Staggered magnet and preparation method and application thereof

Abstract

The invention provides a staggered magnet and a preparation method and application thereof, and belongs to the technical field of magnetic materials. The formation of staggered magnetism can be induced by utilizing the interlayer confinement effect that vanadium intercalation graphite, vanadium atom layers and carbon atom layers are alternately distributed; through the synergistic effect of the graphite carrier and vanadium, the room-temperature-adjustable magnetoelectric coupling characteristic is achieved. The result of the embodiment shows that vanadium atoms in the staggered magnet provided by the invention are uniformly dispersed among graphene layers; in a proof graph for theoretically predicting staggered magnetism, the electronic structure of the material shows that spontaneous clamer degeneration is relieved in a momentum space, the net magnetic moment of the material is zero, and the staggered magnetism is shown; reversible magnetic response is shown in the temperature range of 5-240 K, the room-temperature saturation magnetization is 5-8 emu / g, the coercive force is smaller than or equal to 50 Oe, and the conductivity is larger than or equal to 500 S / cm.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic materials, and in particular relates to an interlaced magnet and a preparation method and application thereof. Background Art

[0002] In recent years, research on magnetic materials has gradually expanded from traditional ferromagnetic and antiferromagnetic systems to novel magnetically ordered states. In altermagnetic materials, the magnetic moments (spins) of adjacent atoms or ions exhibit a periodic alternating arrangement, similar to traditional antiferromagnets. However, unlike traditional antiferromagnets, this alternating arrangement exhibits a unique crystal symmetry, and their electronic band structure exhibits a unique spin polarization in momentum space. Alternated magnetism not only expands the physical implications of magnetic materials but also provides a theoretical basis for the design of novel functional materials.

[0003] Interleaved magnetic materials can be used in low-power spintronic devices, such as spin field-effect transistors or magnetic memories, because they can manipulate spin-polarized current without the need for a net magnetic moment; they also have great application potential in topological quantum computing and high-sensitivity sensors.

[0004] However, research in this field is still in its infancy. The magnetoelectric properties of known interdigitated magnetic material systems, such as certain metal oxides, are difficult to control, which seriously restricts the practical application of such materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a staggered magnet and its preparation method and application. The staggered magnet provided by the present invention has controllable magnetic and electric properties.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides an interleaved magnet. The interleaved magnet is a vanadium intercalation graphite compound. The vanadium intercalation graphite compound comprises alternately distributed vanadium atomic layers and carbon atomic layers.

[0008] Preferably, the interlayer spacing of the carbon atomic layers is 0.45 to 0.5 nm.

[0009] The present invention also provides a method for preparing the staggered magnet described in the above technical solution, comprising the following steps:

[0010] (1) mixing a soluble vanadium source, a chelating agent and an organic solvent and adjusting the pH to 3-4.5 to obtain a vanadium-containing solution;

[0011] (2) adding graphene oxide to the vanadium-containing solution obtained in step (1) for pre-intercalation to obtain pre-intercalated graphene oxide;

[0012] (3) subjecting the pre-intercalated graphene oxide obtained in step (2) to a reduction reaction in a reducing atmosphere to obtain vanadium-intercalated reduced graphene oxide;

[0013] (4) Annealing the vanadium-intercalated reduced graphene oxide obtained in step (3) to obtain an interdigitated magnet.

[0014] Preferably, the molar ratio of the chelating agent to the vanadium in the soluble vanadium source in step (1) is (1-3):1.

[0015] Preferably, the temperature of the reduction reaction in step (3) is 200-300° C., and the insulation time is 1-2 h.

[0016] Preferably, the reducing atmosphere in step (3) is a mixture of hydrogen and an inert gas, and the volume content of hydrogen in the mixture is 5 to 10%.

[0017] Preferably, the annealing temperature in step (4) is 600-1000° C., and the holding time is 0.5-2 h.

[0018] Preferably, the heating rate of the annealing is 4-6°C / min, and the cooling rate of the annealing is 1.5-3°C / min.

[0019] Preferably, the pre-intercalation in step (2) is carried out under stirring conditions, the stirring rate is 400-600 rpm, the stirring temperature is 40-60° C., and the stirring time is 20-30 h.

[0020] The present invention also provides applications of the staggered magnet described in the above technical solution or the staggered magnet prepared by the preparation method described in the above technical solution in the fields of high-frequency magnetic sensors, spintronic devices or electromagnetic shielding coatings.

