A method for synthesizing two-dimensional material Fe3O4 single crystal and modulating magnetic domains

Abstract

This invention provides a method for synthesizing and modulating the magnetic domains of a two-dimensional Fe3O4 single crystal. Ultrathin Fe3O4 single crystals were successfully synthesized using chemical vapor deposition, exhibiting clear magnetic domain signals at room temperature. The Fe3O4 single crystals were annealed at 603K. By applying magnetic fields in different directions in-plane during the annealing process, the appearance and disappearance of stripe-like maze-like magnetic domains were observed within the Fe3O4 single crystals, demonstrating magnetic domain modulation within the Fe3O4 single crystals.

Description

Technical Field

[0001] The present invention relates to the field of electronic memory, and more specifically, to a two-dimensional material Fe3O4 single crystal and a synthesis method. Background Art

[0002] Since the discovery of graphene through mechanical exfoliation, two-dimensional materials have garnered significant attention due to their atomically thin structure, large surface area, tunable band gap, and high carrier mobility. Different crystal structures within two-dimensional materials exhibit distinct properties, demonstrating their potential for development in diverse fields.

[0003] In 2017, the research group of Xiaodong Xu from the University of Washington and the research group of Pablo Jarillo-Herrero from the Massachusetts Institute of Technology published an article in Nature (Reference 1: Huang B, Clark G, Efrén Navarro-Moratalla, et al. Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit [J]. Nature. 2017, 546 (Jun. 8TN. 7657): 270-273.), reporting the first preparation of a single-layer two-dimensional material CrI3 single crystal with intrinsic magnetism, and showing that its Curie temperature is 45K.

[0004] Reference 2: "Gong C, Li L, Li Z, et al. Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals [J]. Nature, 2017, 546(7657):265" discovered spontaneous magnetization in a two-dimensional Cr2Ge2Te6 bilayer, with a Curie temperature of 28K. Since then, two-dimensional materials with intrinsic magnetism have become a research hotspot in physics and other related fields, and hold great promise for future information technology.

[0005] However, research on a series of two-dimensional magnetic materials with intrinsic magnetism, such as Fe3GeTe2 and Cr2Ge2(Si2)Te6, has been slow due to difficulties in preparation methods, detection methods, and magnetic domain modulation, as well as the fact that the Curie temperature is lower than room temperature.

[0006] Currently, there are relatively few two-dimensional materials with room-temperature magnetism, and measurements of magnetic domains at room temperature are also relatively rare, making it difficult to modulate the magnetic domains of two-dimensional materials. While there are reports on the room-temperature magnetic domains of ferrocene and Fe7Se8, and a few studies on the metallic-to-semiconductor phase transition of two-dimensional Fe3O4 crystals at low temperatures, there are no reports on modulating the magnetic domains of two-dimensional Fe3O4 crystals. This is primarily due to the lack of existing technologies for producing single crystals of the two-dimensional Fe3O4 material, and the difficulty in characterizing and modulating the magnetic domains of this ferrimagnetic material. Summary of the Invention

[0007] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and provide a two-dimensional material Fe3O4 single crystal and a synthesis method, which is a two-dimensional material with room temperature properties, based on which the modulation function of the magnetic domain shape that can be used in the field of information storage and encryption is realized.

[0008] The technical solution of the present invention is:

[0009] A method for synthesizing a two-dimensional material Fe3O4 single crystal comprises the following steps:

[0010] S1, prepare raw materials: iron powder, sodium chloride granules; grind the sodium chloride granules into powder in a mortar and pestle, mix with iron powder and place in a porcelain boat;

[0011] S2, the sapphire substrate is placed with the polished surface facing down on a porcelain boat and then placed into a quartz tube;

[0012] S3, turn on the vacuum pump. When the pressure inside the quartz tube reaches 12 Pa, open the gas input end. Flush with argon at a flow rate of 250 sccm for 8 minutes and then adjust to 150 sccm. Turn off the vacuum pump to allow the argon to fill the quartz tube. When the pressure reaches atmospheric pressure, open the gas output end.

[0013] S4, after the argon gas in the quartz tube is kept stable at a flow rate of 50 sccm, the tube furnace is started to start heating;

[0014] S5, take out the product when the temperature of the tube furnace drops to room temperature.

