoresistive material made by the method of manufacture of claim 1 in a magnetic sensor.
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