[0021] The present invention provides a staggered magnet, which is a vanadium intercalation graphite compound, and the vanadium intercalation graphite compound includes alternating vanadium atomic layers and carbon atomic layers. The present invention utilizes vanadium intercalation graphite, and the interlayer confinement effect of the alternating distribution of vanadium atomic layers and carbon atomic layers can induce the formation of staggered magnetism; through the synergistic effect of graphene and vanadium, room temperature adjustable magnetoelectric coupling characteristics are achieved. The results of the embodiment show that the vanadium atoms in the staggered magnet provided by the present invention are uniformly dispersed between the graphene layers; in the proof diagram of the theoretical prediction of staggered magnetism, its electronic structure shows that there is spontaneous Cramer degeneracy relief in momentum space, and the net magnetic moment of the material is zero, showing staggered magnetism; it exhibits reversible magnetic response in the temperature range of 5 to 240K, the room temperature saturation magnetization is 5 to 8emu / g, the coercive force is ≤50Oe, and the electrical conductivity is ≥500S / cm. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1Schematic diagram of the structure of the staggered magnet in Example 1 of the present invention;

[0023] Figure 2 This is a diagram demonstrating the theoretically predicted interlaced magnetism of the interlaced magnet in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0025] There is no particular limitation on the purity of all raw materials in the present invention, and analytically pure raw materials are preferably used in the present invention.

[0026] The present invention provides an interleaved magnet. The interleaved magnet is a vanadium intercalation graphite compound. The vanadium intercalation graphite compound comprises alternately distributed vanadium atomic layers and carbon atomic layers.

[0027] In the present invention, the interlayer spacing of the carbon atomic layers is preferably 0.45 to 0.5 nm. Graphene oxide (GO) is a carbon atomic layer structure with a large interlayer spacing of 0.35 to 0.4 nm. Vanadium intercalation between the carbon atomic layers will expand the interlayer spacing of the carbon atomic layers. The interlayer spacing of the carbon atomic layers within the above range is conducive to the formation of staggered magnetism induced by the interlayer confinement effect of vanadium atoms and carbon atomic layers.

[0028] The present invention utilizes vanadium intercalated graphite, and the interlayer confinement effect of the alternating distribution of vanadium atomic layers and carbon atomic layers can induce the formation of staggered magnetism; through the synergistic effect of graphite carrier and vanadium, the room temperature adjustable magnetoelectric coupling characteristics are achieved.

[0029] The present invention also provides a method for preparing the staggered magnet described in the above technical solution, comprising the following steps:

[0030] (1) mixing a soluble vanadium source, a chelating agent and an organic solvent and adjusting the pH to 3-4.5 to obtain a vanadium-containing solution;

[0031] (2) adding graphene oxide to the vanadium-containing solution obtained in step (1) for pre-intercalation to obtain pre-intercalated graphene oxide;

[0032] (3) subjecting the pre-intercalated graphene oxide obtained in step (2) to a reduction reaction in a reducing atmosphere to obtain vanadium-intercalated reduced graphene oxide;

[0033] (4) Annealing the vanadium-intercalated reduced graphene oxide obtained in step (3) to obtain an interdigitated magnet.

[0034] The invention mixes a soluble vanadium source, a chelating agent and an organic solvent and adjusts the pH value to 3-4.5 to obtain a vanadium-containing solution.

[0035] As an embodiment of the present invention, the soluble vanadium source may be vanadium trichloride; the purity is preferably not less than 99.9%.

[0036] As one embodiment of the present invention, the chelating agent can be one or more of citric acid, EDTA, and tartaric acid. In the present invention, the molar ratio of the chelating agent to the vanadium in the soluble vanadium source is preferably (1-3):1, more preferably (1-2):1. In an embodiment of the present invention, the molar ratio of the chelating agent to the vanadium in the soluble vanadium source is 1:1. The present invention uses a chelating agent to form a stable complex with the vanadium ions to prevent the hydrolysis and agglomeration of the vanadium ions, which is not conducive to the adsorption of vanadium in graphene oxide; the molar ratio of the chelating agent to the vanadium in the soluble vanadium source is within the above range, which is conducive to the dispersion of the vanadium ions.

[0037] As an embodiment of the present invention, the organic solvent may be anhydrous ethanol.