[0015] A method for synthesizing a two-dimensional material Fe3O4 single crystal, comprising the following steps:

[0016] S1, preparation: Place a quartz tube of appropriate size in a tube furnace, which should be sealed with the gas input and gas output ports; take a sapphire substrate, cut it into appropriate sizes using a diamond pen, place it in acetone or ethanol, and clean it in an ultrasonic cleaner;

[0017] S2, weighing iron powder and sodium chloride particles, grinding the sodium chloride into powder using a mortar and pestle, and mixing it evenly with the iron powder; selecting a clean porcelain boat or corundum boat, and pouring the evenly mixed powder into the center of the porcelain boat or corundum boat;

[0018] S3, operations before starting heating:

[0019] S3-1, place the polished surface of the sapphire substrate facing downward directly above the powder in the porcelain boat or corundum boat;

[0020] S3-2, slowly place the quartz tube into the tube furnace from one end, so that the center of the powder coincides with the thermocouple of the tube furnace;

[0021] S3-3, the two ends of the quartz tube are connected to the gas input end and the gas output end respectively through flanges to ensure airtightness;

[0022] S4, heating treatment: Turn on the vacuum pump at the gas output end, extract the air from the quartz tube, then open the gas input end, and slowly input argon or nitrogen into the quartz tube by adjusting the gas flow meter. After a few minutes, turn off the vacuum pump, and open the gas output end after the pressure gauge reaches atmospheric pressure. Set the tube furnace program to heat from room temperature to 800°C in 30 minutes, and keep at this temperature for 30 minutes.

[0023] S5, finally, the Fe3O4 single crystal is collected: when the temperature of the tube furnace drops to 20°, the gas input end is closed by adjusting the gas flow meter, and the Fe3O4 single crystal is taken out.

[0024] Furthermore, the product obtained in S5 is an Fe3O4 single crystal with a magnetic domain signal at 20°. The two-dimensional Fe3O4 single crystal is further subjected to magnetization annealing. During the annealing process, the magnetic domain shape is modulated by changing the direction of the in-plane magnetic field, achieving the appearance and disappearance of striped maze-like magnetic domains, which are erasable.

[0025] The beneficial effects of this application are:

[0026] First, ultrathin two-dimensional Fe3O4 single crystals were successfully synthesized using a simple and controllable chemical vapor deposition method. This invention provides a method for successfully synthesizing two-dimensional Fe3O4 single crystals using chemical vapor deposition. Importantly, magnetic domains were observed in the two-dimensional Fe3O4 single crystals at room temperature. During the annealing process, the magnetic domains in the two-dimensional Fe3O4 single crystals exhibited different shapes when magnetic fields of different directions were applied. This discovery is of great significance for the preparation of two-dimensional materials with room-temperature intrinsic magnetism, as well as the measurement and modulation of room-temperature magnetic domains, and promotes their application prospects in the field of information storage.

[0027] Second, after the sample was annealed at 603K, a maze-like magnetic domain signal was observed in the two-dimensional Fe3O4 single crystal.

[0028] Third, by changing the direction of the magnetic field within the material plane, the appearance and disappearance of strip-shaped maze magnetic domains in the two-dimensional Fe3O4 single crystal were observed, which is erasable. It should be noted that: the method of modulating the magnetic domain signal based on the synthesized two-dimensional material Fe3O4 single crystal in this application is related to "magnetic domain signals at 20°, magnetizing and annealing the two-dimensional Fe3O4 single crystal, and modulating the magnetic domain shape by changing the direction of the magnetic field within the plane during the annealing process to achieve the appearance and disappearance of strip-shaped maze magnetic domains, which is erasable", that is, the product method is related to the product properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described in detail below with reference to the embodiments in the accompanying drawings, but this does not constitute any limitation to the present invention.

[0030] Figure 1 This is a diagram of the chemical vapor deposition experimental system setup.

[0031] Figure 2 This is an optical microscope image of a two-dimensional Fe3O4 single crystal.

[0032] Figure 3 This is a diagram showing the magnetic domain modulation phenomenon of two-dimensional Fe3O4 single crystal. DETAILED DESCRIPTION

[0033] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those commonly understood by those skilled in the art to which this invention belongs. The materials used in the following examples, unless otherwise specified, are conventional materials; and the experimental methods described, unless otherwise specified, are conventional methods.