[0038] As an embodiment of the present invention, the concentration of vanadium trichloride in the vanadium-containing solution may be 0.05 to 0.15 mol / L.

[0039] In the present invention, the pH value of the vanadium-containing solution is adjusted to 3 to 4.5, preferably 3 to 4. The present invention prevents V from 3+ Oxidized to V 4+ , while avoiding hydrolysis to generate V(OH)3 precipitation, which is not conducive to the intercalation of vanadium in graphene oxide.

[0040] As an embodiment of the present invention, the reagent used to adjust the pH value can be 0.1 mol / L dilute hydrochloric acid or ammonia water. Different reagents are selected according to the pH value of the vanadium-containing solution.

[0041] After obtaining the vanadium-containing solution, the present invention adds graphene oxide into the vanadium-containing solution for pre-intercalation to obtain pre-intercalated graphene oxide.

[0042] The present invention does not particularly limit the source of the graphene oxide, and any graphene oxide obtained by a preparation method known to those skilled in the art can be used. As one embodiment of the present invention, the graphene oxide can be prepared by the Hummers method, with a flake diameter of 1 to 5 μm and an oxygen content of not less than 40%.

[0043] As an embodiment of the present invention, the molar ratio of carbon atoms in the graphene oxide to vanadium ions in the vanadium-containing solution can be (1-2):1, and the amount of the graphene oxide and the vanadium-containing solution can be 100 mg:50 mL.

[0044] As an embodiment of the present invention, after graphene oxide is added to the vanadium-containing solution, ultrasonic treatment can be used to uniformly disperse the graphene oxide. The power of the ultrasonic treatment can be 200 W, and the time of the ultrasonic treatment can be 1 hour.

[0045] In the present invention, the pre-intercalation is preferably carried out under stirring conditions. The stirring rate is preferably 400-600 rpm, more preferably 450-550 rpm; as an embodiment of the present invention, the stirring rate may be 400 rpm, 500 rpm or 600 rpm. The stirring temperature is preferably 40-60°C, more preferably 45-55°C; as an embodiment of the present invention, the stirring temperature may be 40°C, 50°C or 60°C. The stirring time is preferably 20-30h, more preferably 23-27h; as an embodiment of the present invention, the stirring time may be 22h, 24h, 26h or 28h. The stirring parameters within the above range are conducive to further improving V 3+ Adsorbed between the carbon atom layers of graphene oxide to complete pre-intercalation.

[0046] As an embodiment of the present invention, after the pre-intercalation is completed, the unadsorbed V can be removed by centrifugation and washing. 3+ As an embodiment of the present invention, the centrifugal speed can be 8000 rpm and the time can be 5 minutes; the washing can use anhydrous ethanol and the number of washing times can be 3; after washing, the pre-intercalated graphene oxide can be vacuum dried at a temperature of 60°C and the time can be 12 hours.

[0047] After obtaining the pre-intercalated graphene oxide, the present invention performs a reduction reaction on the pre-intercalated graphene oxide in a reducing atmosphere to obtain vanadium-intercalated reduced graphene oxide.

[0048] In the present invention, the reducing atmosphere is preferably a mixture of hydrogen and an inert gas, and the volume content of hydrogen in the mixture is preferably 5-10%, more preferably 8-10%. As one embodiment of the present invention, the volume content of hydrogen in the mixture may be 5%, 6%, 7%, 8%, 9%, or 10%. A volume content of hydrogen in the mixture within the above range is conducive to the reduction reaction.

[0049] The present invention has no particular limitation on the inert gas in the mixed gas, as long as it does not react with the pre-intercalated graphene oxide. In an embodiment of the present invention, the inert gas is Ar gas.

[0050] In the present invention, the temperature of the reduction reaction is preferably 200-300°C, more preferably 230-270°C. As one embodiment of the present invention, the temperature of the reduction reaction can be 200°C, 220°C, 250°C, 280°C, or 300°C. In the present invention, the time of the reduction reaction is preferably 1-2 hours, more preferably 1.5-2 hours. In the present invention, controlling the reduction reaction parameters within the above range is conducive to the full progress of the reduction reaction.

[0051] In an embodiment of the present invention, the heating rate of the reduction reaction may be 5° C. / min.

[0052] In an embodiment of the present invention, the reduction reaction can be carried out in a tube furnace; specifically, the pre-intercalated graphene oxide is placed in a quartz boat, placed in the reaction zone of the tube furnace, and vacuumed to 10 -2 Pa, introduce mixed gas with a flow rate of 50 sccm; after the reaction is completed, naturally cool to room temperature.

[0053] After obtaining the vanadium intercalation reduced graphene oxide, the present invention anneals the vanadium intercalation reduced graphene oxide to obtain a staggered magnet.

[0054] In the present invention, the heating rate of the annealing is preferably 4-6°C / min, more preferably 5°C / min. The heating rate of the annealing within the above range is conducive to stabilizing the intercalation structure.

[0055] In the present invention, the annealing temperature is preferably 600-1000°C, more preferably 700-900°C. As one embodiment of the present invention, the annealing temperature can be 650°C, 750°C, 800°C, 850°C, or 950°C. The annealing time is preferably 0.5-2 hours, more preferably 1 hour. Annealing parameters within this range are beneficial for repairing graphite lattice defects and further enhancing the intercalation effect of vanadium atoms.

[0056] In the present invention, the cooling rate of the annealing is preferably 1.5-3°C / min, more preferably 2°C / min. A cooling rate within the above range is beneficial for promoting uniform distribution of vanadium atoms between graphite layers, reducing thermal stress, and further improving the stability of the intercalation structure.

[0057] As an embodiment of the present invention, the annealing can be performed in a tube furnace, and the annealing atmosphere can be Ar gas; after the annealing is completed, the sample can be taken out of the glove box, ground into a uniform powder, and then stored in a sealed bottle in an Ar atmosphere.

[0058] The preparation method provided by the present invention can avoid metal carbonization, intercalate transition metals into graphite layers, and can intercalate different transition metals. The magnetoelectric properties can be regulated by the intercalation amount and annealing process. The preparation process is simple, has low equipment requirements, and has industrial potential.

[0059] The present invention also provides applications of the staggered magnet described in the above technical solution or the staggered magnet prepared by the preparation method described in the above technical solution in the fields of high-frequency magnetic sensors, spintronic devices or electromagnetic shielding coatings.

[0060] The present invention has no particular limitation on the specific manner of application, and conventional application manners in the art may be used.

[0061] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0062] Example 1

[0063] A staggered magnet is a vanadium intercalated graphite compound, wherein the structure of the vanadium intercalated graphite compound is an alternating distribution of vanadium atomic layers and carbon atomic layers, and its structural schematic diagram is as follows Figure 1 As shown, the red spheres in the figure are vanadium atoms, the brown spheres are carbon atoms, and the vanadium intercalated graphite compound is a stage-1 graphite intercalation compound.

[0064] The preparation method is as follows:

[0065] Dissolve equimolar amounts of vanadium trichloride and citric acid in anhydrous ethanol, and add ammonia water to adjust the pH value of the solution to 3.5 to obtain a 0.1 mol / L vanadium-containing solution;

[0066] 100 mg of graphene oxide (prepared by the Hummers method, with a flake size of 1 to 5 μm and an oxygen content of 45%) was added to 50 mL of a vanadium-containing solution. The mixture was ultrasonically treated (power 200 W) for 1 hour, stirred at 500 rpm and 50°C for 24 hours, and centrifuged at 8000 rpm for 5 minutes. The resulting solid was washed three times with anhydrous ethanol and then vacuum-dried at 60°C for 12 hours to obtain pre-intercalated graphene oxide, which was designated as V-GO.

[0067] Place V-GO in a quartz boat, put it into the reaction zone of a tube furnace, and evacuate it to 10 -2 Pa, a mixed gas (H2 / Ar, H2 volume percentage 10%) was introduced at a flow rate of 50 sccm, the temperature was raised to 300°C at a rate of 5°C / min, kept at this temperature for 2 h, and naturally cooled to room temperature to obtain vanadium-intercalated reduced graphene oxide, which was recorded as V-rGO;

[0068] V-rGO was placed in a tube furnace, heated to 800°C at a rate of 5°C / min under Ar atmosphere, kept warm for 1 h, and cooled to room temperature at a rate of 2°C / min. The sample was taken out of the glove box, ground into a uniform powder, and stored in a sealed bottle in Ar atmosphere.