[0034] The present invention will be described in detail below with reference to the accompanying drawings to fully describe the technical solution of the present invention.

[0035] 1. Test Preparation

[0036] The equipment and materials used in the chemical vapor deposition controlled synthesis method of ultra-thin two-dimensional material Fe3O4 single crystal include argon gas, gas input channel, gas flow meter, pressure gauge, tubular furnace, quartz tube, porcelain boat or corundum boat, sapphire substrate, iron powder and sodium chloride particles.

[0037] 2. Test process

[0038] A method for modulating magnetic domain signals based on a synthesized two-dimensional material Fe3O4 single crystal comprises the following steps:

[0039] The first step is to prepare the experimental materials: place a quartz tube of appropriate size in the tube furnace, ensuring that it can be sealed with the gas input and gas output ends; take a sapphire substrate, cut it into suitable sizes with a diamond pen, put it in acetone or ethanol, and clean it in an ultrasonic cleaner; weigh iron powder and sodium chloride particles, grind the sodium chloride into powder with a mortar and pestle, and mix it evenly with the iron powder; select a clean porcelain boat or corundum boat, and pour the evenly mixed powder into the center of the porcelain boat or corundum boat.

[0040] Next, the pre-heating procedures begin: Place the polished surface of the sapphire substrate face down directly above the powder in the porcelain or corundum boat. Slowly lower the quartz tube into the tube furnace from one end, aligning the center of the powder with the furnace's thermocouple. Flanges connect the two ends of the quartz tube to the gas input and output ports, ensuring a leak-proof seal. Turn on the vacuum pump at the gas output port, evacuate the air from the tube, then open the gas input port. Slowly introduce argon or nitrogen into the tube using the gas flowmeter. After several minutes, turn off the vacuum pump. Once the pressure gauge reaches atmospheric pressure, open the gas output port. Depending on the experimental requirements, program the tube furnace to heat from room temperature to 800°C over 30 minutes, then hold for 30 minutes.

[0041] Finally, collect the sample: when the temperature of the tube furnace drops to room temperature, close the gas input end by adjusting the gas flow meter and take out the sample.

[0042] 3. Magnetic domain signals in ultra-thin two-dimensional Fe3O4 single crystals at room temperature, and study the method of its shape tuning.

[0043] First, a two-dimensional Fe3O4 single crystal was prepared using the above-mentioned chemical vapor deposition method. The sample was then annealed at 603K, and magnetic domains were observed at room temperature. After that, magnetic fields in different directions were applied, and the strip-like maze magnetic domains in the two-dimensional Fe3O4 single crystal would appear or disappear, showing erasability.

[0044] Example 1:

[0045] Preparation of a two-dimensional Fe3O4 single crystal: Weigh 0.096g of iron powder and 0.036g of sodium chloride granules. Grind the sodium chloride granules into a powder in a mortar, mix with the iron powder, and place the mixture evenly in a porcelain boat. Place the sapphire substrate, polished side down, on the boat and place it in a quartz tube. Turn on the vacuum pump. Once the pressure in the quartz tube reaches 12 Pa, open the gas inlet. Flow argon at a rate of 250 sccm for 8 minutes, then adjust to 150 sccm. Turn off the vacuum pump, allow the quartz tube to fill with argon, and once the pressure reaches atmospheric pressure, open the gas outlet. Maintain a stable argon flow rate of 50 sccm in the quartz tube, then start heating in the tube furnace.

[0046] When the temperature of the tube furnace dropped to room temperature, the sample was taken out and annealed at 603K. A two-dimensional Fe3O4 single crystal was selected and the magnetic domain signal ( Figure 3 b, h).

[0047] Example 2:

[0048] The two-dimensional Fe3O4 single crystal selected in Experimental Case 1 was found to have magnetic domains at room temperature. The sample was then annealed at 603K. At the same time, a 1T magnetic field perpendicular to the longest side of the single crystal was applied to the same single crystal in Experimental Case 1. It was found that the magnetic domains observed in Experimental Case 1 were transformed into strip-shaped maze magnetic domains ( Figure 3 c, i) in .

[0049] Example 3:

[0050] The two-dimensional Fe3O4 single crystal with the strip-like maze magnetic domains in Example 2 was selected and annealed at 603K again. A magnetic field of 1T parallel to the longest side of the single crystal was applied. It was found that the strip-like maze magnetic domains observed in Example 2 disappeared ( Figure 3 d, j).

[0051] Example 4:

[0052] The two-dimensional Fe3O4 single crystal in which the stripe-shaped maze magnetic domains disappeared in Example 3 was selected and annealed at 603K again. A magnetic field with the same magnitude and direction as in Example 2 was applied to the crystal. It was found that the stripe-shaped maze magnetic domains observed in Example 3 reappeared ( Figure 3 e, k in ).

[0053] Example 5:

[0054] The two-dimensional Fe3O4 single crystal with the stripe-shaped maze magnetic domains in Example 4 was selected and annealed at 603K. A magnetic field with the same magnitude and direction as in Example 3 was applied. It was found that the stripe-shaped maze magnetic domains observed in Example 4 disappeared again ( Figure 3 f, l) in.

[0055] Through the experimental results of the above five experimental cases (see Figure 3 ), the magnetic domain signal of the two-dimensional Fe3O4 single crystal prepared by chemical vapor deposition at room temperature can be clearly observed. By comparison, it can also be seen that the magnetic domain modulation can be carried out in the two-dimensional Fe3O4 single crystal at room temperature by changing the direction of the magnetic field during annealing, realizing the appearance and disappearance of strip-like maze magnetic domains, which is erasable.

[0056] The above embodiments are preferred implementation modes of the present invention and are only used to facilitate the explanation of the present invention. They are not intended to limit the present invention in any form. Any person with ordinary knowledge in the technical field can, without departing from the scope of the technical features of the present invention, make partial changes or modifications to the technical contents disclosed in the present invention and make equivalent embodiments without departing from the technical features of the present invention. Such modifications still fall within the scope of the technical features of the present invention.

Claims

1. A method for modulating magnetic domain signals based on a synthesized two-dimensional material Fe3O4 single crystal, characterized in that: A method for synthesizing a two-dimensional material Fe3O4 single crystal comprises the following steps: S1, preparation: Place a quartz tube of appropriate size in a tube furnace, which should be sealed with the gas input and gas output ports; take a sapphire substrate, cut it into appropriate sizes using a diamond pen, place it in acetone or ethanol, and clean it in an ultrasonic cleaner; S2, weighing iron powder and sodium chloride particles, grinding the sodium chloride into powder using a mortar and pestle, and mixing it evenly with the iron powder; selecting a clean porcelain boat or corundum boat, and pouring the evenly mixed powder into the center of the porcelain boat or corundum boat; S3, operations before starting heating: S3-1, place the polished surface of the sapphire substrate facing downward directly above the powder in the porcelain boat or corundum boat; S3-2, slowly place the quartz tube into the tube furnace from one end, so that the center of the powder coincides with the thermocouple of the tube furnace; S3-3, the two ends of the quartz tube are connected to the gas input end and the gas output end respectively through flanges to ensure airtightness; S4, heating treatment: Turn on the vacuum pump at the gas output end, extract the air from the quartz tube, then open the gas input end, and slowly input argon or nitrogen into the quartz tube by adjusting the gas flow meter. After a few minutes, turn off the vacuum pump, and open the gas output end after the pressure gauge reaches atmospheric pressure. Set the tube furnace program to heat from room temperature to 800°C in 30 minutes, and keep at this temperature for 30 minutes. S5, finally, the Fe3O4 single crystal is collected: when the temperature of the tube furnace drops to 20°, the gas input end is closed by adjusting the gas flow meter, and the Fe3O4 single crystal is taken out; The Fe3O4 single crystal has a hexagonal structure; The Fe3O4 single crystal with hexagonal structure was annealed at 603K, and the magnetic domain signal in the two-dimensional Fe3O4 single crystal with hexagonal structure was observed at room temperature. The pair was annealed again at 603K, and a 1T magnetic field perpendicular to the longest side of the single crystal was applied, causing the magnetic domains to transform into strip-shaped maze magnetic domains. The single crystal was annealed again at 603K and a magnetic field of 1T parallel to the longest side of the single crystal was applied, and the strip-like maze magnetic domains disappeared.

Images