[0069] The staggered magnetism of vanadium intercalated graphite compounds was predicted by DFT, and the theoretical prediction of staggered magnetism was obtained, as shown in the figure. Figure 2 As shown. Figure 2 It can be seen that on the path from the high symmetry point L2 (0, 1 / 2, 1 / 2) to (0, 0, 0) to M2 (-1 / 2, 1 / 2, 1 / 2) in the reciprocal space, the red dotted line and the blue solid line represent the spin-up and spin-down energy bands respectively, and the band structure on both sides of the Γ point shows alternating spin splitting; there is spontaneous Cramer degeneracy relief in the momentum space, and the net magnetic moment of the material is zero, showing staggered magnetism.

[0070] The phase analysis of the staggered magnet of Example 1 was performed using an X-ray diffractometer, and it was found that the original graphite (002) peak (2θ≈26.5°) disappeared, and a new peak appeared at 2θ≈19° (corresponding to an interlayer spacing of 0.46nm); there was no VC impurity peak (the (111) peak of VC was at 2θ≈37.5°).

[0071] The staggered magnet of Example 1 was analyzed using a Raman spectrometer and it was found that the D peak (1350 cm -1 ) and G peak (1580cm -1 ) intensity ratio (ID / IG) < 0.2, indicating low defect density.

[0072] The staggered magnet of Example 1 was analyzed using an X-ray photoelectron spectrometer and it was found that V 2p 3 / 2 Peak binding energy 513.5eV (corresponding to V 2+ or V 0 ), no VC bond signal (283 eV); the CO bond disappears in the C 1s peak, indicating that GO is successfully reduced.

[0073] The staggered magnet of Example 1 was analyzed using a transmission electron microscope and an energy dispersive spectrometer, and it was found that vanadium atoms (bright spots) were uniformly dispersed between the graphene layers.

[0074] Air exposure experiment: After the staggered magnet sample of Example 1 was placed in air for 24 hours, there was no shift in the XRD peak position, indicating that the vanadium was not oxidized.

[0075] High temperature stability: The staggered magnet sample of Example 1 was heated to 500° C. in Ar and maintained for 2 hours. No VC impurity peak was generated in XRD.

[0076] It exhibits reversible magnetic response in the temperature range of 5 to 240 K, with a room temperature saturation magnetization of 5 to 8 emu / g, a coercive force ≤ 50 Oe, and a conductivity ≥ 500 S / cm.

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A staggered magnet, characterized in that The staggered magnet is a vanadium intercalation graphite compound, which includes alternately distributed vanadium atomic layers and carbon atomic layers.

2. The staggered magnet according to claim 1, characterized in that The interlayer spacing of the carbon atomic layers is 0.45 to 0.5 nm.

3. The method for preparing the staggered magnet according to claim 1 or 2, comprising the following steps: (1) mixing a soluble vanadium source, a chelating agent and an organic solvent and adjusting the pH to 3-4.5 to obtain a vanadium-containing solution; (2) adding graphene oxide to the vanadium-containing solution obtained in step (1) for pre-intercalation to obtain pre-intercalated graphene oxide; (3) subjecting the pre-intercalated graphene oxide obtained in step (2) to a reduction reaction in a reducing atmosphere to obtain vanadium-intercalated reduced graphene oxide; (4) Annealing the vanadium-intercalated reduced graphene oxide obtained in step (3) to obtain an interdigitated magnet.

4. The preparation method according to claim 3, characterized in that In the step (1), the molar ratio of the chelating agent to the vanadium in the soluble vanadium source is (1-3):

1.

5. The preparation method according to claim 3, characterized in that The temperature of the reduction reaction in step (3) is 200-300° C., and the insulation time is 1-2 hours.

6. The preparation method according to claim 3, characterized in that The reducing atmosphere in step (3) is a mixture of hydrogen and inert gas, and the volume content of hydrogen in the mixture is 5-10%.

7. The preparation method according to claim 3, characterized in that The annealing temperature in step (4) is 600-1000° C., and the holding time is 0.5-2 h.

8. The preparation method according to claim 7, characterized in that The heating rate of the annealing is 4-6°C / min, and the cooling rate of the annealing is 1.5-3°C / min.

9. The preparation method according to claim 3, characterized in that The pre-intercalation in step (2) is carried out under stirring conditions, the stirring rate is 400-600 rpm, the stirring temperature is 40-60° C., and the stirring time is 20-30 h.

10. Use of the staggered magnet according to claim 1 or 2 or the staggered magnet prepared by the preparation method according to any one of claims 3 to 9 in the fields of high-frequency magnetic sensors, spintronic devices or electromagnetic shielding coatings.

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